Story by Darren
- How the universe will end is an ongoing debate among cosmologists, and outcomes vary depending on specific theories.
- A new paper analyzes the end of the universe in relation to a theory known as “holographic dark matter,” in which gravity and space form a quantum illusion of our true, 2D reality.
- The study finds that, in this scenario, the universe would eventually grind to a halt and decay into nothing, a process these scientists call the “long freeze.”
All good things must come to an end, and that includes the universe. But exactly how that end will arrive is a long-standing debate among cosmologists, who offer up theories with terrifying monikers such as “big freeze” or “big crunch.” Now, a pair of scientists from the U.S. and India have another idea that instills a similar amount of foreboding—the “long freeze.”
The idea comes from a theory known as “holographic dark energy,” which tries to explain the mysteries of quantum gravity. This theory posits that the force of gravity is actually a hologram of some lower-dimensional reality. In other words, our known universe is actually two-dimensional, but quantum forces create the illusion of gravity and 3D space. This holographic principle is also a feature of theoretical frameworks like string theory.
Dark energy is the force many cosmologists believe is behind the expansion of the universe. Although decades have passed since its first “discovery,” no scientist has ever observed dark energy directly (if they did, you would have definitely heard about it). Dark energy makes up roughly 70 percent of everything in the universe, and as it expands, its density decreases. In this new, non-peer reviewed paper published on the preprint server arXiv, scientists decided to follow this holographic theory of dark matter to its conclusion, and calculate how the universe would end if its theoretical assumptions were proved true.
In this scenario, as dark energy dissipated across the universe, so too would dark matter, and the universe would eventually grind to halt, according to Live Science. This is the “long freeze”—a period of time during which the universe’s expansion would have completely stopped, and the lack of any new energy sources would cause existing stars to slowly wink out of existence. According to most cosmologists, the last “normal” structures of matter would be black holes, but eventually, even these monstrosities of space-time would meet their ultimate ends.
The “long freeze” is distinct from another cosmological end state known as the “big freeze,” which similarly enters a state of cascading entropy. However, the “big freeze” crucially continues to expand, whereas the “long freeze” takes a finite shape after it stops expanding. For the matter facing oblivion at the end-time of the universe, this may all seem a bit like rearranging the deck chairs on the Titanic, but this paper’s thought experiment helps stress-test possible cosmological theories and understand their ultimate conclusions.
Luckily for us, the Stelliferous Era—that is, the universe’s star-making era—isn’t scheduled to end for roughly another 100 trillion years. And even then, it will be followed up by the Degenerate Era and the Black Hole era, the latter of which is estimated to occur roughly 10 duodecillion to 1 googol after the Big Bang.
