What was Einsteins theory about time?

Einsteins theory about time says:

Time slows down or speeds up depending on how fast you move relative to something else (So when I'm having fun time move fast, and when I'm doing my homework, time moves slow :( )

Explanation:

Have a great summer :)

hey , the answer is c

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )