Albert Einstein predicted that we all experience time differently depending where on the world we are, and NASA thinks it's all about speed.

Albert Einstein’s Theory of Relativity is a concept that dates back to 1905, when the scientist began the quest to prove that large objects cause a distortion in space-time; a theory which he finally published in 1915. To simplify the general concept Einstein had come up with, the more massive a particular object is, the slower time moves around it – all thanks to gravity. For those of us on Earth, where the planet’s gravitational pull is substantial, those closer to Earth’s core theoretically age slower than those further away from it. That means that if you happen to live on the top floor of a swank high rise condo, not only do you get a better view of the neighborhood, but technically you age slower than the guy three blocks over stuck in a basement apartment. It’s why astronauts, miles above the planet and further away from Earth’s core and its gravitational pull, age slower than the rest of us. Don’t go looking for visible evidence of the concept, since we’re only talking fractions of a second difference over the span of a year.