2 months ago
Last edited at 7:46PM on 10/24/2013
Time dilation is a phenomenon in which time passes at a slower rate due to a couple factors: gravity and speed.
Take the astronauts aboard the International Space Station, for example. Because the astronauts are further away from Earth's center, time passes at a faster rate for them. We, on the ground, are closer to the center, and so time passes at a slower rate. The gravity of any object slows down time, depending on the mass. Black holes, of course, are the most extreme. Their gravity slows down time to a virtual halt. This is known as gravitational time dilation.
In the case of speed, the faster you travel, the slower time passes. If you were to get on a spaceship and leave Earth for 1 year, traveling at 99.99% light speed, you will return to Earth 22,000 years later. Since you are traveling at a tremendous speed, time slows down so that you age only 1 year when you return. The reason for this is because space and time are relative, and must work together to keep the speed of light as a constant--the end result is a decrease in the rate of time's passage. This is known as special relativistic time dilation.