Albert Einstein’s theory of general relativity tells us that gravity is a curve in the fourth dimension of space and time.
What causes the curve is mass. Seriously weighty objects can bend the fabric of space-time. It explains why the planets orbit around the sun. The sun is so incredibly massive it essentially bends the space around it, pulling into orbit lesser objects (like planets) nearby. Similarly, with enough mass an object can even cause an otherwise straight beam of light to curve. In astronomy, that’s called gravitational lensing.
“They always say time changes things, but you actually have to change them yourself.” ― Andy Warhol
Time is not immune to the effects of gravity either. It passes more quickly the less gravity there is, a phenomenon known as gravitational time dilation. On most days you might not credit gravity with anything more than keeping pigs on the ground (and preventing nature from creating Pink Floyd album cover-like scenes), but a gravitational field can also warp time. That’s gravitational time dilation in a nutshell, and for an example of time dilation in action, we need look no further than the nearest geosynchronous satellite.
Even with ultra-precise atomic clocks, satellites would inevitably wind up a few microseconds fast without correctional programming. This is because massive objects such as suns and planets warp time. Yes, time passes a little slower on Earth than it does in orbit. It would pass even slower on the surface of a Jupiter-sized planet and get slower still near a black hole. NASA even purposely ‘misadjusts’ the clocks before lift-off on space shuttle missions, so that time on the shuttle will sync properly with time down here on Earth at Mission Control.
“Physics isn’t the most important thing. Love is.”
― Richard P. Feynman [Nobel Prize in Physics, 1965]