Science & Technology

Black Holes Might Not Exist, So Here Are 5 Weirder Alternatives

Black holes are infinities wrapped in infinities: objects containing an infinitely small point with infinite density that warps spacetime to such a degree that not even light can escape. But the laws of physics say information can't be destroyed, so if nothing can escape a black hole ... can a black hole even exist? As much as the experts say they do (and, we should emphasize, they are winning this theoretical race by a pretty wide margin) we've still never seen one. What if the hulking objects that form when a massive star collapses are really something else? When you start pondering that question, things get really weird, really quickly. Below are five alternatives to the object we know as the black hole.

Wormholes

That infinitely small point within a black hole is known as a singularity, and it's a mess for physicists. In 1925, physicists Albert Einstein and Nathan Rosen pointed out that you might be able to avoid the idea of a singularity if you extended a black hole to a second location, creating what we now call a wormhole. Black holes have an event horizon: a point of no return that surrounds the singularity and prevents information from escaping, causing that pesky information-destroying issue known as the black hole information paradox. Wormholes have no such event horizon. Instead, whatever goes in would come out the other side.

It's even possible that the gravitational waves we've been detecting aren't from the collision of two black holes, as we thought, but the collision of two wormholes. Earlier this month, researchers from Belgium and Spain calculated that the gravitational waves produced by two spinning wormholes running into each other would be very similar to those generated by merging black holes. The only difference would be in the echo they'd produce in their final moments. Gravitational waves were first detected by LIGO in 2015, but the device wouldn't have been strong enough to detect those echoes in its current configuration. But scientists think it's possible, and we may be looking for wormhole echoes soon enough.

Fuzzballs

Yes, fuzzballs. To explain fuzzballs, we'll have to venture into the realm of string theory. String theory reimagines every particle in the universe as a tiny loop of string that vibrates at a particular frequency — vibrate in this way, you get an electron, vibrate in another way, and you get a quark. Fuzzballs are string theory's answer to the problem of black holes: instead of a singularity surrounded by an event horizon, the whole shebang is a tangled ball of "strings" with a fuzzy surface, more like a planet than a hole.

So what happens if you fall into one — or onto one, as the case may be? Some say you'd hardly notice. The "strings" that make up your subatomic particles would combine with other strings to form longer strings with the same characteristics. In other words, you'd be turned into a copy of yourself embedded in the surface of the fuzzball. How you'd experience that is anyone's guess.

Boson Stars

Speaking of subatomic particles, one contender for an alternative to the black hole is a star made of force-carrier particles called bosons. While the matter particles (fermions) that make up normal stars have to follow particular rules about how they arrange themselves, bosons can huddle together so tightly that they become one big collective particle called a Bose-Einstein condensate (which we've made in a lab here on Earth.) If this mysterious stuff formed a star, it'd be a transparent, donut-shaped blob that would emit no light but possess an intense gravitational pull. You know, kind of like what black holes are supposed to do. "Boson stars could mimic black holes," theorist Steve Liebling tells New Scientist. "And it is possible that we are getting tricked."

How would we know? Just like wormholes, colliding boson stars would produce a telltale echo that sensitive-enough equipment might be able to detect. Even more exciting, the Event Horizon Telescope, which has already sent back data that scientists are currently analyzing, might end up showing us a picture of a boson star. It might look so similar to a black hole that we wouldn't be able to tell the difference, but its transparent nature might mean we could see matter at its center. That's something you can't do with a black hole.

Gravastar

Boson stars might be theoretical, but at least they're made of stuff we know about. No such luck for the gravitational vacuum condensate star (stage name: Gravastar). Black holes are theorized to form when a massive star collapses into itself until it becomes a singularity. Gravastars are also thought to form from a collapsing star except that early on in that collapse, the star's regular matter turns into "exotic matter" that keeps it from fully caving in. (That's the same theoretical stuff that's supposed to keep wormholes open, by the way). The final product would be nearly as compact as a black hole, but not quite enough to form that tricky event horizon. As for detecting them, well, researchers already analyzed gravitational waves for gravastar echoes in 2016. "As a theoretical physicist I'm always open to new ideas no matter how exotic," Professor Luciano Rezzolla from Goethe University in Germany said at the time. "At the same time, progress in physics takes place when theories are confronted with experiments. In this case, the idea of gravastars simply does not seem to match the observations."

Magnetospheric Eternally Collapsing Objects

In 2006, a team of researchers peered 9 billion light-years away to check out a quasar: a super-bright, compact object that's believed to be generated by a ravenous black hole. When the team probed the structure of the quasar, however, something was amiss. The glowing accretion disc that surrounded the object was too wide, suggesting that it had been pushed out by magnetic forces. A black hole shouldn't have a magnetic field, and this one clearly did. That pointed to the likelihood that this wasn't a black hole, but something called a MECO: a magnetospheric eternally collapsing object. The idea here is that as a collapsing object gets super dense and super hot, the radiation it produces creates outward pressure that prevents its collapse, leaving it as a hot ball of plasma rather than a black hole. It's hard to know how accurate the team's hypothesis is, though. We don't know enough about black holes to know how different they are from MECOs, so definitive proof is still a long ways off.

If you can't get enough of this theoretical magic, check out "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory," a national bestseller by physicist Brian Greene. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Five Black Hole Puzzles Answered

Written by Ashley Hamer June 25, 2018

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