Scientists Estimate At Least 17 Billion Earth-Size Planets Inhabit Milky Way • Hacker News Board

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

#11

Post by mistercow » Mon, Jan 07, 2013, 10:39 PM UTC

jonknee wrote: post #10

Fascinating. Our little rock could be "one in a billion" and we would still have 16 other civilizations to meet. Just in our galaxy.

Actually we would expect to have 17 other civilizations to meet. The events are independent, so observing our own civilization doesn't affect the odds for the rest of the galaxy.

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

#12

Post by ra » Mon, Jan 07, 2013, 10:40 PM UTC

I'm in awe of how much we've discovered about the universe in the last decade of science exploration.

The space programs Cassini, Kepler and Curiosity, as well as earth bound programs like VLT and LHC really have expanded our understanding of the laws of nature to levels I didn't think I'd see in my lifetime.

We live in fascinating times.

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

#13

Post by 31reasons » Mon, Jan 07, 2013, 10:58 PM UTC

jonknee wrote: post #10

Fascinating. Our little rock could be "one in a billion" and we would still have 16 other civilizations to meet. Just in our galaxy.

I am curious How did you get to this number ?

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

#14

Post by jonknee » Mon, Jan 07, 2013, 11:22 PM UTC

31reasons wrote: post #13

jonknee wrote: post #10

Fascinating. Our little rock could be "one in a billion" and we would still have 16 other civilizations to meet. Just in our galaxy.

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.

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

#15

Post by marshray » Mon, Jan 07, 2013, 11:42 PM UTC

mistercow wrote: post #11

jonknee wrote: post #10

Fascinating. Our little rock could be "one in a billion" and we would still have 16 other civilizations to meet. Just in our galaxy.

Actually we would expect to have 17 other civilizations to meet. The events are independent, so observing our own civilization doesn't affect the odds for the rest of the galaxy.

But we're not interested in Earth, so we'd expect to see 16.999999999 other civilizations.

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

#16

Post by mistercow » Mon, Jan 07, 2013, 11:44 PM UTC

marshray wrote: post #15

mistercow wrote: post #11

Earlier quoted context omitted.

Actually we would expect to have 17 other civilizations to meet. The events are independent, so observing our own civilization doesn't affect the odds for the rest of the galaxy.

But we're not interested in Earth, so we'd expect to see 16.999999999 other civilizations.

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

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

#17

Post by mikeash » Mon, Jan 07, 2013, 11:47 PM UTC

pedalpete wrote: post #2

I didn't think there was anything special about the size of the earth (and apparently I'm right). Can anybody explain why this is important, I don't think the article did a very good job of that.

Too small, and the planet won't be able to retain an atmosphere (e.g. Mars). Too large, and it'll probably retain too much.

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

#18

Post by nfg » Mon, Jan 07, 2013, 11:56 PM UTC

CapitalistCartr wrote: post #6

ceejayoz wrote: post #5

Earlier quoted context omitted.

Mercury and Venus aren't tidally locked.

They're quite close to it. Mercury takes two of its own years to have one day, and Venus's year is less than two of its days.

This is generally suspected to be because of large primordial impacts, much like the one which it is proposed created our moon. I don't think there's anything intrinsic about Goldilocks zone orbiting rocky planets which would lend to tidal-locking with the star.

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

#19

Post by andrewfelix » Mon, Jan 07, 2013, 11:57 PM UTC

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.

I'd be curious too. For me the Fermi paradox is best satisfied by the 'Rare Earth' hypothesis. There are just too many infinitely rare combinations of variables required to support the kind of life we see on our planet.

I don't hold out any hope of finding much beyond the odd microbe.

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

#20

Post by marshray » Mon, Jan 07, 2013, 11:59 PM UTC

mistercow wrote: post #16

marshray wrote: post #15

Earlier quoted context omitted.

But we're not interested in Earth, so we'd expect to see 16.999999999 other civilizations.

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

So does 17 :-)