It's no exaggeration to say the sun sustains life here on Earth -- it provides not only light and warmth but also the energy that helps keep us supplied with oxygen and food. But what if the sun exploded or suddenly went cold -- or simply blinked out of existence?
The first big change we'd notice would be the absence of light. Of course, this wouldn't happen instantaneously -- it takes eight minutes and 20 seconds for sunlight to reach Earth.
But once there's no more sunlight, would we be able to see?
"The Milky Way contributes about as much light as 1/300th of a full moon," Stevens says in the video. "So there would be enough light from space for us to see around a bit, but of course electricity and fossil fuels will still be usable for a while. So cities and towns could continue to be lit by manmade sources, just like a typical night, except it would be night everywhere."
Without sunlight, photosynthesis would cease. After all, photosynthesis is how plants and some organisms use sunlight to make food from carbon dioxide and water.
"This is huge, 99.9 percent of the natural productivity on Earth is done by photosynthesis, which requires the sun," Stevens says. "Without the sun, plants would no longer be able to inhale carbon dioxide and exhale life-sustaining oxygen."
And without sunlight, the Earth would get very, very cold. Earth's surface temperature now averages about 57 degrees Fahrenheit, but by the end of the first week without the sun, the average surface temperature would be below the freezing point.
The planet's ocean surfaces would freeze over, but deep below some liquid water could remain, along with life on the deep sea floor. Stevens says, "The Earth would be a spaceship for these little earthlings basically."
One last thing to consider: The sun not only illuminates and heats our planet but also provides the gravitation that keeps us in orbit. So, as Popular Science explains: "If its mass suddenly disappeared (this is equally impossible, by the way), the planet would fly off, like a ball swung on a string and suddenly let go."