This is sort of terrifying, given that we haven't observed any space-faring species from any of those other Earth-sized planets yet.
Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
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Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#32Fascinating. Our little rock could be "one in a billion" and we would still have 16 other civilizations to meet. Just in our galaxy.
One in a billion, though, what are the odds of life existing? It might be much higher than that. I really don't know much in this area of science though.
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#33Regarding the Fermi paradox: one of the civilization has to be the most advanced and has to be so intelligent that it obviously knows the Fermi paradox ("probably" under another "name" ; ) all too well.
Must s*ck to be that one civilization: being right about the universe actually holding several carbon-based lifeforms and yet scratching their heads thinking "We can't be the most advanced, we can't be the most advanced".
: )
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#34This is sort of terrifying, given that we haven't observed any space-faring species from any of those other Earth-sized planets yet. http://en.wikipedia.org/wiki/Great_Filter
Maybe we are who we are looking for:
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#35This is interesting, but I think an estimate of the number of planets with lots of liquid water on the surface would be more exciting. Liquid water is key to life as we know it, so knowing how common it is in the galaxy might give us some idea how likely we are to find extraterrestrial life.
There's a lot more to life than just liquid water. In fact there are a huge array of requirements including distance from the sun, right arrangement of planets, tidal systems, plate tectonics...
i think it's the opposite of that. by all evidence, life on Earth began as soon as it was possible, and that's just this particular kind of life with this set of particular elements under these particular constraints. there may be other chemical/physical configurations under which life is even easier, etc
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#36Regarding the Fermi paradox: one of the civilization has to be the most advanced and has to be so intelligent that it obviously knows the Fermi paradox ("probably" under another "name" ; ) all too well. Must s*ck to be that one civilization: being right about the universe actually holding several carbon-based lifeforms and yet scratching their heads thinking "We can't be the most advanced, we can't be the most advanc…
The universe is relatively young in the sense that metal-rich solar systems are probably a requirement for advanced lifeforms and we haven't had that many generations of stars yet. Our sun is a "Population I" star (counter-intuitively, astrophysicists are counting backwards here) that has taken heavy elements as building material for the whole solar system from the remnants of earlier stars.
However, the Milky Way is at the same time certainly old enough to suggest we shouldn't be the first. Evolutionary timescales probably depend a lot on the environment, but even if we're taking the development of our biosphere as one of the fast examples, there should still be other comparable planets billions of years younger than ours lending credibility to the assumption that there should have been civilizations before us.
One of the big questions is also how long civilizations stay in the "compatible" phase on average. If they disappear (either going extinct or transcending into another stage) fast enough, finding and communicating with them in time will be very difficult. Like I said, extinction isn't necessarily the driving force. For example, our own sci-fi stories are absolutely rife with slightly advanced civilizations that very likely would never communicate with us.
Another favorite explanation of mine is that there could be some unknown local issue in our stellar neighborhood. Candidates scenarios for this are myriad, and they fall into two categories: there isn't anyone nearby, or we are artificially isolated somehow.
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#37This is sort of terrifying, given that we haven't observed any space-faring species from any of those other Earth-sized planets yet. http://en.wikipedia.org/wiki/Great_Filter
I don't worry about that too much.
Consider a community of people with little technology that live away from any major trade routes, and thus don't see ships or planes. They would be oblivious to all the internet, TV, radio and postal traffic going on around them despite its huge volume. Now, I can't think of any such islands that are totally out of contact in 2013, but there are still uncontacted tribes in the Amazon basic (that we know about) and probably a few in other places (that we don't know about).
Since interstellar travel would require something like a warp drive to be any way practical, and we have yet to crack that problem, it seems quite likely to me that we're also incapable of observing traffic of that kind going on in our (galactic) vicinity. I don't see any particular reason that more advanced civilizations would go out of their way to reveal themselves to us; indeed, it bothers me that most alien invasion movies/novels tend to skip over the question of what is so special about Earth that aliens should cross vast distances to plunder our resources in particular when it would be so much easier to just grab a passing asteroid or comet.
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#38Regarding the existence of life...
Seems all that's really required to kickstart life and evolution is any self-replicating structure.
Chemicals are well suited for creating complex structures, but it doesn't rule out self-replicating forms embedded in other kinds of matter held together with other kinds of force.
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#39This is sort of terrifying, given that we haven't observed any space-faring species from any of those other Earth-sized planets yet. http://en.wikipedia.org/wiki/Great_Filter
Human recorded history is what 5-10k years? Pretty tiny in comparison to the 4 billion years earth has been around. We might've had visitors already!
Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way
#40Earlier quoted context omitted.
There's a lot more to life than just liquid water. In fact there are a huge array of requirements including distance from the sun, right arrangement of planets, tidal systems, plate tectonics...
i think it's the opposite of that. by all evidence, life on Earth began as soon as it was possible , and that's just this particular kind of life with this set of particular elements under these particular constraints. there may be other chemical/physical configurations under which life is even easier, etc
Just look at the difference an active core makes by observing the difference between Earth and Mars. How likely is it that a planet has all the right things: liquid water, enough gravity (mass), active core, planets further out sweeping up the debris so it doesn't destroy said planet over and over, tidally locked moon, etc.
My guess is that Earth is very, very unique.