Water being common doesn't mean life is common. We have the intuition to be aware that the exact atomic configuration of a boeing 747 getting replicated by pure chance on a planet 500 light years away is impossibly low. So impossibly low that I'm willing to bet my life that it won't ever happen, not just on a planet 500 light years away, but on every planet in the universe. What are the chances of life being on a planet 500 light years away? Unfortunately the definition of life is vague and the chemical processes required by life aren't even completely understood.
Without knowing the processes/materials necessary to ignite the self replicating processes required for life we don't possess the information necessary to know whether life is probable or improbable. Even in a universe with plentiful water and plentiful habitable planets, without context on what started it all we can't make any meaningful prediction. Is life like the boeing 747 or is it not?
I always find it ludicrous when someone says the universe is just so vast that life has to exist somewhere else. We just don't have enough understanding/context to know.
Of course, there is a planet that astronomers and others are very familiar where 747s appear all the time. They just happen through complex chemical reactions. Apparently they do that near some hive of theirs called "Seattle"
To answer the question about if life is rare we need to visit Europa and Enceladus in our solar system. If those places have life, then life might be quite common in our universe. If they do not have life, then we are likely very alone in the universe.
Maybe the probability that that life will occur is one planet out of every thousand planets. Then the probability of Europa having life is small. However one out of a thousand in a universe with billions of planets is a meaningful number. If this is the case, then examining our own solar system for life, which is comprised of far fewer then 1000 planets, will not be a worthwhile endeavor.
I think the key is understanding the process itself. What does it take to create the minimal self replicating machines necessary to evolve into the complex forms we see today? Once we are aware of the processes involved in the formation of life then we have the context to hypothesize about the probability that these reactions will spontaneously occur.
Things like the Drake equation are meaningless and made up. You can easily make up an identical bullshit equation about the chances of a 747 spontaneously being thrown together on another planet. We can easily see that it's impossible because we know how the 747 is made, we have context. For life? We have no context, no knowledge of where it came from, and therefore the drake equation and any other statement about life on other planets is meaningless.
Most discovered planets to date are larger than Earth and closer to the star, but that's probably because it's easier to discover those planets given our current technology...
Interesting to think that the size of planets would limit exploration though (from the article):
If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport.
It's possible to do better than lump all of the discovered planets together and complain that the set is biased. For example, Kepler can detect a planet iff there is a chance alignment of its orbit with our line of sight, so for each discovered planet, it's possible to compute the probability that its orbit was correctly aligned, and divide by it to compensate. That way it's possible to make unbiased statements about the distribution of planet sizes and orbits, the fraction of stars with planets, etc.
And the other options are...? I can think of nuclear thermal, which has its risks, and Orion-like bomb propulsion which no sane civilization would use. What else?
Most non-chemical propulsive mechanisms considered for space travel do not have the ISP necessary to launch from the bottom of a deep gravity well. We will probably continue to use chemical rockets to leave this Earth, at least until the first space elevator is built, and that itself will require quite a bit of up mass.
On the other hand, Earth is a very dense planet (in part due to the accidental formation of the Moon), so bigger planets might still have a lower gravity on average. Also, if they spin faster, getting into orbit will be easier.
Maybe Earth is indeed at a comparatively bad place in the gravity spectrum of habitable planets. Getting things up there is difficult enough that we can't have big payloads, but it's still easy enough to justify not building a self-sufficient infrastructure out there.
When I was young, the big mystery of pop astronomy was: are there any other planets like Earth?
And does water exist anywhere outside Earth.
At some point during my lifetime, exoplanets have been discovered and at some other point, the idea that planets, including earth-sized planets are almost as widespread (or rarefied) as stars themselves. At least 10 billion earth-sized planets in our galaxy alone.
So it seems like the Universe is full of Planets and a lot of those planets contain water.
The next logical step is that extra-terrestrial Life is just as common as water, planets and stars.
If that is the case, that means that life is a natural consequence of star formation/runtime, which is extremely interesting.
Which, if we now really think about it, is not entirely out of the question, in fact, it's quite probable.
Was this a big pop science mystery back in the day? The simplicity of the composition of water ("burned hydrogen gas") would lead me to think that we should expect to find it in some phase of matter fairly regularly. Caveat though: I'm not a chemist.
We have proof. So far we already have detected a planet with Earth-like conditions (called Earth). Life formed on it. Possibly several times independantly.
The statistics for life on very earth-like planets are staggering.
It doesn't surprise me how much water there is in the solar system, considering how simple of a chemical water is. Life itself is a chemical reaction that takes much longer to complete (though I'm starting to think that it's more abundant than I think :P).
And at the edge of the known universe, an expanding shockwave from a supernovae fuses hydrogen into oxygen, forming the largest known water bubble totaling ten trillion times all the water on earth.
For future reference, fusion happens in stars (and at the center of supernovas). H combining with O2 is a chemical reaction rather than a nuclear reaction.
On the other hand, the question regarding how supernovas combine/mix heavy atoms to form chemicals would be a very interesting PhD thesis. :D
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Without knowing the processes/materials necessary to ignite the self replicating processes required for life we don't possess the information necessary to know whether life is probable or improbable. Even in a universe with plentiful water and plentiful habitable planets, without context on what started it all we can't make any meaningful prediction. Is life like the boeing 747 or is it not?
I always find it ludicrous when someone says the universe is just so vast that life has to exist somewhere else. We just don't have enough understanding/context to know.
I think the key is understanding the process itself. What does it take to create the minimal self replicating machines necessary to evolve into the complex forms we see today? Once we are aware of the processes involved in the formation of life then we have the context to hypothesize about the probability that these reactions will spontaneously occur.
Things like the Drake equation are meaningless and made up. You can easily make up an identical bullshit equation about the chances of a 747 spontaneously being thrown together on another planet. We can easily see that it's impossible because we know how the 747 is made, we have context. For life? We have no context, no knowledge of where it came from, and therefore the drake equation and any other statement about life on other planets is meaningless.
I think life is created right now on Earth from scratch (chemical elements), but we need to find proof.
If most planets are larger than we are, their populations will struggle even harder than we do, getting off their rock.
[1] https://www.nasa.gov/mission_pages/station/expeditions/exped...
[2] no link needed
Do you have a source for that assertion?
Most discovered planets to date are larger than Earth and closer to the star, but that's probably because it's easier to discover those planets given our current technology...
Interesting to think that the size of planets would limit exploration though (from the article):
If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport.
It's possible to do better than lump all of the discovered planets together and complain that the set is biased. For example, Kepler can detect a planet iff there is a chance alignment of its orbit with our line of sight, so for each discovered planet, it's possible to compute the probability that its orbit was correctly aligned, and divide by it to compensate. That way it's possible to make unbiased statements about the distribution of planet sizes and orbits, the fraction of stars with planets, etc.
Most non-chemical propulsive mechanisms considered for space travel do not have the ISP necessary to launch from the bottom of a deep gravity well. We will probably continue to use chemical rockets to leave this Earth, at least until the first space elevator is built, and that itself will require quite a bit of up mass.
Maybe Earth is indeed at a comparatively bad place in the gravity spectrum of habitable planets. Getting things up there is difficult enough that we can't have big payloads, but it's still easy enough to justify not building a self-sufficient infrastructure out there.
At some point during my lifetime, exoplanets have been discovered and at some other point, the idea that planets, including earth-sized planets are almost as widespread (or rarefied) as stars themselves. At least 10 billion earth-sized planets in our galaxy alone.
So it seems like the Universe is full of Planets and a lot of those planets contain water.
The next logical step is that extra-terrestrial Life is just as common as water, planets and stars.
If that is the case, that means that life is a natural consequence of star formation/runtime, which is extremely interesting.
Which, if we now really think about it, is not entirely out of the question, in fact, it's quite probable.
Was this a big pop science mystery back in the day? The simplicity of the composition of water ("burned hydrogen gas") would lead me to think that we should expect to find it in some phase of matter fairly regularly. Caveat though: I'm not a chemist.
If this is logic, it's purely inductive. We have no evidence for how likely it is that life form under water-like conditions.
The statistics for life on very earth-like planets are staggering.
On the other hand, the question regarding how supernovas combine/mix heavy atoms to form chemicals would be a very interesting PhD thesis. :D
Dead Comment
It may be detectably frosted since the solar wind would push it in that direction.