The Big Freeze is the most accepted theory of the fate of our universe.

    The Big Freeze explains that since the universe is expanding, the heat in the universe will be evenly distributed, meaning that no usable heat energy will exist. That means that motion will not be possible, ultimately leading to the end of everything.

It's a simple theory with a terrible ending.

Note: The picture above represents the Big Freeze, as well as 2 other theories: the universe will continue to exist at a constant size or the universe will gradually reach a maximum point and then begin to condense.