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Saturday, July 13, 2024
Dr. Brown: Black holes can be destroyers as well as creators
The intense gravitational fields of giant black holes are capable of shredding planets and star-sized bodies. DIMA ZEL/SHUTTERSTOCK

In 1916, Einstein’s great masterpiece — general relativity, which described the relationship between mass and space-time — was published and soon after read by Schwarzschild, a brilliant mathematician and physicist, then serving as an artillery officer on Germany’s eastern front in the First World War. 

Simplified to its bare essentials and without math, general relativity states that mass curves space-time, and the curvature of space-time tells mass where to go.

Schwarzschild realized that if such a mass was dense enough, it could collapse space-time into a tiny, what was called a singularity, where all the mass was concentrated in an infinitely tiny spot.

Later work would strongly suggest that our universe began with just such a singularity containing all the energy and mass that would become our universe.   

Later in the 20th century, scientists such as Stephen Hawking and Roger Penrose speculated that large masses could create black holes — places where the gravitational force associated with a very dense mass could be so high that even light could not escape the gravitational grip of the black hole.

Thus we have the black hole (surrounded by a corona of high-energy particles) and the outer bright ring surrounding the black hole. 

The first black hole was not photographed until 2019. It’s gargantuan, billions of times the mass of the sun and much larger than the giant black hole found at the centre of our Milky Way, for which studies a Nobel prize was awarded and shared with evidence that general relativity provided a “robust explanation” for the shape of black holes. 

Some of the largest black holes, surrounded by enormously bright coronas, formed within several hundred million years following the Big Bang and to this day provide bright beacons useful for navigation in space.

Those quasars formed before all but the simplest of elements were formed in stars and are unusually bright because there was little star dust to scatter their light in the early universe. 

The first collision between two very modest-sized black holes was detected by two land-based highly sensitive gravitational wave detectors in 2015 and led to the awarding of a Nobel prize for the efforts of an American team of physicists and engineers working over three decades.

The detection of those waves — ripples in space-time — was yet more compelling evidence that Einstein’s general relativity hypothesis was correct but that supersensitive wave detectors might be capable of detecting similar waves generated by the Big Bang itself.  

Now, to the matter of destructive versus creative properties of black holes.

There’s no doubt the intense gravitational fields of giant black holes are capable of shredding planets and star-sized bodies.

What’s perhaps not so obvious is that same gravitational field around a black hole, also helps to coalesce matter into what will become nascent and eventually mature stars and planet systems. That’s the creation side of black holes. 

Those gravitational fields also change the trajectory of stars from what otherwise might be expected: changes which were the all-important clue to the presence of a giant black hole at the centre of our universe well before the black hole was actually seen.  

Some physicists, such as Penrose, suggest that black holes are nature’s recycling tools for universes by gobbling up the remains of stars and star systems, and merging with other black holes to become even larger.

Then, at some time far in the future, a truly giant black hole might form, by gathering all the matter and energy of the universe in one place with sufficient mass to collapse into a singularity again and trigger the explosive development of yet another universe. And that’s not the end of the story.

There might be many, some would argue a near infinite number of universes, perhaps working by different natural laws though it’s hard to believe that nature would come up with different fundamental particles. 

There’s another note worth making here: the energy associated with those intense coronas surrounding the earliest black holes (quasars) is almost as old as the universe itself.

What we see is old light, whose original source is long gone, refashioned perhaps into several generations of stars. 

To see far out in space is indeed to look back in time because of the fixed speed of light and the vast distances in an ever-expanding universe. 

As an electrical engineer friend of mine keeps telling me, it is mind-blowing and, in this matter, he is surely correct.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.  

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