Passage A (9%)
P1 One of Albert Einstein's greatest works was realizing that time is relative; there is no real or absolute time. It speeds up or slows down depending on how fast one thing is moving relative to (in comparison with) something else.
P2 Think about when you feel like time moves very quickly and sometimes very slowly or like how the hours fly by when you're hanging out with a close friend, or how seconds drag on so slowly when you're stuck in traffic on a hot day. Yet, you can't actually speed time up or slow it down—it always flows at the same rate, right?
P3 Albert Einstein didn't think so. His idea was that, theoretically, the closer/nearer we come to traveling at the speed of light (186,000 miles per second), the more time would appear to slow down for us from the eyes of someone who, in relation to us, was not moving. He called the slowing of time due to motion time dilation.
P4 Imagine you're standing on Earth holding a clock. Your friend is in a rocket in space moving past you at nearly 186,000 miles per second. Your friend is also holding a clock. If you could see your friend's clock, you would notice that it seems to be moving a lot more slowly than yours. So, what could be an effect of this time dilation?
P5 Here is the answer: people will age slowly if they travel in space. As an illustration, an astronaut traveling at the speed of light would age at a slower rate than those he/she left behind on earth. If such an astronaut left earth and then returned, everyone they know would have aged at a quick rate while the astronaut remained relatively young. Here's a helpful visual: