Now, to pick up where we left off from all that gravity business, I will now reveal our fifth point (first point for the General Theory of Relativity): gravity slows time down.
Since we’ve established that the abilities of gravity and acceleration are the same, then gravity slowing time down is more understandable since we’ve discussed that time moves in a moving — or accelerating — vehicle. Gravity curves and light and slows it down, which means that it also slows down light clocks.
True, these kind of effect would be imperceptible to us since Earth’s gravity is not as strong as those in, for example, a black hole. Clocks on Earth slow down by a second a century. Compare that with black holes that not only suck in light but also stops time. That’s how strong their gravity pull is.
So let’s say your parents went on a vacation in a black hole. Of course, this is purely imaginary. Since time passes a hell lot more slowly for them, it’s highly likely that they’d return and you’d be older than them. What might seem like a week-long vacation to your folks would be 20 years for you. They come back and you’re a grandpa or grandma and they didn’t age a bit. That’s just freaky.