This composite image shows the Cartwheel Galaxy, located about 500 million light-years away. In the heat death scenario, the universe would expand so far that the light of one galaxy would be unable to reach its neighbor.

NASA, ESA, CSA, STScI

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NASA, ESA, CSA, STScI

This composite image shows the Cartwheel Galaxy, located about 500 million light-years away. In the heat death scenario, the universe would expand so far that the light of one galaxy would be unable to reach its neighbor.

NASA, ESA, CSA, STScI

Will it be a slow fade? A big rip? An abrupt disintegration?

We don’t know for sure how the universe will end. But thanks to theoretical astrophysicists like Katie Mack, we can speculate.

That speculation requires theorizing about dark energy, the mysterious force that’s driving the accelerated expansion of the universe. What happens at the end of that expansion? Scientists say it could eventually lead to heat death: A cold, dark cosmos populated by isolated galaxies, fading stars — and even the evaporation of black holes.

That’s just one potential option.

Other scientists theorize that the universe could rip itself apart … or that a quantum fluctuation could destroy us all in a matter of seconds.

But how does it all work? And how will it all end? To know for sure, scientists will need a lot more data — or for humanity to survive trillions of years.

Listen to Short Wave on Spotify and Apple Podcasts.

Want to hear more about outer space? Email us at shortwave@npr.org. We’d love to hear from you!

The original version of this episode was produced by Rebecca Ramirez, edited by Viet Le, and fact checked by Berly McCoy. Hannah Chinn, Emily Kwong, and Regina Barber did the Space Camp version. The audio engineer was Patrick Murray.

Special thanks to our friends at the U.S. Space & Rocket Center, Home of Space Camp®.