Let's speculate for a moment; what would happen if our sun suddenly went out for an hour or for a month or  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 at the heart of our solar system has stopped functioning.
  ‎
Eight to nine minutes later the sky turns black. Darkness has come upon the entire planet. no matter whether at the moment it's the deep dark of midnight or a bright sunny noon time at your location you can quickly and easily see the difference.
‎
‎The stars are now all clearly visible against the shear black backdrop of the sky. the Moon is not visible at all since there is no longer any sunlight for it to reflect. a moment before the onset of the all in shrouding Darkness bright Northern Lights may appear due to changes in the magnetic field around the earth and disturbances in the ionosphere field.
‎
‎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  difficulties for every living being.
‎
after an hour true Panic Reigns over the side heretofore day time side of the earth. power and communication outages propagate across the entire planet. Temperatures everywhere drop by several degrees and the Earth's surface begins to slowly cool. but from the inside the planet is still heated by its molten core.
‎
‎24 hours in and  dawn has not and will not arrive. panic and Chaos are enveloping the entire world.  state authority 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 to 7 degrees Celsius that's about 41 to 45 degrees Fahrenheit. And has now decreased by About 15 to 20 degrees Celsius that's a drop of about 30 degrees Fahrenheit.
‎
some species of plants and micro-organisms 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 now minus 17 degrees C, that's about 1 degrees  in Fahrenheit.
‎
In areas where there are tectonic faults It's still warm, thanks to geothermal energy not letting these 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 ocean, phytoplankton 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 organized and equip shelter.  one month in and the Earth is continuing to cool the average temperature is now about -30°c. That's minus 22 degrees Fahrenheit and almost the entire planet is now coated with ice.
‎
virtually all plants and cyanobacteria have perished. some species of tree,  especially conifers, are still alive but with the lack of sunlight even they are not producing oxygen.  in fact most of the Earth's living things have die,  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 underwater.  interestingly the layer of ice on the surface of the oceans slows down there cooling. 
‎
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 covered with a thick layer of ice. the temperature on the surface of the Earth dropped to about-40°c and that's the same in Fahrenheit.

Life endures now only deep in the earth ocean, and perhaps some group 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.

The earth will continue to cool for another thousand years until the surface temperature reaches approximately-160°c that's about-256°f. At that point,  life on the planet,  in the usual sense of the word will simply become impossible

But of course that just speculation. Scienctist believed that the end of life would be In a couple of billion years. The sun was supposed to end up swelling and turning into a red giant.

Our star would have swallowed mercury and Venus, and earth and mars would have been heated up by several thousand degrees.

The sun was supposed to explode and throw off its outer envelope, leaving behind a gradually cooling Steller core, a white dwarf around which will orbit whatever reminded after the explosion.

Sometimes scientist can only come up with theories and never have any proof of their ideas. Just like the theory of a missing sun. Humans were going to die. Yet humans are like roaches, if there is a will there is a way.