Cracked.com: 5 Scientific theories that will make your head explode

5 Scientific theories that will make your head explode

20/8/08 – This is a particularly mind-boggling page, with some interesting facts for teaching about space.  Just how big is the universe?

Right now, on your computer screen [click the above link to view], are approximately 10,000 galaxies.

Each of those galaxies contains anywhere from ten million to one trillion stars.

The average star is roughly a million times the size of Earth.

And yet, with all that junk, the Universe is more than 90 percent empty space.

All of that, in this tiny photo. A photo that took 400 orbits and 800 exposures to take.

And the kicker? The photo covers one thirteen-millionth of the entire night sky.