Manifold: Time by Stephen Baxter

Stephen Baxter’s Manifold Time, the first of the Manifold Trilogy introduces an extraordinarily long view of time, expressed later in this series when a character sums up the immensity of the scale of time covered in this series with the statement;
“It began in the afterglow of the big bang, that brief age when stars still burned.”
This implies the history of the universe up to our time as a mere flicker on the timescale of that long view. Twenty billion years is just a fraction of the ‘brief’ time referred to. He is talking Deep time here.

If you assume the universe will last forever, then the timescales we think of as immense become inconsequential.

Much of this series involves the Fermi paradox; “ If there are billions upon billions of stars and many of these must have planets, the universe should be teeming with life. So why haven’t aliens been here?” The answer in Manifold: Time, is because there are none. In the universe created by Baxter only humans exist and no other life is found.

Over the mind bogglingly large timescales that Baxter contemplates, it becomes reasonable to assume that star creation will eventually cease as all matter in the universe is gathered up into stars. Stars that over the successive Terayears will run their lifecycle until there will be no visible stars left anywhere, with all matter in the universe ultimately accumulated into black holes that themselves will eventually evaporate into nothing.
This energy death of the universe presents something of a problem to our distant ancestors and they plan to try to do something about it.
Life is incredibly rare in this particular universe, and so we are shown the dismal prospect of our distant ancestors destined to a long long lonely and ultimately meaningless fight to survive as the universe slowly decays around them.
Sounds depressing but it is in fact a really good read, with startling concepts and continuous action as the main character Malenfant discovers a way out of this mess - perhaps.