NASA image of a black hole

Bye, black holes: white holes are even weirder

Contributed by
Apr 29, 2018

If there is a phenomenon out there that is actually more bizarre than black holes, it has to be white holes. Black holes can’t say that they might be the answer to where so much of the dark matter—and even most of the matter—in the universe is lurking.

The gravitational pull of a black hole is so insanely strong that not even light (so much for being the fastest entity in the cosmos), can defy it. Nothing can save you once you pass the grim point of no return otherwise known as the event horizon. However, observed that when Einstein predicted the existence of black holes in his theory of relativity, he also predicted the theoretical reverse of these galactic monsters. A white hole would be no threat to objects in space passing dangerously close, nothing can even enter its event horizon.

When black holes devour massive amounts of matter and energy, it is thought that everything which appears to vanish forever actually emerges from a white hole. Exactly where the victims of a black hole come out could be anywhere from another place in this universe to another universe entirely. Theoretical physicist Carlo Rovelli theorized something even stranger linking the two. Black holes result from collapsed stars, but when these astral corpses die, they may actually turn into white holes.

Back up a second. According to the late Stephen Hawking, black holes evaporate with age, and the “death” of a black hole happens when it has shrunken to the point that it seems to vanish.

physicist Carlo Rovelli's white hole diagram

Rovelli's white hole diagram. Credit: Carlo Rovelli

Rovelli argues that the quantum nature of spacetime makes it impossible for a black hole to just disappear. Physics is based on quantum theory, which uses indivisible quantities called quanta to explain how matter and energy behave on the atomic and subatomic level.

Spacetime can’t be shrink infinitely. Rovelli believes that when a dwindling black hole reaches a certain size over a timespan around one quadrillion times the age of our universe, it then morphs into a white hole. Even microscopic white holes are thought to have high masses, if micro-black holes that weigh more than the moon are any indication. They now also thought to be the stuff of dark matter.

"A component of dark matter could be formed by remnants of evaporated black holes," said Rovelli and colleague Francesca Vidotto in a study recently submitted to the Gravity Research Foundation.

What exactly dark matter is made of remains a mystery, since it it invisible in every sense and does not respond to light in any way. White holes comprising dark matter would be much smaller than a wavelength of light and also invisible. Any protons or other particles coming into contact with white holes would just bounce off, as Rovelli believes. Some of these white holes are thought to be the remnants of black holes that formed immediately after the Big Bang, or primordial black holes, while others could be even older than the universe itself. Maybe they even came from a previous universe.

Try not to let that blow your mind too much.