Echoes From a Black Hole

Earlier this year, physicists celebrated the Laser Interferometer Gravitational-Wave Observatory's (LIGO) discovery of gravitational waves — ripples in spacetime curvature — at the site of a black hole merger as it confirmed part of Albert Einstein's theory of general relativity. However, that discovery might now be hinting that the very same theory breaks down at the edge of black holes.

Physicists studying LIGO's data on the black hole merger claim it reveals “echoes” of gravitational waves that contradict predictions made by Einstein's general theory, which has been proven by LIGO on more than one occasion now. Previously, physicists believed that Einstein's theory broke down in extreme conditions, such as those found at a black hole's core. However, these recently discovered echoes seem to indicate that relativity fails around a black hole's edges, far from its center.

As part of the standard model based on Einstein's theory, nothing should be found at the edge of a black hole (its event horizon). This contradicts other theories such as the one that corresponds to quantum physics, which suggests that an event horizon should have a firewall, a ring of high-energy particles, around it.

Cosmologist Niayesh Afshordi at the University of Waterloo in Canada created models of these black hole mergers that assumed they did have something at their event horizons. The timing of the echoes following the release of gravitational waves in the mergers recorded by LIGO matched up perfectly with those expected by Afshordi's models. This supports the idea that the edges of black holes do have some structure and not a whole lot of nothingness as suggested by Einstein's theory.

The Puzzle That Is the Universe

“The LIGO detections, and the prospect of many more, offer an exciting opportunity to investigate a new physical regime,” said black-hole researcher Steve Giddings from the University of California, Santa Barbara (UCSB).

For now, more research is needed to see if these echoes were a fluke or something that will completely reshape our understanding of a black hole's event horizon. If proven to be permanent fixtures of a merger, we would need a new theory to explain this and similar phenomenon — at least until the elusive theory of everything comes along.

In any case, observation of future black hole mergers can confirm whether these echoes were just flukes or random noise. "The good thing is that new LIGO data with improved sensitivity will be coming in, so we should be able to confirm this or rule it out within the next two years," said Ashfordi.

It's no surprise that the universe continues to confirm theories of physics one minute and break them the next. So much of the universe is still a big unknown as far as we're concerned. Theories come and go, and although Einstein's has been relatively successful, the emergency of new technologies will continue to allow us to challenge earlier assumptions.

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