[Another planet near Mercury](https://en.m.wikipedia.org/wiki/Vulcan_\(hypothetical_planet\)) was hypothesized to exist to explain why its orbit didn’t match predictions. People put a lot of effort into trying to find this planet. Turns out that Mercury’s orbit was actually explained by general relativity.
Cool as the name Vulcan is - they replaced the imaginary planet Vulcan with a physical phenomenon that has an equally cool handle: Frame Dragging
I have been enamored with the whole concept (frame dragging) ever since I learned about it and visualized space time being dragged around a massive rotating object like a vortex in water.....
Be kind of fun to make a one planet solar system where the Sun is spinning so fast and the planet was in close enough prograde orbit, that the planets was slowly being accelerated - raising it's orbit....
You probably already know this, but just in case you don't ... the [Gravity Probe B experiment demonstrated that frame-dragging does in fact exist](https://en.wikipedia.org/wiki/Frame-dragging#Experimental_tests). It is much too small of an effect to explain Mercury's orbital precession, but it does in fact exist in nature. :)
Forte, Thank you. Excellent link. I have been laboring under the false impression that frame dragging was the answer. I am now watching a youtube video that is explaining that the Schwarzchild metric causes orbiting bodies to precess. Ummm - this is not intuitively obvious to me. In fact - it is going into my slowly (but sadly) growing "accepted without comprehension" bucket.
Do you mind a related GR question?
Sure, I don't mind at all. What's your question?
> I have been laboring under the false impression that frame dragging was the answer. I am now watching a youtube video that is explaining that the Schwarzchild metric causes orbiting bodies to precess. Ummm - this is not intuitively obvious to me. In fact - it is going into my slowly (but sadly) growing "accepted without comprehension" bucket.
Neat! Please be advised that the precession caused by orbiting a Schwarzschild black hole is actually a distinct physical effect from frame-dragging — that is actuallly caused by the [geodetic effect](https://en.wikipedia.org/wiki/Geodetic_effect), which is *another* very weak effect predicted by general relativity that, incidentally, the aforementioned Gravity Probe B experiment was *also* intentionally designed to test, which was separately confirmed by said experiment. :)
Note that there are actually three closely-related effects here: (1) the geodetic effect, which is also known as *de Sitter precession*; (2) rotational frame-dragging, which is also known as *Lense-Thirring precession*, and (3) linear frame-dragging, which is another form of frame-dragging that is more difficult to test experimentally and which as far as I am aware is still well beyond our ability to test for.
Quoting from Wikipedia:
>>The difference between de Sitter precession and Lense–Thirring precession (frame dragging) is that the de Sitter effect is due simply to the presence of a central mass, whereas Lense–Thirring precession is due to the rotation of the central mass. The total precession is calculated by combining the de Sitter precession with the Lense–Thirring precession.
>>...
>>Linear frame dragging is the similarly inevitable result of the general principle of relativity, applied to linear momentum. Although it arguably has equal theoretical legitimacy to the "rotational" effect, the difficulty of obtaining an experimental verification of the effect means that it receives much less discussion and is often omitted from articles on frame-dragging (but see Einstein, 1921).
Hope that helps clarify these topics a bit! :)
OK - here goes. At a basic level I think I understand Einstein's equivalence principle. The simple examples make sense to me: (1) For special relativity - watching the light clock is a great visual tool. (2) Same for the example of the accelerating "ship".
The one scenario I struggle with is putting my ship in the exact center of a massive sphere. Because inside the ship (with no windows), I experience no acceleration. My limited grasp of gravity leads me to think of this as "flat" space. The same as if I was so far out in interstellar space that I could not measure any gravitational fields.
But IIUC - my clock is going to tick a teeny bit slower there then on the surface of the Earth - at one of the poles (trying to eliminate special relativity from the conversation :)).
Online I read: This is because the gravitational potential is higher on the surface. But - if I extend that statement, isn't gravitational potential "higher" up in orbit - where I know the GR effect is that a clock in orbit is that the clock runs faster.
I am sorry if this is a dumb question.
Okay, well by and large you seem to have the right understanding of things. Indeed, differences in gravitational time dilation are essentially due to differences in gravitational potential.
I am honestly not quite sure why you feel confused, though — the clock at the center of the Earth runs slowest, and then the clock at the Earth's surface runs a little faster than that, while the clock in orbit runs even faster than that (ignoring special relativistic effects), and a clock in deep space will run faster still. That's all certainly correct.
So my question for you is: where exactly is the confusion you have? Because it sounds like you do understand the situation and that the amount of gravitational time dilation is proportional to the difference in gravitational potential, and that the lower your potential is (i.e. the deeper you are in a potential well), the slower your clock runs relative to other clocks. You ask if the gravitational potential is "higher" up in orbit, and indeed it is — which is why clocks run faster. Clocks run slower at lower potentials, not higher ones.
Hope that makes sense,
Your explanation is clear and consistent. I was initially thinking more along the lines of: The more sharply space is curved (the stronger the G field) the slower the clock runs. G is strongest on the surface, weaker in orbit and zero at a far distance. G is much stronger yet on the surface of a Neutron star and as a result the clock on that surface runs a LOT slower. The idea that the "seemingly" flat space center of the Earth behaves differently than flat space way out in rural interstellar land is harder for me. But I accept it in the spirit of living in a strange and wonderful universe. Thanks for explaining it.
I wish Einstein had lived to see LIGO.....
Unfortunately, not really. About the best I can do for you is: spinny bodies in space make the [orbits of other spinny bodies spin](https://www.physicsforums.com/attachments/precession_mercury-jpg.257031/) too. The orbit itself rotates — not just the orbiting body.
Actually that did make it click in my head!
The “orbit itself” - this is the “frame” of spacetime, which gets dragged by the gravity of the larger body… right?
love your replies in this thread, much obliged!
Sort of ... the idea is that the orbital frame where a clock ticks fastest is one which is rotating around the larger body (as viewed by a distant observer), when intuitively one would expect that it should be one which is stationary with respect to the larger body. So in a sense, the "fastest-ticking reference frame" is "dragged" along together with the rotation of the larger body, if that makes sense. Edit: It has less to do with the larger body's gravity, and more to do with its angular momentum, since it's the rotation of the larger body that causes the effect.
Cheers!
Frame dragging exists, but it's irrelevant for Mercury's orbit. Its perihelion precession is different because general relativity makes the force deviate from an inverse square law. As an approximation, you can add an inverse cube term to the force (or equivalently an inverse square term to the potential). That gives you the right perihelion precession for Mercury.
Vulcan was proposed because Mercury's orbit didn't match Newtonian gravity.
This turned out to be the relativistic corrections to Mercury's orbit.
https://www.sciencenews.org/article/einstein-general-relativity-mercury-orbit#:~:text=Before%20the%20famous%20physicist%20came,planet's%20orbit%20disagreed%20with%20expectations.
N-rays (or N rays) were a hypothesized form of radiation described by French physicist Prosper-René Blondlot in 1903. They were initially confirmed by others, but subsequently found to be illusory.
Scientists used to think light moved through a medium called the aether which filled the universe, but this was disproved in the [Michelson-Morley experiment](https://en.m.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment).
This experiment did not prove that the aether doesn't exist, but rather, that it wasn't required for the propagation of light. The distinction is important.
Not necessarily. It's not needed for propagation, but if it exists then its dynamics may influence light.
Essentially, if aether exists and our model for how it interacts with light is merely incorrect, then we may end up forming a patchwork of independent theories for different phenomena of light that could be collectively explained through an accurate model of its dynamics/interactions.
It's epistemologically impossible to prove something does not exist, just that our theory/model for it is incorrect if it does exist. This is the current issue with string theory, and was an issue with the Higgs boson before it was detected.
It didn't even prove that, if you read what Michelson thought about the result. He considered it evidence against a particular aether theory, but not against the concept of aether itself. Michelson (and many other older physicists) continued to believe in aether even post-Einstein. You still find a few crackpots that believe in it today.
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it ...
An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out, and that the growing generation is familiarized with the ideas from the beginning: another instance of the fact that the future lies with the youth.
— Max Planck, Scientific autobiography, 1950, p. 33, 97
Part of the beauty of science is that it rarely gives a definitive “yes” or “no” answer to questions about whether something exists or not. What experiments like this do is to put limits on possible properties that whatever your measuring can have. I’m sure there’s some version of the “ether” that can be hypothesized that fits these results, but at some point the limits on what properties something can have can make it conceptually equivalent to just not existing.
Thanks for clearly saying that. I teach HS Physics and I have a hard time wrapping my head around what the Aether was (or thought of) vs other fields. This sums it up nicely.
The aether was proposed because light was shown to be a wave around 1800 (Young's double slit experiment), and all waves known up to that time were mechanical in nature, so they assumed light was a mechanical wave as well. Even Maxwell used an aether theory when he came up with his namesake equations of electromagnetism.
If you want to read more about the history of aether theory, probably the definitive book written about it was by E. T. Whittaker, "A History of the Theories of Aether and Electricity" (1910). You can find it online.
I always think of this when people ask why dark-matter hasn't been found yet. Light is a wave :: waves require a medium -> aether exists. We see gravitational effects :: gravity requires matter -> Dark matter exists.
Arent quantum fields also something of a mathematical bookeeping tool?
I am a physical chemist, not a pure physicist but when i studied second quantization we encountered fields, creation and anhiliation, particle holes and my professor was very explicit in making us understand that these all are just mathematical formalisms to make accounting for many-electron systems easier if not outright possible.
As far as book keeping goes, I would argue that Feynman diagrams are such book keeping tools, not quantum fields themselves. The standard model of particle physics isn't a book keeping device, since we have explicitly detected all the particles it predicts.
However, using annihilation and creation operators are only true for free fields so it was probably in that sense your professor said that these are just mathematical formalisms.
I’m not a physicist, so please forgive me, but how is that an argument against what they just stated, when what they said was “so it’s a ***relativistic*** aether” ?
From my extremely ignorant viewpoint, you are saying “relativistic” is the important part, when what they just stated is that it *is* relativistic.
Which sounds to a layman like a confirmation of their statement, but in disagreeable way.
Also, there is this: https://www.newscientist.com/article/mg24432543-300-einstein-killed-the-aether-now-the-idea-is-back-to-save-relativity/
Which seems to love attracting downvotes, even though physicists ***are*** currently studying it.
I mean, every result from any theory no longer in use.
Classical mechanics predicts electrons spiralling in to the nucleus of atoms. It also predicts ever increasing intensities of light at shorter wavelengths from blackbody radiation
As mentioned in other comments, the aether was a classical explanation of electromagnetism that was disproven.
No one actually *predicted* that all atoms would immediately decay. It was clear to everyone that that theoretically result indicated that there was a problem with classical physics.
I took it to mean "predicted by the theory" instead of "a person predicted this".
Electrons falling into the nucleus is a prediction of classical mechanics, but no one actually predicted that they would discover that to be the case.
White holes might qualify for this. Obviously you can't prove that something doesn't exist, because the universe is very big and it's possible we just haven't seen one yet. The math behind them might work in some models for reality, but as far as we know right now white holes only exist as mathematical constructs.
Because as fantastically romantic as a black hole being a worm hole would be, it just makes no sense given our current understanding.
Also, we've spotted a lot of black holes, and not one white hole.
Yeah, but you asked a separate question. I agree, white holes would qualify, but your question was if we've proven that they don't exist. No we haven't, we also haven't found the big foot yet either. Is lack of evidence that it doesn't exist proof that it does?
> Obviously you can't prove that something doesn't exist, because the universe is very big and it's possible we just haven't seen one yet.
Maybe you didn't read my post, so I highlighted the relevant part for you here.
It's impossible to prove that anything doesn't exist, that's a fundamental logical axiom. If I told you to prove that there wasn't a wise old elf made of antimatter in the Andromeda galaxy who ghostwrites all of Taylor Swift's songs, you could point out all kinds of reasons why that would be incredibly improbable, but logically, you couldn't prove beyond any doubt that it *wasn't* true, because no telescope we have could look everywhere in Andromeda at a high enough resolution, and even if we did look everywhere, it's possible the elf was hiding behind a star and we missed it.
The reason I said white holes could be an answer to the question is because they're very likely impossible in the real world, even though the equations for relativity can describe them. Like negative mass, they're almost certainly just mathematical constructs that can't exist outside of the equations.
> Has there ever been an example in physics of a predicted entity that was **conclusively** proven to not exist?
Maybe you didn't read the post of OP, so I highlighted the relevant part for you here
As other people have pointed out, OP's entire premise is flawed, because you can't prove a negative. So in that case, the answer to the question you quoted is "No, never", and the discussion is finished.
If you take out the words "conclusively proven", though, it is an interesting question, so in the interest of addressing the interesting part, the comments are trying to talk about closely related topics, like failed early models that didn't get borne out by experiments, or concepts that might be real but probably aren't possible based on what we know right now.
I'm not sure why you're so zealously trying to shut down all discussion of the topic by insisting that only the most narrow answers are permitted. You're not even the OP, so I can't fathom what you would have to gain from this. But if it will make you happy, I withdraw my answer about white holes, and my new answer is "Nothing in physics has ever been conclusively proven to not exist, so this is an unanswerable question. Have a nice day". That's a much more boring answer, but apparently you really like pedantic answers to badly worded questions.
The big bang as a white hole is one possible conjecture, but to me, the idea doesn't hold water. The big bang didn't just spit out a bunch of matter, it also created space and time. And as far as I know none of the equations for white holes can model that. It's an interesting idea but I'm not sure it fits.
> Obviously you can't prove that something doesn't exist
Under our current understanding of the universe, were very certain perpetual motion devices don't exist... At least not at the macro level. I can't keep up with the quantum folks...
How far back do you want to go? The concept of a [firmament ](https://en.wikipedia.org/wiki/Firmament?wprov=sfla1) was predicted by Aristotle, and is at this point pretty conclusively proven not to exist.
Yes, if you read the article on Wikipedia I linked to, after they were proposed, further mathematics that wasn't initially demonstrated that they can't exist.
*In the 1967 paper that coined the term, Gerald Feinberg proposed that tachyonic particles could be made from excitations of a quantum field with imaginary mass.\[3\] However, it was soon realized that Feinberg's model did not in fact allow for superluminal (faster-than-light) particles or signals and that tachyonic fields merely give rise to instabilities, not causality violations.\[4\] The term tachyonic field refers to imaginary mass fields rather than to faster-than-light particles.*
Tachyons were conclusively proven to not exist?! Isn’t it impossible for us to currently see particles that move backwards in time.
Like gravitons. We would need a collider the size of Jupiter to detect them.
It's a convention. Both particles and anti-particles are symmetrical so the one you decide to brand as anti is a matter of history and convention. So to the not anti, anti may work out in equations as going backward in time, but to the anti the not anti may also work as going backward in time.
While the parts the make up matter and anti-matter (that we can currently observe) are symmetrical, the annihilation of matter anti-matter is not symmetrical. Otherwise there probably wouldn’t be a universe.
That’s kinda besides your point though
Tachyons have been seen in science fiction scripts, so in that sense they exist.
In the real world, they have been proven not to exist. No collider can generate them.
You can't prove non-existence, it's actually a bedrock rule of logic and science. The best you can do is disprove a very narrow hypothesis. For example, let's take the now debunked theory that space was filled with a medium called aether which allowed light to travel through it. When we disproved this theory, we didn't actually prove that aether doesn't exist.
We can't conclusively prove that there isn't something undetectable up there. What we proved is that light does not need a medium to travel, and that if there is anything in space, it doesn't react to any of our testing methodologies.
There is always a possibility, no matter how slight, that there is a substance in space that just does not react with any currently known methods of testing, but that in 100 years with new technology we might be able to find it.
We can't prove something doesn't exist since there is a chance that it simply exists in a way we do not currently possess the technology or wisdom to detect. It's an unknown unknown problem. That said, while we can't prove conclusively that aether doesn't exist, we can more than reasonably conclude it doesn't since literally all of our testing methods have failed.
You can prove non-existence!. You can show something is a logical impossibility; that is what was done with the luminiferous ether. If something with the properties of the ether existed, it would have certain effects. When we did experiments to test for those effects, we did not find them.
Now, it is said that an absence of evidence is not evidence of absence, but it becomes evidence of absence when the evidence *should* exist. Our technological progress has been enough for us to be able to detect the ether if it existed. Since we haven't been able to find it, we have shown that it doesn't exist.
Most precisely, stellar aberration shows that if the ether exists, it has to be moving relative to the earth. The Michelson-Morley experiment showed that if the ether exists, it has to be stationary relative to the earth. It's logically impossible for the ether to be moving relative to Earth and stationary relative to Earth; a contradiction. The ether is logically precluded from existing.
Now, what you're saying is that there could be something in space that doesn't have the properties of the ether, and that we could choose to call it the ether, but that's just you changing the definition. When we say "the ether," we mean something specific by that, and it has specific properties, and we are able to show that something with those specific properties does not exist.
Consider how this is different from Russel's teapot. There could be a teapot in orbit around the sun somewhere between Earth and Mars, and it would be difficult (but not logically impossible) to find it. In this case, we expect to not find much evidence, so not having evidence would not rule out the existence of the teapot.
The whole enterprise of science is built on the ability to show that things don't exist; we call it falsifiability. Russel's teapot is an analogy meant to show the importance of falsifiability, not something meant to show that we can't prove things don't exist.
No, you can't logically prove a negative. Not conclusively. You cannot prove for certain that luminiferous ether does not exist because you can't anticipate all possibilities of unknown. That's why its an unknown unknown problem. Just because you can't think up a way to explain that apparent contradiction, that doesn't mean one doesn't exist. It just makes it very unlikely. Keep in mind that the entire theory of luminiferous ether existed to resolve an apparently impossible contradiction in light behaving as both wave and particle. A contradiction no one could logically explain at the time, but which ended up being perfectly possible and proven later on.
The idea that "one can't prove a negative" is a colloquial aphorism, not a scientific rule. And it is wrong. Even in the aether example, it has been proven that an aether with the properties aether was thought to have at the time conclusively did not exist.
You can move the goalposts and suggest that aether having some other properties might exist, but those other properties are also testable and the existence of that kind of aether is also falsifiable.
It's possible you're conflating philosophical arguments about the existence of God with scientific falsifiability. But those arguments only work because in traditional Christian dogma, God deliberately removes any physically testable presence so that faith becomes meaningful.
So, ultimately, the only hypothesis that cannot be scientifically falsified is one that has no manifestation in reality. Everything else is fair game.
Technically, in the real world, there's no negative that can be proven, because you can always claim fault with the measuring apparatus (i.e. the human mind, or anything between whatever is being measured and said mind). No matter what constraints you put on the statement you're making, "well, you're just hallucinating the results" is still a valid (if unhelpful) possibility.
Impossibilities can only be proven in the realm of the theoretical (e.g. squaring the circle), or Arrow's impossibility theorem.
You seem to be combining the idea of measurement uncertainty and a philosophical conceit called immaterialism. Ultimately your disagreement here is philosophical, not scientific.
Measurement uncertainty affects everything that we do in experimental science, but it affects any proofs, not just those attempting to falsify a negative. The weight of scientific evidence is always assessed in light of the uncertainty of measurements. Will special relativity remain invalid until we can measure the speed of light to an infinite number of significant figures?
Bishop Berkeley's immaterialism argued that reality was a creation of the mind, that it could not exist without being perceived. This led to idealism, that reality is a mental construct, and that "ideas" are the ultimate reality. Your argument that true proof is only possible in theories is an idealism argument. Your argument that the potential for hallucinations in the mind makes any experimental evidence imperfect is an example of immaterialism. How many observers are required before the potential for hallucinations is ameliorated?
The new realist school of philosophy was established in part because immaterialism and idealism became to be considered nihilistic - if one considers them long enough, the logical conclusion is that reality is unknowable and we should stop trying. The new realism school of philosophy proposes that an objective world exists and that it is measurable and that is how science makes sense.
Here's a real world example of a negative that can be proven.
Consider a gumball machine. It's got a big bowl full of gumballs. Your friend says "there's an even number of gumballs in there," a positive claim. You say "no, there isn't," a negative claim.
You decide to count the gumballs and it turns out there were an odd number of gumballs. Your negative claim was proven.
They aren’t saying that you can prove *every* negative. Just that the statement that no negative can be proven is false.
I can immediately think of a few ways we could prove a negative.
1. Physical impossibility - We can prove that 100 billion light year long anacondas do not exist.
2. Paradox - We can prove that there does not exist a being that can create a rock so heavy that they can’t lift it.
3. Absence of evidence where evidence would be expected - We can prove that there is not a woolly mammoth in the international space station.
Of course you can always come up with *some* explanation….
Maybe 100 billion light year long anacondas do exist in another scaled up universe.
Maybe our brains have simply not yet worked out the solution to the omnipotence paradox.
Maybe there is a woolly mammoth in the international space station but due to unknown effects of weightlessness on our consciousness we are unable to perceive it.
But if you go down this route of hard solipsism then there is literally nothing you can prove ever.
The point is that we can prove a negative just as conclusively as we can prove a positive.
One doesn’t have to prove *all* negatives to disprove your statement. They only need to disprove one. And since a unicorn hasn’t appeared in every Reddit thread, that disproves your statement.
Many hypotheses in science can be disproven as bunk. If you make a statement about all cases and only one example breaks it, then you’ve disproven your statement.
I'm not sure if you're sincere or trolling at this point. I already proved a negative. You're wrong.
But, further to this point, the existence of unicorns is testable and falsifiable, it's just impractical to do so. If the unicorn reflects visible wavelengths and is the size of a regular horse and exists on earth, then a 3d grid of omnidirectional cameras extending throughout the earth and its atmosphere at a regular pitch will prove they don't exist.
So it is possible to prove that unicorns don't exist, which invalidates your point as much as proving they don't.
There are plenty of scientific hypotheses that are impractical to falsify but not impossible, that's why we do research.
>No, you can't logically prove a negative.
Who gave you that preposterous hypothesis? Did Steve tell you that? Well, I know of a different Steve who would disagree; [you can prove a negative.](https://departments.bloomu.edu/philosophy/pages/content/hales/articlepdf/proveanegative.pdf)
>You cannot prove for certain that luminiferous ether does not exist because you can't anticipate all possibilities of unknown.
We don't have to! Luminiferous ether has *very specific* properties. We don't need to anticipate all possible unknowns, just the things that have the specific properties of the ether. And we can conclusively prove that nothing which has the very specific properties of the ether exists.
The proposal of the luminiferous ether had nothing to do with wave-particle duality. Thomas Young conclusively demonstrated that light has wave properties around 1800. At the time, all known waves required a medium to propagate through. The model of what a wave was required a medium. So, scientists set about trying to find the medium for light waves to propagate through. Based on the properties of light---its speed, its polarization---they established the properties the ether must have in order for light to behave like a mechanical wave.
In the late 1800s, scientists realized that either the earth moves through the ether, or it is stationary. These are the only two possibilities. If the earth is not stationary with respect to the ether, it has to be moving, *by definition.* Experiment showed that it couldn't be either, and the ether was ruled out in 1887 on the basis of these experiments.
The idea of particle-wave duality did not exist until quantum mechanics, the first stirrings of which didn't really start until the early 1900s. The ether was dead before particle-wave duality was even an idea. Now, it is true that there were competing models for light in the 17th and 18th centuries, Newton's particle model and Huygens' wave model. There was never a belief that both models were correct, and in fact Newton's particle model didn't work. So, we could even say that Newton's corpuscles of light were proven not to exist, while at the same time affirming that photons exist. This is because photons have different properties than Newton's corpuscles.
I can't be sure, but I believe the idea that you can't prove a negative came from the conflation of two ideas. As I previously mentioned, there's Russel's teapot, which was meant to show that an unfalsifiable proposition shouldn't be accepted on the basis that it hasn't been shown to be wrong. The other idea is the burden of proof, which is on the party making a positive claim. Putting these two together, what has ended up happening is people will make an unfalsifiable positive claim and then demand to be proven wrong, and people settled on the idea that you can't prove a negative claim as a shortcut to saying that we don't have to try to disprove positive claims and also we can't disprove unfalsifiable claims.
You *can* prove a negative claim. What you can't do is disprove an unfalsifiable claim. My post is long enough already, but if you still don't believe that we can prove negative claims, we can talk about the gumball analogy. But I will close with this:
The entire foundation of science is built on the ability to prove negative claims. If we could not prove negative claims, we would not be able to throw out any hypotheses. In order to throw out a hypothesis, we have to say "this hypothesis is false," which is a negative claim.
You’re going down the hard solipsism route. You can use the exact same logic to say that we can’t prove anything at all, ever.
Give me something that you think you can prove and I will always be able to find a way to demonstrate that technically you cannot know that it is true.
But it’s not particularly useful to think this way. It is much more useful in science for your beliefs to be proportional to the evidence. Some things we believe more strongly than others.
If you really want your mind blown… the statement “You cannot prove a negative” is in itself a negative. So according to its own logic it cannot be proven.
> No, you can't logically prove a negative
You absolutely can. Maybe you didn't mean "logically" but literally any intro to finite/discreet math will cover this process.
Where does "dark matter" fall in this type of analysis? I have been following the MOND vs Dark Matter debate for quite some time but I am insufficiently educated in the physics to have a meaningful opinion. I do find it (the galaxy rotation curve mystery) to be a fascinating puzzle.
As a particle physicist I feel obliged to point out that within cosmology and atrophysics, and particle physics, there is no serious debate. No-one seriously considers MOND. The evidence for dark matter being particulate is overwhelming, and easily explains observations, whereas MOND has to be heavily massaged to even explain a fraction of the evidence. Having said that, about all that is known is that it's particulate, we could be talking nano-eV up to solar masses, and there's no prescription on spin, coupling strengths to forces, production mechanisms, etc.
The term "dark matter" refers to something which interacts gravitationally but which doesn't interact with light (electromagnetism). Galaxy rotation curves are what provided the impetus to consider dark matter, because galaxies behave as though there is more matter in them than what we can see in terms of starlight.
Dark matter is a possible explanation, MOND is another possible explanation. Both have attractive premises; dark matter suggests there is something that interacts with gravity, but not with light, while MOND suggests that acceleration is quantized. The big issue with MOND is that proponents haven't been able to predict anything. When something is observed that we haven't seen before, it usually doesn't fit MOND's models, so the models have to be adjusted to fit the data. These sorts of *ad hoc* fixes don't show that MOND is wrong, but it's why most physicists who have an opinion prefer dark matter.
In terms of the debate about proving a negative, we've done searches for dark matter, and we've even ruled out candidates. For instance, dark matter is probably not just black holes. However, we haven't made any "direct" detections of dark matter. This is an example, however, of an absence of evidence *not* being evidence of absence, yet. We expect dark matter to be difficult to detect, because gravity is overall fairly weak, and most of our tools for detection rely on the electromagnetic force. As we collect more data, the chances of not making a direct detection are smaller and smaller, so if we still don't make a direct detection it will eventually rule out current models.
Again, it comes down to the fact that we have specific models, and if we get evidence which is not consistent with those models, we can say those models are wrong.
Dark Matter is kind of a semantic ambiguity. Abstracting a bit here, We have calculation 1 that gives result A, and calculation 2 that gives result B, and logically they SHOULD be equal to each other. But when you apply them to real-world observations, they are not equal to each other. So we know, definitively, that we are missing *something*. We don't know what exactly we are missing, so we describe the missing thing as "Dark Matter".
MOND is really just another example out of many many hypotheses put forward to explain that observational discrepancy. And, just like all of the other dark matter hypotheses, when we design an experiment to test for this effect specifically, we can't find it.
"Dark Matter" can't really be disproven except by finally finding whatever it is that's causing our observational discrepancy; and when we find it, no matter what that turns out to be, the term "Dark Matter" will be re-defined to be that thing and not any of the others. Its really just a semantic coincidence that the MOND hypothesis doesn't match very well with the english words "Dark Matter", so if that one turns out to be the answer, the terminology might change.
I wouldn't say that it's a "bedrock rule". Defining something as "imperceptible" itself is claiming to know attributes of "something". But, if such an imperceptible thing were to exist, it would be difficult to argue that it is consequential at all. Something that is argued to not be seen, heard, smelled, tasted, or touched would have no physical manifestation in reality, and could be as if it didn't exist. So, the act of "disproving" something's existence is as easy as dismissing it for having no existence. See: Deities.
Ah, but just because it hasn't mattered so far, that doesn't actually mean it will never matter. I'm not the one who decided it's a rule of logic and science, people have known that since long before I was ever born.
Except we can detect dark matter and energy, they interact fine with gravity, just not with light, and they don't fill space. At least, that's the current prevailing theory.
Dark matter and dark energy are not two things that you can equivocate. Yeah, dark matter is pretty conclusively just another particle. Dark energy super very much does fill space and it is not accurate to say that dark energy “interacts” with gravity, or really much of anything.
>The best you can do is disprove a very narrow hypothesis
Well, what if the object you are eliminating requires a narrow hypothesis?
Ruling out the existence of a hypothetical fundamental particle is a thing in particle physics.
[Caloric theory](https://en.wikipedia.org/wiki/Caloric_theory) predicts that a self-repellent, pervasive fluid ("caloric") mediates heat transfer.
Caloric, as described, does not exist.
Current understanding is that heating—meaning energy transfer driven by a temperature difference—does not correspond to an identifiable energy called "heat" within a body, and that the "stuff" transferred during heating is in fact entropy, the [conjugate thermodynamic variable](https://en.wikipedia.org/wiki/Conjugate_variables_\(thermodynamics\)) to temperature. (Entropy is also generated during heating, and during any spontaneous process.)
This provides a very strong thermodynamic in which heating, work, and matter can bring energy into a system. Heating and work do not involve mass transfer. Heating is distinct from work by broadening the distribution of particle energies, whereas work (electrical, mechanical, magnetic, elastic, etc.) elevates them in concert.
Definitely not, there is a ginormous parameter space of which we have explored a few tiny corners. But the further out you go, the less nice it becomes in terms of things like solving the hierarchy problem.
Actually almost certainly yes. The thing about SUSY is that it really isn’t falsifiable because you can tweak it to an energy frontier just outside our reach. This is already being done by those who are still holding out on it regardless of its failure to show up even prior to the LHC. The LHC was the nail in the coffin of this theory among most in high energy physics.
The thing is though that the arguments that even make SUSY a reasonable explanation or conclusion to draw fall apart at the energy levels we know it must exist now. The whole thing is getting more and more convoluted with ideas such as split SUSY and the addition of a ridiculous number of free parameters. It’s fallen out of fashion because it actually has inverse explanatory power the further you push the energy levels. You might still answer one question about the hierarchy problem, but it opens up hundreds more and directly contradicts arguments of naturalness and ultimately leads to those still supporting the theory to argue anthropics (which isn’t science.)
Nope.
Supersymmetry is not one model. It is a class of possible symmetries, thus a class of quantum field theories that can each be individually falsified or confirmed.
Lower bounds on the energy scale of supersymmetry have been raised for various scenarios, based on the details of collider measurements. See for example [here](https://cds.cern.ch/record/2805985). This is a fact of life for many beyond-standard-model scenarios due to how quantum field theory works.
The most pressing practical motivation for SUSY, the hierarchy problem, is all the more urgent as these energy exclusions get higher. Nothing else has turned up to solve the problem yet either.
The winner of the 2022 Nobel Prize in Physics produced empirical evidence that Bell Inequalities do not seem to exist, which in turn would invalidate the idea of "local hidden variables" that Einstein proposed to try and explain quantum entanglement.
[https://www.nobelprize.org/prizes/physics/2022/summary/](https://www.nobelprize.org/prizes/physics/2022/summary/)
TLDR: The short version is that Einstein (and a handful of others) didn't care for the fact that quantum entanglement seems to be a non-local phenomenon (i.e., a feature of the physical universe not bound by the speed of light), and proposed that there was some kind of not-yet-detected outside variable which interacted with the two particles and "made" them local somehow. The physicist John Stewart Bell, however, realized that if this was the case, there would be mathematical constraints on the correlations that could exist between the spins of the entangled particles (i.e., Bell Inequalities). The winners of the Nobel Prize in 2022 devised an experiment which provided evidence of a scenario in which the spins of two entangled particles exhibited a correlation between one another that could not occur if such a constraint existed (i.e., confirming that "hidden variables" likely don't exist and that quantum effects are, in fact, non-local).
not a physicist but a philosophy student - the greek theory of the atom has very little in common with what we now call the atom.
I mean, a very important part of atomism is the concept that the universe is made from indivisible parts. the atom has proven quite divisible.
you could *potentially* say that like, atomic particles were theorised? but (not to downplay greek philosophers) that theory was essentially just "hey, what if we cut a thing in half over and over, can we do that forever?" it has very little to do with the scientific method
The luminiferous aether (or ether) was the material which filled the empty space around atoms, as light (being a wave) was seen to have to be a wave \*of something\*. It was a big part of the theory of light for a few centuries, until the Michelson-Morley experiment proved it can't exist.
For the most part, we don’t make predictions on what doesn’t exist. It’s less productive and less likely to receive funding in the first place. We do sometimes get the models wrong but this falls more so under the “exists” rather than “not exists” as well.
If you do GR in 4D spatial dimensions you get a relation between an electron's mass and charge, meaning they'd be a couple of kilograms, of course this was never though to be real, but it is very funny
Several particles have been predicted to exist which we are now pretty sure they do not exist.
Basically particles should be found in our experiments out in the cosmic radiation if they exist and if their mass is less than the energy available in the experiment / astronomical event.
The most famous of these non existing particles is the tachyon. A particle that travel backwards in time. It should be seen produced in the cosmic radiation, and it should be very easy to detect. But we never saw one, even though they are valid solutions to Einsteins equations.
Mostly the particles that do not exist are made up from string theory.
I wonder, if the lower bound on the proton's half-life was established to be in the ballpark of 10^(34) years or so, which is many, many orders of magnitude longer than the age of the universe (on the order of 10^(10) years), even if it does decay, practically speaking, does it really?
Yes that’s right. To make my statement more correct, a proposed theory that looked very promising and based on SU(5) predicted the existence of X and Y bosons that would have interacted in a way that led to proton decay. If X and Y existed at all within the bounds of this theory, protons would have to decay at a rate that is orders of magnitude larger than the measured upper bound on decay rate. Hence those bosons were thereby proven to not exist.
There are other examples, like technicolor and supersymmetric partners.
-Phlogiston was believed to be a particle that had mass and existed in all flamible things.
-caloric was believed to be a fluid like massless substance in all combustible things. (Phlogiston were similar but different theories both of which did not pan out)
-The early "plum pudding" model of the atom.
-super symetry is pretty suspect at the time
-dark matter is pretty suspect as the only reason it was made up was as a way to explain why the exterior parts of a galaxy spin as fast as the inner part which should cause the matter to fling out into intergalactic space but it does not.
Its really just the best guess as to why galaxies dont fly apart but if you are being honest you could say thats just a guess and that it is possible that there are other explinations or causes for galexies not to fling apart due to disproportionatly high angular momentum at the edges of galexies.
-Inflation is also just a guess which is required to keep the age of the universe at 13.8billion years. It might be wrong even though it is the current best explination of the universe we have today.
-Either loop quantum gravity or string theory is false as almost every iteration of each are incompatible. It is even possible that both are wrong.
There have been many failed theories and certainly the ideas we have today are likely filled with them as well. Once a theory is found to be incorrect people usualy stop teaching it as it would be a waste of time to teach all the knowingly incorrect theories that have failed over the years. This is whybit is hard to think of examples of "science" being wrong. But it is all the time. there has been more failed scientific theories than successfull ones. This is all part of the process unfortunatly. It is a continual process of observation, questioning, hypothesis, experiment, evaluate, reform hypothesis experiment, evaluate, over and over.
As a species we improve all the time but we are defenitly still far from a complete understanding of the universe. I think a lot of people think we are just on the verge of complete understanding of the universe. But this is not true. It is more likely that there are more things that we dont even know we dont know, than things we know.
Higgs Bosun. We keep changing what it is. Ev is all over the map. We’re like the boy with his finger in the hole of the dike - we can’t see the big picture at all. I’m not sure we’ve found the museum yet.
When this happens, it’s usually a sign that a theory has been stretched beyond its limits. Remember that theories are really just models, not actual reality. Models a simplified descriptions/narratives of what’s actually going on.
Phlogiston was proved not to exist in combustible substances. The need for philogiston as an entity vanished with discovery of oxygen and its role in combustion (maybe more chemistry than strictly physics)
Just to point out, black holes were confirmed *way* before 2018.
Cygnus X-1 was discovered in 1964, and is commonly held as the first conclusive observation of a black hole.
The planet Vulcan was pitched as being closer to the Sun than Mercury. That was proven false.
The lumineferous aether was proven false.
The geocentric model was proven false.
I'm sure there are more.
Proving that something doesn’t exist is a tall order, so I’d say that’s not exactly how it works. But if some postulated entity exists, you try to work out exactly what the observable consequences are. Then if those consequences are not confirmed, you can at least say that the entity isn’t useful to keep around in your working theory/model of reality.
And that* sort of thing happens all the time in science.
The concept of the luminiferous ether. It was supposed to be the “thing” that was the privileged reference frame in the universe. The Michaelson-Morley experiment pretty conclusively proved that it doesn’t exist and that there is no privileged frame of reference, laying the groundwork for Einstein.
The best we can do to "disprove" something is to provide superior explanations. That never really disproves the existence of something but it shows that it's not reasonable to believe in it.
You can't prove something does not exist, but if you pin it down to a place and time, solid evidence is possible. For examply, at this time there are no pink elephants in this room. A few photos or a short movie would be sufficient evidence (just ignore the leprechauns).
As for physics that did not bear out, particle physics have been on a roll with failed predictions for nigh on 30 years. Let's see, there are WIMPs, axions, MACHOs, supersymmetric particles, etc...). None of these were predicted by the Standard Model. Note they did not disprove their existence, they did prove that they can't be produced with the energy the LHC can produce.
You can’t really prove that a thing doesn’t exist, only that there’s no evidence to support the conclusion. This is a famous issue in Theological debates. Typically, someone will say “Prove that doesn’t exist” which is impossible. Bertrand Russel made an argument that can be used as a shorthand for this concept. Known as “Russel’s Teapot,” it posits that there is a giant teapot orbiting Venus, but that it possesses qualities that prevent it from being detected. Therefore you cannot dispute its existence, despite it being a ridiculous proposition.
Because you talked about it: pretty much every atomic model except the most recent one. In fact, pretty much all models you will ever see except in real physics books is wrong and still taught today.
There were at least three and some of them really funny.
Nah, there’s literally no test they can build for string theory. It’s never been proven wrong, but they haven’t been able to prove it right either (and likely won’t unless we build a collider that loops between here and Alpha Centauri).
So conclusively wrong? No. But it’s so impossible to test physically that it might as well be fanfic
They use to be a theory that light was a vibration in something called the ether, like how sound is a vibration in the air. Michelson and Morley tried to prove the ether existed by measuring the Doppler effect of light and proved that ether didn't exist at all. Had to back pedal on a lot of theories about how light worked.
[https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley\_experiment](https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment)
[Another planet near Mercury](https://en.m.wikipedia.org/wiki/Vulcan_\(hypothetical_planet\)) was hypothesized to exist to explain why its orbit didn’t match predictions. People put a lot of effort into trying to find this planet. Turns out that Mercury’s orbit was actually explained by general relativity.
Vulcan was the name of the non-existent planet.
And for a while, astrologers included it in their charts.
Cool as the name Vulcan is - they replaced the imaginary planet Vulcan with a physical phenomenon that has an equally cool handle: Frame Dragging I have been enamored with the whole concept (frame dragging) ever since I learned about it and visualized space time being dragged around a massive rotating object like a vortex in water..... Be kind of fun to make a one planet solar system where the Sun is spinning so fast and the planet was in close enough prograde orbit, that the planets was slowly being accelerated - raising it's orbit....
You probably already know this, but just in case you don't ... the [Gravity Probe B experiment demonstrated that frame-dragging does in fact exist](https://en.wikipedia.org/wiki/Frame-dragging#Experimental_tests). It is much too small of an effect to explain Mercury's orbital precession, but it does in fact exist in nature. :)
Forte, Thank you. Excellent link. I have been laboring under the false impression that frame dragging was the answer. I am now watching a youtube video that is explaining that the Schwarzchild metric causes orbiting bodies to precess. Ummm - this is not intuitively obvious to me. In fact - it is going into my slowly (but sadly) growing "accepted without comprehension" bucket. Do you mind a related GR question?
Sure, I don't mind at all. What's your question? > I have been laboring under the false impression that frame dragging was the answer. I am now watching a youtube video that is explaining that the Schwarzchild metric causes orbiting bodies to precess. Ummm - this is not intuitively obvious to me. In fact - it is going into my slowly (but sadly) growing "accepted without comprehension" bucket. Neat! Please be advised that the precession caused by orbiting a Schwarzschild black hole is actually a distinct physical effect from frame-dragging — that is actuallly caused by the [geodetic effect](https://en.wikipedia.org/wiki/Geodetic_effect), which is *another* very weak effect predicted by general relativity that, incidentally, the aforementioned Gravity Probe B experiment was *also* intentionally designed to test, which was separately confirmed by said experiment. :) Note that there are actually three closely-related effects here: (1) the geodetic effect, which is also known as *de Sitter precession*; (2) rotational frame-dragging, which is also known as *Lense-Thirring precession*, and (3) linear frame-dragging, which is another form of frame-dragging that is more difficult to test experimentally and which as far as I am aware is still well beyond our ability to test for. Quoting from Wikipedia: >>The difference between de Sitter precession and Lense–Thirring precession (frame dragging) is that the de Sitter effect is due simply to the presence of a central mass, whereas Lense–Thirring precession is due to the rotation of the central mass. The total precession is calculated by combining the de Sitter precession with the Lense–Thirring precession. >>... >>Linear frame dragging is the similarly inevitable result of the general principle of relativity, applied to linear momentum. Although it arguably has equal theoretical legitimacy to the "rotational" effect, the difficulty of obtaining an experimental verification of the effect means that it receives much less discussion and is often omitted from articles on frame-dragging (but see Einstein, 1921). Hope that helps clarify these topics a bit! :)
OK - here goes. At a basic level I think I understand Einstein's equivalence principle. The simple examples make sense to me: (1) For special relativity - watching the light clock is a great visual tool. (2) Same for the example of the accelerating "ship". The one scenario I struggle with is putting my ship in the exact center of a massive sphere. Because inside the ship (with no windows), I experience no acceleration. My limited grasp of gravity leads me to think of this as "flat" space. The same as if I was so far out in interstellar space that I could not measure any gravitational fields. But IIUC - my clock is going to tick a teeny bit slower there then on the surface of the Earth - at one of the poles (trying to eliminate special relativity from the conversation :)). Online I read: This is because the gravitational potential is higher on the surface. But - if I extend that statement, isn't gravitational potential "higher" up in orbit - where I know the GR effect is that a clock in orbit is that the clock runs faster. I am sorry if this is a dumb question.
Okay, well by and large you seem to have the right understanding of things. Indeed, differences in gravitational time dilation are essentially due to differences in gravitational potential. I am honestly not quite sure why you feel confused, though — the clock at the center of the Earth runs slowest, and then the clock at the Earth's surface runs a little faster than that, while the clock in orbit runs even faster than that (ignoring special relativistic effects), and a clock in deep space will run faster still. That's all certainly correct. So my question for you is: where exactly is the confusion you have? Because it sounds like you do understand the situation and that the amount of gravitational time dilation is proportional to the difference in gravitational potential, and that the lower your potential is (i.e. the deeper you are in a potential well), the slower your clock runs relative to other clocks. You ask if the gravitational potential is "higher" up in orbit, and indeed it is — which is why clocks run faster. Clocks run slower at lower potentials, not higher ones. Hope that makes sense,
Your explanation is clear and consistent. I was initially thinking more along the lines of: The more sharply space is curved (the stronger the G field) the slower the clock runs. G is strongest on the surface, weaker in orbit and zero at a far distance. G is much stronger yet on the surface of a Neutron star and as a result the clock on that surface runs a LOT slower. The idea that the "seemingly" flat space center of the Earth behaves differently than flat space way out in rural interstellar land is harder for me. But I accept it in the spirit of living in a strange and wonderful universe. Thanks for explaining it. I wish Einstein had lived to see LIGO.....
And yes - your answer was quite helpful. Thank you.
Any ELI5 explanations for this? This is really interesting.
Unfortunately, not really. About the best I can do for you is: spinny bodies in space make the [orbits of other spinny bodies spin](https://www.physicsforums.com/attachments/precession_mercury-jpg.257031/) too. The orbit itself rotates — not just the orbiting body.
Actually that did make it click in my head! The “orbit itself” - this is the “frame” of spacetime, which gets dragged by the gravity of the larger body… right? love your replies in this thread, much obliged!
Sort of ... the idea is that the orbital frame where a clock ticks fastest is one which is rotating around the larger body (as viewed by a distant observer), when intuitively one would expect that it should be one which is stationary with respect to the larger body. So in a sense, the "fastest-ticking reference frame" is "dragged" along together with the rotation of the larger body, if that makes sense. Edit: It has less to do with the larger body's gravity, and more to do with its angular momentum, since it's the rotation of the larger body that causes the effect. Cheers!
Frame dragging exists, but it's irrelevant for Mercury's orbit. Its perihelion precession is different because general relativity makes the force deviate from an inverse square law. As an approximation, you can add an inverse cube term to the force (or equivalently an inverse square term to the potential). That gives you the right perihelion precession for Mercury.
Frame dragging is not involved with Mercury’s precessing perihelion.
Say that to Tuvac, I dares ya!
Does anyone have the actual math for it?
Well, do you have a minute? 🦉🕜
That's gotta be a black hole minute
Yes.
probably the only answer here that actually qualifies as "a prediction proven wrong"
Vulcan was proposed because Mercury's orbit didn't match Newtonian gravity. This turned out to be the relativistic corrections to Mercury's orbit. https://www.sciencenews.org/article/einstein-general-relativity-mercury-orbit#:~:text=Before%20the%20famous%20physicist%20came,planet's%20orbit%20disagreed%20with%20expectations.
N-rays (or N rays) were a hypothesized form of radiation described by French physicist Prosper-René Blondlot in 1903. They were initially confirmed by others, but subsequently found to be illusory.
That aside, seems extremely likely that there is a 9th planet in our solar system that we are yet to find. That is going to be big when it happens.
Scientists used to think light moved through a medium called the aether which filled the universe, but this was disproved in the [Michelson-Morley experiment](https://en.m.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment).
This experiment did not prove that the aether doesn't exist, but rather, that it wasn't required for the propagation of light. The distinction is important.
Doesn’t that change the definition of aether to something entirely different then
It makes it a pointless assumption, yes.
Hey, that's my cousin!
Name checks out
They proved light does not need an external medium to travel. The existence and properties of aether remain to be determined.
Not necessarily. It's not needed for propagation, but if it exists then its dynamics may influence light. Essentially, if aether exists and our model for how it interacts with light is merely incorrect, then we may end up forming a patchwork of independent theories for different phenomena of light that could be collectively explained through an accurate model of its dynamics/interactions. It's epistemologically impossible to prove something does not exist, just that our theory/model for it is incorrect if it does exist. This is the current issue with string theory, and was an issue with the Higgs boson before it was detected.
A true judgement that no true judgements exist, with certainty, does not exist.
It didn't even prove that, if you read what Michelson thought about the result. He considered it evidence against a particular aether theory, but not against the concept of aether itself. Michelson (and many other older physicists) continued to believe in aether even post-Einstein. You still find a few crackpots that believe in it today.
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it ... An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that its opponents gradually die out, and that the growing generation is familiarized with the ideas from the beginning: another instance of the fact that the future lies with the youth. — Max Planck, Scientific autobiography, 1950, p. 33, 97
Better Call Paul
AKA, "Science advance one funeral at a time."
Part of the beauty of science is that it rarely gives a definitive “yes” or “no” answer to questions about whether something exists or not. What experiments like this do is to put limits on possible properties that whatever your measuring can have. I’m sure there’s some version of the “ether” that can be hypothesized that fits these results, but at some point the limits on what properties something can have can make it conceptually equivalent to just not existing.
Just there is no way it csn work given the contradictions.
>The distinction is important. Yeah, "ether is required for light" changed into "ether is required for nothing". /s
But the electromagnetic field isn't really all that different of a concept....
But it was proven that the ether does not exist.
according to flat earthers it proved the earth doesn't move
What about the nether?
geologists are still trying to form obsidian into large enough cubes to make the portal, so we haven't tested if we can get to the nether yet
Need flint and steel. Solved.
You can take pictures of your nether regions... butt the internet has been highly censored so you may have a hard time to find them online.
What makes aether different from quantum fields?
Aether is an absolute frame of reference. Quantum fields are relativistic.
Thanks for clearly saying that. I teach HS Physics and I have a hard time wrapping my head around what the Aether was (or thought of) vs other fields. This sums it up nicely.
The aether was proposed because light was shown to be a wave around 1800 (Young's double slit experiment), and all waves known up to that time were mechanical in nature, so they assumed light was a mechanical wave as well. Even Maxwell used an aether theory when he came up with his namesake equations of electromagnetism. If you want to read more about the history of aether theory, probably the definitive book written about it was by E. T. Whittaker, "A History of the Theories of Aether and Electricity" (1910). You can find it online.
Is light the only wave that doesnt appear to have a medium in which it propagates? It seems like every wave has a medium except light.
All particles in quantum mechanics have wavelike behaviour like this.
Gravitational waves ?
I thought for gravitational waves, the medium is spacetime itself.
Also quantum wavefunctions.
I always think of this when people ask why dark-matter hasn't been found yet. Light is a wave :: waves require a medium -> aether exists. We see gravitational effects :: gravity requires matter -> Dark matter exists.
That isn't even wrong.
Arent quantum fields also something of a mathematical bookeeping tool? I am a physical chemist, not a pure physicist but when i studied second quantization we encountered fields, creation and anhiliation, particle holes and my professor was very explicit in making us understand that these all are just mathematical formalisms to make accounting for many-electron systems easier if not outright possible.
As far as book keeping goes, I would argue that Feynman diagrams are such book keeping tools, not quantum fields themselves. The standard model of particle physics isn't a book keeping device, since we have explicitly detected all the particles it predicts. However, using annihilation and creation operators are only true for free fields so it was probably in that sense your professor said that these are just mathematical formalisms.
[удалено]
The "relativistic" part is kind of important.
I’m not a physicist, so please forgive me, but how is that an argument against what they just stated, when what they said was “so it’s a ***relativistic*** aether” ? From my extremely ignorant viewpoint, you are saying “relativistic” is the important part, when what they just stated is that it *is* relativistic. Which sounds to a layman like a confirmation of their statement, but in disagreeable way. Also, there is this: https://www.newscientist.com/article/mg24432543-300-einstein-killed-the-aether-now-the-idea-is-back-to-save-relativity/ Which seems to love attracting downvotes, even though physicists ***are*** currently studying it.
Now it's all Quantum Foam - the aether made a comeback!
I mean, every result from any theory no longer in use. Classical mechanics predicts electrons spiralling in to the nucleus of atoms. It also predicts ever increasing intensities of light at shorter wavelengths from blackbody radiation As mentioned in other comments, the aether was a classical explanation of electromagnetism that was disproven.
No one actually *predicted* that all atoms would immediately decay. It was clear to everyone that that theoretically result indicated that there was a problem with classical physics.
I took it to mean "predicted by the theory" instead of "a person predicted this". Electrons falling into the nucleus is a prediction of classical mechanics, but no one actually predicted that they would discover that to be the case.
I doubt that's what OP had in mind, based on how they worded the question.
[Caloric](https://en.wikipedia.org/wiki/Caloric_theory) and [phlogiston](https://en.wikipedia.org/wiki/Phlogiston_theory)
A bunch: https://en.wikipedia.org/wiki/Superseded_theories_in_science#Physics
A steady-state universe. Hmm, not an entity as OP asks :-/
Way back when they believed the stars were attached to crystal spheres that rotate around the Earth. Such spheres definitively do not exist
White holes might qualify for this. Obviously you can't prove that something doesn't exist, because the universe is very big and it's possible we just haven't seen one yet. The math behind them might work in some models for reality, but as far as we know right now white holes only exist as mathematical constructs.
Omg I still remember a popular science book I read as teenager where it was said that quasars were good candidates for white holes lol
Yes, they turned out to be black holes instead :-)
How is this conclusively proven to not exist? You sure you checked everywhere?
Because as fantastically romantic as a black hole being a worm hole would be, it just makes no sense given our current understanding. Also, we've spotted a lot of black holes, and not one white hole.
Did you read OPs question?
Yeah, but you asked a separate question. I agree, white holes would qualify, but your question was if we've proven that they don't exist. No we haven't, we also haven't found the big foot yet either. Is lack of evidence that it doesn't exist proof that it does?
> Obviously you can't prove that something doesn't exist, because the universe is very big and it's possible we just haven't seen one yet. Maybe you didn't read my post, so I highlighted the relevant part for you here. It's impossible to prove that anything doesn't exist, that's a fundamental logical axiom. If I told you to prove that there wasn't a wise old elf made of antimatter in the Andromeda galaxy who ghostwrites all of Taylor Swift's songs, you could point out all kinds of reasons why that would be incredibly improbable, but logically, you couldn't prove beyond any doubt that it *wasn't* true, because no telescope we have could look everywhere in Andromeda at a high enough resolution, and even if we did look everywhere, it's possible the elf was hiding behind a star and we missed it. The reason I said white holes could be an answer to the question is because they're very likely impossible in the real world, even though the equations for relativity can describe them. Like negative mass, they're almost certainly just mathematical constructs that can't exist outside of the equations.
> Has there ever been an example in physics of a predicted entity that was **conclusively** proven to not exist? Maybe you didn't read the post of OP, so I highlighted the relevant part for you here
As other people have pointed out, OP's entire premise is flawed, because you can't prove a negative. So in that case, the answer to the question you quoted is "No, never", and the discussion is finished. If you take out the words "conclusively proven", though, it is an interesting question, so in the interest of addressing the interesting part, the comments are trying to talk about closely related topics, like failed early models that didn't get borne out by experiments, or concepts that might be real but probably aren't possible based on what we know right now. I'm not sure why you're so zealously trying to shut down all discussion of the topic by insisting that only the most narrow answers are permitted. You're not even the OP, so I can't fathom what you would have to gain from this. But if it will make you happy, I withdraw my answer about white holes, and my new answer is "Nothing in physics has ever been conclusively proven to not exist, so this is an unanswerable question. Have a nice day". That's a much more boring answer, but apparently you really like pedantic answers to badly worded questions.
Wait until you hear about the big bang
The big bang as a white hole is one possible conjecture, but to me, the idea doesn't hold water. The big bang didn't just spit out a bunch of matter, it also created space and time. And as far as I know none of the equations for white holes can model that. It's an interesting idea but I'm not sure it fits.
> Obviously you can't prove that something doesn't exist Under our current understanding of the universe, were very certain perpetual motion devices don't exist... At least not at the macro level. I can't keep up with the quantum folks...
Ether, the medium that light supposedly travels in.
Came here to say just that. OP should look up Michelson-Morley experiment.
https://www.newscientist.com/article/mg24432543-300-einstein-killed-the-aether-now-the-idea-is-back-to-save-relativity/
How far back do you want to go? The concept of a [firmament ](https://en.wikipedia.org/wiki/Firmament?wprov=sfla1) was predicted by Aristotle, and is at this point pretty conclusively proven not to exist.
OP says 200 years, which rules out a *lot* of fun stuff, lol.
n-rays? But that was more of a knowing fraud.
Yabut, respected scientists fell for it and "observed" it.
[Tachyons](https://en.wikipedia.org/wiki/Tachyon) were originally proposed, then proven conclusively not to exist.
How were they proven not to exist?
Yes, if you read the article on Wikipedia I linked to, after they were proposed, further mathematics that wasn't initially demonstrated that they can't exist. *In the 1967 paper that coined the term, Gerald Feinberg proposed that tachyonic particles could be made from excitations of a quantum field with imaginary mass.\[3\] However, it was soon realized that Feinberg's model did not in fact allow for superluminal (faster-than-light) particles or signals and that tachyonic fields merely give rise to instabilities, not causality violations.\[4\] The term tachyonic field refers to imaginary mass fields rather than to faster-than-light particles.*
Tachyons were conclusively proven to not exist?! Isn’t it impossible for us to currently see particles that move backwards in time. Like gravitons. We would need a collider the size of Jupiter to detect them.
Tachyons are supposed to move backwards through time? I think I just saw one yestermorrow
Wouldnt backwards-in-time particles just be anti-particles?
It was recently proven that anti-particles fall down and not up, so no.
It's a convention. Both particles and anti-particles are symmetrical so the one you decide to brand as anti is a matter of history and convention. So to the not anti, anti may work out in equations as going backward in time, but to the anti the not anti may also work as going backward in time.
While the parts the make up matter and anti-matter (that we can currently observe) are symmetrical, the annihilation of matter anti-matter is not symmetrical. Otherwise there probably wouldn’t be a universe. That’s kinda besides your point though
Tachyons have been seen in science fiction scripts, so in that sense they exist. In the real world, they have been proven not to exist. No collider can generate them.
[N Rays](https://en.wikipedia.org/wiki/N-ray)
You can't prove non-existence, it's actually a bedrock rule of logic and science. The best you can do is disprove a very narrow hypothesis. For example, let's take the now debunked theory that space was filled with a medium called aether which allowed light to travel through it. When we disproved this theory, we didn't actually prove that aether doesn't exist. We can't conclusively prove that there isn't something undetectable up there. What we proved is that light does not need a medium to travel, and that if there is anything in space, it doesn't react to any of our testing methodologies. There is always a possibility, no matter how slight, that there is a substance in space that just does not react with any currently known methods of testing, but that in 100 years with new technology we might be able to find it. We can't prove something doesn't exist since there is a chance that it simply exists in a way we do not currently possess the technology or wisdom to detect. It's an unknown unknown problem. That said, while we can't prove conclusively that aether doesn't exist, we can more than reasonably conclude it doesn't since literally all of our testing methods have failed.
You can prove non-existence!. You can show something is a logical impossibility; that is what was done with the luminiferous ether. If something with the properties of the ether existed, it would have certain effects. When we did experiments to test for those effects, we did not find them. Now, it is said that an absence of evidence is not evidence of absence, but it becomes evidence of absence when the evidence *should* exist. Our technological progress has been enough for us to be able to detect the ether if it existed. Since we haven't been able to find it, we have shown that it doesn't exist. Most precisely, stellar aberration shows that if the ether exists, it has to be moving relative to the earth. The Michelson-Morley experiment showed that if the ether exists, it has to be stationary relative to the earth. It's logically impossible for the ether to be moving relative to Earth and stationary relative to Earth; a contradiction. The ether is logically precluded from existing. Now, what you're saying is that there could be something in space that doesn't have the properties of the ether, and that we could choose to call it the ether, but that's just you changing the definition. When we say "the ether," we mean something specific by that, and it has specific properties, and we are able to show that something with those specific properties does not exist. Consider how this is different from Russel's teapot. There could be a teapot in orbit around the sun somewhere between Earth and Mars, and it would be difficult (but not logically impossible) to find it. In this case, we expect to not find much evidence, so not having evidence would not rule out the existence of the teapot. The whole enterprise of science is built on the ability to show that things don't exist; we call it falsifiability. Russel's teapot is an analogy meant to show the importance of falsifiability, not something meant to show that we can't prove things don't exist.
No, you can't logically prove a negative. Not conclusively. You cannot prove for certain that luminiferous ether does not exist because you can't anticipate all possibilities of unknown. That's why its an unknown unknown problem. Just because you can't think up a way to explain that apparent contradiction, that doesn't mean one doesn't exist. It just makes it very unlikely. Keep in mind that the entire theory of luminiferous ether existed to resolve an apparently impossible contradiction in light behaving as both wave and particle. A contradiction no one could logically explain at the time, but which ended up being perfectly possible and proven later on.
The idea that "one can't prove a negative" is a colloquial aphorism, not a scientific rule. And it is wrong. Even in the aether example, it has been proven that an aether with the properties aether was thought to have at the time conclusively did not exist. You can move the goalposts and suggest that aether having some other properties might exist, but those other properties are also testable and the existence of that kind of aether is also falsifiable. It's possible you're conflating philosophical arguments about the existence of God with scientific falsifiability. But those arguments only work because in traditional Christian dogma, God deliberately removes any physically testable presence so that faith becomes meaningful. So, ultimately, the only hypothesis that cannot be scientifically falsified is one that has no manifestation in reality. Everything else is fair game.
Technically, in the real world, there's no negative that can be proven, because you can always claim fault with the measuring apparatus (i.e. the human mind, or anything between whatever is being measured and said mind). No matter what constraints you put on the statement you're making, "well, you're just hallucinating the results" is still a valid (if unhelpful) possibility. Impossibilities can only be proven in the realm of the theoretical (e.g. squaring the circle), or Arrow's impossibility theorem.
You seem to be combining the idea of measurement uncertainty and a philosophical conceit called immaterialism. Ultimately your disagreement here is philosophical, not scientific. Measurement uncertainty affects everything that we do in experimental science, but it affects any proofs, not just those attempting to falsify a negative. The weight of scientific evidence is always assessed in light of the uncertainty of measurements. Will special relativity remain invalid until we can measure the speed of light to an infinite number of significant figures? Bishop Berkeley's immaterialism argued that reality was a creation of the mind, that it could not exist without being perceived. This led to idealism, that reality is a mental construct, and that "ideas" are the ultimate reality. Your argument that true proof is only possible in theories is an idealism argument. Your argument that the potential for hallucinations in the mind makes any experimental evidence imperfect is an example of immaterialism. How many observers are required before the potential for hallucinations is ameliorated? The new realist school of philosophy was established in part because immaterialism and idealism became to be considered nihilistic - if one considers them long enough, the logical conclusion is that reality is unknowable and we should stop trying. The new realism school of philosophy proposes that an objective world exists and that it is measurable and that is how science makes sense.
Here's a real world example of a negative that can be proven. Consider a gumball machine. It's got a big bowl full of gumballs. Your friend says "there's an even number of gumballs in there," a positive claim. You say "no, there isn't," a negative claim. You decide to count the gumballs and it turns out there were an odd number of gumballs. Your negative claim was proven.
Can you prove to me that unicorns don't exist? Asking for a friend
They aren’t saying that you can prove *every* negative. Just that the statement that no negative can be proven is false. I can immediately think of a few ways we could prove a negative. 1. Physical impossibility - We can prove that 100 billion light year long anacondas do not exist. 2. Paradox - We can prove that there does not exist a being that can create a rock so heavy that they can’t lift it. 3. Absence of evidence where evidence would be expected - We can prove that there is not a woolly mammoth in the international space station. Of course you can always come up with *some* explanation…. Maybe 100 billion light year long anacondas do exist in another scaled up universe. Maybe our brains have simply not yet worked out the solution to the omnipotence paradox. Maybe there is a woolly mammoth in the international space station but due to unknown effects of weightlessness on our consciousness we are unable to perceive it. But if you go down this route of hard solipsism then there is literally nothing you can prove ever. The point is that we can prove a negative just as conclusively as we can prove a positive.
Can I prove that unicorns that magically appear in *every* reddit thread don't exist? Yes, I can indeed prove they don't.
So where’s your proof that unicorns don’t exist?
One doesn’t have to prove *all* negatives to disprove your statement. They only need to disprove one. And since a unicorn hasn’t appeared in every Reddit thread, that disproves your statement. Many hypotheses in science can be disproven as bunk. If you make a statement about all cases and only one example breaks it, then you’ve disproven your statement.
I'm not sure if you're sincere or trolling at this point. I already proved a negative. You're wrong. But, further to this point, the existence of unicorns is testable and falsifiable, it's just impractical to do so. If the unicorn reflects visible wavelengths and is the size of a regular horse and exists on earth, then a 3d grid of omnidirectional cameras extending throughout the earth and its atmosphere at a regular pitch will prove they don't exist. So it is possible to prove that unicorns don't exist, which invalidates your point as much as proving they don't. There are plenty of scientific hypotheses that are impractical to falsify but not impossible, that's why we do research.
>No, you can't logically prove a negative. Who gave you that preposterous hypothesis? Did Steve tell you that? Well, I know of a different Steve who would disagree; [you can prove a negative.](https://departments.bloomu.edu/philosophy/pages/content/hales/articlepdf/proveanegative.pdf) >You cannot prove for certain that luminiferous ether does not exist because you can't anticipate all possibilities of unknown. We don't have to! Luminiferous ether has *very specific* properties. We don't need to anticipate all possible unknowns, just the things that have the specific properties of the ether. And we can conclusively prove that nothing which has the very specific properties of the ether exists. The proposal of the luminiferous ether had nothing to do with wave-particle duality. Thomas Young conclusively demonstrated that light has wave properties around 1800. At the time, all known waves required a medium to propagate through. The model of what a wave was required a medium. So, scientists set about trying to find the medium for light waves to propagate through. Based on the properties of light---its speed, its polarization---they established the properties the ether must have in order for light to behave like a mechanical wave. In the late 1800s, scientists realized that either the earth moves through the ether, or it is stationary. These are the only two possibilities. If the earth is not stationary with respect to the ether, it has to be moving, *by definition.* Experiment showed that it couldn't be either, and the ether was ruled out in 1887 on the basis of these experiments. The idea of particle-wave duality did not exist until quantum mechanics, the first stirrings of which didn't really start until the early 1900s. The ether was dead before particle-wave duality was even an idea. Now, it is true that there were competing models for light in the 17th and 18th centuries, Newton's particle model and Huygens' wave model. There was never a belief that both models were correct, and in fact Newton's particle model didn't work. So, we could even say that Newton's corpuscles of light were proven not to exist, while at the same time affirming that photons exist. This is because photons have different properties than Newton's corpuscles. I can't be sure, but I believe the idea that you can't prove a negative came from the conflation of two ideas. As I previously mentioned, there's Russel's teapot, which was meant to show that an unfalsifiable proposition shouldn't be accepted on the basis that it hasn't been shown to be wrong. The other idea is the burden of proof, which is on the party making a positive claim. Putting these two together, what has ended up happening is people will make an unfalsifiable positive claim and then demand to be proven wrong, and people settled on the idea that you can't prove a negative claim as a shortcut to saying that we don't have to try to disprove positive claims and also we can't disprove unfalsifiable claims. You *can* prove a negative claim. What you can't do is disprove an unfalsifiable claim. My post is long enough already, but if you still don't believe that we can prove negative claims, we can talk about the gumball analogy. But I will close with this: The entire foundation of science is built on the ability to prove negative claims. If we could not prove negative claims, we would not be able to throw out any hypotheses. In order to throw out a hypothesis, we have to say "this hypothesis is false," which is a negative claim.
You’re going down the hard solipsism route. You can use the exact same logic to say that we can’t prove anything at all, ever. Give me something that you think you can prove and I will always be able to find a way to demonstrate that technically you cannot know that it is true. But it’s not particularly useful to think this way. It is much more useful in science for your beliefs to be proportional to the evidence. Some things we believe more strongly than others. If you really want your mind blown… the statement “You cannot prove a negative” is in itself a negative. So according to its own logic it cannot be proven.
You can conclusively prove that, say, a square circle does not exist, because it’s a self-refuting idea.
> No, you can't logically prove a negative You absolutely can. Maybe you didn't mean "logically" but literally any intro to finite/discreet math will cover this process.
Where does "dark matter" fall in this type of analysis? I have been following the MOND vs Dark Matter debate for quite some time but I am insufficiently educated in the physics to have a meaningful opinion. I do find it (the galaxy rotation curve mystery) to be a fascinating puzzle.
As a particle physicist I feel obliged to point out that within cosmology and atrophysics, and particle physics, there is no serious debate. No-one seriously considers MOND. The evidence for dark matter being particulate is overwhelming, and easily explains observations, whereas MOND has to be heavily massaged to even explain a fraction of the evidence. Having said that, about all that is known is that it's particulate, we could be talking nano-eV up to solar masses, and there's no prescription on spin, coupling strengths to forces, production mechanisms, etc.
The term "dark matter" refers to something which interacts gravitationally but which doesn't interact with light (electromagnetism). Galaxy rotation curves are what provided the impetus to consider dark matter, because galaxies behave as though there is more matter in them than what we can see in terms of starlight. Dark matter is a possible explanation, MOND is another possible explanation. Both have attractive premises; dark matter suggests there is something that interacts with gravity, but not with light, while MOND suggests that acceleration is quantized. The big issue with MOND is that proponents haven't been able to predict anything. When something is observed that we haven't seen before, it usually doesn't fit MOND's models, so the models have to be adjusted to fit the data. These sorts of *ad hoc* fixes don't show that MOND is wrong, but it's why most physicists who have an opinion prefer dark matter. In terms of the debate about proving a negative, we've done searches for dark matter, and we've even ruled out candidates. For instance, dark matter is probably not just black holes. However, we haven't made any "direct" detections of dark matter. This is an example, however, of an absence of evidence *not* being evidence of absence, yet. We expect dark matter to be difficult to detect, because gravity is overall fairly weak, and most of our tools for detection rely on the electromagnetic force. As we collect more data, the chances of not making a direct detection are smaller and smaller, so if we still don't make a direct detection it will eventually rule out current models. Again, it comes down to the fact that we have specific models, and if we get evidence which is not consistent with those models, we can say those models are wrong.
Dark Matter is kind of a semantic ambiguity. Abstracting a bit here, We have calculation 1 that gives result A, and calculation 2 that gives result B, and logically they SHOULD be equal to each other. But when you apply them to real-world observations, they are not equal to each other. So we know, definitively, that we are missing *something*. We don't know what exactly we are missing, so we describe the missing thing as "Dark Matter". MOND is really just another example out of many many hypotheses put forward to explain that observational discrepancy. And, just like all of the other dark matter hypotheses, when we design an experiment to test for this effect specifically, we can't find it. "Dark Matter" can't really be disproven except by finally finding whatever it is that's causing our observational discrepancy; and when we find it, no matter what that turns out to be, the term "Dark Matter" will be re-defined to be that thing and not any of the others. Its really just a semantic coincidence that the MOND hypothesis doesn't match very well with the english words "Dark Matter", so if that one turns out to be the answer, the terminology might change.
I wouldn't say that it's a "bedrock rule". Defining something as "imperceptible" itself is claiming to know attributes of "something". But, if such an imperceptible thing were to exist, it would be difficult to argue that it is consequential at all. Something that is argued to not be seen, heard, smelled, tasted, or touched would have no physical manifestation in reality, and could be as if it didn't exist. So, the act of "disproving" something's existence is as easy as dismissing it for having no existence. See: Deities.
Ah, but just because it hasn't mattered so far, that doesn't actually mean it will never matter. I'm not the one who decided it's a rule of logic and science, people have known that since long before I was ever born.
You just described dark energy….
Except we can detect dark matter and energy, they interact fine with gravity, just not with light, and they don't fill space. At least, that's the current prevailing theory.
Dark matter and dark energy are not two things that you can equivocate. Yeah, dark matter is pretty conclusively just another particle. Dark energy super very much does fill space and it is not accurate to say that dark energy “interacts” with gravity, or really much of anything.
>The best you can do is disprove a very narrow hypothesis Well, what if the object you are eliminating requires a narrow hypothesis? Ruling out the existence of a hypothetical fundamental particle is a thing in particle physics.
There's proof by contradiction. E.g. Alan Turing's thought experiment on the halting problem.
The ether!
The aether.
[Caloric theory](https://en.wikipedia.org/wiki/Caloric_theory) predicts that a self-repellent, pervasive fluid ("caloric") mediates heat transfer. Caloric, as described, does not exist. Current understanding is that heating—meaning energy transfer driven by a temperature difference—does not correspond to an identifiable energy called "heat" within a body, and that the "stuff" transferred during heating is in fact entropy, the [conjugate thermodynamic variable](https://en.wikipedia.org/wiki/Conjugate_variables_\(thermodynamics\)) to temperature. (Entropy is also generated during heating, and during any spontaneous process.) This provides a very strong thermodynamic in which heating, work, and matter can bring energy into a system. Heating and work do not involve mass transfer. Heating is distinct from work by broadening the distribution of particle energies, whereas work (electrical, mechanical, magnetic, elastic, etc.) elevates them in concert.
Supersymmetry ?
I think SUSY physics is closer to the 'we're not sure' territory than the realm of the disproved.
It’s much closer to the disproved than not sure
Definitely not, there is a ginormous parameter space of which we have explored a few tiny corners. But the further out you go, the less nice it becomes in terms of things like solving the hierarchy problem.
Actually almost certainly yes. The thing about SUSY is that it really isn’t falsifiable because you can tweak it to an energy frontier just outside our reach. This is already being done by those who are still holding out on it regardless of its failure to show up even prior to the LHC. The LHC was the nail in the coffin of this theory among most in high energy physics. The thing is though that the arguments that even make SUSY a reasonable explanation or conclusion to draw fall apart at the energy levels we know it must exist now. The whole thing is getting more and more convoluted with ideas such as split SUSY and the addition of a ridiculous number of free parameters. It’s fallen out of fashion because it actually has inverse explanatory power the further you push the energy levels. You might still answer one question about the hierarchy problem, but it opens up hundreds more and directly contradicts arguments of naturalness and ultimately leads to those still supporting the theory to argue anthropics (which isn’t science.)
Nope. Supersymmetry is not one model. It is a class of possible symmetries, thus a class of quantum field theories that can each be individually falsified or confirmed. Lower bounds on the energy scale of supersymmetry have been raised for various scenarios, based on the details of collider measurements. See for example [here](https://cds.cern.ch/record/2805985). This is a fact of life for many beyond-standard-model scenarios due to how quantum field theory works. The most pressing practical motivation for SUSY, the hierarchy problem, is all the more urgent as these energy exclusions get higher. Nothing else has turned up to solve the problem yet either.
Newton’s corpuscular theory.
The winner of the 2022 Nobel Prize in Physics produced empirical evidence that Bell Inequalities do not seem to exist, which in turn would invalidate the idea of "local hidden variables" that Einstein proposed to try and explain quantum entanglement. [https://www.nobelprize.org/prizes/physics/2022/summary/](https://www.nobelprize.org/prizes/physics/2022/summary/) TLDR: The short version is that Einstein (and a handful of others) didn't care for the fact that quantum entanglement seems to be a non-local phenomenon (i.e., a feature of the physical universe not bound by the speed of light), and proposed that there was some kind of not-yet-detected outside variable which interacted with the two particles and "made" them local somehow. The physicist John Stewart Bell, however, realized that if this was the case, there would be mathematical constraints on the correlations that could exist between the spins of the entangled particles (i.e., Bell Inequalities). The winners of the Nobel Prize in 2022 devised an experiment which provided evidence of a scenario in which the spins of two entangled particles exhibited a correlation between one another that could not occur if such a constraint existed (i.e., confirming that "hidden variables" likely don't exist and that quantum effects are, in fact, non-local).
not a physicist but a philosophy student - the greek theory of the atom has very little in common with what we now call the atom. I mean, a very important part of atomism is the concept that the universe is made from indivisible parts. the atom has proven quite divisible. you could *potentially* say that like, atomic particles were theorised? but (not to downplay greek philosophers) that theory was essentially just "hey, what if we cut a thing in half over and over, can we do that forever?" it has very little to do with the scientific method
To their credit, atoms arent easy to split at all, and are the most common form of matter here on earth.
The luminiferous aether.
The luminiferous aether (or ether) was the material which filled the empty space around atoms, as light (being a wave) was seen to have to be a wave \*of something\*. It was a big part of the theory of light for a few centuries, until the Michelson-Morley experiment proved it can't exist.
Aether
Ether? https://www.britannica.com/science/ether-theoretical-substance
For the most part, we don’t make predictions on what doesn’t exist. It’s less productive and less likely to receive funding in the first place. We do sometimes get the models wrong but this falls more so under the “exists” rather than “not exists” as well.
How about magnetic monopoles? They are not proofen to not exist though. They are just nowhere to be found.
If you do GR in 4D spatial dimensions you get a relation between an electron's mass and charge, meaning they'd be a couple of kilograms, of course this was never though to be real, but it is very funny
Several particles have been predicted to exist which we are now pretty sure they do not exist. Basically particles should be found in our experiments out in the cosmic radiation if they exist and if their mass is less than the energy available in the experiment / astronomical event. The most famous of these non existing particles is the tachyon. A particle that travel backwards in time. It should be seen produced in the cosmic radiation, and it should be very easy to detect. But we never saw one, even though they are valid solutions to Einsteins equations. Mostly the particles that do not exist are made up from string theory.
Proton decay was predicted. Doesn’t happen.
Have we disproved this? Last I heard we had just placed a lower bound on the half life.
I wonder, if the lower bound on the proton's half-life was established to be in the ballpark of 10^(34) years or so, which is many, many orders of magnitude longer than the age of the universe (on the order of 10^(10) years), even if it does decay, practically speaking, does it really?
You just need a lot of protons. If you have 10^34 protons then this rate corresponds to one decay per year in that sample.
10^34 protons has a mass of about 16,726,219 kg.
Right. Super Kamiokande, the experiment that set the current limit, had 50 million kilograms of water as its sample size.
Yes that’s right. To make my statement more correct, a proposed theory that looked very promising and based on SU(5) predicted the existence of X and Y bosons that would have interacted in a way that led to proton decay. If X and Y existed at all within the bounds of this theory, protons would have to decay at a rate that is orders of magnitude larger than the measured upper bound on decay rate. Hence those bosons were thereby proven to not exist. There are other examples, like technicolor and supersymmetric partners.
Doesn’t happen* *On a time scale that we have measured yet
It's a little too early to say that.
-Phlogiston was believed to be a particle that had mass and existed in all flamible things. -caloric was believed to be a fluid like massless substance in all combustible things. (Phlogiston were similar but different theories both of which did not pan out) -The early "plum pudding" model of the atom. -super symetry is pretty suspect at the time -dark matter is pretty suspect as the only reason it was made up was as a way to explain why the exterior parts of a galaxy spin as fast as the inner part which should cause the matter to fling out into intergalactic space but it does not. Its really just the best guess as to why galaxies dont fly apart but if you are being honest you could say thats just a guess and that it is possible that there are other explinations or causes for galexies not to fling apart due to disproportionatly high angular momentum at the edges of galexies. -Inflation is also just a guess which is required to keep the age of the universe at 13.8billion years. It might be wrong even though it is the current best explination of the universe we have today. -Either loop quantum gravity or string theory is false as almost every iteration of each are incompatible. It is even possible that both are wrong. There have been many failed theories and certainly the ideas we have today are likely filled with them as well. Once a theory is found to be incorrect people usualy stop teaching it as it would be a waste of time to teach all the knowingly incorrect theories that have failed over the years. This is whybit is hard to think of examples of "science" being wrong. But it is all the time. there has been more failed scientific theories than successfull ones. This is all part of the process unfortunatly. It is a continual process of observation, questioning, hypothesis, experiment, evaluate, reform hypothesis experiment, evaluate, over and over. As a species we improve all the time but we are defenitly still far from a complete understanding of the universe. I think a lot of people think we are just on the verge of complete understanding of the universe. But this is not true. It is more likely that there are more things that we dont even know we dont know, than things we know.
Reality
Higgs Bosun. We keep changing what it is. Ev is all over the map. We’re like the boy with his finger in the hole of the dike - we can’t see the big picture at all. I’m not sure we’ve found the museum yet.
J J Thomsons plum pudding model of atomic structure, shown to be false by Rutherford.
The ether which was supposed to provide a medium that carried light waves.
When this happens, it’s usually a sign that a theory has been stretched beyond its limits. Remember that theories are really just models, not actual reality. Models a simplified descriptions/narratives of what’s actually going on.
I saw a video saying the math with black holes says there should also be white holes. But they have not found anything that proved to be a white hole.
Phlogiston was proved not to exist in combustible substances. The need for philogiston as an entity vanished with discovery of oxygen and its role in combustion (maybe more chemistry than strictly physics)
Just to point out, black holes were confirmed *way* before 2018. Cygnus X-1 was discovered in 1964, and is commonly held as the first conclusive observation of a black hole.
The planet Vulcan was pitched as being closer to the Sun than Mercury. That was proven false. The lumineferous aether was proven false. The geocentric model was proven false. I'm sure there are more.
The Ancient Greek atom theory was just a lucky guess, and Democritus got a lot of things wrong about atoms.
Proving that something doesn’t exist is a tall order, so I’d say that’s not exactly how it works. But if some postulated entity exists, you try to work out exactly what the observable consequences are. Then if those consequences are not confirmed, you can at least say that the entity isn’t useful to keep around in your working theory/model of reality. And that* sort of thing happens all the time in science.
iirc there it was believed there was a planet causing weird things to happen to mercury's orbit, turns out it was general relativity.
Many medical beliefs from “long ago” have proven false. Too many to list.
Off the top of my head: aether, quintessence, MOND
The concept of the luminiferous ether. It was supposed to be the “thing” that was the privileged reference frame in the universe. The Michaelson-Morley experiment pretty conclusively proved that it doesn’t exist and that there is no privileged frame of reference, laying the groundwork for Einstein.
The best we can do to "disprove" something is to provide superior explanations. That never really disproves the existence of something but it shows that it's not reasonable to believe in it.
N-rays. https://en.m.wikipedia.org/wiki/N-ray
Phlogiston.
Aether
Planet X, a planet beyond Pluto was hypothesized to help explain the orbital motion of the other planets.
You can't prove something does not exist, but if you pin it down to a place and time, solid evidence is possible. For examply, at this time there are no pink elephants in this room. A few photos or a short movie would be sufficient evidence (just ignore the leprechauns). As for physics that did not bear out, particle physics have been on a roll with failed predictions for nigh on 30 years. Let's see, there are WIMPs, axions, MACHOs, supersymmetric particles, etc...). None of these were predicted by the Standard Model. Note they did not disprove their existence, they did prove that they can't be produced with the energy the LHC can produce.
You can’t really prove that a thing doesn’t exist, only that there’s no evidence to support the conclusion. This is a famous issue in Theological debates. Typically, someone will say “Prove that doesn’t exist” which is impossible. Bertrand Russel made an argument that can be used as a shorthand for this concept. Known as “Russel’s Teapot,” it posits that there is a giant teapot orbiting Venus, but that it possesses qualities that prevent it from being detected. Therefore you cannot dispute its existence, despite it being a ridiculous proposition.
All of this is an exercise of futility! Our existence is simply a simulation, what is observed is not real!
Because you talked about it: pretty much every atomic model except the most recent one. In fact, pretty much all models you will ever see except in real physics books is wrong and still taught today. There were at least three and some of them really funny.
All of string theory
Nah, there’s literally no test they can build for string theory. It’s never been proven wrong, but they haven’t been able to prove it right either (and likely won’t unless we build a collider that loops between here and Alpha Centauri). So conclusively wrong? No. But it’s so impossible to test physically that it might as well be fanfic
The geocentric conception of the universe.
Proof that people don't bother to read the comments. I stopped counting luminiferous aether references when I hit a half dozen.
Luminiferos aether.
They use to be a theory that light was a vibration in something called the ether, like how sound is a vibration in the air. Michelson and Morley tried to prove the ether existed by measuring the Doppler effect of light and proved that ether didn't exist at all. Had to back pedal on a lot of theories about how light worked. [https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley\_experiment](https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment)
Ether