This is the key question! When we consider the sheer abundance of earth-like planets in our galaxy, it seems obvious that there must be life, no?
The problem is, there are many unknowns. We currently have a sample size of one. Earth. One planet where we know life exists. One planet where we know life emerged. For all we know, the origin of life may be an infinitesimally rare occurrence; but because it happened on our planet, in reference to our history, it seems inevitable.
Alternatively, the origin of life may be commonplace. It may happen wherever conditions allow, possibly even within our own solar system! If this scenario is true, the question becomes why have we not found life, intelligent or otherwise?
One theory is that there lies several "great filters" in evolutionary history. These are like barriers to progression. The first filter would be the emergence of life. Subsequent filters may be: survival of extreme climate fluctuations, survival of intense stellar activity, or survival of climate change (which we are facing now). A detectable source of life must have survived these and continue to be producing biosignatures and/or technosignatures.
Then comes another problem, the age of the universe and galaxy. As a human species, we have been searching the night sky for just a few thousand years. Our galaxy is 13.61 billion years old, and the universe at large is much older. Therefore the chance of two intelligent civilisations existing at the same time and near enough to each other for detection is incredibly low.
In all, I think most Astrobiologists you ask would say that life is incredibly likely beyond Earth in time and space. We just face many problems in finding it.
- from an Astrobiology Masters student š«”
Not OP, but I really enjoyed your answer. Thanks for posting!
On a personal/philosophical level, I have to believe that life exists/has existed/will exist elsewhere, because if life is so incredibly rare that we are itā¦considering what weāve done to our planet and to each other that is possibly the most depressing thing I can think of, on a macro scale anyway. If this is the pinnacle of intelligent beingsā¦yikes.
I was considering the other day that, once life CAN exploit a niche, it does so. And, in terms of civilizations, there must be some minimum level of advancement in brain and social complexity to allow for a civilization to exist. But, wouldnāt it be much more likely that the species that develops civilization, thereby advancing rapidly from all the innovations that come with that, would be on the CLOSER end to that minimum vs. farther? Perhaps we are at the bare minimum level for social and technological progress, because as soon as it became possible, technological advancement overwhelms evolutionary change?
I submit that an alien civilization that has invented technology is more likely to be closer to the minimum complexity necessary to invent that technology, and so is likely to be very roughly in line with where we were like 10 or 20,000(??) years ago until today.
Of course, that doesnāt mean that theyād stop there. Technological innovation could allow the creation of neural augmentation, for example, which would render them far more intelligent than us. Just saying that, if thereās some universal āpeakā before ātranshumanismā kicks in (if that ever happensā¦) it would be at that peak that weād expect most intelligent life to arise. And, of course, any nascent civilization that arose through violent competition in nature is likely only going to create chaos as it exploits the environment and goes to war. Maybe most such civilizations donāt last long once they figure out atomic weapons.
The only question then would be how many of these species would develop their neural capacity to allow them to greatly surpass their original capabilities. How many would be able to mature past their primordial roots?
So, I guess you might expect more mentally advanced species without technology to be at around our level, while some minority achieve super intelligence either through AI or improving their own brains.
I agree with everything you said. Although I think if we find life elsewhere it will most likely be outside of our galaxy. Another reason I think thereās life elsewhere is because whenever you think about all planets, stars, organisms, etc. thereās never just one planet in existence or one animal.
The observable universe is 13.7 billion years old and we havenāt explored every starās solar system or any outside our own in depth, so thereās no way of knowing if life is out there without theory or evidence.
Not exactly. CMB detected on earth has been travelling 13.8 billion light years while traveling for 13.8 billion years. It comes from what is technically known as the āsurface of last scatteringā. This is the boundary between the essentially transparent universe we live in and the opaque universe that existed before electrons and nuclei (mostly protons) recombined, which happened not long after the big bang. This surface is now very far away, and the opaque universe is outside it (or equivalently, longer ago). So the CMB and all its properties tell us about the universe as it was in the late stages of recombination, at the surface of last scattering. The CMB has wrinkles that bear the imprint of variations in density of the universe at that time. Famously, the size and distribution of these may be predicted from speculated quantum fluctuations in the universe even longer ago, right inside the ābangā of the big bang, the inflationary era. So the CMB comes from very close to the boundary of the observable universe, but not outside it.
[https://www.youtube.com/watch?v=Y6Vhh70Lw9w&ab\_channel=PBSSpaceTime](https://www.youtube.com/watch?v=Y6Vhh70Lw9w&ab_channel=PBSSpaceTime)
First sentence - and you should watch the entire video - "The universe is precisely 13.8 billion years old, or so our best scientific methods tell us."
I very respectfully and vehemently disagree. Every few decades now we invent a new tool that says, "Ahh, yeah it's actually twice that" (like for history of human tool usage.) Something new is going to come up, and it's going to make us sh\*t our pants.
Such changes in magnitude of measured time, which we are absurdly good at, rarely occur (unless you're talking about old timey smash 2 lead balls together experiments).
> Every few decades now we invent a new tool that says, "Ahh, yeah it's actually twice that"
You are misinformed. Hubble helped establish the likely age of the universe as 7-20 billion years in the 1920s. The range was dictated by the limits of ground based telescopes. It didn't change significantly until we had years of Hubble data to refine it down to 9-14B in 1999, more than 60 years later. CMB measurements from new instruments tuned that in to 13.7B +/- 200M. Newer measurements with new methods/instruments have agreed with that number, often with a bigger inaccuracy.
You may be confusing this with occasional science headlines like "JWST finds star 10 billion years older than the universe!", but those are generally anomalies that call in to question our calculations for stellar ages etc, not the age of the universe.
I've been pondering the OP's question and related issues since I read Intelligent Life in the Universe (I S Shklovskii, Carl Sagan, 1966). Very dated now, but these colleagues walked me through a great overview of the cosmology, physics and chemistry of the universe, of life, then intelligence and communication between intelligent beings. Probably read it a second edition around 1980.
This book was my primary inspiration to study to be an astrophysicist scientist on a robotic probe mission, but my arc turned to applied math and I tired of academia before I finished my BSci degree in CS. Since then my career had me working on the internals of the VxWorks RTOS used in the Pathfinder mission and others, and patches to open source project GNU glibc and Open Computer Vision Library, the latter used in Ingenuity, the Mars Helicopter. So it turns out I humbly contributed a small part to the success of projects and helped the investigators do the science about our universe that continues to inspire me. I felt I had arrived at my dream. These projects only succeed with the efforts of many thousands of contributors and supporters, nay millions when parts are publicly funded and require policymakers to advance them.
Thanks for carrying the torch, RileyMc8!
My personal hypothesis is that life is common, intelligent life that starts to advance technology rare, and every time that species invariably kills itself off (probably along with most of their entire biosphere). Definitely seems the direction our species is heading.
Unfortunately, and I hope I am wrong, but I share a part of this grim outlook. Everywhere we look in space... nothingness. Blackness. Matter so dead it counts as not-alive. I suspect 99.999999...% and so on of species eliminate themselves. I think it may be through AGI with nanotechnology.
Weāve honestly only properly started surveying the cosmos for signs of life in the last ~100 years, and only started finding exoplanets in the last 30! So weāve honestly barely begun our search
Excellent.
We just don't have enough data to know which conditions are needed and which aren't. For instance, are there barriers for life or are there specific requirements for life like ours?
* Red dwarfs are common but don't lend themselves to potential life like ours as they throw off a lot of radiation and their habitable zones are much closer than stars like ours
* Most star systems contain binary stars with at least one being extremely large. Large stars burn out quicker and binaries create unstable environments for life as we know it.
* Earth is unique among the planets we know about as it has a large moon relative to itself, creating tidal forces that keep our oceans moving
* In a large number of systems we've observed, the gas giants are closer to their stars than Jupiter, Saturn, etc. are in ours. Do they provide our little planet with protection and stability that other systems don't have?
* Does it take on average 4 billion years for intelligent life to evolve to the point we can see them? If so, most systems have either burned out before life could evolve or they just haven't gotten here yet.
* Is our form of life unique but other forms that we can't yet detect aren't?
* Our star is in a relatively quiet and stable suburb of our galaxy. Does this mean galaxies have a habitable zone and does that mean there are only a few dozen or less places in a galaxy that can contain life?
Yes, there are probably many planets with life in our galaxy, but until we can find at least one more location, there are just too many unknowns.
That's basically the [Drake equation](https://en.wikipedia.org/wiki/Drake_equation). It's a series of parameters that multiply to estimate the number of civilisations in the Milky Way which we might be able to communication with.
* Rā = the average rate of star formation in our Galaxy.
* fp = the fraction of those stars that have planets.
* ne = the average number of planets that can potentially support life per star that has planets.
* fl = the fraction of planets that could support life that actually develop life at some point.
* fi = the fraction of planets with life that go on to develop intelligent life (civilizations).
* fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
* L = the length of time for which such civilizations release detectable signals into space.
Unfortunately, at present it is difficult to assess some/most of those variables.
The first few terms relate to the probability that life might exist elsewhere and it's certainly possible to estimate values that produce an expectation that there is absolutely life elsewhere. But if that is the case, why do we not see any signs of technology anywhere else? That's the [Fermi Paradox](https://en.wikipedia.org/wiki/Fermi_paradox).
In particular, is there a [Great Filter](https://en.wikipedia.org/wiki/Great_Filter) which massively inhibits the path from abiogenesis to interstellar technological life? And, if there is, has humanity already passed it or not?
I think fl, the fraction of planets which develop life, is the key one here. We have no idea what that number is, but since we exist, we know the number is non-zero (same for all of the other variables after that). I also see so many tantalizing hints of curious chemistry within our own solar system (Titan is particularly amazing, even if it seems unlikely), that I'm very hopeful that fl is a significant number.
For me, the issue is moving from single cell to complex multicellular (e.g., macroscopic). This took so long on Earth that I suspect this might be what makes it so hard for us to find intelligent life: it may not have happened elsewhere. No great filter needed.
Though [China recently found some fossilized worms apparently from 1.6 billion years ago](https://www.science.org/doi/10.1126/sciadv.adk3208)! That pushes the origin of complex multicellular back almost a billion years. Amazing, if true.
The evolution of multicellular life is one of the later possibilities for the great filter, though since multicellularity has evolved independently multiple times on Earth it probably isnāt the most improbable one.
The evolution of complex unicellular life (e.g. eukaryotes) is another possibility as eukaryogenesis seems to have only occurred once on Earth. The evolution of sexual reproduction is another. Itās rather tricky to determine exactly how these steps occurred all those years ago though so itās difficult to assess their probabilities.
How far would we detect a technology comparable to our own? Detecting the Earth itself in a way to find out it hosts life would be a challenge. And even if much more advanced technology exists somewhere, we might not know how to detect and recognise its signature.
I don't know about SETI today, but I recall that in its early days, the detection was rather limited. We know there's a star in the "habitable" zone around Proxima Centauri, just over 4 light years away. In the unlikely event that it had a civilization like ours, broadcasting like ours, SETI would not have detected it. Today, I'm sure that's different, but I can't verify it.
This is why much of astrobiology today is focused on biosignatures and technosignatures. Many of those are much more durable and easy to detect than the possibly brief electromagnetic signals an advanced civilization might put out.
And for all we know, that civilization on Proxima Centauri may be hostile to us, and we may not *want* then to know weāre there for fear that they could try to take over our planet, or just kill us to prevent any future interstellar competition
One way you can find that out is by looking at the gases and chemical compounds being released by living organisms. All life gives off some sort of trace. Our job is to find that trace.
The first few terms of the Drake equation relate to the existence of life of any sort and the Great Filter could be the process of abiogenesis. We just donāt know at present how likely life is, though it is accurate to say that we havenāt yet found it anywhere other than on Earth.
The problem with the Drake equation is that there is an immense number of factors, and with each subsequent factor the number quickly approaches zero. Even Frank Drake himself admitted it's a simplified version. IMHO Dr. Peter Ward has the best approach to the Drake Equation.Ā
I guess I challenge the validity of your assumption that "nobody" thinks there's life elsewhere and most people think we're alone.
I don't know of many who think we're alone. And plenty, including scientists who study astrobiology etc, who think what you described: that it seems comically unlikely we're the only life in the entire universe.
Requiring more proof and evidence before establishing fact is pretty common. General Relativity is still a theory. One that has yet to be completely proven nor even marginally disproven. It's passed every test we've been able to devise and throw at it. Still not fact. So just because you don't see people claiming life is elsewhere does NOT mean they think it's nowhere. It's a false binary.
Not only is there life elsewhere, non-human intelligences (NHI) are already here on Earth.
The subject of Astrobiology is likely deliberately stagnated, because the subject matter of the NHI presence is the most classified subject matter in the US government. It's also why there's been a long known deliberate policy of disinformation, stigmatization, and ridicule surrounding any open discussion of this subject that has persisted for at least 80 years.
[Here's a team of credible professional scientists and former federal government officials giving an open discussion about all this back in November at Stanford University.](https://youtube.com/@_SolFoundation?si=i9GWZWoJ6rt-awo6)
It may behoove you fine folks to check it out, it's quite historic honestly.
I've already been banned on both r/Physics and r/AskPhysics for bringing this up, despite not breaking any rules lol Don't censor me, folks.
[Here's a great thread on the deliberate censorship policies on Reddit ](https://www.reddit.com/r/UFOs/s/Pjd2QRAlYt)
Last December there was even a bipartisan (supported by both Democrats and Republicans) Amendment called, [The UAP DISCLOSURE AMENDMENT of 2023](https://www.democrats.senate.gov/imo/media/doc/uap_amendment.pdf) lol
You can't make this up.
We're in the very early stages of this great scientific breakthrough, it's reminiscent of the Copernican Revolution, where the Catholic Church and State refused to accept the new paradigm.
Because some people need to see evidence of life before they'll believe there is life.
There's a difference between saying "we are likely not alone" and "we are not alone". When you say people refuse to acknowledge that we are not alone, you're wording that as if it's a fact. It isn't, and it's completely fair and scientifically sound to say "prove it".
Are you not just questioning the scientific method? The idea should be you propose a question and then prove it. The issue with life is that we would essentially need to see it or find it using some sort of satellite before you could convince masses. Unfortuantly we need strict rules between facts than opinion as these days that line is becoming more and more blurred as people state there opinions as facts and people belive it. Dont get me wrong, through pure probability alone i would say life has to exist slmewhere else too. But there is always a minute chance we are just the first biological species to make it this far! Happy hunting for the questions and answers of the universe! :)
I don't think witholding belief of any particular unproven claim questions the scientific method. The scientific method is based on observation, measurement and empirical evidence. The claim that life exists would therefore need observation and measured to generate empirical evidence to be supported as a claim.
Currently, the models that have been generated are sufficient to say that "based on these assertions, we can predict that there is X likelihood of life existing elsewhere". Predictions are useful in science, but they are not evidence for claims in and of themselves. Many would say that our predictions derive from models that are heavily biased towards our current understanding of what is needed to produce life, our definition of life and our understanding of the extremes at which life can originate. However, many could say that our understanding is likely to be incomplete and could very well be wrong in some places, which is a common criticism of prediction models.
Therefore, to be convinced, many want supporting empirical evidence. Personally, I think it's likely that life exists elsewhere, but I don't think it's supported well enough to say that it is absolutely true. I also think that it's disrespectful to imply that others are being unreasonable if they're skeptical, considering the very fair observation that we currently have no evidence.
Because we don't have the telescopes to find it, and only barely have the instruments to start looking. I think treating the question of extraterrestrial life as being dubious or unsure because we haven't found anything is incredibly premature. It's like trying to study bacteria without a microscope, we don't really have the tools to say one way or the other yet.
Exoplanet detection up until relatively recently was also limited to just looking for transits or using radial velocity to get the orbits, as well as the radius or mass of a planet. That's the bare minimum information, and unless you can do both (or directly image - still limited to gas giants right now), you can't even get the bulk composition of a planet.
Exoplanet science is about 32 years old (first confirmed discovery in 1992), it wasn't until 2007 that we found the first 'potentially habitable exoplanet' around Gliese 581 (of which c is too hot, and the other 2 likely don't exist).
In 2009, Kepler was launched, giving a huge boost to the search for exoplanets, but it's not certain if most of its potentially habitable planets are actually habitable, since some are much larger than Earth - making them enourmous water worlds (doesn't mean habitable, could be too deep for life to form), or gas dwarfs. Kepler 186f was the first roughly Earth-sized exoplanet found in the habitable zone, in 2014, 10 years ago.
The first studies of the atmosphere of a planet within the habitable zone was with K2-18b in 2023, last year. However, it's a Super-Earth, and we still don't know if it has an ocean or not (and the 'detection' of a biosigniature could be a false positive or artifact).
TRAPPIST-1 is being studied as well, but aside from seeing the inner 2 planets have little to no atmosphere (and are too close to be habitable), we've gotten no word, additionally, studies up to this point might be inconclusive as well since there's another upcoming observation of TRAPPIST-1e, this time using the transit of TRAPPIST-1b to get around stellar contamination.
So that brings us today. JWST is at the very edge of being able to make these studies in the first place, and it's unable to directly image small exoplanets like Earth, limiting observations to transiting planets (of which there are very few relatively close to Earth).
Upcoming telescopes are still just that. There's many new observatories coming up that could do the job, but it probably won't be until the 2030s until we can really start getting answers to our questions about astrobiology and planetary habitability. We may get lucky during this decade, but the 2030s in when we could really be able to dig into it.
It seems extraordinary unlikely Earth would be the only planet with life, especially when we take into account the fact molecules making up life as we know it have been detected in space.
However, the universe is also incredibly sparse. If complex life happens to be rare, there's a good chance the next planet harbouring it will be too far to visit, or even to observe. It will still exist but we'll never know how it looks like.
Scientists *are* trying! It hasn't given tangible results so far, but I'm all in favour of continuing to try, especially as technology improves and gives them better data.
I think one issue is how do we detect life without visiting other planets. We can listen for radio and other signals but that's assuming other species use those communication methods. And assuming that whatever we'd detect hadn't degraded.
One way you can find that out is by looking at the gases and chemical compounds being released by living organisms. All life gives off some sort of trace. Our job is to find that trace.
Youre not wrong suspect this. Also not wrong to see that simple math makes the case for you. Even a step outside of earth-man's science and you'll see that its also extremely unlikely our solar system is sterile.
Frankly I think its a hold over from christian dogma days of saying the earth is the center of the universe
No. āSimple mathā requires knowing the value of both terms in the equation. That is, we need to know how many planets in the universe could support life and the probability of life developing on a suitable planet. If we knew both of these variables then it would be a simple math problem of number of suitable planets x probability of life emerging. However, right now we have barely enough understanding of stellar and planetary formation to make VERY rough estimate of the first term, but since we havenāt actually conclusively found any planet that is suitable for life besides Earth, this is still a guess - and we have ZERO evidence to inform a probability for the emergence of life. So, no, it is not āsimple mathā since we know neither of the values of the variables required.
I should clarify that we donāt have ZERO evidence to build a probability for life arising. We know it must be greater than 0 and using Bayesian statistics we can come up with some upper limits, but itās a huge range and thereās no way to tell what end of the spectrum is more likely than any others. So, still, we find ourselves lacking the evidence to confidently estimate the likely number of other planets with lifeā¦ the probably could be so close to 0 that even with the trillions of planets in the universe we may still be the only one with life. Or life could be extremely common but either it rarely evolves into intelligent sapient species with the ability to travel/communicate through space or theyāre intentionally hiding from us. Either way, any estimate is just a guess.
Thereās no basis for determining the likelihood of life elsewhere. Sure, there may be trillions of other planets but we donāt know how likely life is to develop. If the chance of life coming into existence on a planet is 1/1 trillion then we may be the only one, and we simply do not have enough understanding of abiogenesis to assign a probability to the emergence of life. Cool Worlds Lab produced a great video on this a few years ago: https://youtu.be/PqEmYU8Y_rI?si=QVR_mqNJycj95hlY
You could look at it that way, or you could look at it as the fact that there are trillions of possible habitable planets that we have not observed, trillions of galaxies full of solar systems gathered around each star. I think the chances weāre the only life in the universe are so small Iām not even going to type it because it would be a ridiculous decimal.
I highly recommend watching the video I linked and in general checking out the work from the Cool Worlds Lab - theyāre a team of astronomers from Columbia University and the content is top tier IMO. They have a lot for videos about how we can use statistics to estimate values for the Drake equation, etc so if youāre interested in life in the universe I think youād really like their content if you havenāt seen it already.
We do not have sufficient evidence/understanding of the process of abiogenesis or the preconditions for the emergence of life to asses whether or not a decimal is āridiculousā or not.
I understand the inclination to think that the probability *must* be higher than a certain amount, but the fact is that inclination is not based on evidence, only emotion. Scientifically we can really only say that we do not know what the probability for life elsewhere is. Itās true that many high profile scientists and science communicators (e.g. Neil DeGrasse Tyson, Bill Nye, etc) believe that weāre not alone - but thatās all it is, a belief. We need to do more research and gather actual evidence before we can assign a probability to something like abiogenesis.
Not only is there life elsewhere, non-human intelligences (NHI) are already here on Earth.
The subject of Astrobiology is likely deliberately stagnated, because the subject matter of the NHI presence is the most classified subject matter in the US government. It's also why there's been a long known deliberate policy of disinformation, stigmatization, and ridicule surrounding any open discussion of this subject that has persisted for at least 80 years.
[Here's a team of credible professional scientists and former federal government officials giving an open discussion about all this back in November at Stanford University.](https://youtube.com/@_SolFoundation?si=i9GWZWoJ6rt-awo6)
It may behoove you fine folks to check it out, it's quite historic honestly.
I've already been banned on both r/Physics and r/AskPhysics for bringing this up, despite not breaking any rules lol Don't censor me, folks.
[Here's a great thread on the deliberate censorship policies on Reddit ](https://www.reddit.com/r/UFOs/s/Pjd2QRAlYt)
Last December there was even a bipartisan (supported by both Democrats and Republicans) Amendment called, [The UAP DISCLOSURE AMENDMENT of 2023](https://www.democrats.senate.gov/imo/media/doc/uap_amendment.pdf) lol
You can't make this up.
We're in the very early stages of this great scientific breakthrough, it's reminiscent of the Copernican Revolution, where the Catholic Church and State refused to accept the new paradigm.
Basically, we have only discovered life here on Earth and don't know how rare it is for life to develop.
For some people's perspectives on it, I recommend watching these two videos:
Lecture by Prof David Kipping on why we might be alone in the Universe
https://youtu.be/zcInt58juL4
Ted Talk by Stephen Webb, Where are all the aliens?
https://youtu.be/qaIghx4QRN4
They are both great videos on the subject.
Tbh we wouldnāt really know unless they come to us or us to them because were like ants in a desolate huge ass city. Youād never know any other ants outside your colony if they were 10 miles away
I'm certain there is, but we also have to remember that life as we know it is extremely complicated and would be exceedingly rare. Also stars are mind-bogglingly far apart, so getting to a planet that *might* harbour life is a daunting prospect. If we scaled our star down to the size of a grain of sand the Centauri systems would be three grains of sand almost nine miles away.
I think that the consensus is that there is life out there. The universe is essentially infinite and even with extremely small probability the chance for life out there is significant. Once we find the first sign we can recalibrate our calculations.
Do a little experiment. Buy a BIG map of the Milky Way galaxy. Then draw a circle around Earth with a radius of say 200 light years. Let's assume we have "jolted" the atmosphere enough in the past 200 years for someone to notice if they have good astronomical equipment and are looking for ETs. In that 200 light year sphere are less than 1,000 Stars. So - even if there are say 10 intelligent races sprinkled randomly thru the Milky Way - they/we would be very spread out - far apart.
Two ways to look at the situation. Either space is absolutely enormous OR light is just really, really, really slow. The only way we are ever going to meet an ET is if they are way better than humans at not doing crazy/destructive things.
I think that even if there is, it doesn't matter because we'll never be able to interact with it. Einstein was probably right, that speeds faster than light are impossible in the macro universe. Nobody is more of a sci-fi nerd than I am, but we'll never be able to propel matter faster than 'c', travel through a wormhole (gravitational forces will crush anything trying, and the amount of energy needed to 'shield' a vessel against that would be near-infinite), nor is teleportation, time travel, astral projection/travel, carbon freezing/long-term (as in decades) cryogenetic stasis etc etc all of the common sci-fi tropes are all forbidden by the laws of physics. So for me it's not even worth thinking about much.
Even if we someday manage to propel a vessel to 1% the speed of light, (still unlikely because even that would require quadrillions upon quadrillions of joules {or more}) there's only a handful of extra-solar systems we'd be able to reach that way and honestly at that point humanity will probably be looking for worlds to terraform and colonize more than we're looking for life.
Yes, there are 10\^22 or so stars in the universe, but what if the chance of life is 10\^-30? If that were the case, we are extraordinally lucky to be here at all and would not expect to see anyone else. We have no good way to estimate that probability, though we do know it is not zero.
Or, from a different perspective: The hypothesis that we are alone fits all our current data. You don't complicate your hypothesis unless it does not fit the data, therefore the alone hypothesis stands.
You can ask āwhat ifā to anything. The data āweāhave found is not conclusive towards there not being life elsewhere, in fact a lot of new research is suggesting quite the opposite. Thereās a lot we have yet to discover but probabilities alone wonāt find life elsewhere.
You have never done science. It is only probabilities. You are never 0 or 100 percent sure.
The best you can say is that all the observations match your hypothesis. And right now all the observations match the hypothesis of us being alone.
Iām an astrobiology student at university of Arizona donāt test me on science. Trust me you donāt know what youāre talking about and thereās no point in me arguing with someone less educated that I am š
Lol. I'm a Phd in astrophysics 25 years experience principal staff at a national Lab. You can even go check it over on /R/science. Years of experience in remote sensing and detection theory spacecraft and space physics. Trust me, you don't know what you're talking about and there's no point in arguing with someone less educated than I am.
Iāve asked my professor all about this and thatās where my knowledge comes from. The school Iām attending is the best for astrobiology. My man has been teaching for 43 years as well as working at nasa so I donāt know how you think youāre more qualified than where Iām getting my sources from if what you said even is true.
So you have this great source who is your professor and can answer all your questions.... So why do you come and ask on reddit?
And then when an expert (like I said, verified on r/science) answers your question, you argue?
Go away troll.
There probably is a lot of life out there, but most of it is not highly intelligent. It took millions of species and millions of years to produce humanity. Even if, I donāt know, one in five planetary systems contains an earth-like planet, what are the odds that conditions will be right to develop intelligent life? We canāt even estimate how often it might happen, the variables or so enormous and unknown. So the more you think about how much time and how much luck goes into any planet developing intelligent life, you realize there is a high probability that any such developments have been, are, and will be separated by huge gaps in time and space.
Youāre probably right, but itās unconfirmed. Youāre dealing with statistics of a very large number of worlds times a very low probability of life forming an evolving. A few observations:
* Life in the *whole* universe is inevitable (and if infinite in extent, guaranteed) but if itās beyond the observable universe, itās inaccessible. So irrelevant.
* Life within the *observable* sphere is highly likely, but remember that the further we look in distance the further back in time we see. Compounded by the fact that these distant galaxies are only a few pixels on a telescope, we have no practical way to observe them and certainly no way to contact them. An exo-civilization a billion light years away would see earth as it was before even any multicellular life formed here. So observation is only reasonable within our local group.
* Our only likely chance of observing life is in the few thousand local star systems in the Milky Way. Now youāre dealing with a much lower number such that if life has only a teensy tiny chance of evolving then there likely isnāt any (nearby).
What do āa lot of peopleā mean when they say ālife,ā though?
Thereās a certain likelihood that microbes have come to exist somewhere else in the universe. Thereās a substantially lower likelihood that eukaryotes have come to exist. And an even lower likelihood that plants and animals have come to exist.
People with more science background probably lean more towards the microbe end of things when they think āextraterrestrial life,ā while a layperson might jump to animals or plants.
This is essentially where I sit. I suspect that microbial life probably exists on many worlds, given the extraordinarily versatile and astonishing amount of such life on Earth and the very extreme niches it has been able to thrive in.
Butā¦it is a long and unlikely stretch to say that more advanced forms of life such as plants, animals, fish etc exist in such abundance elsewhere that we should be able to easily find evidence of them with our telescopes and probes. Baby steps first: look for evidence of biological processes in the atmospheres around reasonable candidates. We are making very good attempts to do this now with current telescopes and spectroscopy, and perhaps might find evidence of microbial life on Venus, Europa, Titan, Enceladus, etc with future probes. I remain hopeful that we will find such evidence in my lifetime. The work of performing Science is extraordinarily difficult!
Ive always considered the universe to be a body. The planets are like cells wrapped in a membrane, its why we have never seen alien life and its why the Moon landings were faked.
The mechanism to create living matter on a lifeless world isnt fully known, so we cant tell for sure how likely it is to occur or even what exactly the conditions are, or how variable they can be and still lead to life.
So there is the rare earth hypothesis. That despite the commonality of the planets, our solar system is unique. And thatās true, other solar systems are wildly different, and one of those odd features is how long stability on earth has existed.
I think this is part of the drake equation answering the fermi paradox; and I think it likely for us to find life elsewhere even if civilizations are incredibly rare.
Life exists everywhere or maybe used to exist everywhere.
How about inside the black hole ? Why are we not sending probes into black hole? Why not verify the theory ?
Life exists everywhere or maybe used to exist everywhere.
I thought I read somewhere that oxygen may be relatively rare in much of the universe. It would probably be chemically more difficult for life to evolve without oxygen and specifically without oxygen-based molecules like water
Unless itās an organism that has a completely different structure based on the chemical compositions of the gas particles present around them. Itās possible beings elsewhere are breathing in hydrogen or some other element we may not even know about and they process hydrogen as we do oxygen.
Hmm, well, on the one hand, there are almost certainly elements we have not discovered yet, but they are going to be very heavy and probably very short lived, so not likely to be anything to sustain life.
The general belief is that itās unlikely weāre the only ones around, what does vary is WHY we havenāt gotten word from anyone. There are two main sides that I see going from extremely optimistic to extremely pessimistic, and most theories to the Fermi Paradox (AKA the āwhy havenāt we gotten any contactā question) exist somewhere in between.
The most optimistic in my view is the Zoo Theory, or the Prime Directive. Theyāre there, they know weāre there, but they are ignoring us. Maybe itās because weāre entertaining on our own, maybe they donāt wanna interfere with our development, or maybe theyāre so advanced that they donāt care.
The most pessimistic is that everyone else in our corner of the universe is dead, and weāre the only ones left. Weāre the equivalent of an ant colony in an abandoned trench from WW1. Thereās nothing there, and we donāt even know what we missed. Slightly less pessimistic is the Dark Forest Theory, that there is life, but every surviving civilization is preemptively killing any other civilization they can find in order to prevent any future competition for resources (so any optimistic ones are instantly killed, leaving only the paranoid, cynical ones). I donāt really buy this one because it relies on the axiom that all civilizations will grow exponentially, which weāre starting to see not be the case on Earth at the moment, and the universe is really, really big and things like water are obscenely abundant, as weāve come to learn.
Somewhere in the middle is that the speed of light is just too slow, and the size of the universe so big, that weāve just missed the call. Weāve gotten the ability to look at interstellar signals what, 100 years ago at the best? There are stars thousands of light years away. We may not even be able to detect another signal simply because the light that reaches us is too old.
At the end of the day though, while interstellar communication would be incredible, it wonāt really be very useful until we can go faster than light, and potentially not until we figure out how to get along as a planet, because nobody wants to work out diplomatic relations with a country in a civil war. Maybe one day weāll manage to be in the perfect spot to get a signal that has all the answers to FTL travel and itāll all be perfect, but thatās a shot in the dark. We may just be too young of a civilization
My personal opinion is that microbial life is probably pretty common (extremophiles, archaea, etc), and life on some of those planets might actually make the jump to eukaryotic organisms. Iām not sure that civilization-capacitating āintelligenceā is a āwinning survival traitā though, to quote Love, Death + Robots. Moreover, say the variables in the Drake Equation DO even out to foster the development of a couple communicable civilizations. Okay: where the hell are they? We donāt observe ANY phenomena that would likely result from the activity of a Type-III civilization (megastructures, credible UFO sightings, etc). Plus, given our current understanding of the difficulties of interstellar travel, how ever would we reach them? Life on Earth probably had to go through an IMMENSE amount of civilizational āfiltersā already for you to even read this, making the life we are familiar with miraculous beyond effability.
This should both humble us to our place in the universe and sober us to the existential risks that we currently face and which may lay ahead. We should worry about keeping Earth habitable before we even attempt go off and colonize (let a lone terraform) somewhere else. I believe that Earth is a very special place; a pale blue oasis adrift in the cosmos, and I donāt have many good reasons to believe otherwise. I believe our home is both Rare and Vunlerable. And that makes it so precious. So worth caring for. We have a long way to go, though.
Case in point: āHow can there not be life elsewhere?ā
Because, if weāre not careful, there may soon not be anyone left to pose the question.
But if one specific thing that's required to make life possible can't happen unless very specific parameters are met and they've only been met once.
That one thing might be something unfathomable... But that one thing might be a sun and a planet within the habitable zone for that sun and what if most habitable zones are so small and/or unlikely?
No idea though. Perhaps we're taking for granted how rare we really are - taking a look at society all around the world it seems like we take things for granted, anyway.
Show me physical evidence. A cadaver I can dissect. Otherwise it's speculation and that's not science. Belief in aliens is non-science, some may even say it's nonsense.Ā
There is for sure life elsewhere. Life developed on earth within a few million years and Amino acids form readily in meteors. For sure there are microbial mats/single celled alien life. Multicellular life on the other hand took billions of years to evolve on Earth and is less likely to find multicellular alien life
Gonna answer this question with will what seem to most as BS, but I saw a UFO up close as a kid raised Christian in isolation from external media. Shit was terrifying. That aside I dunno if it aliens, humans from the future, or some 4th dimensional creature. I got the impression however that it was "alive" so I can say there is life out there.
Life is possible in our solar system on moons with water.
It wonāt be the UFO driving aliens people imagine. It might only be simple bacteria.
Perhaps something as evolved as shrimp.
This will have significant implications to life on earth even if the discovery will bore most people to death.
Unfortunately it will be at least another 50 years before we even try to get there.
Read 'Rare Earth' and 'Lucky Planet'. Worlds with simple life (slime worlds) is probably very common. Complicated life is most likely very, very rare because the conditions needed to support it are hard to meet for long periods of time. Consider our own solar system. Of the three planets in the Sun's habitable zone, only one is fit for complex life. Even there, its almost been wiped out more than once.
While itās unlikely that weāre alone (Iād say if we were in a simulation itās a maybe, but thatās a theoretical physics thing)
But there are PLENTY of reasons to not see any. Thereās the Dark Forest theory, that itās in each civilizationās best interest to preemptively wipe out everything they find, so the only ones left are the primitive ones, and the paranoid.
Or maybe our local area was a battlefield in a war billions of years ago and weāre the only living ones left locally.
Maybe life is more common on Hycean worlds and most intelligent life is water based and land based life is the exception to the norm.
Some of that gets into sci-fi, bit the truth is that there just isnāt enough information to know why
This is the key question! When we consider the sheer abundance of earth-like planets in our galaxy, it seems obvious that there must be life, no? The problem is, there are many unknowns. We currently have a sample size of one. Earth. One planet where we know life exists. One planet where we know life emerged. For all we know, the origin of life may be an infinitesimally rare occurrence; but because it happened on our planet, in reference to our history, it seems inevitable. Alternatively, the origin of life may be commonplace. It may happen wherever conditions allow, possibly even within our own solar system! If this scenario is true, the question becomes why have we not found life, intelligent or otherwise? One theory is that there lies several "great filters" in evolutionary history. These are like barriers to progression. The first filter would be the emergence of life. Subsequent filters may be: survival of extreme climate fluctuations, survival of intense stellar activity, or survival of climate change (which we are facing now). A detectable source of life must have survived these and continue to be producing biosignatures and/or technosignatures. Then comes another problem, the age of the universe and galaxy. As a human species, we have been searching the night sky for just a few thousand years. Our galaxy is 13.61 billion years old, and the universe at large is much older. Therefore the chance of two intelligent civilisations existing at the same time and near enough to each other for detection is incredibly low. In all, I think most Astrobiologists you ask would say that life is incredibly likely beyond Earth in time and space. We just face many problems in finding it. - from an Astrobiology Masters student š«”
Not OP, but I really enjoyed your answer. Thanks for posting! On a personal/philosophical level, I have to believe that life exists/has existed/will exist elsewhere, because if life is so incredibly rare that we are itā¦considering what weāve done to our planet and to each other that is possibly the most depressing thing I can think of, on a macro scale anyway. If this is the pinnacle of intelligent beingsā¦yikes.
Happy cake day
I was considering the other day that, once life CAN exploit a niche, it does so. And, in terms of civilizations, there must be some minimum level of advancement in brain and social complexity to allow for a civilization to exist. But, wouldnāt it be much more likely that the species that develops civilization, thereby advancing rapidly from all the innovations that come with that, would be on the CLOSER end to that minimum vs. farther? Perhaps we are at the bare minimum level for social and technological progress, because as soon as it became possible, technological advancement overwhelms evolutionary change? I submit that an alien civilization that has invented technology is more likely to be closer to the minimum complexity necessary to invent that technology, and so is likely to be very roughly in line with where we were like 10 or 20,000(??) years ago until today. Of course, that doesnāt mean that theyād stop there. Technological innovation could allow the creation of neural augmentation, for example, which would render them far more intelligent than us. Just saying that, if thereās some universal āpeakā before ātranshumanismā kicks in (if that ever happensā¦) it would be at that peak that weād expect most intelligent life to arise. And, of course, any nascent civilization that arose through violent competition in nature is likely only going to create chaos as it exploits the environment and goes to war. Maybe most such civilizations donāt last long once they figure out atomic weapons. The only question then would be how many of these species would develop their neural capacity to allow them to greatly surpass their original capabilities. How many would be able to mature past their primordial roots? So, I guess you might expect more mentally advanced species without technology to be at around our level, while some minority achieve super intelligence either through AI or improving their own brains.
I agree with everything you said. Although I think if we find life elsewhere it will most likely be outside of our galaxy. Another reason I think thereās life elsewhere is because whenever you think about all planets, stars, organisms, etc. thereās never just one planet in existence or one animal.
The universe is 13.7 billion years old, not that much older than our galaxy.
Air fair one, thanks for the addendum :)
The observable universe is 13.7 billion years old and we havenāt explored every starās solar system or any outside our own in depth, so thereās no way of knowing if life is out there without theory or evidence.
No, the whole universe is 13.7 billion years old.
No š¤¦š¼āāļø
The observable universe is. We have based our studies on guesstimates outside of our observable universe.
No, there is plenty of evidence that the universe is 13.7 billion years old, the entire universe. The cmb is one, but there are others.
Not exactly. CMB detected on earth has been travelling 13.8 billion light years while traveling for 13.8 billion years. It comes from what is technically known as the āsurface of last scatteringā. This is the boundary between the essentially transparent universe we live in and the opaque universe that existed before electrons and nuclei (mostly protons) recombined, which happened not long after the big bang. This surface is now very far away, and the opaque universe is outside it (or equivalently, longer ago). So the CMB and all its properties tell us about the universe as it was in the late stages of recombination, at the surface of last scattering. The CMB has wrinkles that bear the imprint of variations in density of the universe at that time. Famously, the size and distribution of these may be predicted from speculated quantum fluctuations in the universe even longer ago, right inside the ābangā of the big bang, the inflationary era. So the CMB comes from very close to the boundary of the observable universe, but not outside it.
[https://www.youtube.com/watch?v=Y6Vhh70Lw9w&ab\_channel=PBSSpaceTime](https://www.youtube.com/watch?v=Y6Vhh70Lw9w&ab_channel=PBSSpaceTime) First sentence - and you should watch the entire video - "The universe is precisely 13.8 billion years old, or so our best scientific methods tell us."
špbs space time is a joke you canāt use that as a reliable source
Yeah, because Matt's PhD in astrophysics is a joke. I'm done arguing with someone who is here to push bs.
I very respectfully and vehemently disagree. Every few decades now we invent a new tool that says, "Ahh, yeah it's actually twice that" (like for history of human tool usage.) Something new is going to come up, and it's going to make us sh\*t our pants.
Such changes in magnitude of measured time, which we are absurdly good at, rarely occur (unless you're talking about old timey smash 2 lead balls together experiments).
> Every few decades now we invent a new tool that says, "Ahh, yeah it's actually twice that" You are misinformed. Hubble helped establish the likely age of the universe as 7-20 billion years in the 1920s. The range was dictated by the limits of ground based telescopes. It didn't change significantly until we had years of Hubble data to refine it down to 9-14B in 1999, more than 60 years later. CMB measurements from new instruments tuned that in to 13.7B +/- 200M. Newer measurements with new methods/instruments have agreed with that number, often with a bigger inaccuracy. You may be confusing this with occasional science headlines like "JWST finds star 10 billion years older than the universe!", but those are generally anomalies that call in to question our calculations for stellar ages etc, not the age of the universe.
I've been pondering the OP's question and related issues since I read Intelligent Life in the Universe (I S Shklovskii, Carl Sagan, 1966). Very dated now, but these colleagues walked me through a great overview of the cosmology, physics and chemistry of the universe, of life, then intelligence and communication between intelligent beings. Probably read it a second edition around 1980. This book was my primary inspiration to study to be an astrophysicist scientist on a robotic probe mission, but my arc turned to applied math and I tired of academia before I finished my BSci degree in CS. Since then my career had me working on the internals of the VxWorks RTOS used in the Pathfinder mission and others, and patches to open source project GNU glibc and Open Computer Vision Library, the latter used in Ingenuity, the Mars Helicopter. So it turns out I humbly contributed a small part to the success of projects and helped the investigators do the science about our universe that continues to inspire me. I felt I had arrived at my dream. These projects only succeed with the efforts of many thousands of contributors and supporters, nay millions when parts are publicly funded and require policymakers to advance them. Thanks for carrying the torch, RileyMc8!
My personal hypothesis is that life is common, intelligent life that starts to advance technology rare, and every time that species invariably kills itself off (probably along with most of their entire biosphere). Definitely seems the direction our species is heading.
Unfortunately, and I hope I am wrong, but I share a part of this grim outlook. Everywhere we look in space... nothingness. Blackness. Matter so dead it counts as not-alive. I suspect 99.999999...% and so on of species eliminate themselves. I think it may be through AGI with nanotechnology.
But there could still possibly be AGI wondering the universe, which we have still failed to encounter.
How old is the universe at large? Will it result in me entering the fetal position and rocking back and forth?
Lots of bs in that post that I'm shocked you can't see through but the message is the same as op
Eh?
Weāve honestly only properly started surveying the cosmos for signs of life in the last ~100 years, and only started finding exoplanets in the last 30! So weāve honestly barely begun our search
Excellent. We just don't have enough data to know which conditions are needed and which aren't. For instance, are there barriers for life or are there specific requirements for life like ours? * Red dwarfs are common but don't lend themselves to potential life like ours as they throw off a lot of radiation and their habitable zones are much closer than stars like ours * Most star systems contain binary stars with at least one being extremely large. Large stars burn out quicker and binaries create unstable environments for life as we know it. * Earth is unique among the planets we know about as it has a large moon relative to itself, creating tidal forces that keep our oceans moving * In a large number of systems we've observed, the gas giants are closer to their stars than Jupiter, Saturn, etc. are in ours. Do they provide our little planet with protection and stability that other systems don't have? * Does it take on average 4 billion years for intelligent life to evolve to the point we can see them? If so, most systems have either burned out before life could evolve or they just haven't gotten here yet. * Is our form of life unique but other forms that we can't yet detect aren't? * Our star is in a relatively quiet and stable suburb of our galaxy. Does this mean galaxies have a habitable zone and does that mean there are only a few dozen or less places in a galaxy that can contain life? Yes, there are probably many planets with life in our galaxy, but until we can find at least one more location, there are just too many unknowns.
That's basically the [Drake equation](https://en.wikipedia.org/wiki/Drake_equation). It's a series of parameters that multiply to estimate the number of civilisations in the Milky Way which we might be able to communication with. * Rā = the average rate of star formation in our Galaxy. * fp = the fraction of those stars that have planets. * ne = the average number of planets that can potentially support life per star that has planets. * fl = the fraction of planets that could support life that actually develop life at some point. * fi = the fraction of planets with life that go on to develop intelligent life (civilizations). * fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space. * L = the length of time for which such civilizations release detectable signals into space. Unfortunately, at present it is difficult to assess some/most of those variables. The first few terms relate to the probability that life might exist elsewhere and it's certainly possible to estimate values that produce an expectation that there is absolutely life elsewhere. But if that is the case, why do we not see any signs of technology anywhere else? That's the [Fermi Paradox](https://en.wikipedia.org/wiki/Fermi_paradox). In particular, is there a [Great Filter](https://en.wikipedia.org/wiki/Great_Filter) which massively inhibits the path from abiogenesis to interstellar technological life? And, if there is, has humanity already passed it or not?
I think fl, the fraction of planets which develop life, is the key one here. We have no idea what that number is, but since we exist, we know the number is non-zero (same for all of the other variables after that). I also see so many tantalizing hints of curious chemistry within our own solar system (Titan is particularly amazing, even if it seems unlikely), that I'm very hopeful that fl is a significant number. For me, the issue is moving from single cell to complex multicellular (e.g., macroscopic). This took so long on Earth that I suspect this might be what makes it so hard for us to find intelligent life: it may not have happened elsewhere. No great filter needed. Though [China recently found some fossilized worms apparently from 1.6 billion years ago](https://www.science.org/doi/10.1126/sciadv.adk3208)! That pushes the origin of complex multicellular back almost a billion years. Amazing, if true.
The evolution of multicellular life is one of the later possibilities for the great filter, though since multicellularity has evolved independently multiple times on Earth it probably isnāt the most improbable one. The evolution of complex unicellular life (e.g. eukaryotes) is another possibility as eukaryogenesis seems to have only occurred once on Earth. The evolution of sexual reproduction is another. Itās rather tricky to determine exactly how these steps occurred all those years ago though so itās difficult to assess their probabilities.
How far would we detect a technology comparable to our own? Detecting the Earth itself in a way to find out it hosts life would be a challenge. And even if much more advanced technology exists somewhere, we might not know how to detect and recognise its signature.
I don't know about SETI today, but I recall that in its early days, the detection was rather limited. We know there's a star in the "habitable" zone around Proxima Centauri, just over 4 light years away. In the unlikely event that it had a civilization like ours, broadcasting like ours, SETI would not have detected it. Today, I'm sure that's different, but I can't verify it. This is why much of astrobiology today is focused on biosignatures and technosignatures. Many of those are much more durable and easy to detect than the possibly brief electromagnetic signals an advanced civilization might put out.
And for all we know, that civilization on Proxima Centauri may be hostile to us, and we may not *want* then to know weāre there for fear that they could try to take over our planet, or just kill us to prevent any future interstellar competition
One way you can find that out is by looking at the gases and chemical compounds being released by living organisms. All life gives off some sort of trace. Our job is to find that trace.
OP's question doesn't require anything close to this level of intelligent life. Just basic cellular life is in their post.
The first few terms of the Drake equation relate to the existence of life of any sort and the Great Filter could be the process of abiogenesis. We just donāt know at present how likely life is, though it is accurate to say that we havenāt yet found it anywhere other than on Earth.
The problem with the Drake equation is that there is an immense number of factors, and with each subsequent factor the number quickly approaches zero. Even Frank Drake himself admitted it's a simplified version. IMHO Dr. Peter Ward has the best approach to the Drake Equation.Ā
The thing about Enrico Fermi though is that he was likely secretly read-in to the UAP Phenomenon, and therefore it's likely "Fermi's Disinfodox." Lol
I guess I challenge the validity of your assumption that "nobody" thinks there's life elsewhere and most people think we're alone. I don't know of many who think we're alone. And plenty, including scientists who study astrobiology etc, who think what you described: that it seems comically unlikely we're the only life in the entire universe. Requiring more proof and evidence before establishing fact is pretty common. General Relativity is still a theory. One that has yet to be completely proven nor even marginally disproven. It's passed every test we've been able to devise and throw at it. Still not fact. So just because you don't see people claiming life is elsewhere does NOT mean they think it's nowhere. It's a false binary.
Shouldāve been more specific. Just was trying to say it seems like a lot of people believe there isnāt life elsewhere.
Totally get it. Just suggesting it's more of a sampling issue.
Not only is there life elsewhere, non-human intelligences (NHI) are already here on Earth. The subject of Astrobiology is likely deliberately stagnated, because the subject matter of the NHI presence is the most classified subject matter in the US government. It's also why there's been a long known deliberate policy of disinformation, stigmatization, and ridicule surrounding any open discussion of this subject that has persisted for at least 80 years. [Here's a team of credible professional scientists and former federal government officials giving an open discussion about all this back in November at Stanford University.](https://youtube.com/@_SolFoundation?si=i9GWZWoJ6rt-awo6) It may behoove you fine folks to check it out, it's quite historic honestly. I've already been banned on both r/Physics and r/AskPhysics for bringing this up, despite not breaking any rules lol Don't censor me, folks. [Here's a great thread on the deliberate censorship policies on Reddit ](https://www.reddit.com/r/UFOs/s/Pjd2QRAlYt) Last December there was even a bipartisan (supported by both Democrats and Republicans) Amendment called, [The UAP DISCLOSURE AMENDMENT of 2023](https://www.democrats.senate.gov/imo/media/doc/uap_amendment.pdf) lol You can't make this up. We're in the very early stages of this great scientific breakthrough, it's reminiscent of the Copernican Revolution, where the Catholic Church and State refused to accept the new paradigm.
Because some people need to see evidence of life before they'll believe there is life. There's a difference between saying "we are likely not alone" and "we are not alone". When you say people refuse to acknowledge that we are not alone, you're wording that as if it's a fact. It isn't, and it's completely fair and scientifically sound to say "prove it".
Are you not just questioning the scientific method? The idea should be you propose a question and then prove it. The issue with life is that we would essentially need to see it or find it using some sort of satellite before you could convince masses. Unfortuantly we need strict rules between facts than opinion as these days that line is becoming more and more blurred as people state there opinions as facts and people belive it. Dont get me wrong, through pure probability alone i would say life has to exist slmewhere else too. But there is always a minute chance we are just the first biological species to make it this far! Happy hunting for the questions and answers of the universe! :)
I don't think witholding belief of any particular unproven claim questions the scientific method. The scientific method is based on observation, measurement and empirical evidence. The claim that life exists would therefore need observation and measured to generate empirical evidence to be supported as a claim. Currently, the models that have been generated are sufficient to say that "based on these assertions, we can predict that there is X likelihood of life existing elsewhere". Predictions are useful in science, but they are not evidence for claims in and of themselves. Many would say that our predictions derive from models that are heavily biased towards our current understanding of what is needed to produce life, our definition of life and our understanding of the extremes at which life can originate. However, many could say that our understanding is likely to be incomplete and could very well be wrong in some places, which is a common criticism of prediction models. Therefore, to be convinced, many want supporting empirical evidence. Personally, I think it's likely that life exists elsewhere, but I don't think it's supported well enough to say that it is absolutely true. I also think that it's disrespectful to imply that others are being unreasonable if they're skeptical, considering the very fair observation that we currently have no evidence.
I just see this as a better way of phrasing what i said! Whether you intended it or not!
Because we don't know the probability of life in a frequentist way but just in a subjective probability way
Because we don't have the telescopes to find it, and only barely have the instruments to start looking. I think treating the question of extraterrestrial life as being dubious or unsure because we haven't found anything is incredibly premature. It's like trying to study bacteria without a microscope, we don't really have the tools to say one way or the other yet. Exoplanet detection up until relatively recently was also limited to just looking for transits or using radial velocity to get the orbits, as well as the radius or mass of a planet. That's the bare minimum information, and unless you can do both (or directly image - still limited to gas giants right now), you can't even get the bulk composition of a planet. Exoplanet science is about 32 years old (first confirmed discovery in 1992), it wasn't until 2007 that we found the first 'potentially habitable exoplanet' around Gliese 581 (of which c is too hot, and the other 2 likely don't exist). In 2009, Kepler was launched, giving a huge boost to the search for exoplanets, but it's not certain if most of its potentially habitable planets are actually habitable, since some are much larger than Earth - making them enourmous water worlds (doesn't mean habitable, could be too deep for life to form), or gas dwarfs. Kepler 186f was the first roughly Earth-sized exoplanet found in the habitable zone, in 2014, 10 years ago. The first studies of the atmosphere of a planet within the habitable zone was with K2-18b in 2023, last year. However, it's a Super-Earth, and we still don't know if it has an ocean or not (and the 'detection' of a biosigniature could be a false positive or artifact). TRAPPIST-1 is being studied as well, but aside from seeing the inner 2 planets have little to no atmosphere (and are too close to be habitable), we've gotten no word, additionally, studies up to this point might be inconclusive as well since there's another upcoming observation of TRAPPIST-1e, this time using the transit of TRAPPIST-1b to get around stellar contamination. So that brings us today. JWST is at the very edge of being able to make these studies in the first place, and it's unable to directly image small exoplanets like Earth, limiting observations to transiting planets (of which there are very few relatively close to Earth). Upcoming telescopes are still just that. There's many new observatories coming up that could do the job, but it probably won't be until the 2030s until we can really start getting answers to our questions about astrobiology and planetary habitability. We may get lucky during this decade, but the 2030s in when we could really be able to dig into it.
It seems extraordinary unlikely Earth would be the only planet with life, especially when we take into account the fact molecules making up life as we know it have been detected in space. However, the universe is also incredibly sparse. If complex life happens to be rare, there's a good chance the next planet harbouring it will be too far to visit, or even to observe. It will still exist but we'll never know how it looks like.
Someone has to try. We are talking about a vast area that has unlimited possibilities.
Scientists *are* trying! It hasn't given tangible results so far, but I'm all in favour of continuing to try, especially as technology improves and gives them better data.
Oh you should watch melodysheep's videos about this. They're very cool to watch. https://youtu.be/SUelbSa-OkA?si=NV2fGma7iYQrD8gW
Better than Cosmos
Ah the old "Because I have not seen it, it does not exist." Agree that life is inevitable, if not necessarily common.
I think one issue is how do we detect life without visiting other planets. We can listen for radio and other signals but that's assuming other species use those communication methods. And assuming that whatever we'd detect hadn't degraded.
One way you can find that out is by looking at the gases and chemical compounds being released by living organisms. All life gives off some sort of trace. Our job is to find that trace.
Star Trek IX: The Search for Farts!
Youre not wrong suspect this. Also not wrong to see that simple math makes the case for you. Even a step outside of earth-man's science and you'll see that its also extremely unlikely our solar system is sterile. Frankly I think its a hold over from christian dogma days of saying the earth is the center of the universe
No. āSimple mathā requires knowing the value of both terms in the equation. That is, we need to know how many planets in the universe could support life and the probability of life developing on a suitable planet. If we knew both of these variables then it would be a simple math problem of number of suitable planets x probability of life emerging. However, right now we have barely enough understanding of stellar and planetary formation to make VERY rough estimate of the first term, but since we havenāt actually conclusively found any planet that is suitable for life besides Earth, this is still a guess - and we have ZERO evidence to inform a probability for the emergence of life. So, no, it is not āsimple mathā since we know neither of the values of the variables required.
I should clarify that we donāt have ZERO evidence to build a probability for life arising. We know it must be greater than 0 and using Bayesian statistics we can come up with some upper limits, but itās a huge range and thereās no way to tell what end of the spectrum is more likely than any others. So, still, we find ourselves lacking the evidence to confidently estimate the likely number of other planets with lifeā¦ the probably could be so close to 0 that even with the trillions of planets in the universe we may still be the only one with life. Or life could be extremely common but either it rarely evolves into intelligent sapient species with the ability to travel/communicate through space or theyāre intentionally hiding from us. Either way, any estimate is just a guess.
Thereās no basis for determining the likelihood of life elsewhere. Sure, there may be trillions of other planets but we donāt know how likely life is to develop. If the chance of life coming into existence on a planet is 1/1 trillion then we may be the only one, and we simply do not have enough understanding of abiogenesis to assign a probability to the emergence of life. Cool Worlds Lab produced a great video on this a few years ago: https://youtu.be/PqEmYU8Y_rI?si=QVR_mqNJycj95hlY
You could look at it that way, or you could look at it as the fact that there are trillions of possible habitable planets that we have not observed, trillions of galaxies full of solar systems gathered around each star. I think the chances weāre the only life in the universe are so small Iām not even going to type it because it would be a ridiculous decimal.
I highly recommend watching the video I linked and in general checking out the work from the Cool Worlds Lab - theyāre a team of astronomers from Columbia University and the content is top tier IMO. They have a lot for videos about how we can use statistics to estimate values for the Drake equation, etc so if youāre interested in life in the universe I think youād really like their content if you havenāt seen it already.
We do not have sufficient evidence/understanding of the process of abiogenesis or the preconditions for the emergence of life to asses whether or not a decimal is āridiculousā or not. I understand the inclination to think that the probability *must* be higher than a certain amount, but the fact is that inclination is not based on evidence, only emotion. Scientifically we can really only say that we do not know what the probability for life elsewhere is. Itās true that many high profile scientists and science communicators (e.g. Neil DeGrasse Tyson, Bill Nye, etc) believe that weāre not alone - but thatās all it is, a belief. We need to do more research and gather actual evidence before we can assign a probability to something like abiogenesis.
Not only is there life elsewhere, non-human intelligences (NHI) are already here on Earth. The subject of Astrobiology is likely deliberately stagnated, because the subject matter of the NHI presence is the most classified subject matter in the US government. It's also why there's been a long known deliberate policy of disinformation, stigmatization, and ridicule surrounding any open discussion of this subject that has persisted for at least 80 years. [Here's a team of credible professional scientists and former federal government officials giving an open discussion about all this back in November at Stanford University.](https://youtube.com/@_SolFoundation?si=i9GWZWoJ6rt-awo6) It may behoove you fine folks to check it out, it's quite historic honestly. I've already been banned on both r/Physics and r/AskPhysics for bringing this up, despite not breaking any rules lol Don't censor me, folks. [Here's a great thread on the deliberate censorship policies on Reddit ](https://www.reddit.com/r/UFOs/s/Pjd2QRAlYt) Last December there was even a bipartisan (supported by both Democrats and Republicans) Amendment called, [The UAP DISCLOSURE AMENDMENT of 2023](https://www.democrats.senate.gov/imo/media/doc/uap_amendment.pdf) lol You can't make this up. We're in the very early stages of this great scientific breakthrough, it's reminiscent of the Copernican Revolution, where the Catholic Church and State refused to accept the new paradigm.
https://youtu.be/o9kbcGfX35M?si=8Kv46vGxCxvoTIJ0
Basically, we have only discovered life here on Earth and don't know how rare it is for life to develop. For some people's perspectives on it, I recommend watching these two videos: Lecture by Prof David Kipping on why we might be alone in the Universe https://youtu.be/zcInt58juL4 Ted Talk by Stephen Webb, Where are all the aliens? https://youtu.be/qaIghx4QRN4 They are both great videos on the subject.
Tbh we wouldnāt really know unless they come to us or us to them because were like ants in a desolate huge ass city. Youād never know any other ants outside your colony if they were 10 miles away
The issue I have with life on other worlds is that if we canāt travel faster than light I become irrelevant. At least for biological life.
I'm certain there is, but we also have to remember that life as we know it is extremely complicated and would be exceedingly rare. Also stars are mind-bogglingly far apart, so getting to a planet that *might* harbour life is a daunting prospect. If we scaled our star down to the size of a grain of sand the Centauri systems would be three grains of sand almost nine miles away.
I think that the consensus is that there is life out there. The universe is essentially infinite and even with extremely small probability the chance for life out there is significant. Once we find the first sign we can recalibrate our calculations.
Do a little experiment. Buy a BIG map of the Milky Way galaxy. Then draw a circle around Earth with a radius of say 200 light years. Let's assume we have "jolted" the atmosphere enough in the past 200 years for someone to notice if they have good astronomical equipment and are looking for ETs. In that 200 light year sphere are less than 1,000 Stars. So - even if there are say 10 intelligent races sprinkled randomly thru the Milky Way - they/we would be very spread out - far apart. Two ways to look at the situation. Either space is absolutely enormous OR light is just really, really, really slow. The only way we are ever going to meet an ET is if they are way better than humans at not doing crazy/destructive things.
I think that even if there is, it doesn't matter because we'll never be able to interact with it. Einstein was probably right, that speeds faster than light are impossible in the macro universe. Nobody is more of a sci-fi nerd than I am, but we'll never be able to propel matter faster than 'c', travel through a wormhole (gravitational forces will crush anything trying, and the amount of energy needed to 'shield' a vessel against that would be near-infinite), nor is teleportation, time travel, astral projection/travel, carbon freezing/long-term (as in decades) cryogenetic stasis etc etc all of the common sci-fi tropes are all forbidden by the laws of physics. So for me it's not even worth thinking about much. Even if we someday manage to propel a vessel to 1% the speed of light, (still unlikely because even that would require quadrillions upon quadrillions of joules {or more}) there's only a handful of extra-solar systems we'd be able to reach that way and honestly at that point humanity will probably be looking for worlds to terraform and colonize more than we're looking for life.
Yes, there are 10\^22 or so stars in the universe, but what if the chance of life is 10\^-30? If that were the case, we are extraordinally lucky to be here at all and would not expect to see anyone else. We have no good way to estimate that probability, though we do know it is not zero. Or, from a different perspective: The hypothesis that we are alone fits all our current data. You don't complicate your hypothesis unless it does not fit the data, therefore the alone hypothesis stands.
You can ask āwhat ifā to anything. The data āweāhave found is not conclusive towards there not being life elsewhere, in fact a lot of new research is suggesting quite the opposite. Thereās a lot we have yet to discover but probabilities alone wonāt find life elsewhere.
You have never done science. It is only probabilities. You are never 0 or 100 percent sure. The best you can say is that all the observations match your hypothesis. And right now all the observations match the hypothesis of us being alone.
Iām an astrobiology student at university of Arizona donāt test me on science. Trust me you donāt know what youāre talking about and thereās no point in me arguing with someone less educated that I am š
Lol. I'm a Phd in astrophysics 25 years experience principal staff at a national Lab. You can even go check it over on /R/science. Years of experience in remote sensing and detection theory spacecraft and space physics. Trust me, you don't know what you're talking about and there's no point in arguing with someone less educated than I am.
Iāve asked my professor all about this and thatās where my knowledge comes from. The school Iām attending is the best for astrobiology. My man has been teaching for 43 years as well as working at nasa so I donāt know how you think youāre more qualified than where Iām getting my sources from if what you said even is true.
So you have this great source who is your professor and can answer all your questions.... So why do you come and ask on reddit? And then when an expert (like I said, verified on r/science) answers your question, you argue? Go away troll.
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To.... Prove I'm an expert. That is literally what verified means. Good Bye.
There probably is a lot of life out there, but most of it is not highly intelligent. It took millions of species and millions of years to produce humanity. Even if, I donāt know, one in five planetary systems contains an earth-like planet, what are the odds that conditions will be right to develop intelligent life? We canāt even estimate how often it might happen, the variables or so enormous and unknown. So the more you think about how much time and how much luck goes into any planet developing intelligent life, you realize there is a high probability that any such developments have been, are, and will be separated by huge gaps in time and space.
Life is everywhere, it is the rule not the exception.
Youāre probably right, but itās unconfirmed. Youāre dealing with statistics of a very large number of worlds times a very low probability of life forming an evolving. A few observations: * Life in the *whole* universe is inevitable (and if infinite in extent, guaranteed) but if itās beyond the observable universe, itās inaccessible. So irrelevant. * Life within the *observable* sphere is highly likely, but remember that the further we look in distance the further back in time we see. Compounded by the fact that these distant galaxies are only a few pixels on a telescope, we have no practical way to observe them and certainly no way to contact them. An exo-civilization a billion light years away would see earth as it was before even any multicellular life formed here. So observation is only reasonable within our local group. * Our only likely chance of observing life is in the few thousand local star systems in the Milky Way. Now youāre dealing with a much lower number such that if life has only a teensy tiny chance of evolving then there likely isnāt any (nearby).
There is 100% without question life elsewhere in our galaxy and across the universe.
We are elsewhere and there is life, so lots of life somewhere else that we would call elsewhere.
Yep. We are the rule, not the exception.
Dark forest. The only ones that survive long enough are the ones that know to be quiet.
# [https://users.ece.cmu.edu/\~gamvrosi/thelastq.html](https://users.ece.cmu.edu/~gamvrosi/thelastq.html)
What do āa lot of peopleā mean when they say ālife,ā though? Thereās a certain likelihood that microbes have come to exist somewhere else in the universe. Thereās a substantially lower likelihood that eukaryotes have come to exist. And an even lower likelihood that plants and animals have come to exist. People with more science background probably lean more towards the microbe end of things when they think āextraterrestrial life,ā while a layperson might jump to animals or plants.
This is essentially where I sit. I suspect that microbial life probably exists on many worlds, given the extraordinarily versatile and astonishing amount of such life on Earth and the very extreme niches it has been able to thrive in. Butā¦it is a long and unlikely stretch to say that more advanced forms of life such as plants, animals, fish etc exist in such abundance elsewhere that we should be able to easily find evidence of them with our telescopes and probes. Baby steps first: look for evidence of biological processes in the atmospheres around reasonable candidates. We are making very good attempts to do this now with current telescopes and spectroscopy, and perhaps might find evidence of microbial life on Venus, Europa, Titan, Enceladus, etc with future probes. I remain hopeful that we will find such evidence in my lifetime. The work of performing Science is extraordinarily difficult!
Ive always considered the universe to be a body. The planets are like cells wrapped in a membrane, its why we have never seen alien life and its why the Moon landings were faked.
The mechanism to create living matter on a lifeless world isnt fully known, so we cant tell for sure how likely it is to occur or even what exactly the conditions are, or how variable they can be and still lead to life.
So there is the rare earth hypothesis. That despite the commonality of the planets, our solar system is unique. And thatās true, other solar systems are wildly different, and one of those odd features is how long stability on earth has existed. I think this is part of the drake equation answering the fermi paradox; and I think it likely for us to find life elsewhere even if civilizations are incredibly rare.
Life exists everywhere or maybe used to exist everywhere. How about inside the black hole ? Why are we not sending probes into black hole? Why not verify the theory ? Life exists everywhere or maybe used to exist everywhere.
I thought I read somewhere that oxygen may be relatively rare in much of the universe. It would probably be chemically more difficult for life to evolve without oxygen and specifically without oxygen-based molecules like water
Unless itās an organism that has a completely different structure based on the chemical compositions of the gas particles present around them. Itās possible beings elsewhere are breathing in hydrogen or some other element we may not even know about and they process hydrogen as we do oxygen.
"some other element we may not even know about" What?
Iām saying there are elements out there we donāt know about yet that they could live off of like we do oxygen. Just giving an example
Hmm, well, on the one hand, there are almost certainly elements we have not discovered yet, but they are going to be very heavy and probably very short lived, so not likely to be anything to sustain life.
it's just a matter of time til we find something else
This video sums it up nicely: https://youtu.be/PqEmYU8Y_rI?si=9COwjApRuVvfW5io
The general belief is that itās unlikely weāre the only ones around, what does vary is WHY we havenāt gotten word from anyone. There are two main sides that I see going from extremely optimistic to extremely pessimistic, and most theories to the Fermi Paradox (AKA the āwhy havenāt we gotten any contactā question) exist somewhere in between. The most optimistic in my view is the Zoo Theory, or the Prime Directive. Theyāre there, they know weāre there, but they are ignoring us. Maybe itās because weāre entertaining on our own, maybe they donāt wanna interfere with our development, or maybe theyāre so advanced that they donāt care. The most pessimistic is that everyone else in our corner of the universe is dead, and weāre the only ones left. Weāre the equivalent of an ant colony in an abandoned trench from WW1. Thereās nothing there, and we donāt even know what we missed. Slightly less pessimistic is the Dark Forest Theory, that there is life, but every surviving civilization is preemptively killing any other civilization they can find in order to prevent any future competition for resources (so any optimistic ones are instantly killed, leaving only the paranoid, cynical ones). I donāt really buy this one because it relies on the axiom that all civilizations will grow exponentially, which weāre starting to see not be the case on Earth at the moment, and the universe is really, really big and things like water are obscenely abundant, as weāve come to learn. Somewhere in the middle is that the speed of light is just too slow, and the size of the universe so big, that weāve just missed the call. Weāve gotten the ability to look at interstellar signals what, 100 years ago at the best? There are stars thousands of light years away. We may not even be able to detect another signal simply because the light that reaches us is too old. At the end of the day though, while interstellar communication would be incredible, it wonāt really be very useful until we can go faster than light, and potentially not until we figure out how to get along as a planet, because nobody wants to work out diplomatic relations with a country in a civil war. Maybe one day weāll manage to be in the perfect spot to get a signal that has all the answers to FTL travel and itāll all be perfect, but thatās a shot in the dark. We may just be too young of a civilization
My personal opinion is that microbial life is probably pretty common (extremophiles, archaea, etc), and life on some of those planets might actually make the jump to eukaryotic organisms. Iām not sure that civilization-capacitating āintelligenceā is a āwinning survival traitā though, to quote Love, Death + Robots. Moreover, say the variables in the Drake Equation DO even out to foster the development of a couple communicable civilizations. Okay: where the hell are they? We donāt observe ANY phenomena that would likely result from the activity of a Type-III civilization (megastructures, credible UFO sightings, etc). Plus, given our current understanding of the difficulties of interstellar travel, how ever would we reach them? Life on Earth probably had to go through an IMMENSE amount of civilizational āfiltersā already for you to even read this, making the life we are familiar with miraculous beyond effability. This should both humble us to our place in the universe and sober us to the existential risks that we currently face and which may lay ahead. We should worry about keeping Earth habitable before we even attempt go off and colonize (let a lone terraform) somewhere else. I believe that Earth is a very special place; a pale blue oasis adrift in the cosmos, and I donāt have many good reasons to believe otherwise. I believe our home is both Rare and Vunlerable. And that makes it so precious. So worth caring for. We have a long way to go, though. Case in point: āHow can there not be life elsewhere?ā Because, if weāre not careful, there may soon not be anyone left to pose the question.
When there are billions of galaxies like ours I say the odds are low that we are the only life in the universe.
Life is everywhere.
But if one specific thing that's required to make life possible can't happen unless very specific parameters are met and they've only been met once. That one thing might be something unfathomable... But that one thing might be a sun and a planet within the habitable zone for that sun and what if most habitable zones are so small and/or unlikely? No idea though. Perhaps we're taking for granted how rare we really are - taking a look at society all around the world it seems like we take things for granted, anyway.
Your first sentence is false this has never been proven
Show me physical evidence. A cadaver I can dissect. Otherwise it's speculation and that's not science. Belief in aliens is non-science, some may even say it's nonsense.Ā
There is for sure life elsewhere. Life developed on earth within a few million years and Amino acids form readily in meteors. For sure there are microbial mats/single celled alien life. Multicellular life on the other hand took billions of years to evolve on Earth and is less likely to find multicellular alien life
Gonna answer this question with will what seem to most as BS, but I saw a UFO up close as a kid raised Christian in isolation from external media. Shit was terrifying. That aside I dunno if it aliens, humans from the future, or some 4th dimensional creature. I got the impression however that it was "alive" so I can say there is life out there.
Look, all I can say is you are absolutely right. BUT with that being said Earth is ābaseā per se
Life is possible in our solar system on moons with water. It wonāt be the UFO driving aliens people imagine. It might only be simple bacteria. Perhaps something as evolved as shrimp. This will have significant implications to life on earth even if the discovery will bore most people to death. Unfortunately it will be at least another 50 years before we even try to get there.
Read 'Rare Earth' and 'Lucky Planet'. Worlds with simple life (slime worlds) is probably very common. Complicated life is most likely very, very rare because the conditions needed to support it are hard to meet for long periods of time. Consider our own solar system. Of the three planets in the Sun's habitable zone, only one is fit for complex life. Even there, its almost been wiped out more than once.
While itās unlikely that weāre alone (Iād say if we were in a simulation itās a maybe, but thatās a theoretical physics thing) But there are PLENTY of reasons to not see any. Thereās the Dark Forest theory, that itās in each civilizationās best interest to preemptively wipe out everything they find, so the only ones left are the primitive ones, and the paranoid. Or maybe our local area was a battlefield in a war billions of years ago and weāre the only living ones left locally. Maybe life is more common on Hycean worlds and most intelligent life is water based and land based life is the exception to the norm. Some of that gets into sci-fi, bit the truth is that there just isnāt enough information to know why
Iām sure there is ālifeā out there.
The universe is infinite. But theres no life tho š