## May 25, 2004

### The Universe is Freakin' Massive, Dude

Paul Hughes over at Future Hi has given some thought to the recent news about the size of the universe. It turns out that the universe's radius is 78 billion light years, or 156 billion light years across, minimum.

Okay, that's big. Colossal. Actually, there isn't a word in the English language that describes this enormity, except for maybe infinity -1. And maybe that's not enough either.

Paul Hughes explains how big this is by analogy:
According to the standard inflationary model of cosmology, the visible portion of our universe; the one mapped by our telescopes is an infinitesimally small speck in a much larger universe of at least a 10X35 light-year across! I admit this number is really, really big, and almost impossible to imagine. So lets shrink everything down, WAY down, just so we can get a better grasp of it. Let's imagine that the entire universe that we have seen in all the world telescopes, all the galaxies, all trillion of them, extending out 13 billion light years in every direction is shrunk down to the size of a golf ball. Now you are holding the entire visible universe in the palm of your hand. So how big is the actualy 10X35 lightyear universe in comparison? If we do a volume calculation, the actual universe contains 10X60 of those golf balls! Wow, I guess we didn't shrink things down far enough, but this will have to do. So how big a volume would 10X60 golf balls fill up? Try a sphere 850 light years across! So imagine a mass of golf balls that big, and each one of those golf balls contains all the stars and galaxies that we can see through our telescopes.

That's a lot of golfballs. Not satisifed? How about this:
This is still almost beyond imagining, so lets take a slightly different approach. Imagine you are travelling so fast that you can go from on end of the galaxy to the other in just one second. That's a speed of 100,000 ly/sec. At this speed the entire galaxy would be in reach before you can say the word "go", and wam, you're there. At this speed, you could travel to the nearest galaxy Andromeda in 22 seconds. And you could cross from end of the visible universe to the other in 72 hours. Continuing on at this speed, it would take 115 days to travel a trillion light years, 315 years to travel a quadrillion, and 315,000 years to travel a quintillion or 10X18 light years. And yet you have barely moved at all in comparison to the universe which is 10X35 light years across. So, lets speed up our warp vehicals again, so that we can travel a quintllion light years every second. At such a speed we could cross the known universe 100 million times in one second. Ok, so now that we are travelling at a speed that might as well be infinite, how long would it take to cross from one side of the univese to the other?

3.7 billion years

What does this mean? Well, a number of things.

It means that the Rare Earth Hypothesis might be shot right out of the water. There are so many galaxies in the universe that even if you have a one in a trillion chance of having a space-faring civ, you're still going to have more civs than there are atoms in our solar system spread across the entire universe.

It also means the Fermi Paradox is that much more spookier :-|

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