A couple of months ago, I discovered the science fiction/horror classic The Nightland by William Hope Hodgson. The Night is a poignant story of love and adventure set in a dying world millions of years in the future. In the Nightland the Sun has long ago gone out and the world is shrouded in an eternal night without even the Moon or stars to relieve the darkness of the night sky. The surface of the Earth is frozen and uninhabitable and life is only possible at the bottom of a canyon hundreds of miles deep where there is still some warmth from the Earth’s cooling core. There the last remnant of humanity survives in a gigantic pyramid-shaped Last Redoubt besieged by monsters and eldritch forces of evil. There is no chance for humanity to break the siege or defeat the evil forces arrayed against it. They can only wait until the Earth Current which powers the defenses of the Last Redoubt fail at last and the evil forces destroy them.
This story has made quite an impression on me and lately, I find myself thinking about endings. Maybe it is because I am getting older and can see the end coming, Maybe current events seem to be pointing towards the decline and fall of the American Empire as we watch. Whatever the reason, I have been thinking about the end of all things.
The Nightland was written in 1912 and so the science in the book is more than a little dated. We now know that the Sun is powered by nuclear fusion, not by gravitational collapse, and is going to continue burning for billions rather than millions of years. We also know that the Sun will grow hotter and brighter as it exhausts its hydrogen, that it will become a red giant and will swallow Mercury, Venus, and probably Earth before settling down to become a white dwarf slowly cooling down to become a black dwarf. The Earth, assuming it survives, will have long since become uninhabitable, and the human race, unless we have colonized other star systems, will be extinct.
But what about the universe as a whole? Assuming we have learned to travel the vast distances between the stars and made new homes on other planets, how long can we expect to survive. How long will the universe last? Will the world in fire or ice, as the poet said?
Well, the universe certainly began in fire, according to current scientific theory. To be less poetic, the universe began in a state of extreme temperature and density being very much smaller than it is at present, perhaps even beginning as a singularity of infinite density and infinitesimal size. From this point, the big bang, the universe began to expand very rapidly in the process, creating the matter that currently makes up the universe.
Since the big bang, the universe has continued to expand, becoming ever larger and cooler. The question of whether the universe will end in fire or ice depends on whether that expansion will continue forever or whether at some point it will stop and the universe will begin contracting back to a hotter, denser state, perhaps all the way back into a singularity. Maybe the history of the universe is a never-ending cycle of expansion and contraction. Maybe the universe will end in fire to rise again from its own ashes like the phoenix
That doesn’t seem to be the case, though. The does not seem to be enough matter in the universe to slow its expansion and in fact, the rate of expansion seems to be accelerating due to a mysterious force scientists call. dark energy. If current theories are true, the universe will end in ice. We are living in a universe that will grow ever larger, colder, darker, and emptier without any definite end. The stars will die out as they exhaust their nuclear fuel and after some time there will not be not hydrogen gas in space to create new stars. The galaxies will be filled with the corpses of stars, bodies of degenerate matter such as white dwarfs, neutron stars, and black holes.
Over the limitless eons, the black holes will attract most of the matter in the universe to themselves with their immense gravitational pull, and eventually, the universe will consist almost entirely of black holes.
This is not quite the end, though. Black Holes do not last forever. According to Stephen Hawking, black holes are not entirely black. For complicated reasons having to do with quantum mechanics, black holes actually emit a small amount of thermal or black body radiation. As they emit this radiation, black holes slowly lose mass, until eventually a black hole is unable to hold itself together with its gravity and it explodes. Paradoxically, larger black holes emit less such radiation than smaller ones. At present, a black hole will take in far more matter and radiation than it could possibly lose through Hawking radiation, but as the universe grows cooler and emptier, black holes will begin to lose mass. This will only happen in the far, distant future and the process of black hole evaporation will take an inconceivably long time, but we are talking about such immense stretches of time that all the thirteen billion years from the big bang to the present is just an eyeblink.
The last events that anyone will observe, if any observers exist, will be the very occasional, perhaps once every billion years, death of a black hole. After the last black hole is gone then night will fall and the universe will be shrouded in darkness, eternal and inescapable. Even matter itself, as we know it will no longer exist if protons decay, as some theories suggest.
Or, maybe not. All of this assumes that our current understanding of the laws of nature over the long eons is correct. It may not be. In fact, it is more than a little presumptuous to imagine that we can know what is really going to happen in the distant future. The universe is full of surprises. In particular, not very much is known about the mysterious dark energy that is accelerating the expansion of the universe. The term dark energy seems to me to be a sort of place holder, a short way of saying we don’t know what it is, or anything about it. For all anyone knows, dark energy could reverse itself and cause the universe to contract. Even if our ideas about the future of the universe are correct, they may not be complete. There may be emergent properties in the universe, yet to develop.
To understand what I mean, imagine some form of intelligence arising in the seconds after the big bang. These beings might consider the future of the universe as growing ever colder and darker over such unimaginable lengths of time as days, years, or centuries. They could have no conception that such objects as stars or planets, or even atoms might develop, filling the universe with light and life. In like fashion, it is possible that new forms of matter and energy might develop in the extremely distant future. There could be lifeforms spanning thousands of light-years living for eons who look back on our time as simply the last stage of the big bang, never imagining that anything could live in the dense, hot universe of the past. Perhaps night will not fall, but the universe will continue to be filled with life in forms we cannot imagine.
Maybe the universe will end in fire, maybe in ice, or maybe there will never be an end, just a continual evolution into new and very different forms. Perhaps we will never know.