Can you skydive at 40000 feet?
No, since the air is too thin - there is not enough oxygen to breathe.
It can be done, but you have to wear an oxygen mask. The military does HALO (high altitude, low opening) jumps from 35,000+.
Can skydiving cause headaches?
Yes, being an extreme sport skydiving causes high level of emotions. It's possible to cause headaches or other health problems to people who aren't in good health. However headaches are in no way a typical problem caused by skydiving.
What is a normal height to skydive from?
Skydivers like to go at between 14,000 and 15,000 Altitude Above Ground Level, so they get more time to do tricks, practice relative work or just enjoy the feeling of dropping like a rock at 120mph for as long as possible.
How old do you have to at least be to officially sky dive?
18 years old in most states (16 with parent's consent)