When could life theoretically exist in any star system after the Big Bang?

[lucas_]

Theoretically how many billions of years after the Big Bang when life could theoretically exist in any star system?

I am thinking how old they are now. And how big the accelerator they had built to probe the Planck scale. Couldn't very advanced civilization created solar system size accelerators for instance? How can these be detected if they don't give of light and don't orbit around the sun?

 

[phyzguy]

Theoretically how many billions of years after the Big Bang when life could theoretically exist in any star system?

Nobody knows the answer. We don't know what the requirements are for life to develop, and we don't know how likely it is to develop on a given planet. All we know for sure is that it developed here on the Earth. Everything else is speculation.

 

[lucas_]

Nobody knows the answer. We don't know what the requirements are for life to develop, and we don't know how likely it is to develop on a given planet. All we know for sure is that it developed here on the Earth. Everything else is speculation.

Or how many billions of years before planets were cold enough? How long does it take for one to cold down?

 

[Michael Price]

Nobody knows the answer. We don't know what the requirements are for life to develop, and we don't know how likely it is to develop on a given planet. All we know for sure is that it developed here on the Earth. Everything else is speculation.

Yes, speculation, of course, but still worth exploring. John Gribbin's Alone in the Universe: Why our Planet is Unique
https://en.m.wikipedia.org/wiki/Alone_in_the_Universe_(book)Makes out a good case that life couldn't have arisen much earlier than today, due to the low metallicity of the early stars. With successive supernova the metal content rises.
Short Wikipedia article, but the reviews are worth reading.

 

[kimbyd]

Theoretically how many billions of years after the Big Bang when life could theoretically exist in any star system?

Nobody can say for sure. But it probably can't. At a very fundamental level, life requires heavier elements than just hydrogen and helium (because life requires complex chemistry, and hydrogen and helium can't produce anything more complicated than ##H_2##), and temperatures low enough for matter solids/liquids to exist (gases and plasmas are too chaotic for stable structures). And there's no guarantee that such heavy elements will ever exist outside of the stars themselves in every solar system.

If you want to know how long it will take until every solar system that might ever result in life will, then that number is probably close to the time it takes for star formation to cease, which occurs sometime around 1-100 trillion years from now (per this Wikipedia article).

I am thinking how old they are now. And how big the accelerator they had built to probe the Planck scale. Couldn't very advanced civilization created solar system size accelerators for instance? How can these be detected if they don't give of light and don't orbit around the sun?

It's highly unlikely that it's possible to produce a pocket universe in a particle accelerator. At least, not one that can ever be probed. The reason for this is the detection of ultra high-energy cosmic rays which impact atoms in our atmosphere at in excess of ##10^{20}##eV, which is tens of millions of times the energies probed in current particle accelerators (see here)

Thus if a measurable "universe" can be created by high-energy particle collisions that are remotely measurable, it would already be happening in our atmosphere as these ultra high-energy particles impact it. Creation of particle accelerators which allow for substantially higher energies are likely impossible. But we'd never be able to know even if it was possible at higher energies even if such accelerators were possible: either there would be (most likely) no measurable consequences, or it'd destroy the universe.

There are two general ways in which such a universe would be produced. If its vacuum energy was higher than the vacuum energy in our universe, then it would present as a microscopic black hole that is created and instantly evaporates. As I understand it, it is plausible that such pocket universes could continue to exist, but they would forever be disconnected from our universe. If we ever did measure such a microscopic black hole, we'd never have any way of knowing whether it initiated a new universe or not (barring some as-yet-unknown discovery which allows that experimental determination: it's hard to say for sure that it will always be impossible, but it probably is). This concept is related to the idea of Lee Smolin's fecund universe. This idea is probably impossible to verify experimentally.

The other option is if the new universe has a lower vacuum energy than ours. In that case it would start to expand rapidly, with the boundary between our universe and the new one reaching near the speed of light within about a second. It would result in the complete destruction of everything within the future horizon of the event (meaning all galaxies for tens of billions of light years).

Such events, though theoretically possible, must be incredibly rare or else our universe would not have lasted as long as it has. The plausibility of this means that it's probably a bad idea to attempt to probe energies above those of ultra high-energy cosmic rays, even if the technology to do so does exist sometime in the future. This process is known as Vacuum decay, and would be plausible if our universe was in a false vacuum state and the interaction energy was greater than the amount required to efficiently access other vacuum states (likely somewhere between the Planck scale and the GUT scale, i.e. ##10^{25}##eV to ##10^{28}##eV).

 

[mfb]

@kimbyd: Be careful to not mix particle energies with center of mass energies. An E = 10²¹ eV proton hitting a proton in the atmosphere leads to a collision with a center of mass energy of ##\sqrt{2 E m_p} = 1.4\cdot 10^{15}\, \mathrm{eV} = 1400\, \mathrm{TeV}##. That is a factor 100 higher than the LHC energy. Still a lot, but we might get there at some point. Plasma wakefield acceleration has demonstrated accelerating gradients exceeding 50 GeV/m. At such a gradient a linear collider for 1400 TeV needs 28 km of acceleration. Add focusing and so on and we probably need 50-100 km, still not completely unthinkable.

 

[kimbyd]

@kimbyd: Be careful to not mix particle energies with center of mass energies. An E = 10²¹ eV proton hitting a proton in the atmosphere leads to a collision with a center of mass energy of ##\sqrt{2 E m_p} = 1.4\cdot 10^{15}\, \mathrm{eV} = 1400\, \mathrm{TeV}##. That is a factor 100 higher than the LHC energy. Still a lot, but we might get there at some point. Plasma wakefield acceleration has demonstrated accelerating gradients exceeding 50 GeV/m. At such a gradient a linear collider for 1400 TeV needs 28 km of acceleration. Add focusing and so on and we probably need 50-100 km, still not completely unthinkable.

Hmm. I expected the difference between the two to be immaterial, but I guess the way that center of mass energy comes in, it really isn't. I had completely forgotten that center-of-mass energy isn't approximately linear with particle energy in relativistic collisions.

 

[mfb]

It is the reason we have colliders. Shooting the (soon*) 7 TeV LHC beam on a fixed target would give a center of mass energy of just 114 GeV, a factor 120 below the center-of-mass energy of the LHC as collider.

*6.5 TeV so far, 7 TeV coming.

 

[MikeeMiracle]

I would think we would need at least 3 generations of stars to produce enough of the heavier elements to be produced that can support life as we know it. I think we are looking at around 1 billion years after the big bang assuming the 3 generations were all early type very big fast burning/fusing types that only last for a hundred or so million years with several 10's of millions of years before the previous supernova remnants collapse back into a viable star.

 

[kimbyd]

It is the reason we have colliders. Shooting the (soon*) 7 TeV LHC beam on a fixed target would give a center of mass energy of just 114 GeV, a factor 120 below the center-of-mass energy of the LHC as collider.

*6.5 TeV so far, 7 TeV coming.

Makes sense. Especially for linear colliders which would have a choice in design between a one-sided collision on a stationary target with twice the acceleration length vs. a head-on collision.

However! The fact that these particles strike our atmosphere at these energies does not mean that that's the only way they ever interact. Such particles are rare, but it should in principle be possible for them to very very rarely collide with one another nearly head-on. Such events are surely so rare that they could never be observed, but as long as they happen more than once every few billion years in a volume billions of light years across, then such events still place lower limits on the energies required to cause universe-destroying collisions. They might not be quite as high as ##10^{22}##eV, but are surely much higher than the center-of-mass energies achieved in our atmosphere.

 

[mfb]

(0.001/(km^2 * year))^2 * 100 millibarn * (1 gigaparsec)^3 * (10 billion years)/ (speed of light) = 3*10²³ suggests these collisions between cosmic rays are indeed common. The flux value is the approximate flux at 10²⁰ eV.

 

[kimbyd]

(0.001/(km^2 * year))^2 * 100 millibarn * (1 gigaparsec)^3 * (10 billion years)/ (speed of light) = 3*10²³ suggests these collisions between cosmic rays are indeed common. The flux value is the approximate flux at 10²⁰ eV.

One issue here is that such particles are at high enough energies that they're slowed substantially by the CMB, and thus don't have terribly long ranges and will therefore be of higher density within galaxies than outside them. This probably drops the expected rate by a few orders of magnitude, but I'm not sure of a good way of doing a back-of-the-envelope calculation for that. See here:
https://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit

Granted, this limit is close to the upper limit of ultra high-energy cosmic rays, so even if ##10^{20}## eV collisions are rare due to this limit, ##10^{19}##eV collisions probably aren't, so the overall picture isn't changed by much.

 

[mfb]

With 20,000 light years cubed (some very rough approximation for our galaxy) you get 70 million. In each galaxy our size. It surprised me, but ultimately space is big and 10 billion years are a long time. 1 such collision every 100 years in the galaxy, give or take a few orders of magnitude.

 

[bahamagreen]

Kepler discovered a system of 11-billion-year-old planets

The example of the Earth is that life (self replicating molecules) emerged after about a half billion years. It took another three billion years to produce the multi-cellular microscopic worm, but only another one billion years to get from the worm to man.

Intelligent life beginning from a similar scenario as on Earth (taking 4.5 billion years) but starting on 11 billion year old planets would be 6.5 billion years advanced of us... I imagine whatever they might have become, there might be few things they have not been able to do.

 

[Michael Price]

Intelligent life beginning from a similar scenario as on Earth (taking 4.5 billion years) but starting on 11 billion year old planets would be 6.5 billion years advanced of us... I imagine whatever they might have become, there might be few things they have not been able to do.

But life could not have arisen 11 billion years ago - the metallicity was too low. There are so many factors that have to be just right for planets to support life. Earth-type planets are probably extremely rare, requiring an improbably large moon (which no other planet in the solar system possesses) and a host of other just-so requirements.
https://en.m.wikipedia.org/wiki/Rare_Earth_hypothesisAnd you should still read John Gribbin's 'Alone in the universe ', which I mentioned earlier.
https://en.m.wikipedia.org/wiki/Alone_in_the_Universe_(book)Gribbin's book was especially strong on the astrophysics (habitable zones in galaxies and such like) - he has an astro PhD.

 

[bahamagreen]

"Because of their small size, the authors conclude that the bodies are almost certainly rocky, and likely Earth-like in composition."

I have not seen the paper...

 

[MikeeMiracle]

I think we limit outselves in debates about life due to expecting it to be like life here on Earth and also this obsession with a "habitable" zone.

What is life? If we remove water from our bodies then we are left with a bunch of chemicals / molecules. the "water" is the agent that allows these to travel / mix / interact with each other to produce the life we know. Why do we believe that it is only liquid water that can fulfil this function? Why could not any suitable "liquid" funfil this function? We have liquid nitrogen on the outer solar system bodies, why could that not be used as the agent that allows life's chemicals / molecules to interact. If this is possible then the whole idea of a "habitable zone" is redundant as it currently refers to areas only where liquid water could exist.

 

[Michael Price]

I think we limit outselves in debates about life due to expecting it to be like life here on Earth and also this obsession with a "habitable" zone.

What is life? If we remove water from our bodies then we are left with a bunch of chemicals / molecules. the "water" is the agent that allows these to travel / mix / interact with each other to produce the life we know. Why do we believe that it is only liquid water that can fulfil this function? Why could not any suitable "liquid" funfil this function? We have liquid nitrogen on the outer solar system bodies, why could that not be used as the agent that allows life's chemicals / molecules to interact. If this is possible then the whole idea of a "habitable zone" is redundant as it currently refers to areas only where liquid water could exist.

I suggest you raise the query about water on a separate thread - but water does have many unique properties required for life.

 

[sysprog]

Well, let's please not disregard the fact that Carbon, clearly due to its abundancy of available electrons, has the most reactions of any of the elements. I think it's plain to that see that Hydrogen got here early. Oxygen and Carbon and metals and other elements necessary for anything that by us would be called life got here much later, but, as others here have made clear by their insightful remarks, we don't know even approximately when life arrived; we know only that on the grand scale, even though it was from our perspective very long ago, from the perspective of the age of the Universe, the beginning of life as we know it must, comparatively, be extremely recent.

 

[PeterDonis]

life could not have arisen 11 billion years ago - the metallicity was too low. There are so many factors that have to be just right for planets to support life. Earth-type planets are probably extremely rare, requiring an improbably large moon (which no other planet in the solar system possesses) and a host of other just-so requirements.

water does have many unique properties required for life.

Given how little we know about how life originated on Earth, or how stringent the conditions actually were that were required, or what properties are really required for life of any kind (as opposed to the particular kind of life we know), we should not have very high confidence in any claim about under what conditions life could or could not have arisen elsewhere. The references you give are not scientific theories supported by evidence; they are hypotheses which might seem plausible but which have yet to be tested.

 

[Michael Price]

I suggest you raise the query about water on a separate thread - but water does have many unique properties.required for life.

Given how little we know about how life originated on Earth, or how stringent the conditions actually were that were required, or what properties are really required for life of any kind (as opposed to the particular kind of life we know), we should not have very high confidence in any claim about under what conditions life could or could not have arisen elsewhere. The references you give are not scientific theories supported by evidence; they are hypotheses which might seem plausible but which have yet to be tested.

Since we can't test any ideas about xenobiology, for the foreseeable future, all we can do is speculate about hypotheses. However the Rare Earth Hypothesis does resolve the Fermi Paradox, and more convincingly than ideas such as the Dark Forest.

 

[mfb]

We have liquid nitrogen on the outer solar system bodies, why could that not be used as the agent that allows life's chemicals / molecules to interact.

For reasons discussed in hundreds of publications. Liquid nitrogen is not such a good solvent, it is too cold to make many reactions possible even with catalyzers, and many more I have never heard about. I do have heard about the conclusion, however: Water seems to be by far the best liquid. It is also the one where we are sure it can lead to life.

Kepler discovered a system of 11-billion-year-old planets

Too hot, but there could be other, colder old planets of course.

We know how long it took on Earth until humans were around, but we don't know if that is typical. Maybe 15 billion years is a much more likely time span? Maybe our high intelligence is such a freak occurrence that even 100 billion years are unlikely to lead to it?

 

[PeterDonis]

Since we can't test any ideas about xenobiology, for the foreseeable future, all we can do is speculate about hypotheses.

Yes, and discussion of speculations is limited by the PF rules precisely because they can't be resolved.

Which is a good note on which to close this thread.