Scioly.org

This is the I Bet You Didn't Know This Game. You post a random fact, following "I Bet You Didn't Know". Then the next person posts if they already knew that or not, then another "I bet you didn't know that (insert fact here.)
Ex.
P1: I bet you didn't know that Jupiter doesn't have seasons.
P2: I did.
I bet you didn't know that kamikaze actually means "divine wind."
P3: I didn't.
I bet you didn't know that brown dwarfs fuse deuterium.

Alright I'll start.
I bet you didn't know that all the asteroids combined only have a mass on about 4% of that of the Moon.

I didn't.
I bet you don't know that only 1% of all species ever to evolve are still extant.

I didn't
I bet you didn't know that the production of iron in a star makes it die.

I didn't. (But I had some idea of what you meant.)

I bet you didn't know that Midtown New York City doesn't have 4th Avenue. (Probably you will.)

Actually I didn't
I bet you didn't know that the discovery of Pluto, by Percival Lowell, was a complete coincidence because upon modern investigation it was found that all his calculations were incorrect

I actually read something like that the other day.

I bet you didn't know the heliocentric model of the solar system was proposed before Copernicus by Aristarchus, a student of Plato, back in 3rd century BC.

Interesting, I didn't know that.

I bet you didn't know that the Department of Agriculture was founded in 1862.

Why would I want to know that?

Bet you didn't know that Columbus wasn't the first to believe that the Earth was round. Greeks knew that thousands of years ago.

I knew it wasn't Columbus.

I bet you didn't know that the platypus is not endangered or vulnerable.

I did.
I bet you didn't know that the sun is only ever directly overhead on the equator.