Quote:
Originally Posted by CraigS
Warren;
Science and mathematics can say nothing in favour of one perspective over the other.
There simply isn't enough data to create a significant sample instance to draw from. One needs to look at the probability of creating life, from scratch, and then look at the numbers of planets which may be out there to support it, in order to balance the equation. I mean, the chances of creating life from scratch are also astronomical. You may need squillions of planets for it to occur from scratch .. and ours may be the one and only instance of it!
Then again, it might not be the one and only instance of it.
Once an instance of exo-life IS discovered, then statistically, things change but until that happens, its a matter of personal taste and gut-feel.
Acknowledgement of it all being driven by gut-feel is a good place to start a conversation from.
Cheers
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Nor is there enough data for some to say that life doesn't exist and that we are the only ones. But statistical records show that if something has happened once it is more likely to happen again and that the more chances it has to happen again "ie" more stars and therefore more planets the more likely it is to happen. I think that we consider that other planets must be like Earth to evolve life but NASA's announcement shows that the old thoughts on what is needed for life has to be changed and new possibilities considered.
Quote:
The statitistics
1) The number of galaxies. An estimated 50 billion galaxies are visible with modern telescopes and the total number in the universe must surely exceed this number by a huge factor, but we will be conservative and simply double it. That's 100,000,000,000 galaxies in the universe.
2) The number of stars in an average galaxy. As many as hundreds of billions in each galaxy.
Lets call it just 100 billion.
That's 100,000,000,000 stars per galaxy.
3)The number of stars in the universe.
So the total number of stars in the universe is roughly 100 billion x 100 billion.
That's 10,000,000,000,000,000,000,000 stars, 10 thousand, billion, billion. Properly known as 10 sextillion. And that's a very conservative estimate.
4) The number of stars that have planetary systems. The original extra-solar system planet hunting technology dictated that a star needed to be to close to us for a planet to be detected, usually by the stars 'wobble'. Better technology that allows us to measure the dimming of a stars brightness when a planet crosses its disk has now revolutionised planet hunting and new planets are being discovered at an ever increasing rate. So far (August 2003) around 100 have been discovered so we have very little data to work on for this estimate. Even so, most cosmologists believe that planetary formation around a star is quite common place. For the sake of argument let us say it's not and rate it at only one in a million and only one planet in each system, as we want a conservative estimate, not an exaggerated one. That calculation results in:
10,000,000,000,000,000 planets in the universe. Ten million, billion, as a conservative estimate.
5) The number planets capable of supporting life. Let's assume that this is very rare among planets and rate it at only one in a million. Simple division results in:
10,000,000,000 planets in the universe capable of producing life. Ten billion!
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http://www.thekeyboard.org.uk/Extrat...ial%20life.htm
I am really enjoying this discussion
