Friends, Tumblr, and Blog: If you leave Earth at the age of 15 in a spaceship
 at the speed of light and spend 5 years in space,
 when you get back on Earth you will be 20 years
 old and all your friends who were 15 when you
 left will be 65 years old. This phenomenon is
 known as "time dilation" in physics.
 /didyouknowpagel @didyouknowpage
catchymemes:
Astronomy in a nutshell

