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Black Holes are fascinating objects. They are often thought to have been postulated by Albert Einstein in 1916 and predicted due to his General Theory of Relativity. That is partially true…
According to his equations, when a star (at least three times bigger than our Sun) dies, the small remnant left behind would be so dense that gravity would overwhelm the other forces and trap even photons. If light could not escape, it would appear “black” from lack of emitted light of any kind.
John Michell (1724-1793) proposed such an object to exist about two centuries earlier! An object at the Sun’s surface would need a velocity of more than 600 kilometers per second to escape its gravity. That would be very hard to attain for most objects. For example, our permanently trapped Earth orbits at 30 km/s; Jupiter orbits at 13 km/s, at about five times the distance; and Neptune moves at 5.4 km/s, at 30 times the distance.
More than 600 km/s would be unattainable for just about everything except light which travels consistently at 300,000 km/s. Michell wondered about a larger body than the Sun. As it got progressively bigger, its gravity would increase. Could it reach such a mass that gravity’s escape velocity exceeded 300,000 km/s? If so, even light could not escape, and the object would become invisible to our eyes.
Michell was a brilliant person, a natural philosopher (the title we used before scientists became popular), an early physicist, and a clergyman, which was not uncommon for early scientists. But, unfortunately, he didn’t have selfies, the Internet, and a strong desire to self-promote genuinely clever ideas. As a result, all his brilliance was lost until rediscovered by others 200 years later…
Of course, there are innumerable stars that are many times the mass of our Sun, and they are not black holes. As long as they have fuel to power their fusion reactions, they can balance the crushing gravity with the expansion energy of their fusion reactions.
It’s only when they run out of fusion fuel that they experience a massive collapse that starts the cascade of gravitational effects resulting in a big crunch. Strong nuclear forces are overcome; weak nuclear forces are overcome; electromagnetic forces are overcome. Protons and electrons begin to lose their identity until only an untidy soup of neutrons is left, hence the name Neutron Star.
If the gravitational collapse continues, the Neutron Star remnant will become a black hole. However, Einstein did not give these objects their common moniker “Black Holes.” That task fell to physicist John Wheeler (d. 2008) in 1967.
While attending a conference, attendees were looking for a substitute to the cumbersome description “gravitationally completely collapsed star,” and an audience member suggested “black hole.” Wheeler immediately glommed onto that phrase because it was so precise and described exactly what was happening. He pressed for people to use it to describe the phenomena. It worked.
In his autobiography, he said that the black hole “teaches us that space can be crumpled like a piece of paper into an infinitesimal dot; that time can be extinguished like a blown-out flame; and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but!”
These massive stellar remnants are the ultimate players in the cosmological game of hide-and-seek. They hide in plain sight by pulling the space-time continuum in around themselves like a cloak, infinitely curved, with matter infinitely dense inside. They are invisible.
While they do gobble up a lot of space to hide, you have to remember it is a space-time continuum they are consuming. SO it’s not just empty space inside there—it’s a lot of very densely packed space in a tiny volume.
If it were formed by a star 10 times bigger than the Sun (which is already more than a million kilometers across), once it collapsed, it would be no larger than a big Earth-city, like New York.
Stephen Hawking was also interested in Black Holes. The first object to be seriously considered a black hole was the stellar object named Cygnus X-1. In 1974 he made a bet with Kip Thorne (emeritus professor at Caltech and now considered a leading authority on black holes) that Cygnus X-1 was not a black hole. It took 16 more years to be certain, but Hawking finally conceded the bet in 1990.
Theoretical physics is a tough slog for the uninitiated. It is math-dense and full of mind-boggling concepts. But, even with that as a tool, black holes can’t be explained without a rudimentary understanding of Quantum Mechanics.
Since this article is not designed for third-year theoretical physics students, let’s explain it with a simplified example. The English physicist, Stephen Hawking, proposed that black holes radiate energy, flying directly in the face of conventional wisdom that said this was impossible.
In 1974 he combined aspects of the Theory of General Relativity and Quantum Mechanics to explain how it worked. Scientists at the time didn’t like his explanation. Still, eventually, he showed it mathematically, though with such complex mathematics that only a few dozen people on the planet could understand it. It turns out, however, that he was probably right, and his theory gained acceptance.
Essentially, quantum mechanics stipulates that every particle in existence has an antiparticle. These spontaneously generate and annihilate constantly.
The conditions at the edge of a black hole, what we call the Event Horizon, are such that once you go past that point, you’re in the black hole forever. Conventional physics says that nothing can escape from a black hole because gravity is too strong.
Quantum Mechanics causes a problem at this interface because due to the constant creation and destruction of particles everywhere in the Universe, some of those interactions will happen here, too. Now, what happens if these matching particles come into existence at the event horizon and only one particle gets drawn in?
The particle drawn in will be the negative energy particle, and the escaping particle with be the positive energy particle (because opposites attract). The negative energy particle is a decrease in the mass of the black hole because it annihilates another particle, and the positive particle increases the mass of the Universe. This constitutes a “leak” in the black hole.
What does this mean? Eventually, and very slowly, black holes will simply evaporate as this quantum effect slowly steals away their mass. The escaping positive particle can appear as many different types of radiation from gamma to visible light.
Small black holes should evaporate relatively quickly this way, and larger ones much more slowly. Ultimately, however, this is the fate of all black holes.
Eventually, other physicists accepted his theory, and this new form of radiation from black holes was named after him: Hawking Radiation. But, unfortunately, it is formed at such a low temperature (just a few nano kelvins above absolute zero) that it will likely never be detectable over the background microwave radiation of the entire Universe, formed during the Big Bang.
These are a tool of Science Fiction, used as plot devices. Some speculate that black holes are the entrances, and somewhere in the Universe, a white hole is an exit so that matter is constantly being pumped out somewhere as black holes suck it like a trans-galactic vacuum cleaner. There is no mechanism for their creation and no explanation that would allow their existence… or is there?
Could a Black Hole suddenly go into reverse and spit out a fully functioning star? Not really. The outgoing matter would collide with itself, the gravity would get too powerful, and the whole thing would collapse into a black hole again. If white spots were possible, they would be a very short-lived phenomenon!
Besides this, a star collapsed because it ran out of hydrogen. So this “white hole” isn’t suddenly going to “undo” all that nuclear fusion and make enough hydrogen to power a star.
That would be akin to a scrambled egg unscrambling itself, growing a shell, and popping back inside a chicken… Moreover, it would be in direct violation of entropy which says the Universe gradually moves towards complete chaos, not greater organization!
So black holes are confirmed according to modern physics and quantum mechanics. They have a sound basis in reality, and though they may have been disbelieved three decades ago, distrusted two decades ago, and fairly accepted last decade, the mathematical models are so strong now that few doubt their reality
We’ve just recently photographed a black hole for the first time, and at the time of writing, we have just discovered polarized light around that black hole at the photo-op. That showed us interesting new magnetic fields that may help explain how black holes can eject jets of gas, which has puzzled scientists for a long time.
There’s a lot more to this story, so let’s keep an eye on new developments! Remember, the meek shall inherit the Earth…the rest of us are going to the stars![/vc_column_text][/vc_column][/vc_row]
