If you’re having trouble sleeping at night, have you tried to induce total existential dread by contemplating the end of the entire Universe?

If not, here’s a rundown of five ideas exploring how “all there is” might become “nothing at all.”

The heat death

We’ll start our survey with the classic scenario, what you might call the default. It’s the future predicted to come about if everything we know about the Universe is largely correct and all that stuff in the cosmos continues to behave the way it has for the past few billion years.

The Big Rip

The heat death of the Universe is a rather morose picture, but it seems inevitable based on the fact that dark energy is a constant. No matter where or when you are in the Universe, dark energy is always there, seemingly never getting stronger, never getting weaker.

But measurements of the strength of dark energy made over the past two decades have raised questions about that “seemingly.” Instead, they lean in a threatening direction, indicating that dark energy might be getting stronger with time.

The Big Crunch

Dark energy may evolve in such a way that the current phase of accelerated expansion is just a passing fad, and, at some point in the future, the Universe’s expansion will slow down, stop, and then reverse. Assuming that it continues in that new, reversed trajectory unabated, the cosmos will then enter into what’s called a Big Crunch.

The phase transition

If that wasn’t unpleasant enough for you, consider this: Perhaps the Universe will take some weird physics to the extreme and disintegrate in a flash of energy. The best part? We wouldn’t even know it’s coming.

The party never stops

Perhaps all this overwhelming negativity regarding the end of the Universe is what prompted Nobel laureate Roger Penrose in 2010 to propose a completely different mechanism for the long-term fate of the Universe, something dubbed conformal cyclic cosmology, or CCC.