On a larger scale, the removal of the sun would also remove its protective magnetic field from around our solar system. By removing the heliosheath for a second, we’d be allowing all of this radiation into our solar system.

With no sunlight, photosynthesis would stop, but that would only kill some of the plants—there are some larger trees that can survive for decades without it. Within a few days, however, the temperatures would begin to drop, and any humans left on the planet’s surface would die soon after.

If the sun would disappear for three days… Everyone Dies. The temperature would drop drastically, Earth would lose orbit and possibly crash into other planets or asteroids… Yeah, it’s not fun.

If that were true, then the first thing that would happen when the sun disappeared is that Earth, along with all the other planets, would go flying off into space. It would be complete and utter chaos in our solar system. Therefore, we would still see the sun in our sky eight minutes after it was gone.

So what would happen to that life if the Sun suddenly went out? Because light from the Sun takes eight and a half minutes to reach Earth, we wouldn’t notice immediately if the Sun suddenly went out. Nine minutes later, though, we’d find ourselves in complete darkness.

A relatively simple calculation would show that the Earth’s surface temperature would drop by a factor of two about every two months if the Sun were shut off. The current mean temperature of the Earth’s surface is about 300 Kelvin (K). This means in two months the temperature would drop to 150K, and 75K in four months.

In about 5 billion years, the hydrogen in the Sun’s core will run out and the sun will not have enough fuel for nuclear fusion. So, in about 5 billion years, the Sun will stop shining.

But in about 5 billion years, the sun will run out of hydrogen. For about a billion years, the sun will burn as a red giant. Then, the hydrogen in that outer core will deplete, leaving an abundance of helium.