Black Holes & Space-Time

In 1915, Albert Einstein discovered that space and time are woven together like one giant, stretchy fabric. He called it space-time. Heavy objects make a dent in it, like a bowling ball on a trampoline. When smaller things roll by, they curve toward the dent. That's gravity!

The heavier and more squished an object is, the deeper the dent. A black hole makes a dent so deep that it's like a bottomless well.

Most black holes start as giant stars, at least about 20 times heavier than our Sun. A star shines by burning fuel in its core. When a giant star runs out of fuel, gravity wins: the core collapses in a split second, the outer layers blast away in a gigantic explosion called a supernova, and the crushed core can become a black hole.

☀️ Don't worry: our Sun is NOT heavy enough to become a black hole. In about 5 billion years, it will become a white dwarf instead.

Strong gravity makes time run slower. This is called time dilation. Near a black hole, it's extreme: an astronaut close to the edge could feel just a few minutes pass while years go by back on Earth!

🛰️ This happens on Earth too, just a tiny bit. GPS satellites are farther from Earth's gravity, so their clocks run a little FASTER than clocks on the ground (by about 38 microseconds a day). If engineers didn't correct for Einstein's space-time, your phone's map would be wrong by miles every day!