Today I wish to consider the prospect of the future. Not simply the future, mind, but the deep, deep future. I want to examine the depths where everything becomes irretrievably dark, and see what awaits us in the deepest future of the cosmos. And why do I want to do this? Partly because I can. Partly because I must.
It starts with the stars. Stars are element factories. They smash hydrogen together and create heavier elements. The first stars were massive, and lived their lives in a figurative cosmic heartbeat. They exploded, new second generation stars formed from their remains. These too exploded, giving rise to a third generation. The cycle can only occur a limited number of times.
There is only enough hydrogen in the universe for another one or two generations, and then, slowly but surely, the stars will start going out. The biggest stars will go first. Sirius, Vega and their kin will be extinguished in mere hundreds of millions of years.
In three billion years, our own Milky Way galaxy will have begun to merge with our largest neighbour, Andromeda. They will circle each other for a time, their arms mingling. The galactic union will be consummated by the merging of the supermassive black holes that form the cores of both galaxies.
In five billion years, our own sun will take its last breaths and venture quietly into the night. There will no spectacular farewell for our parent star - it is not massive enough. No, the sun will simply inflate and fizzle. This will probably mark the end of the road for Earth as well, but the descendants of today's humans might still survive by journeying to other stars. The party isn't fun any more - everyone's leaving.
But the universe is a closed system. You can buy time, but sooner or later, everything winds down to nothing.
By the year one trillion, there will be no stars like the sun left. The only stars left will be diminutive red dwarfs, tiny balls glowing feebly with a barely perceptible incandescence. By this time, star formation will have slid to a half as hydrogen stores run dry throughout the universe.
But wait, there's more.
Red dwarfs need fuel, just like the long-dead larger stars. They don't burn it as quickly, but by the year twenty trillion, the last red dwarfs will be winking out. The universe will have become very dark, and the last sources of light are going. To our eyes, it would be simple blackness. No constellations. No nebulae. No galaxies. Planets and moons might still exist, but nothing we'd recognise as life could survive on their now-frigid surfaces.
Continuing to forge through deep, logarithmic time, black holes will eventually be the only objects in the universe. All activity in the cosmos will wind down to a halt.
But the cosmos has one last surprise. Black holes don't live forever either. They constantly lose imperceptible amounts of mass, evaporating over time. The universe's last call will be the death of the last black hole. From that second onward, the universe will consist of nothing but elementary particles, separated by great stretches of space.
These particles will continue to spread apart as space expands, but the universe is now essentially dead.
In the deep future, the universe will get painfully dark, painfully cold, and painfully big. The immense nothingness alone would eliminate us, if we somehow managed to survive for that long. This is all that awaits us. There will be no eleventh-hour rescues, no escapes, no way out. This future is inevitable, and it gets closer each passing day.
So take these thoughts and internalise them. Realise that This. Will. Happen. Make yourself realise that this is not a fiction, not a story. It is reality, and reality is hard to take sometimes.
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