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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

#41

Post by andrewfelix »

noiv wrote: post #28
andrewfelix wrote: post #21

Earlier 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...

Why there are so many constraints on life listed? Is it to make more us special? Some people follow a different approach and say the purpose of life is to hydrogenate carbon dioxide. http://blogs.discovermagazine.com/cosmicvariance/2010/03/10/... I very much like the idea that life might be a consequence of entropy and emerges everywhere where energy is in flux and matter poses a threshold against the arrow of time.

It's a nice idea, but I find the 'Rare Earth' hypothesis convincing: http://en.wikipedia.org/wiki/Rare_Earth_hypothesis#Rare_Eart...

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#42

Post by marshray »

Udo wrote: post #36
martinced wrote: post #33

Regarding 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…

Yeah, it's not like some alien benefactors would have placed a geodesic array of transmitters in the Oort cloud that would cancel out all our inane radio spectrum emissions.

Or could they? Hmmm...

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#43

Post by marshray »

anigbrowl wrote: post #37
Symmetry wrote: post #31

This 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 Amazo…

Why, to collect us for their zoos of course.

We may also make good pets, like the monkey on the shoulder of some alien Michael Jackson.

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#44

Post by tokipin »

jstalin wrote: post #40
tokipin wrote: post #35

Earlier quoted context omitted.

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.

yea but that doesn't mean that Earth's configurations are the only ones that yield life. example: the role water plays here on earth might not even be necessary in other chemical/physical systems, or could be played by other chemicals given different gravitational/atmospheric pressures, etc

and i don't think there is anything about earth that is unsusual as far as planetary systems go

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#45

Post by BerislavLopac »

anigbrowl wrote: post #37
Symmetry wrote: post #31

This 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 Amazo…

"Now, I can't think of any such islands that are totally out of contact in 2013"

We can always count on Cracked to point the way. ;-)

http://www.cracked.com/article_19976_6-isolated-groups-who-h...

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#46

Post by protomyth »

vorg wrote: post #30
protomyth wrote: post #26

Earlier quoted context omitted.

I remember an old Chaos Manor column that talked about a book detailing what was needed, but I have not been able to find the book or remember the title.

Perhaps "Rare Earth" by Peter Ward and Donald Brownlee. http://www.amazon.com/Rare-Earth-Complex-Uncommon-Universe/d...

nice book, but it was much, much older - mentioned in a column in the 80's

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#47

Post by JoeAltmaier »

ceejayoz wrote: post #5
mullingitover wrote: post #4

I'm curious how many Earth-sized planets have a twin planet like our moon. Without the moon we'd be tidally locked, and despite all our water we wouldn't be nearly as life-friendly.

Mercury and Venus aren't tidally locked.

Mercury is in a more elliptical orbit; its 'tidally locked' at the perihelion but when its further away it gets a half-turn in. So each side spends half a year baked, half a year frozen.

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#48

Post by mistercow »

marshray wrote: post #20
mistercow wrote: post #16

Earlier quoted context omitted.

Yes, but I think you may have a few too many sig figs there.

So does 17 :-)

I guess the number of sig figs when you write out "a billion" is ambiguous.

Re: Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way

#49

Post by mistercow »

jonknee wrote: post #14
31reasons wrote: post #13

Earlier quoted context omitted.

I am curious How did you get to this number ?

If there are 17 billion Earth sized planets out there and we're "one in a billion" that would mean there are 17 planets as perfect as ours that there is life. 17 - 1 = 16. The billion figure was just pulled out of thin air, "one in a X" is a common expression and for this purpose billion seemed appropriate. If we're actually only one in a million, we'll be busy meeting our new friends.

>If we're actually only one in a million, we'll be busy meeting our new friends.

The Milky Way is roughly a disk, so let's think in two dimensions, and for the sake of being reasonable, let's just talk orders of magnitude.

The area of the Milky Way disc is on the order of 10^9 square light years. If there are 10^4 civilizations in the Milky Way, that means we should expect one other civilization within a 10^5 square light year neighborhood, meaning that we would expect the nearest civilization to be on the order of 100 light years from us.

Over that distance, it would be plausible for two civilizations to transmit information to each other, but "conversations" would take generations. And that's if we ever managed to find them.

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