Because it was deep space . (the joke is how the outer space was very deep)
If someone comments saying you posted an antijoke and that you should rather post your joke in /r/antijokes.
Jokes on
X-post) http://www.reddit.com/r/AskHistorians/comments/2krnv8/whatistheoldestjokewehaveonrecord/
Because they don't understand how to use Logic or Reason.
It's a vacuum!
