Stephen Hawking Might Be Right About Black Holes Having “Hair”

Scientists from the University of Waterloo may have just found evidence of gravitational wave echoes, which would prove Hawking’s idea of a quantum fuzz on the edge of black holes true. In their paper published in the Journal of Cosmology and Astroparticle Physics, they described how they used data from the LIGO/Virgo interferometers to detect what they believe are reflections off of this fuzz of the first gravitational wave detected in 2015.

If confirmed, they claim this would “have significant consequences for both physics of quantum black holes and astrophysics of binary neutron star mergers.” This would also help resolve some of the paradoxes that spring up at the intersection of Einstein’s Relativity and quantum mechanics, such as the information paradox.

Black Holes and Event Horizons

A black hole is a region of space with so much gravitational pull that nothing can escape it. Whether it’s a star, a planet, a fundamental particle, or even light, once it goes in, there’s no chance of retrieving it.

Back holes form when enough mass is crammed into a small enough area, at which point the force of gravity is enough to overcome the natural repulsion of its fundamental particles. For example, at the end of its life, a large star exhausts its fuel and can no longer maintain its core temperature, which helps give it an internal pressure capable of resisting the inward pull of gravity. At this point, gravity begins to take over, and, if there is enough mass, gravity will force electrons into electrons, protons into protons, etc. With no opposition to gravity, the mass will reach a greater and greater density, with theory suggesting that the center of a black hole is a singularity with infinite density.

An event horizon is essentially the point of no return surrounding a black hole. On one side, information such as light can escape, while on the other, gravity is strong enough to prevent it from reaching an observer. What exactly happens on this boundary is hotly debated, as the two major school of physics–Einstein’s Relativity and quantum mechanics–lead to different predictions.

Relativity vs. Quantum Mechanics

Einstein’s Relativity and quantum mechanics have radically expanded our understanding of the universe, but, when combined, seemingly unresolvable paradoxes pop up.

On one hand, Relativity accurately describes how mass bends spacetime. The more mass an object has the more spacetime is warped, meaning that the 3 spacial dimensions and the 1 dimension of time are stretched. Therefore, gravity does not actually exist, in that objects merely fall into the depression caused by another object, like a bowling ball sitting on a rubber sheet. Black holes stretch spacetime so far that the distance is far too great for even light to travel.

On the other hand, quantum mechanics describes subatomic particles in terms of probability, as described by Schrödinger’s wave function. This leads to some truly bizarre results, in particular virtual particles. According to quantum mechanics the fabric of spacetime has an inherent energy, called zero point energy, that can give rise to a pair of particles, one matter, one antimatter.

On an event horizon, one of these particles may get pulled in, while the other is shot out into space, a process known as Hawking radiation. This means that event horizon becomes fuzzy or “hairy.” Over long periods of time, Hawking radiation causes the black hole to evaporate, eventually disappearing entirely. However, according to Relativity this shouldn’t happen, as it predicts a smooth event horizon and perpetual black holes.

Gravity Waves and “Hair”

In September 2015, physicists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer detected a ripple in the fabric of spacetime caused by the merger of two black holes over 1.4 billion light-years away. Known as a gravity wave, this ripple was powerful enough to reach Earth, where it was detected by specialized equipment that were sensitive enough to measure minute changes in the distance to a laser travels due to the warping of space.

Gravity waves are a prediction made by Einstein’s Relativity, and those that were integral in their first detection were awarded a Nobel Prize.

However, the immense amount of data collected by LIGO and Virgo continued to bear fruit. Physicists from the University of Waterloo scoured the data and found less powerful gravity waves reaching Earth in the wake of the first one. This matched the predictions made by their computer models of how gravity waves would behave with fuzzy black holes. That is, their models show that the successive pulses of weaker gravity waves most likely came from reflections of the fuzziness on the event horizon.

If their measurements are confirmed, the researchers believe this would be the first direct measurement of spacetime’s quantum framework.

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