Originally posted by tothetenthpower
#1 is entirely nonsensical.
Just based on the math. If there's anything I trust more than opinion, it's math .
I can get the others for sure.
IMO it's a combination of the following:
1. We've done nothing but kill each other over the last 10k years. Who wants to meet that?
2. Non Interventionist Policy
3. No Interest.
4. Faster than light travel is actually impossible and therefore only local systems could be visited.
I lean towards 1 and 2 as my main hypothesis.
I think you are discounting math here even though you suggest you trust it the most. If we just stick to our own galaxy since I think we can both
agree that if we cannot find space fairing life here than how can we suggest it is in other galaxies.
When we say life in general then I would say our galaxy is teaming with it, but as we add more and more discriminators to the equations the odds get
less and less, so let's look at those...
Physically capable complex life
Physically capable complex intelligent life
Physically capable complex intelligent advance life
Physically capable complex intelligent advance space faring life
As we add more and more discriminators we are not talking about life in general anymore. Humans are not proof of anything yet, but we are the best so
far the earth has put forth to meet all the discriminators to make this happen. This means after 4.5 billion years and trillions of life forms the
earth has finally maybe made one. In a galaxy that is less than 9 billion years old and has an average of 300 billion stars there are hard limits
It seems once the conditions are right life is hard to kill, and there has been many attempts on earth in the past to do just that. When we look at
snowball earth, life was basically reset back to almost the microbe stage but here we are today. The problem here is the more complex life becomes the
more fragile it also becomes, and so just maybe advance life is not a very good evolutionary progression since normal natural events seems to
continually reset it all the time. We also need to look at evolution and once again life in general is hard to kill but species are easy to extinct
and come and go all the time. We will come and go too...
We talked about discriminators with life so let's talk about discriminators with planets that can sustain life.
Out of 300 billion stars 90% are main sequence stars (ones that most likely would support life). 23% of these are F,G and K stars with smaller ones
having a habitable zone too close and larger stars would not last long enough for evolution to do its work, so we are down to 62 billion stars now. It
has been measured that 30% +- 10% of these stars will have Neptune mass planets with 50% rock and 50% gas, so that is 15% of 62 billion stars will
have rock planets...down to 10 billion stars.
Of the 330+ exoplanets found so far 30 are in the habitable zone, so with 10% we are down to 1 billion stars. With one final suggested point that
there is most likely a Galactic habitable zone too and that would say only 10% of stars are capable, so our number would be 50 million habitable zone
exoplanets in the Milky Way. Also using the Drake Equation it yields about 25 million habitable moons.
When we also add in some other seemly needed discriminators to suggest advance life these numbers get smaller and smaller.
1. Needs a Jupiter type planet to be the solar system's vacuum cleaner to allow evolution to do its work without many resets all the time.
2. Planet needs to have a long term liquid core for electromagnet protection for advance life to form. Mars is a good example of what happens when the
3. A moon is needed for stability, so even with earth if it did not have the moon advance life would not be here due to the extremes in temperatures
it would have.
4. Having water is also a big factor......
Finally a lot of luck, or bad luck is needed. If the dinosaurs were not wiped out then mammals would still be rodents. With all this I think it is
safe to say there is life throughout our universe, but it is also safe to say the chances of a space traveling advance race is almost zero too.
edit on 23-2-2013 by Xtrozero because: (no reason given)