Milky Way Star Births May Have Influenced Life

eldavojohn writes "Space.com has an interesting article that speculates that the period when our galaxy was giving birth to stars resulted in huge fluctuations and impact on earth. From the article, 'Some 2.4 billion years ago when the Milky Way started upping its star production, cosmic rays — high-speed atomic particles — started pouring onto our planet, causing instability within the living. Populations of bacteria and algae repeatedly soared and crashed in the oceans.' Causes one to wonder what the probability for life arising on a planet is given that our own seemed to be in a very unique situation on many different counts."

Comments

Probability theory

[PhotoJim]

Even if the chances were one in a billion or one in a trillion, the sheer number of stars and planetary systems in the galaxy (and indeed the universe) make it entirely unlikely that there *isn't* life out there somewhere. Humans seem to want to be perceived as being special on both an individual and a collective level. We don't really want to accept being common or normal or average. There is life out there somewhere. We'll never find it because of the distances involved, but I am convinced it's there. I think we beat huge odds to get here, but there are still huge numbers of other civilizations that beat similar odds.

Not too much different from other changes

[Josh Lindenmuth]

In general, any period of time where there is massive stress on a population would likely see rapid evolutionary changes. Whether it's volcanos, or asteroids hitting the planets, an ice age, or interstellar radiation, the effect is basically the same - an initial decimation of existing populations with amazing biodiversification thereafter.

100 Billion

[Gotung]

To borrow a theme from Carl Sagan.
Estimations are that there are 100 Billion stars in our galaxy. Thats:

100,000,000,000 -- Let's say 1 in ten of those are in a good region of the galaxy (not a bunch of cataclysmic crap going on)
Thats: 10,000,000,000 -- Let's say 1 in ten of those have planets.
Thats: 1,000,000,000 -- Let's say 1 in ten of those have a planet in the stars habitable zone
Thats: 100,000,000 -- Lets say 1 in ten of those have adequate amounts of water
Thats: 10,000,000 -- Lets say on 1 in ten of those simple life arises.
Thats: 1,000,000 -- Lets say on 1 in ten of those complex life develops.
Thats: 100,000 -- Lets say on 1 in ten of those intelligent life develops.
Thats: 10,000 -- Lets say on 1 in ten of those advanced civilization pops up.
Thats: 1000

10,000,000 planets that foster life, and 1000 advanced civilizations.

I think the chances are pretty good. :P

Re:100 Billion

[CmdrGravy]

The trouble is that the Universe is maybe 17 Billion years old and although we have no figures on the length of time you can expect an intelligent species to survive for it's probably a small fraction of 17 Billion. It's likely that intelligent species will not have the capability for space travel or inter-stellar communication for their entire existence which cuts the percentage down further.

The rate at which a species can expand through the galaxy is likely to be quite an awful lot slower than the maximum speed of whatever craft they have developed so for us to ever be aware of anyone else in the Universe we'd have to have arrived in a similar time frame and be very close to them spacially. It's possible there may be a fantastic co-incidence and a probe or exploration vehicle come across us but really the universe is so huge both us and them would need huge blocks of inhabited space which would at some point need to intersect.

Re:100 Billion

[shma]

The problem is that there's no reason one of your 'one in ten' couldn't be '1 in a billion', in which case, you only have a one in a million chance of developing an advanced civilization per galaxy. For starters, there's no reason to believe that 10% of planets in stars habitable zones will have an adequate amount of water. In fact, we don't even know what a reasonable estimate of an adequate amount of water IS (certainly nothing more specific than "no more than what we have"). We have no way of knowing how likely it is that any kind of complex life forms from simple life, or intelligent life forms from complex life, simply because we've only had our own planet to study, and we're the only intelligent life on it.

And then there's the problem of coexistance. If advanced civilizations live only on average for a million years (still ~100 times longer than us, depending on your definition of 'advanced'), than the probability that two such civilizations would overlap is extremely tiny. Remember, our earth is over 4.5 billion years old, and life giving stars have been around for even longer.

Personally, I think the chances of finding other life in the galaxy are very low.

Fermi Paradox

[benhocking]

Let's say 1 in 10 of those decide to start colonizing other star systems with generational ships. Where are they?

Re:Non-unique

[Anonymous Coward]

Just to make this clear, Earth is unique among all the planets we know simply because we can't detect Earth-like planets around other stars.

We really don't know how common planets like Earth are, but if you're interested in finding out be sure to write to your politicians and ask them to fund the planet-finding telescopes and spacecraft that are in the pipeline :)

Until you consider exponential growth

[benhocking]

Read the link in my GP post about the Fermi Paradox. It explains that once a civilization develops that starts colonizing other worlds, it will tend to generate two (or more) other inhabited planets. This will then lead to 4, 8, 16, until after 40 such doublings you have over a trillion inhabited planets (i.e., about 10 for every star in the Milky Way). Obviously there will be limiting factors (such as the number of inhabitable planets), but you'd think that eventually (i.e., in less than a few million years), they'd find Earth - we wouldn't need to find them.

Re:The same time span

[joto]

the complete lack of evidence that other races exist means that no other intelligent races arose significantly before us (in cosmic time), or else any that did wiped themselves out as far as we can tell, either through no longer using electromagnetic waves of any kind (making their stray radiation invisible to us), killing themselves off, or something else.

I wouldn't call stop using electromagnetic waves as killing yourself off. Besides, even on earth, our radio transmissions becomes more and more difficult to detect. Our transmissions look more and more like noise, heavily compressed digital data. Instead of AM and FM, we increasingly use more obscure technologies, even multiband. And we use lower power in our transmissions. Add a few thousand years to that, and I doubt we would be able to detect ourselves.

Also, radio is a pretty recent invention. It's not something humanity has depended upon for millenia. If we are still using radio in 5000 years, you might have a point. As of now, I don't think it's completely unthinkable that we will invent something better. Perhaps as a result of finally finding a grand unified theory in physics, or something else way longer down the road. Remember, the perspectives we are talking about in cosmic scale is billions of years. Here we keep complaining that progress in AI, fusion, string theory, etc is slow because nothing has happened in 50 years.

So, either we are in roughly the same boat as any other sentient species out there, or else post- or pre-date them.

That, at least, is for sure!

Don't have the data (yet) on likelihood of life

[quixote9]

Hard radiation to generate mutations can't be a limiting factor because it's not in short supply in the universe. Without Earth's magnetic blanket, we'd be getting so much, even without major galactic star formation, the trick would be staying alive rather than generating enough mutations to do anything interesting.

The probability of life arising is much more difficult to pin down. Right now, we have one data point: Earth. Kind of hard to extrapolate any sort of line from that. Invented probabilities, like those in the Drake equation or Sagan's discussions, may be plausible, but since they're not factual we can argue about them forever.

What we do know is that life arose on Earth very quickly after the initial heavy bombardment slowed down. Very quickly means a few hundred million years. That's fast enough to mean that life probably arose several times, each time getting wiped out in a new wave of bombardments, until the meteor strikes finally weren't big enough to liquefy the whole surface of Earth. Or until life was widespread enough that devastating half the Earth wasn't enough to kill it. Here again, we have no proof that repeated chemical evolution of life happened, but the speed with which it did happen, at least once, implies that it's not a particularly iffy process.

The lack of a second data point is why solar system exploration is so hugely important. Mars had a few hundred million years with liquid water. If there is evidence of fossil bacteria from that time, it'll mean there is life everywhere in the universe where there is water. I can't imagine anything more significant than that. And if exploration of, say, Europa, also turns up bacteria, well, then it'll be all over except the shouting. NASA, ESA, Japan, _everybody_ needs to hurry up and send those critical missions out there so that we have our answers, and this forum can sink it's teeth into them!