For an hour, or for a month, or let’s say even for a whole year?

What would happen to mankind?

The very last photons from the surface of our star and the last particles that make up the solar wind have started their final flight towards the Earth. No one yet suspects that the heart of our solar system has stopped functioning. 8 to 9 minutes later and the sky suddenly turns black. Darkness descends upon the entire planet. No matter whether at the moment it’s the deep dark of midnight or a bright sunny noontime at your location, you can quickly and easily see the difference. The stars are now all clearly visible against the sheer black backdrop of the sky. The Moon is not visible at all since there’s no longer any sunlight were it to reflect. A moment before the onset of the all and shrouding darkness bright Northern Lights may appear. Due to changes in the magnetic field around the Earth and the disturbances in the ionosphere. The most dreadful consequence of all is the complete and utter cessation of the process of photosynthesis resulting in plants and cyanobacteria no longer producing oxygen. This will soon lead to, how shall we say it, difficulties for every living begin. After an hour, true panic reigns over the heretofore day times side of the earth. Power and communication outages propagate across the entire planet. Temperatures everywhere drop by a several degrees and the Earth surface begins to slowly cool. But from the inside the planet is still heated by its molten core.
24 hours in, darn has not and will not arrive. Panic and chaos are enveloping the entire world state authorites have almost zero control over the situation. Humankind is trying to figure out what the hell happened while coping with massive power and water supply outages. The temperature on the surface falls to between 5°C to 7°C and has now decreased by about 15°C to 20°C. Some species of plants and microorganisms begin to die. The inhabitants of the ocean for the time being feel almost no changes.

After 7 days, it’s still dark.

The average temperature on earth is not -17°C. In areas where there are tectonic faults, it’s still warm. Thanks to geotermal energy not letting the surface freeze over. Most plants have already died due to cold or lack of light. Herbivorous and heat loving animals also begin to die. In the oceans, phytoplanktons begin to die as well. The inhabitants of shallow waters suffer tremendously from the cold and the surface of the ocean is beginning to turn to ice. By now scientists and other individuals have realized what has happened and rushed to organize and equip shelters. One month in and the Earth is continuing to cool. The average temperature on the surface is now about -30 °C. And almost the entire planet is now coated with ice. Virtually all plants and cyanobacteria have perished. Some species of trees, especially confers, are still alive. But with the lack of sunlight, even they are not producing oxygen. In fact most of the earth living things have died. But... some bacteria still carry on with their normal life activity. Most of the remaining life on earth is now found only near geothermal springs and under water. Interestingly, the layer of ice on the surface of the ocean slows down their colling. And in the areas of oceanic tectonic faults and geothermal sources, the water is still warm. Obviously being naturally heated. But even in the ocean the drama of a mass extinction event begins to unfold.

One year in and the surface of the Earth and the oceans are convered with a thick layer of ice.

According to professor David Stevenson at CallTech the temperature on the surface of the earth should drop to about -40°C . Life endures now only deep in the earth oceans, and perhaps some groups of humans might be able to survive on the surface of the planet in places like Iceland and other areas with large amounts of geothermal activity. Professor Stevenson believes that the Earth will continue to coll for another several thousand years. Until the surface temperature reaches approximately -160°C. At that point, life on the planet in the usual sense of the word will simply become impossible. And let’s not forget about the gravity of the Sun. After all, it’s unlikely that the Sun could suddenly go out without losing its gravitational pull. If the Sun ceases to hold the planets and other celestial bodies in their orbit then the planets and asteroids will simply fly away into outer space. Some of them possibly even colliding with one another. The Earth for one will soar out into deep space where it could get bombarded with asteroids, comets and radiation collide with another planet or even some day end up in the gravity well of black hole. There’s also a very small possibility that after wandering through space for a very long time, the Earth would be able to integrate into another stellar system and find a new sun.