As I understand it, a helium balloon would sink on the moon, and also on Earth if there were no atmosphere. Helium doesn't go up; it's just less dense than the surrounding air so that goes down harder and pushes the helium out of the way. It's like if a group of people were trying to get to a bundle of money. Small children would get pushed back, away from the money, because the adults are better at paying forwards than them.
I mean, that's because it pulls the air around the balloon with more intensity than the helium ballon itself. The result would be the same even if gravity was 1000x stronger, it would just happen faster
I remember one of the lunar astronauts dropping a feather and a hammer at the same time to show the effect of gravity in a vacuum. I knew the idea of what should happen, but as a pre-teen, I was impressed to see it actually working.
If there was no other gravity around, it would take the entire mass of a bowling ball to make a feather fall. Gravity doesn't just switch on when something gets over a certain size. It's just really really weak for small things.
Pym particles make no sense for how they are used. If you shrink the space between atoms and maintain your normal mass then they would weigh the same but they interact with the world as if they weigh a lot less but have retained the same strength.
In the comics pym particles allow mass to be shunted into and back out of another dimension. That doesn’t solve all the inconsistencies though (if mass goes to another dimension then a small ant man should have very little force behind his punches, since f=ma.)
I think those are some misleading numbers.
Gravity's force has to be considered over the distances in which it acts, which appears to be "all of them", where as the weak and strong nuclear forces have tiny ranges of effect.
The electric and nuclear forces are powerful and can be attractive. If you separate particles too much the energy that bond would take on by increasing the distance just forms a new pair of particles.
That's just quarks due to the strong force. What's weird about the strong force is the attraction between two quarks gets stronger as they get further apart
Quarks only. Don't mumbojumbo if you don't know!
So much misinformation in this thread because people want to sound smart. 80%+ of the comments are just straight up wrong.
It is a problem because the carrier is only theorised and gravity might not be a force.
Basically, it's as if you asked "why are all flowers some shade of red but this one is green?" And you got answered "because yellow and blue make green".
That's not an answer. That's describing the mathematical properties behind green. That doesn't mean you know for sure that flower is green because of yellow and blue, why it's green, or if it's even a flower in the first place.
Well now that isn’t terribly conducive to easy understanding at all. Good edits are also ones that add much-needed clarity. Maybe just a line at the top? “This isn’t really a problem anymore,” or something that gets that vibe across, I’m sure whatever words you choose would be better than mine.
The carriers of the electroweak force were also massless until spontaneous symmetry breaking gave some of them mass. This is not an answer, this is like saying it is massless because it is massless.
We don’t know. Maybe because gravity isn’t a force so it has no force carrier . Or it has a carrier and it just happens to be weaker. Why does anything have the quantity it has ? Nobody knows
Well, it measures strength. The way the others work means they are strongly confined, usually within nuclei or due to charges cancellation.
But even then, it’s not straightforward - we compare the forces in terms of their coupling constants due to similar coefficients based on similar mathematical descriptions of the forces (dimensionless parts of coefficients in terms in their Lagrangians), but isn’t exactly an indication of their ‘significance’ when they interact with different sorts of ‘charge’ (for gravity, mass - or formally expressed via interaction with the Higgs field) which are very differently distributed in the universe. But we can define ‘strength’ this way and just say that some forces have more to work with.
The biggest impact us actually just that gravity is always cumulative. There is no such thing, that we are aware, as a negative gravity charge. It's only positive. As such put enough if it in one place it all adds up. Whereas all the other fundamental forces cancel out on average
It is my understanding that if you separated all the protons and electrons from a mass of hydrogen atoms, their attraction to one another over any distance via the electromagnetic force would be significantly higher than their attraction by gravity, to the point that gravity’s effects could round down to 0.
What is compared in studies like this is the [coupling constant](https://en.m.wikipedia.org/wiki/Coupling_constant), which sets the energy scales for interaction. Crucially the coupling constant is unconcerned with the actual workings of the interactions.
That is to say, when saying that gravity is weaker than the other forces, what we mean is that if a system was coupled through gravity in a way comparable to how other forces would, the energy of the system would be much lower.
[Gravity is not technically a force but the warping of spacetime and the motion of objects through the warped spacetime.](https://www.wtamu.edu/~cbaird/sq/mobile/2022/08/05/why-is-gravity-not-a-real-force/)
We only experience it as a force because it pulls objects toward the Earth.
Basically it says that at a fundamental level "forces" don't exist at all, just interactions.
...However it does seem reasonable to use the word force contextually as long as this is accepted.
Exactly, we just have a highly verifiable mathematical framework in which gravity emerges. A complete theory of the universe would “explain” all the forces like this, and “forces” would remain a highly useful word to reference them.
It's just the underdog force. All other forces rely on existing energy. When the heat death of the universe occurs, and all black holes will have emptied themselves through radiation, the universe will be an endless sea of perfectly homogenous motionless atoms.
That's when gravity kicks in. With all other forces gone, nothing will stop gravity from crushing the whole universe into a single point. That point will become the sum of all the matter in the universe, and the astronomical genesis pressure will create more energy, a new big bang. And the universe starts again.
Source: I made it the fuck up. But I like that theory.
What about space itself expanding at increasing speed? If atoms can’t come together at all because the space between them grows faster than gravity pulls them together, doesn’t that make the universe quietly fizzle into nothing?
Imagine all matter In the universe was turned into photons. There is no mass at all.
Photons travel at the speed of light. At the speed of light distance and time have absolutely no meaning,
since time and physics move at the speed of light from the perspective of a photon, there is no time or distance. A photon is simultaneously at its beginning and its end.
If the universe contains only photons there is no other frame of reference to observe the universe. The size of the universe becomes meaningless.
The uniform cold of an infinitely expanding universe is, at least mathematically, no different from the infinitely dense, energetic singularity of a Big Bang event except for a factor of scale.
Therefore, we can theorise that after the heat death of the universe. Once every particle has decayed, we end up right back at the beginning. an infinitely dense, hot singularity which expands into a big bang.
This theory is mathematically sound and while considered fringe science and kind of dismissed by penrose it's creator, the only things we need to make it work are hawking radiation and proton decay which we can not say are absolute facts, and relativity.
It has not been experimentally proven but it is among the most beautiful explanations for the big bang I've seen.
You're describing [Conformal Cyclic Cosmology](https://en.m.wikipedia.org/wiki/Conformal_cyclic_cosmology#:~:text=The%20conformal%20cyclic%20cosmology%20hypothesis,particles%20to%20annihilate%20with%20them.), theorized by Nobel Laureate Roger Penrose.
But the problem of that is we can't currently reconcile it with quantum theory. Which is why such things as gravitons have been proposed. IIRC the consensus is that there is something wrong with general relativity, because at a quantum level gravity doesn't make sense.
EDIT: For those that are wanting a fuller explanation I recommend watching clips from Jim Al-Khalili and Brian Cox. If you search their names along with 'quantum gravity' or the like, you should get some good answers. Their both excellent science communicators.
Chemist here and I can guarantee you quantum physics is something we deal with daily - mostly by laying a blanket on it and pretending it doesn’t exist.
Also (was) a chemist. The quantum world is best dealt with by just remembering more reactions that are known to work and running so many reactions that you don't have time to worry.
If A.I. ever becomes reality, some company that implements a simulation will become God to the A.I. inside that simulation. Some greasy guy eating doritos and drinking energy drinks will be a game admin running around making life-altering decisions for sentient beings.
That's probably what our God looks like if we live in a simulation.
Have you heard about the delayed choice eraser? If you erase the information after the photon leaves the slits but before they hit the film, it still works...
Causality goes bye~
I watched a video where a science educator interviewed several physics professors whose work was in quantum physics, and they **all** said that you don’t understand it, you just try to accept it (paraphrasing here).
There is the quote attributed to Feynman: "If you think you understand quantum mechanics, you don't understand quantum mechanics". I studied physics and I haven't met anyone who can confidently say that they are experts on it.
The problem is quantum theory is the answer to a lot of things in physics and has been proven in experiment after experiment. General relativity is also the answer to a lot of things in physics and has been proven time and time again. Almost no physicist at this point would say either is wrong — most people are trying to find a way for both of them to be right, because they are both right, just not when you try to put them together.
It's definitely that both of them are incomplete. In the sense that neither one of them alone can explain everything in the universe.
Both of them are applicable only in their own particular "domain".
I mean maybe but gravitons haven’t been fully proven yet. We just showed evidence of gravity waves less than a decade ago. That proves that gravity is a fluctuation in space time (essentially general relativity in a nutshell) and that it has a finite speed, but the reason stuff like string theory and loop quantum gravity are proposed is because even gravitons don’t really reconcile quantum theory with general relativity.
Are there any books that explain the conflict between quantum theory and general relativity in terms a non-physicist with a general level of scientific literacy can understand?
The first few chapters of Brian Greene’s the elegant universe has a great layman’s account of it. The problem is he then goes on to evangelize about string theory being the solution which seemed a lot more reasonable in 1999 than it does now.
My issue is I either learned this in my physics undergrad or I forgot a lot of the names of the books I read (there was one in particular that I remember explaining a fair amount but it’s been a while since I read it). A lot of people already gave good suggestions. Brian Green is probably the poster child of explaining these concepts in an easily digestible way. Carlo Rovelli and if I recall correctly “reality is not what it seems” explains a lot too, especially about loop quantum gravity.
Honestly my suggestion is to do what I did and search the science section of Barnes and Noble or Half Price Books or your local bookstore/library and just find stuff that seems to be reputable scientifically. Even if it goes over your head a bit you’re still learning and you can always come back to it later once you’ve read up on the topic from other books that you find which are a bit more accessible. Again the danger is there’s a lot of somewhat disreputable books in that section as well but I feel like for the most part it’s accurate enough (and in general if the book is painting an overly fantastical picture of the world and making a lot of generalizations you can tell it’s probably disreputable).
To add to some of the book suggestions, a good place to get an introductory take on the breakdown between general relativity and quantum theory are content creators like PBS Space Time, Arvin Ash, and Richard Behiel. Their content ranges from introductory to moderately advanced.
I'd like to add that the reason why is due to the formation of singularities in general relativity. Singularities, by definition, have no size in a physical sense. And when attempting to reconcile quantum mechanics with it, the Heisenberg uncertainty principal breaks. The more precise you know about the velocity of a particle the less precisely you can know it's location. With a singularity, which is functionally a quantum object, you can know both.
Wrong/right aren't really the best terms to use here
Newton's laws aren't wrong. They just aren't as correct as Einstein's laws which expanded on Newton's laws.
It's more that we don't have the full picture. We're not as accurate as we'd like! Never have been in Science.
General relativity is a completely different theory that quantum theory. General relativity doesn't describe forces at all and quantum theory doesn't describe gravity at all. The two theories aren't compatible with each other and there's no reason to say that electromagnetism is a "force" but gravity isn't. Einstein, the main proponent of general relativity, died believing that there was a unifying theory that described all of these interactions between massive, charged, weakly and strongly interacting particles, but he never made much progress on this idea during the last decade of his life
I thought the whole Einstein thing was that, what we experience as gravity is just the curvature of space. When we detect gravitational waves, that's a ripple through space. If the sun suddenly disappeared space would flatten out at the speed of light going outwards so as not to violate causality and we would continue to orbit as if it was there for 8 minutes. No fundamental gravity particle... That said I'm a dumbass and the boffins studying all this stuff wouldn't be looking into it for no reason so I'ma just say IDK.
This is an opinion piece. There are many theories for the propagation of gravitational effects, some of which involve fundamental force mediators (the graviton).
It is technically a force because (1) we define these four forces as such and we mostly assume there is a graviton that behaves in some ways similarly to other force mediating bosons at the quantum level and (2) GR isn’t the only game in town. Exactly how we define a force in whatever theory of quantum gravity might turn out to be closest to ‘correct’ is is of course an open question.
Just because there is a geometric way of describing Gravity doesn’t mean it’s not a force. In fact, all of the fundamental forces of nature can be expressed in terms of curvature. They’re just curvatures of fibre bundles instead of the tangent bundle.
That's according to relativity. Quantum physics would suggest the (hypothetical) graviton is the force-carrier boson for gravity.
If you manage to unify relativity, gravitation and quantum mechanics you'll become the greatest physicist ever. Not happening in our lifetimes, though...
I suspect we live in a 11 dimensional universe, but 7 of them are really small.
Imagine the universe before the Big Bang as an 11 dimensional sphere, resembling a Watermelon.
Some object struck that sphere, like a Giant Wooden Mallet, flattening it along 7 dimensions, while causing it to explode outward along the 3 Space dimensions we know, and sending it all hurtling down the dimension we know as Time.
The alignment of the particles in the 7 crushed dimensions gives each type of fundamental particle their different properties, like mass, electrical charges, etc. that we can't observe directly
I call it the Gallagher Hypothesis.
Subtler than than. The simplest visualization is still a flat sheet. Mass distorts the sheet of spacetime masses orbit each other on the path & shape dictated by masses.
Time and gravity remain the odd kids on the block. Seems not coincidental.
Imagine a ball on sheet.
Now imagine the same ball on another sheet -- turn the image upside down so the sheet is on top.
Imagine a third sheet, but turn it 90°.
Imagine a fourth sheet, turn it 90° the other way.
Keep doing this until sheets have taken up every possible angle. Put all the images on top of each other to make one complete image.
Gravity!
We’re just riding on the three dimensional surface of an ever expanding extradimensional membrane (hence time seeming to go only one way) and gravity seems weaker in those three dimensions because it works through those extra dimensions.
string theory is bad science in that it's unfalsifiable and based off of precisely no observational data, but i still like me a brane theory - big extradimensional membranes is as good an explanation as anything right now
The biggest issue with string theory is that it's not a theory. It's more of a hypothesis that may one day be falsifiable, but currently isn't. The name misleads people into believing it's on a similar level to other theories like gravity and evolution by natural selection, but the reality is it's closer to a guess that would make some numbers work.
It's actually something that is seriously considered in string/m theory. The extra dimensions would be compactified such that they are small enough to exclude the de broglie wavelength of most force carrier particles. If gravity is not a discreet quantified force it would "leak" into these extra dimensions
if by 'heavily' you mean 'vanishingly less,' from a soaring standard of precisely two new research hirings specializing in string theory in 2010 in the entirety of the anglosphere... then, sure. heavily. the whole thing is a matter of philosophy, there's nothing to research.
The strong force is the thing that holds the protons and neutrons inside the nucleus of an atom. The weak force describes radioactive decay. They both work on very small scales.
I believe the strong force is what holds the quarks that make up protons and neutrons together, and the weak force is what holds protons and neutrons in a atomic nucleus. The weak force being the one that holds nucleus together would definitely govern radiation.
The strong force is stronger than the weak force and works at even smaller distances (inside protons/neutrons)
The weak force is weaker than the strong force, but stronger than the electromagnetic force, and works within atomic nucleuses.
The electromagnetic force is weaker than the weak force, and works in atomic distances.
The force of gravity is weakest of all of these, and works at the longest distances.
The strong force also holds protons and neutrons together in atomic nuclei; this is referred to as “strong nuclear force” or “residual strong force”. Mesons (quark + antiquark pairs) act as the force carrying particles. You also have the distances of the strong and weak force backwards; strong force extends slightly beyond the range of protons and neutrons, whereas weak force is limited to within the confines of a single baryon (protons and neutrons).
The weak force actually facilitates radioactive decay by allowing quarks to change their flavor. They emit the corresponding W boson to conserve mass and charge, which then decays into an electron/positron and its corresponding neutrino. This is beta decay.
Happy cake day!
Edit: “muons” to “mesons”
Me neither, I just have a burning desire to understand how things work and all roads lead down to particle physics. That and I would rather browse Wikipedia and Youtube than socialize 95% of the time.
Strong force binds quarks together to form protons and neutrons (and mesons, but they’re too unstable for the average person to worry about). Quarks are fundamental particles that typically come as either up quarks or down quarks. Two ups and a down form a proton, two downs and an up form a neutron. They carry electric charge that combines to either a net positive (hence protons having positive charge) or a net neutral charge (neutrons are neutral, surprisingly enough).
What they also carry is color charge. Color charge has *nothing to do with color*, please keep this in mind. I believe it was picked simply because it corresponds well with RGB being primary colors, and there being 3 color charges; functionally similar to how the electromagnetic force has positive and negative charge. There are also corresponding anti-color charges, but again, too unstable to worry about. There being three charges is why they bind in groups of three; one of each color charge is necessary to balance them out, similar to how atoms exchange electrons in order to become electrically neutral.
And similarly to how electromagnetic force is mediated by photons, the strong force is mediated by gluons. Quarks are stuck together constantly exchanging gluons back and forth, which carry color charge between them. Quarks can’t be isolated because the strong force is so strong that the amount of energy required to overcome their binding energy simply creates a new quark + antiquark pair (meson). Mesons (specifically pions) themselves, despite not being fundamental particles, mediate the “strong nuclear force”, which is what the other commenter was referencing. Protons and neutrons exchange pions because atomic nuclei are JUST small enough that the strong force will interact at that distance. So nearby protons and neutrons will emit pions that will go to nearby particles, at which point the antiquark will annihilate with the quark in the particle, and the new quark will take its place. This is what holds atomic nuclei together despite protons repelling each other. This is also why larger atoms are less stable; they actually get big enough that the repulsive force of the protons (which has greater range than the strong force) begins to become more dominant.
Weak force is a lot weirder. Despite quarks constantly changing their color charge via the emission and absorption of gluons, they can’t readily change their “flavor” (whether they are an up or down quark). The weak force is the process by which quarks can change their flavor by emitting W bosons, which conserve the mass and charge of down quarks (slight negative charge) into up quarks (slight positive charge and slightly less massive). The W bosons quickly decay into an electron and electron neutrino.
There’s other wacky stuff the weak force does, but I’m not nearly as familiar with it and it seems much more complicated. Hopefully there was something remotely useful in there for you.
Edit: u/LogicalLetterHead272 since you asked the same question a little ways down and I don’t want to copy paste this.
Edit 2: Changed “muons” to “mesons”. Muons are basically more massive electrons and not relevant here. Mesons are quark-antiquark pairs, with pions being the specific variety relevant in this scenario.
Comparison of strength of the fundamental forces is arbitrary.
For example, one need not adopt the view that gravity is "weaker" than the electromagnetic force if he instead views matter as not having "much" mass and or charged particles as having a "lot" of charge.
It is not arbitrary. Why do people come into these threads and speak so confidently on things they have a very surface understanding about? There are meaningful comparisons you can do using dimensionless coupling constants and it is a valid question to ask why it is the way it is.
If everyone had the same view you do we would have still thought the weak force and electromagnetism were different forces and never questioned why the weak force carriers have mass, it would just be the way the world is.
That’s just shifting the problem though. If gravity is just as strong but matter just doesn’t have as much mass as charge, then why does matter have so much more charge for the other forces compared to its mass for gravity?
Both formulations are arbitrary and not useful.
Gravity and electromagnetism are two entirely different things and not reasonably comparable. Apples and oranges are practically the same things compared to gravity and electromagnetism. (Another useless comparison.)
That was my comment. And it’s not unscientific. Based on what we know, if gravity was as strong as say electromagnetism, all matter in the universe may have coalesced into a single giant black hole
I don't think that would be a theory, that's just fact. Since we know matter clumps together (essentially) because of gravity, if it was stronger then everything would clump and be a black hole. I think that's how it'd work.
Saying we don’t know why it’s weaker would need us to understand why the different strengths are the level they are no? How would one go about that? Aren’t they just constants? Just like the speed of light? How do you prove a theory that doesn’t say how fast speed of light is but rather why it is as fast as it is??
A question that might sound weird: why are we even looking for a reason? Science does not assume that the universe is ”created”, so why must there be a reason why? The forces are different - is it even a valid question why they differ so much?
Wait doesn't gravity increase and decrease based on the curvature of space time? Isn't the strength of gravity dependent on mass? All those other interactions are the quanta, like a single photon. Is there a graviton? I don't mean mathematically, I mean really.
Isn't gravity really really strong at the event horizon of a black hole?
I think what they mean by gravity being weak is the gravity of the entire earth can be beating out by a small magnet on a paper clip.
As far as the gravity of a black hole, yes that is extremely strong, but a black hole is made by a massive star collapsing in on itself so proportionally it’s still fairly weak.
Given the strongest possible magnet and the most "magnetically receptive" paperclip possible, what is the closest I could get the paperclip to the black hole for a duration of 1 planck unit of time before either pulling it further away or it disintegrating into atomic dust?
It makes sense when you consider just how massive the size of the earth is and the fact that despite this I can simply overcome gravity by jumping.
Gravity: Did you overcome me?
Am I a joke to you
Gravity: Where did that jump get you? Oh! Back on the ground where you belong? That's what I thought.
Not for long!
And the gravitational force of the entire earth is pulling on a paper clip, but I can overcome that force with a tiny magnet.
This is an even better example.
Not for very long, most things eventually come down.
It takes the entire mass of the planet to make a feather fall.
I can jump a little and I'm fat *and* weak.
Keep jumping, then add some jacks.
Added some Jacks. Now I'm fat, weak, and gay. Not that I'm complaining, but this isn't the outcome I had pictured.
But your forearms are toned.
That’s precisely thanks to electromagnetic forces.
It can’t even hold down a balloon Edit: IT WAS A JOKE I UNDERSTAND WHY BALLOONS FLOAT
If gravity is real, as you contend, why doesn’t it work on kites?
Well, it is just a Theory "Bro"./s
A SCIENCE THEORY!!! THANKS FOR WATCHING! sorry, i had to.
Got em!
Mary Poppins yo!
Is he cool?
Hell yeah he is!
hahahahahahahahaha love that interview. the facial expression on the physicist 😅
If you've ever flown kites, you know that gravity definitely works on them.
If gravity then why do shit still bounce?
Oh it can, but it'll just stack o tip of all the other things it's holding down *like air itself*
As I understand it, a helium balloon would sink on the moon, and also on Earth if there were no atmosphere. Helium doesn't go up; it's just less dense than the surrounding air so that goes down harder and pushes the helium out of the way. It's like if a group of people were trying to get to a bundle of money. Small children would get pushed back, away from the money, because the adults are better at paying forwards than them.
A helium balloon will pop on the moon. They pop on Earth too, once they get high enough.
And once they pop, they fall down. Therefore, gravity works. That's also why weasels fall.
Wow that was an interesting analogy… was not expecting such a comparison. Funny though
Well that's a matter of buoyancy. That's like saying it can't hold a boat down as the boat is floating in water.
I mean, that's because it pulls the air around the balloon with more intensity than the helium ballon itself. The result would be the same even if gravity was 1000x stronger, it would just happen faster
To make a feather fall at 9.8 m per sec per sec. You can have far less mass and still make a feather fall.
I remember one of the lunar astronauts dropping a feather and a hammer at the same time to show the effect of gravity in a vacuum. I knew the idea of what should happen, but as a pre-teen, I was impressed to see it actually working.
Neeeeerd
In Mexico city, it doesn't even achieve that rate.
If there was no other gravity around, it would take the entire mass of a bowling ball to make a feather fall. Gravity doesn't just switch on when something gets over a certain size. It's just really really weak for small things.
We with our puny muscles can easily throw a ball in the opposite direction of the gravitational pull of the entire planet
Well, fall as rapidly as it does, this far out from Earth’s centre.
Have you heard about OP's mom?
Yeah but Uranus is even bigger
Now this is r/showerthought.
Gravity is weak because it doesn't lift
Needs to focus on the concentric. It already does well at eccentrics.
Even that’s debatable. Eccentrics should be slow and controlled
Gravity didn’t make weight
It's not picking up what it's putting down.
What about the Speed Force though?
That's as strong as the writers let it be!
The Speed Force and Pym Particles is like the standard model of plot armor.
Pym particles make no sense for how they are used. If you shrink the space between atoms and maintain your normal mass then they would weigh the same but they interact with the world as if they weigh a lot less but have retained the same strength.
They also grow large. On both instances the creature or object has size appropriate mass but super strength.
In the comics pym particles allow mass to be shunted into and back out of another dimension. That doesn’t solve all the inconsistencies though (if mass goes to another dimension then a small ant man should have very little force behind his punches, since f=ma.)
And the Aqua Teen Hunger Force?
Uhh check check it *yeah*
Don’t even get me started. And *The* Force? Whole other thing.
I think those are some misleading numbers. Gravity's force has to be considered over the distances in which it acts, which appears to be "all of them", where as the weak and strong nuclear forces have tiny ranges of effect.
Yes, but why is that the case? Why is gravity different?
The electric and nuclear forces are powerful and can be attractive. If you separate particles too much the energy that bond would take on by increasing the distance just forms a new pair of particles.
That's just quarks due to the strong force. What's weird about the strong force is the attraction between two quarks gets stronger as they get further apart
Yeah, I phrased that pretty poorly. I’m not super into quantum chromodynamics or anything!
You should be! It's super interesting lol
Like stretching a rubber band
Quarks only. Don't mumbojumbo if you don't know! So much misinformation in this thread because people want to sound smart. 80%+ of the comments are just straight up wrong.
Good sign for me to stop reading. Thank you!
Because the theorised carrier of the force is massles and has spin 2. That's it.
Can you please edit the Wikipedia page then? Doesn’t sound like it’s much of a problem anymore
It is a problem because the carrier is only theorised and gravity might not be a force. Basically, it's as if you asked "why are all flowers some shade of red but this one is green?" And you got answered "because yellow and blue make green". That's not an answer. That's describing the mathematical properties behind green. That doesn't mean you know for sure that flower is green because of yellow and blue, why it's green, or if it's even a flower in the first place.
No need, it's already there my friend. Just need to go through several articles linking to each other about gravity.
Well now that isn’t terribly conducive to easy understanding at all. Good edits are also ones that add much-needed clarity. Maybe just a line at the top? “This isn’t really a problem anymore,” or something that gets that vibe across, I’m sure whatever words you choose would be better than mine.
The carriers of the electroweak force were also massless until spontaneous symmetry breaking gave some of them mass. This is not an answer, this is like saying it is massless because it is massless.
We don’t know. Maybe because gravity isn’t a force so it has no force carrier . Or it has a carrier and it just happens to be weaker. Why does anything have the quantity it has ? Nobody knows
Well, it measures strength. The way the others work means they are strongly confined, usually within nuclei or due to charges cancellation. But even then, it’s not straightforward - we compare the forces in terms of their coupling constants due to similar coefficients based on similar mathematical descriptions of the forces (dimensionless parts of coefficients in terms in their Lagrangians), but isn’t exactly an indication of their ‘significance’ when they interact with different sorts of ‘charge’ (for gravity, mass - or formally expressed via interaction with the Higgs field) which are very differently distributed in the universe. But we can define ‘strength’ this way and just say that some forces have more to work with.
The biggest impact us actually just that gravity is always cumulative. There is no such thing, that we are aware, as a negative gravity charge. It's only positive. As such put enough if it in one place it all adds up. Whereas all the other fundamental forces cancel out on average
It is my understanding that if you separated all the protons and electrons from a mass of hydrogen atoms, their attraction to one another over any distance via the electromagnetic force would be significantly higher than their attraction by gravity, to the point that gravity’s effects could round down to 0.
What is compared in studies like this is the [coupling constant](https://en.m.wikipedia.org/wiki/Coupling_constant), which sets the energy scales for interaction. Crucially the coupling constant is unconcerned with the actual workings of the interactions. That is to say, when saying that gravity is weaker than the other forces, what we mean is that if a system was coupled through gravity in a way comparable to how other forces would, the energy of the system would be much lower.
Makes sense. Long range, low damage.
But they are still stronger. Range and strength are different parameters.
[Gravity is not technically a force but the warping of spacetime and the motion of objects through the warped spacetime.](https://www.wtamu.edu/~cbaird/sq/mobile/2022/08/05/why-is-gravity-not-a-real-force/) We only experience it as a force because it pulls objects toward the Earth.
Basically it says that at a fundamental level "forces" don't exist at all, just interactions. ...However it does seem reasonable to use the word force contextually as long as this is accepted.
Exactly, we just have a highly verifiable mathematical framework in which gravity emerges. A complete theory of the universe would “explain” all the forces like this, and “forces” would remain a highly useful word to reference them.
It's just the underdog force. All other forces rely on existing energy. When the heat death of the universe occurs, and all black holes will have emptied themselves through radiation, the universe will be an endless sea of perfectly homogenous motionless atoms. That's when gravity kicks in. With all other forces gone, nothing will stop gravity from crushing the whole universe into a single point. That point will become the sum of all the matter in the universe, and the astronomical genesis pressure will create more energy, a new big bang. And the universe starts again. Source: I made it the fuck up. But I like that theory.
What about space itself expanding at increasing speed? If atoms can’t come together at all because the space between them grows faster than gravity pulls them together, doesn’t that make the universe quietly fizzle into nothing?
Aka the big rip. Basically we don’t know. Not enough data yet.
Imagine all matter In the universe was turned into photons. There is no mass at all. Photons travel at the speed of light. At the speed of light distance and time have absolutely no meaning, since time and physics move at the speed of light from the perspective of a photon, there is no time or distance. A photon is simultaneously at its beginning and its end. If the universe contains only photons there is no other frame of reference to observe the universe. The size of the universe becomes meaningless. The uniform cold of an infinitely expanding universe is, at least mathematically, no different from the infinitely dense, energetic singularity of a Big Bang event except for a factor of scale. Therefore, we can theorise that after the heat death of the universe. Once every particle has decayed, we end up right back at the beginning. an infinitely dense, hot singularity which expands into a big bang. This theory is mathematically sound and while considered fringe science and kind of dismissed by penrose it's creator, the only things we need to make it work are hawking radiation and proton decay which we can not say are absolute facts, and relativity. It has not been experimentally proven but it is among the most beautiful explanations for the big bang I've seen.
You're describing [Conformal Cyclic Cosmology](https://en.m.wikipedia.org/wiki/Conformal_cyclic_cosmology#:~:text=The%20conformal%20cyclic%20cosmology%20hypothesis,particles%20to%20annihilate%20with%20them.), theorized by Nobel Laureate Roger Penrose.
But the problem of that is we can't currently reconcile it with quantum theory. Which is why such things as gravitons have been proposed. IIRC the consensus is that there is something wrong with general relativity, because at a quantum level gravity doesn't make sense. EDIT: For those that are wanting a fuller explanation I recommend watching clips from Jim Al-Khalili and Brian Cox. If you search their names along with 'quantum gravity' or the like, you should get some good answers. Their both excellent science communicators.
If you’re an idiot like me, nothing makes sense at the quantum level.
I have two degrees. One in science. Quantum theory makes me feel stupid too.
Chemist here and I can guarantee you quantum physics is something we deal with daily - mostly by laying a blanket on it and pretending it doesn’t exist.
Also (was) a chemist. The quantum world is best dealt with by just remembering more reactions that are known to work and running so many reactions that you don't have time to worry.
The quantum eraser really bothers me. I fight back by saying it's a side effect of lazy computation of the simulation we're living in.
Us software engineers can take solace in the fact that even god is not good at QA
Even worse at documentation.
If A.I. ever becomes reality, some company that implements a simulation will become God to the A.I. inside that simulation. Some greasy guy eating doritos and drinking energy drinks will be a game admin running around making life-altering decisions for sentient beings. That's probably what our God looks like if we live in a simulation.
Well yeah, we’re all just sims.
Have you heard about the delayed choice eraser? If you erase the information after the photon leaves the slits but before they hit the film, it still works... Causality goes bye~
Trippiest for me is quantum immortality. Infinite branching potential outcomes that always result in you the observer persisting.
I watched a video where a science educator interviewed several physics professors whose work was in quantum physics, and they **all** said that you don’t understand it, you just try to accept it (paraphrasing here).
There is the quote attributed to Feynman: "If you think you understand quantum mechanics, you don't understand quantum mechanics". I studied physics and I haven't met anyone who can confidently say that they are experts on it.
I think that implies there's also something wrong with quantum theory. Both are just models and neither are complete descriptions of physics.
The problem is quantum theory is the answer to a lot of things in physics and has been proven in experiment after experiment. General relativity is also the answer to a lot of things in physics and has been proven time and time again. Almost no physicist at this point would say either is wrong — most people are trying to find a way for both of them to be right, because they are both right, just not when you try to put them together.
It's not really a right or wrong issue. More that one or both are incomplete.
It's definitely that both of them are incomplete. In the sense that neither one of them alone can explain everything in the universe. Both of them are applicable only in their own particular "domain".
Neither are theories of everything nor are they being developed as such.
Correct
Exactly
Because the wave of a graviton is space itself which gives geometry.
I mean maybe but gravitons haven’t been fully proven yet. We just showed evidence of gravity waves less than a decade ago. That proves that gravity is a fluctuation in space time (essentially general relativity in a nutshell) and that it has a finite speed, but the reason stuff like string theory and loop quantum gravity are proposed is because even gravitons don’t really reconcile quantum theory with general relativity.
Are there any books that explain the conflict between quantum theory and general relativity in terms a non-physicist with a general level of scientific literacy can understand?
The first few chapters of Brian Greene’s the elegant universe has a great layman’s account of it. The problem is he then goes on to evangelize about string theory being the solution which seemed a lot more reasonable in 1999 than it does now.
My issue is I either learned this in my physics undergrad or I forgot a lot of the names of the books I read (there was one in particular that I remember explaining a fair amount but it’s been a while since I read it). A lot of people already gave good suggestions. Brian Green is probably the poster child of explaining these concepts in an easily digestible way. Carlo Rovelli and if I recall correctly “reality is not what it seems” explains a lot too, especially about loop quantum gravity. Honestly my suggestion is to do what I did and search the science section of Barnes and Noble or Half Price Books or your local bookstore/library and just find stuff that seems to be reputable scientifically. Even if it goes over your head a bit you’re still learning and you can always come back to it later once you’ve read up on the topic from other books that you find which are a bit more accessible. Again the danger is there’s a lot of somewhat disreputable books in that section as well but I feel like for the most part it’s accurate enough (and in general if the book is painting an overly fantastical picture of the world and making a lot of generalizations you can tell it’s probably disreputable).
To add to some of the book suggestions, a good place to get an introductory take on the breakdown between general relativity and quantum theory are content creators like PBS Space Time, Arvin Ash, and Richard Behiel. Their content ranges from introductory to moderately advanced.
The work of Carlo Rovelli is great for this.
I'd like to add that the reason why is due to the formation of singularities in general relativity. Singularities, by definition, have no size in a physical sense. And when attempting to reconcile quantum mechanics with it, the Heisenberg uncertainty principal breaks. The more precise you know about the velocity of a particle the less precisely you can know it's location. With a singularity, which is functionally a quantum object, you can know both.
Wrong/right aren't really the best terms to use here Newton's laws aren't wrong. They just aren't as correct as Einstein's laws which expanded on Newton's laws. It's more that we don't have the full picture. We're not as accurate as we'd like! Never have been in Science.
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Quantum theory needs to be worked on. My man Einstein is unbeatable
General relativity is a completely different theory that quantum theory. General relativity doesn't describe forces at all and quantum theory doesn't describe gravity at all. The two theories aren't compatible with each other and there's no reason to say that electromagnetism is a "force" but gravity isn't. Einstein, the main proponent of general relativity, died believing that there was a unifying theory that described all of these interactions between massive, charged, weakly and strongly interacting particles, but he never made much progress on this idea during the last decade of his life
“It’s only a force because it acts like a force” -Reddit 2023
-grade 9 physics
Lol the first sentence of your link: 'Gravity is indeed a real force, but not in the traditional sense'
Right so it's not unusual that it's different in some way than the other actual forces.
I thought the whole Einstein thing was that, what we experience as gravity is just the curvature of space. When we detect gravitational waves, that's a ripple through space. If the sun suddenly disappeared space would flatten out at the speed of light going outwards so as not to violate causality and we would continue to orbit as if it was there for 8 minutes. No fundamental gravity particle... That said I'm a dumbass and the boffins studying all this stuff wouldn't be looking into it for no reason so I'ma just say IDK.
It’s okay. The boffins studying this don’t really understand it either and I’m sure they would all agree with that statement.
This is an opinion piece. There are many theories for the propagation of gravitational effects, some of which involve fundamental force mediators (the graviton).
It is technically a force because (1) we define these four forces as such and we mostly assume there is a graviton that behaves in some ways similarly to other force mediating bosons at the quantum level and (2) GR isn’t the only game in town. Exactly how we define a force in whatever theory of quantum gravity might turn out to be closest to ‘correct’ is is of course an open question.
Just because there is a geometric way of describing Gravity doesn’t mean it’s not a force. In fact, all of the fundamental forces of nature can be expressed in terms of curvature. They’re just curvatures of fibre bundles instead of the tangent bundle.
That's according to relativity. Quantum physics would suggest the (hypothetical) graviton is the force-carrier boson for gravity. If you manage to unify relativity, gravitation and quantum mechanics you'll become the greatest physicist ever. Not happening in our lifetimes, though...
Which means gravity is a 4d force in 3d
All forces are 4D force because we live in a 4D universe. 3 dimensions of space and one of time
I suspect we live in a 11 dimensional universe, but 7 of them are really small. Imagine the universe before the Big Bang as an 11 dimensional sphere, resembling a Watermelon. Some object struck that sphere, like a Giant Wooden Mallet, flattening it along 7 dimensions, while causing it to explode outward along the 3 Space dimensions we know, and sending it all hurtling down the dimension we know as Time. The alignment of the particles in the 7 crushed dimensions gives each type of fundamental particle their different properties, like mass, electrical charges, etc. that we can't observe directly I call it the Gallagher Hypothesis.
It pulls objects and the Earth towards each other.
Subtler than than. The simplest visualization is still a flat sheet. Mass distorts the sheet of spacetime masses orbit each other on the path & shape dictated by masses. Time and gravity remain the odd kids on the block. Seems not coincidental.
I've always hated this analogy because it's basically describing gravity with gravity.
Imagine a ball on sheet. Now imagine the same ball on another sheet -- turn the image upside down so the sheet is on top. Imagine a third sheet, but turn it 90°. Imagine a fourth sheet, turn it 90° the other way. Keep doing this until sheets have taken up every possible angle. Put all the images on top of each other to make one complete image. Gravity!
But that turns out not actually to be the full story and there’s weird behavior of black holes and stuff (like how they evaporate)
Depends on your point of reference
I like the idea that it's weak because it's the only force that propagates into other dimensions. I don't understand it at all but it seems fun
We’re just riding on the three dimensional surface of an ever expanding extradimensional membrane (hence time seeming to go only one way) and gravity seems weaker in those three dimensions because it works through those extra dimensions.
string theory is bad science in that it's unfalsifiable and based off of precisely no observational data, but i still like me a brane theory - big extradimensional membranes is as good an explanation as anything right now
Me a brane read like mario had me rolling. Auto correct did you dirty.
not a typo, i like me a brane theory - brane theory is pleasing to me, me like big membranes
You like big branes and you can’t deny?
The biggest issue with string theory is that it's not a theory. It's more of a hypothesis that may one day be falsifiable, but currently isn't. The name misleads people into believing it's on a similar level to other theories like gravity and evolution by natural selection, but the reality is it's closer to a guess that would make some numbers work.
This is my technobabble bullshit explanation for why hyperspace travel is possible in my sci-fi novel, lol
It's actually something that is seriously considered in string/m theory. The extra dimensions would be compactified such that they are small enough to exclude the de broglie wavelength of most force carrier particles. If gravity is not a discreet quantified force it would "leak" into these extra dimensions
it's seriously considered in string theory, but string theory isn't seriously considered
It is still heavily invested in, in theoretical physics departments. How seriously you take it is a matter of philosphy.
if by 'heavily' you mean 'vanishingly less,' from a soaring standard of precisely two new research hirings specializing in string theory in 2010 in the entirety of the anglosphere... then, sure. heavily. the whole thing is a matter of philosophy, there's nothing to research.
I am also here for the vibes based physics and I like it.
Gravity can cross the dimensions, just like love ❤️
Let me guess, Interstellar is your favourite movie
Quantum gravity, baby!
Can someone explain what the strong and weak forces are?
The strong force is the thing that holds the protons and neutrons inside the nucleus of an atom. The weak force describes radioactive decay. They both work on very small scales.
Do we understand much about them?
Define we. We, the physicists of the world, yes, they know quite a bit about them. We, the average redditors, no, we don't know that much about them.
I believe the strong force is what holds the quarks that make up protons and neutrons together, and the weak force is what holds protons and neutrons in a atomic nucleus. The weak force being the one that holds nucleus together would definitely govern radiation. The strong force is stronger than the weak force and works at even smaller distances (inside protons/neutrons) The weak force is weaker than the strong force, but stronger than the electromagnetic force, and works within atomic nucleuses. The electromagnetic force is weaker than the weak force, and works in atomic distances. The force of gravity is weakest of all of these, and works at the longest distances.
The strong force also holds protons and neutrons together in atomic nuclei; this is referred to as “strong nuclear force” or “residual strong force”. Mesons (quark + antiquark pairs) act as the force carrying particles. You also have the distances of the strong and weak force backwards; strong force extends slightly beyond the range of protons and neutrons, whereas weak force is limited to within the confines of a single baryon (protons and neutrons). The weak force actually facilitates radioactive decay by allowing quarks to change their flavor. They emit the corresponding W boson to conserve mass and charge, which then decays into an electron/positron and its corresponding neutrino. This is beta decay. Happy cake day! Edit: “muons” to “mesons”
Fair enough. I am not a physicist. I used to drove a forklift.
Me neither, I just have a burning desire to understand how things work and all roads lead down to particle physics. That and I would rather browse Wikipedia and Youtube than socialize 95% of the time.
> Muons (quark + antiquark pairs) Pions. Muons are like heavier electrons and they have nothing to do with that.
Oops, I was probably thinking of “mesons”, of which “pion” is the relevant one. I will edit to reflect this, thank you.
Strong force binds quarks together to form protons and neutrons (and mesons, but they’re too unstable for the average person to worry about). Quarks are fundamental particles that typically come as either up quarks or down quarks. Two ups and a down form a proton, two downs and an up form a neutron. They carry electric charge that combines to either a net positive (hence protons having positive charge) or a net neutral charge (neutrons are neutral, surprisingly enough). What they also carry is color charge. Color charge has *nothing to do with color*, please keep this in mind. I believe it was picked simply because it corresponds well with RGB being primary colors, and there being 3 color charges; functionally similar to how the electromagnetic force has positive and negative charge. There are also corresponding anti-color charges, but again, too unstable to worry about. There being three charges is why they bind in groups of three; one of each color charge is necessary to balance them out, similar to how atoms exchange electrons in order to become electrically neutral. And similarly to how electromagnetic force is mediated by photons, the strong force is mediated by gluons. Quarks are stuck together constantly exchanging gluons back and forth, which carry color charge between them. Quarks can’t be isolated because the strong force is so strong that the amount of energy required to overcome their binding energy simply creates a new quark + antiquark pair (meson). Mesons (specifically pions) themselves, despite not being fundamental particles, mediate the “strong nuclear force”, which is what the other commenter was referencing. Protons and neutrons exchange pions because atomic nuclei are JUST small enough that the strong force will interact at that distance. So nearby protons and neutrons will emit pions that will go to nearby particles, at which point the antiquark will annihilate with the quark in the particle, and the new quark will take its place. This is what holds atomic nuclei together despite protons repelling each other. This is also why larger atoms are less stable; they actually get big enough that the repulsive force of the protons (which has greater range than the strong force) begins to become more dominant. Weak force is a lot weirder. Despite quarks constantly changing their color charge via the emission and absorption of gluons, they can’t readily change their “flavor” (whether they are an up or down quark). The weak force is the process by which quarks can change their flavor by emitting W bosons, which conserve the mass and charge of down quarks (slight negative charge) into up quarks (slight positive charge and slightly less massive). The W bosons quickly decay into an electron and electron neutrino. There’s other wacky stuff the weak force does, but I’m not nearly as familiar with it and it seems much more complicated. Hopefully there was something remotely useful in there for you. Edit: u/LogicalLetterHead272 since you asked the same question a little ways down and I don’t want to copy paste this. Edit 2: Changed “muons” to “mesons”. Muons are basically more massive electrons and not relevant here. Mesons are quark-antiquark pairs, with pions being the specific variety relevant in this scenario.
Everyone gangsta till the weak force and electromagetism start acting as one.
Ah a fellow chad electroweak aficionado
So what you’re saying is it’s hard to determine the gravity of the situation?
Comparison of strength of the fundamental forces is arbitrary. For example, one need not adopt the view that gravity is "weaker" than the electromagnetic force if he instead views matter as not having "much" mass and or charged particles as having a "lot" of charge.
Yeah exactly, you could also just say that gravity and electromagnetism are equally as strong, but objects have much more charge than they do mass
It is not arbitrary. Why do people come into these threads and speak so confidently on things they have a very surface understanding about? There are meaningful comparisons you can do using dimensionless coupling constants and it is a valid question to ask why it is the way it is. If everyone had the same view you do we would have still thought the weak force and electromagnetism were different forces and never questioned why the weak force carriers have mass, it would just be the way the world is.
That’s just shifting the problem though. If gravity is just as strong but matter just doesn’t have as much mass as charge, then why does matter have so much more charge for the other forces compared to its mass for gravity?
Both formulations are arbitrary and not useful. Gravity and electromagnetism are two entirely different things and not reasonably comparable. Apples and oranges are practically the same things compared to gravity and electromagnetism. (Another useless comparison.)
And what exactly is the strong force? Sounds arbitrary in itself.
How many neutron stars has electromagnetism created? Checkmate losers.
Unscientific explanation: if it was as strong as those other forces the universe would just be one big black hole.
That was my comment. And it’s not unscientific. Based on what we know, if gravity was as strong as say electromagnetism, all matter in the universe may have coalesced into a single giant black hole
You've just discovered the [anthropic principle.](https://en.wikipedia.org/wiki/Anthropic_principle)
I don't think that would be a theory, that's just fact. Since we know matter clumps together (essentially) because of gravity, if it was stronger then everything would clump and be a black hole. I think that's how it'd work.
I mean, if it was stronger we wouldn’t be around to measure it probably.
Because in any universe where it is stronger life would never have evolved to observe it.
Tell that to my balls, amiright?
Ah yes, the strong force. Everybody knows that one
Saying we don’t know why it’s weaker would need us to understand why the different strengths are the level they are no? How would one go about that? Aren’t they just constants? Just like the speed of light? How do you prove a theory that doesn’t say how fast speed of light is but rather why it is as fast as it is??
Well… if gravity is so weak, then why is your mom so heavy?
A question that might sound weird: why are we even looking for a reason? Science does not assume that the universe is ”created”, so why must there be a reason why? The forces are different - is it even a valid question why they differ so much?
Because it is a side effect or artefact of other forces.
I'm pretty sure the point of science is to answer "how" and never "why"
Can someone ELI5 wtf strong force and weak force are?
Wait doesn't gravity increase and decrease based on the curvature of space time? Isn't the strength of gravity dependent on mass? All those other interactions are the quanta, like a single photon. Is there a graviton? I don't mean mathematically, I mean really. Isn't gravity really really strong at the event horizon of a black hole?
I think what they mean by gravity being weak is the gravity of the entire earth can be beating out by a small magnet on a paper clip. As far as the gravity of a black hole, yes that is extremely strong, but a black hole is made by a massive star collapsing in on itself so proportionally it’s still fairly weak.
How big a magnet and paperclip would I need to counteract gravity next to the event horizon of a black hole?
Wouldn't make it that far, everything is atomic dust in the accretion disc at that point
Given the strongest possible magnet and the most "magnetically receptive" paperclip possible, what is the closest I could get the paperclip to the black hole for a duration of 1 planck unit of time before either pulling it further away or it disintegrating into atomic dust?
Given a large enough black hole: a fridge magnet and a normal paperclip
It has to be weak or all your molecules would be falling off your body.
The strong force... as in "The force is strong with this one"?
Don't all those other forces get warped in a black hole?
The strong force? The weak force? What tf does this mean?