[Hebrews 11:6]

When you consider the millions/billions of galaxies each with millions/billions of stars the possibility of Earth [sic--more properly Terra] being unusual becomes a little difficult to believe...the odds are simply against it.

I used to think exactly that; in fact, forty years ago I wrote a long school paper arguing exactly that. Indeed, that was Carl Sagan's argument.

However, it turns out to be a totally fallacious argument. Sagan posited two parameters (you mentioned only one) for the existence of life on even one planet anywhere in the universe. But scientists have been looking into that, and now they have over 200 (and rising rapidly) such parameters, all of which must be exquisitely fine-tuned for life to exist anywhere. The true odds of even one planet being able to support life anywhere in the universe are (very conservatively stated) much less than one in 10 to the 40th.

I'll mention just two examples:
* If earth were just 1% closer to or farther from the sun, the water cycle would break down and life would not exist on earth. (Actually, this is two parameters: not only must earth's orbit be the right distance, but it also must be nearly circular.)
* If earth's mass (i.e., its gravity) were 2% larger or smaller, life would not exist on earth. You've noticed that water vapor (H2O, atomic weight 18) rises as clouds. If the earth were slightly smaller, those clouds would simply keep on going, higher and higher, until they were in space. However, if the earth were slightly larger, then methane gas (CH5, atomic weight 17) would not escape into space as it does, and we would all suffocate. Methane gas is the technical term for flatulence--not a pretty picture, is it?

There are over 200 parameters like that which must be right for life to exist on a planet. These factors work on the extra-galactic level, the galactic level, the solar-system level, and the planetary level.

Don't take my word for it--see for yourself:
http://www.reasons.org/resources/apologetics/index.shtml#design_in_the_universe

[fish hawk]

not only that but if we didn't have a moon at its very distance from Earth and size, life would not exist. "I Am" did it right the first time. Did he do it more than once? That is the question. I don't believe he did, myself.

[7MMmag]

I'll take your word for;

The true odds of even one planet being able to support life anywhere in the universe are (very conservatively stated) much less than one in 10 to the 40th.

The mockers might post something like;

Well, isn't that *extra* special?

Yeah, it's "special", all right. What is more amazing is the spirit.
Shared, given from on high, given to (for?) mankind. What a gift!

[The Toad]

I'm familiar with Sagan's "calculation" and many of the things he said I didn't agree with.

We'll probably never know either way in our lifetimes, but it's fun to speculate.

Thanks for the link--I'll check it out.

[AntiGuv]

I've been reading down the list on the first link at that webpage and I just wanted to mention that much of that is pure nonsense. There's just way too much there to bother dealing with, but figured you should know. I actually started drafting a reply, but gave up after the first four items alone took so long.

[Tymesup]

"If earth were just 1% closer to or farther from the sun, the water cycle would break down and life would not exist on earth.

* If earth's mass (i.e., its gravity) were 2% larger or smaller, life would not exist on earth. "

These examples assume that life needs water, clouds and the escape of methane. They also assume there is no other way for these parameters to be satisfied.

[Purple GOPer]

Your parameters only work if you believe that the universe has worse tolerances for differences than the most complex machine ever devised. I prefer to think of it as a cooking recipe, if you have the basic ingredients you will get something good.

BTW the number of ~known~ stars is 70 to the 22nd so the total number is probably high enough to beat even your pessimistic average.