What would happen if – all of a sudden – the Sun just disappeared? Well, 8 minutes later (the time it takes for light from the Sun to reach the Earth), it would be a whole lot of bad. First, the gravitational pull from the Sun would also disappear, so the Earth would veer off in some direction in to space, since it would have nothing left to orbit. Next, it would go dark. There would be no sunlight, and the moon would be nearly impossible to detect, except for the light that reflects off the Earth.
Within a few days, the temperature would drop to 150 degrees Kelvin, or roughly -123 degrees Celsius. Humanity would be forced underground for shelter. On the surface, photosynthesis would stop, killing off plants. Without plants, herbivores would die, and shortly thereafter, carnivores. Scavengers would survive a little longer. Microorganisms that rely on different food sources for energy – like those deep in the ocean near thermal vents – would survive longer still.
Within 2 months, the ocean surface would begin to freeze over in places that never froze before, killing off most aquatic life that managed to survive near the surface. On land, however, the largest of trees, even without photosynthesis, would still manage live for several years (if not decades) using stored energy reserves… but they would inevitably die off as well.
At around 1,000 years, the ocean’s surface would begin to freeze through. It would take thousands of years for the ocean to freeze completely solid, especially the deepest areas closest to thermal vents. Once the oceans freeze solid, the Earth’s temperature would be a frigid -240 degrees Celsius, which would cause the Earth’s atmosphere to collapse, exposing the planet to the harsh radiation of space.
And our planet would continue to drift off into the vastness of space.
TLDR; if the Sun disappeared, it would be the end-times for Earth as we know it.
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