How fast is gravity, exactly?

Gravity is the most familiar of the fundamental forces we know about, and it's also the one that holds the Universe together by connecting galaxies in a vast, interconnected web.

We know that the speed of light is 300,000 kilometers per second, which is 186,000 miles per second.

We know how far away the Earth is from the Sun (150 million km, or 93 million miles), so we can figure out how long it would take for us to notice that the Sun had disappeared.

It would take around eight minutes and twenty seconds before the sky at midday turned completely dark.

If the sun disappeared away, it would not only stop giving off light, but it would also stop being the source of the planets' gravity.

If the speed of gravity is infinite, then it would vanish at the same time as the Sun vanished from the face of the earth.

If gravity moved at the speed of light, Earth's orbit would last 8 minutes and 20 seconds. Afterwards, it would stop following its usual path.

Einstein thought gravity traveled at light speed. He anticipated humans will observe the Sun's absence and Earth's route change simultaneously.

A precise measurement shows that gravity and light move at the same speed. It proves Einstein right once more, and it hints at something deep about how space works.