Universe expected to decay in 10⁷⁸ years, much sooner than previously thought

The universe is decaying much faster than thought. This is shown by calculations of three Dutch scientists on the so-called Hawking radiation. They calculate that the last stellar remnants take about 10⁷⁸ years to perish. That is much shorter than the previously postulated 10¹¹⁰⁰ years.

The researchers have published their findings in the Journal of Cosmology and Astroparticle Physics.

The research by black hole expert Heino Falcke, quantum physicist Michael Wondrak, and mathematician Walter van Suijlekom (all from Radboud University, Nijmegen, the Netherlands) is a follow-up to a 2023 paper by the same trio.

In that paper, they showed that not only black holes, but also other objects such as neutron stars, can “evaporate” via a process akin to Hawking radiation. After that publication, the researchers received many questions from inside and outside the scientific community about how long the process would take. They have now answered this question in the new article.

Ultimate end

The researchers calculated that the end of the universe is about 10⁷⁸ years away, if only Hawking-like radiation is taken into account. This is the time it takes for white dwarf stars, the most persistent celestial bodies, to decay via Hawking-like radiation.

Previous studies, which did not take this effect into account, put the lifetime of white dwarfs at 10¹¹⁰⁰ years. Lead author Heino Falcke said, “So the ultimate end of the universe comes much sooner than expected, but fortunately it still takes a very long time.”

The researchers did the calculations dead-seriously and with a wink. The basis is a reinterpretation of Hawking radiation. In 1975, physicist Stephen Hawking postulated that contrary to the theory of relativity, particles and radiation could escape from a black hole. At the edge of a black hole, two temporary particles can form, and before they merge, one particle is sucked into the black hole and the other particle escapes.

One of the consequences of this so-called Hawking radiation is that a black hole very slowly decays into particles and radiation. This contradicts Albert Einstein’s theory of relativity, which says that black holes can only grow.

Neutron star as slow as black hole

The researchers calculated that the process of Hawking radiation theoretically also applies to other objects with a gravitational field. The calculations further showed that the evaporation time of an object depends only on its density.

To the researchers’ surprise, neutron stars and stellar black holes take the same amount of time to decay: 10⁶⁷ years. This was unexpected because black holes have a stronger gravitational field, which should cause them to evaporate faster.

“But black holes have no surface,” says co-author and postdoctoral researcher Michael Wondrak, “They reabsorb some of their own radiation which inhibits the process.”

Man and moon: 10⁹⁰ years

Because the researchers were at it anyway, they also calculated how long it takes for the moon and a human to evaporate via Hawking-like radiation. That’s 10⁹⁰ years. Of course, the researchers subtly note, there are other processes that may cause humans and the moon to disappear faster than calculated.

Co-author Walter van Suijlekom, professor of mathematics at Radboud University, adds that the research is an exciting collaboration of different disciplines and that combining astrophysics, quantum physics and mathematics leads to new insights.

“By asking these kinds of questions and looking at extreme cases, we want to better understand the theory, and perhaps one day, we will unravel the mystery of Hawking radiation.”