The universe is in its infancy. Stars and planets form, and galaxies shine. But what will the universe be like when it runs out of energy? Will there come a time in our universe when all available fuel for stars and galaxies is used up? What will happen to the universe then?
We asked astronomers who study the big questions of the universe — how it began, how it’s evolving, and how it’ll end. They say that the universe began expanding with the Big Bang, about 15 billion years ago. Recent evidence gathered by orbiting spacecraft and Earth’s largest telescopes points to endless expansion — that is, the galaxies will never stop moving outward and never fall back together again.
If that were true, then the universe would eventually become cold, dark, and empty. All the matter in the universe would become locked up in high-density objects — white dwarf stars, neutron stars, and black holes — making it unavailable to make new stars. White dwarfs slowly cool and fade. As the universe expanded, the galaxies would move farther apart. Eventually, no galaxy would be able to see any other.
But this scenario would play out over hundreds of billions of years — long enough for some unusual processes to occur. At some point, proton decay might make all matter evaporate and disappear. And some believe that physical laws might manifest in new ways — making it impossible to predict the fate of the future universe.