Scientists tell us that after about five billion years the sun will begin to die, even as all stars do. First, the sun will get hotter, then it’ll probably swell. Slowly it will become much, much bigger. As it grows bigger, its color will change from yellow to red .as it grows bigger it will pour out more heat. All of the rivers, ponds, lakes, and oceans will boil and turn to steam because the Earth will get so hot.
After about a billion more years, the sun will start shrinking. It will eventually shrink down to the size of the Earth and turn into a lifeless, dark ball. When the heat given by the sun starts reducing, the clouds of steam around the earth will turn back into water and fall as rain. Oceans and lakes will fill up again .but as the sun grows cooler, the earth will also grow colder. All the water will freeze. Earth will turn into a lifeless, ice-cold, quiet, and black lump of rock.
We’ve got the science on this down very well today. The sun is currently operating in what’s called the “main sequence”. It is a sequence common for suns of comparable size to ours. It is a period when the sun’s gravity and the fusion of its components, mostly hydrogen, achieve a balance between internal nuclear processes and the pull of gravity.
This will continue until the mass of the sun and the fuel it is burning reach a point where main sequence sustainability can no longer be maintained. Four our sun, as it leaves the main sequence, it will likely become a red giant, and then a white dwarf. At this stage, although it would still emit light, it will for our purpose here, no longer be “shining” in the sense of this discussion.
The reason it is no longer shining is that it has consumed the fuel necessary to keep shining.