Some Staggering Numbers

The latest estimate for the number of stars in the observable universe is now 70 sextillion, or 70 thousand million million million. This "is greater than the estimated number of sand grains on all the world's beaches and deserts - about 10 times more." Note that this is just the estimate for the observable universe, as the scope of the actual universe "could be much, much larger still - some people think it is infinite."

As of December, 2007, 270 planets outside the solar system have been discovered. It "is estimated that at least 10% of sun-like stars have planets, and the true proportion may be much higher."

If only one in a million stars had a planet that could support life, and one in a million of those had a planet that did support life, that would provide 70 billion planets with life in the observable universe. If advanced civilizations such as ours occurred on only one in a million worlds with life, there would be 70,000 advanced civilizations in the observable universe.

With these odds, doesn't it seem unlikely that we're alone in the universe?

Now for some more mind-boggling numbers. The age of the universe is estimated to be 13.7 billion years (the clock having started at the Big Bang). When we look out at those 70 sextillion stars, we are looking into the past, seeing the light from these distant objects looking as it did when it was emitted. Therefore, the furtherst objects appear 13+ billion light years away and are 13+ billion light years old.

But the universe is expanding at a rate faster than the speed of light, so the current position of these furthest stars is estimated to be over 40 billion light years away. "The observable universe is thus a sphere with a diameter of 92–94 billion light-years."

Stay with me, I'm about to make a point...

The fastest craft ever launched from Earth, Voyager 1, has had a top speed of 38,000 mph. Though not headed in the direction of Proxima Centauri, our closest celestial neighbor at 4.2 light years, it could have reached this star in 72,000 years. Even if far-future technology were able to attain half the speed of light, it would still take over 8 years to reach just the closest star. Forget about the 70 sextillion!

The universe is mind-blowingly large, and we are incomprehensively small. If the universe were created for the sake of humanity - as many people believe - why would it need to be so big? A little excessive, wouldn't you say?