Hal Haggard, Bard College – Black Hole Life Cycles

Hal Haggard

How does a black hole die?

Today on The Academic Minute, Hal Haggard, physicist at Bard College, describes the life cycle of black holes.

Hal Haggard, a theoretical physicist at Bard College, explores the overlap of quantum mechanics and gravity searching for new understandings of space and time within an atom and throughout the cosmos.

Dr. Hal Haggard is a theoretical physicist at Bard college who studies the conceptual and practical questions that surround building a quantum theory of gravity. He has recently pointed out, in work with C. Rovelli, a new mechanism for black hole decay, which provides a radically different perspective on the black hole information problem. He has explored the possibility that space is fundamentally discrete and made of indivisible grains of space and has pioneered the study of quantum chaos in quantum gravity. Haggard was a co-founder of the award winning Compass Project, dedicated to improving undergraduate physics education and increasing the retention of underrepresented students in the physical sciences. He was a National Science Foundation International Research Fellow in Marseille, France and is currently enjoying working on an International Space Sciences Institute grant mapping exoplanets with a team of astronomers.

Black Hole Life Cycles


Black holes are out there.

Stars in the center of our milky way twirl about a huge black hole right now. Black holes, so named because light cannot escape their interiors, can even wear a luminous skin; for if a lamp falling in let out a burst of light right as it entered the black hole that light would remain stuck, trying to speed outward but pulled to a stop by gravity. I find this a wonderful image­—a black hole dressed in light.

But what happens later? Are black holes really the fearsome eaters so often regaled in scientific tales? While we know much of black holes many physicists feel we still haven’t discovered their hearts. Perhaps the greatest mystery lies with how they die. Mine is a tale of a phoenix from the ashes, a tale of the transformation of a black hole into its seeming opposite, an explosive transformation to a white hole.

How does the gravity of a black hole imprison light, that fastest of movers?

Gravity doesn’t try to grab the light or exert a force on it, but instead molds the very fabric of space and time that it moves through.

By bending spacetime gravity makes the hill that light has to climb so steep that the light falls back the same amount as it progresses in every moment.

The new possibility we have uncovered is that quantum mechanics, the operating system for all of physics, may allow this spacetime landscape to metamorphose too. A steep rise of spacetime geometry can be replaced by a sharp decline and everything that is trapped inside could come rushing out of a black hole—suddenly a white hole is born.  Is this really how black holes die? I’m not sure yet, but its an exciting possibility.

Read More: VICE: The Black Holes We See in Space Might Already Be White Holes

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