What Would Happen If The Sun Disappeared?
If the sun disappeared, for eight-and-a-half minutes we’d have no idea that the sun had gone. We’d still see it as an eerie sight, lingering, like a ghost in the sky above Earth’s day side.
Just imagine, nobody on earth could foretell what was about to happen! As soon as the last of the sun’s light reached us – eight-and-a-half minutes after the sun itself disappeared – the sun would blink out and night would fall over the entire Earth.
Not until that instant would Earth sail off in a straight line into space. Einstein’s special theory of relativity tells us that no signal in the universe – not even the tug of gravity – can travel faster than the speed of light – about 300,000 kilometers, or 186,000 miles, per second. Though free from the sun’s gravity, we’d be traveling at the same speed as before – about 18 miles, or 30 kilometers per second. So Earth would be traveling at the same speed as always into eternal night.
If you were on Earth’s night side when the sun disappeared, you might not notice anything … at first. But then the night sky would begin to change. For example, if there were a full moon – which shines with reflected sunlight – its light would disappear a few seconds after the sun’s light blinked out. Over the course of several hours, the planets would wink out one by one, as they reflected the last of the sun’s light to us. Source: EarthSky
Is It a Coincidence That Moon Keeps One Face To Earth?
No, it’s not a coincidence. The constant pull of Earth’s gravity has slowed down the spinning moon so now it’s in what’s called “synchronous rotation.” In other words, the moon spins once for each of its orbits around Earth – and that’s why the moon always keeps a single face turned our way.
Billions of years ago, the moon was spinning faster than it does today – and it was also much closer to Earth. But Earth’s gravity put “the brakes” on the moon – and gradually increased its distance. This happened because Earth pulls one side of the moon more strongly than the other side. And the moon does the same to Earth. Both worlds attempt to “stretch” each other from the shape of a sphere into more of an egg shape. We see this “tidal effect” strongly in ocean tides. But the Earth and moon also raise “tides” of solid ground on each other.
Because their tidal bulges do not line up exactly between the center of Earth and the moon, the rotation rates of both worlds have slowed down over time. Now the moon is locked with one face perpetually turned toward Earth. And the moon is getting farther away from Earth at about 1.5 inches – or 3.8 centimeters – per year.