The Night Land by William Hope Hodgson – Project Gutenberg.
A seriously creepy tale, by dint of the setting in time and space. “The Night Land” is millions of years in the future, after the Sun has become too cold to be visible to human eyes. Life on Earth has been preserved in a vast ravine a hundred miles deep into the mantle, warmed and powered by volcanism. Humanity struggles on, preserved against the “Night Land”, in the Last Redoubt, which is a huge pyramidal Arcology, several miles square on its base and projecting eight miles into the endless night. It is threatened by weird creatures, chiefly vastly old and patient “Watchers” and darker (!) forces of spiritual evil. Billennia before, it’s revealed, humans had experimented in space-time and let in “Things” – spiritual lifeforms that predate on human minds/souls.
The basic tale I’ll save for next time, but for now I wanted to examine the physics. Basically we’re talking about the Kelvin-Helmholtz timescale for the Sun’s contraction and its powering by gravitational potential energy being converted into heat energy. Essentially every mass falling into another mass will release energy and the total energy represented by all the mass of an object falling together into its current configuration is its binding energy.
Back in the 19th Century the only energy source known powerful enough to keep the Sun shining for millions of years was gravitational energy. But there was a problem – the Sun’s present configuration represented a binding energy of 18.75 million years of sunshine at present levels. Allowing for unknowns about the insides of the Sun, the total lifespan to date of the Sun was less than 100 million years and probably less than 30 million years.
That produced two problems. Firstly, geology seemed to imply Earth was at least 100 million years old and probably much older. Secondly, it meant that without a continuing infall of mass on to the Sun, it would grow cold and go out within a few million years.
The first problem is another tale, but the second inspired SF for several decades after Lord Kelvin first posed it in the 1860s. H.G.Wells visited an Earth orbitting a Sun grown cold in his “The Time Machine”, mentioning the infall of both Mercury and Venus which kept the Sun glowing hot for a bit longer. In 30 million years from his own time, his Time Traveller sees a huge red Sun over a chilled Earth which is facing its Final Winter. The Sun hasn’t grown huge like it is imagined to in present day astrophysics – instead Earth has slowly spiralled in towards it. And it is only shining like a red-hot ember, albeit a gigantic one, that’s rapidly losing its warmth.
By 1912, in William Hope Hodgson’s tale, the discovery of radioactivity was giving some geologists hope that the interior of the Earth would remain warm, but no one was too sure about the Sun and the other stars. Einstein’s work on the interconversion of mass and energy hadn’t filtered through to most fictioneers or astrophysicists, though very soon people would be talking about powering the Sun through annihilation of mass. But Hodgson doesn’t show any awareness of this, though he does indicate knowledge of speculations about non-Euclidean geometry with his “Doorways of the Night”, akin to the modern-day ‘wormhole’.
In an earlier tale Hodgson has a character visit the very end of the Cosmos as the corpse of the Sun itself collides with the “Central Star” – a speculation of the 19th Century that eventually gravity would bring everything together, at least in this “Island Universe”. But that fate is for much later than “The Night Land”…