Black holes are undoubtedly among the most mysterious types of objects in the universe. Scientists realized their existence in the early 20th century after Albert Einstein’s revolutionary suggestions about gravity. It took until 1964 for scientists to even suggest they had observed one, and it was only in 2019 that astronomers were able to publish the now-famous photo of the supermassive black hole at the center of galaxy M87, the first real image of it. a black hole.
However, Christopher Nolan’s blockbuster “Interstellar,” which featured a rather remarkable black hole, was released in 2014. So Nolan had no choice but to use computers to create the film’s black hole, even if he chose to avoid CGI. And the only reason it could do this was because there was a long tradition of producing images of black holes, dating back to 1979.
It seems the universe likes to follow rules. The entire history of physics—indeed, the entirety of science—can be summed up in a single sentence: the quest to find out what the rules of the universe are. Scientists define these rules using mathematical equations. So all it took to create an image of a black hole was to plug these equations into a computer and let the result emerge. How difficult could it be? It turned out to be incredibly difficult because the first problem was finding the equations in the first place.
For a long time, scientists understood gravity as formulated by Isaac Newton in 1687: Every object in the universe exerts a force on every object in the universe, and this force is proportional to the product of the masses of the objects (how come there are so many of them) and the centers of the objects It is inversely proportional to the square of the distance between them. In simpler terms, larger objects and shorter distances produce more gravity.
Then Einstein came along and made everything much more complicated. As it turns out, there were a few cases where Newton’s theory of gravity failed to accurately predict what was going on. Although Newton was able to describe the force created by gravity, he was never able to determine what this force was; He gave us the “what” but not the “how” and “why.” Einstein’s theories drew on the work of Newton and other physicists to fill this gap, and in doing so solved some cases where Newton’s theory broke down.
In 1905, Einstein introduced the special theory of relativity, which was based on two ideas: first, the idea that the laws of physics never change as long as you move at a constant speed, and second, the idea that the speed of light in vacuum is always the same. It’s the same no matter what. If you’ve ever heard of the concepts of “space-time” or “space-time continuum”, this is where the term comes from. For the speed of light to always remain the same, time and distance must both change, sometimes in unexpected ways (the famous time dilation). This strange, counterintuitive connection between physical space and the passage of time is a critical part of the workings of our universe.
For the next 10 years, Einstein tried to find out if he could fit gravity into his theory of space-time, and general relativity did just that. To simplify, every object in the universe physically bends the space-time field, changing the trajectory of any object that passes by. According to Einstein’s theory, we perceive the change in orbit as gravity, and nothing, not even light, is immune from this.
Soon after, some physicists such as Karl Schwarzschild recognized a potential problem: What if an object had a mass so large that it warped spacetime so much that even light, the fastest object in the universe, could not escape? When light is absorbed by something, our eyes perceive that object as black. And this black object would have to be absurdly dense; It was so dense that it would appear to have created a tiny hole in the fabric of space-time at its center.
In other words – wait, they’re actually the same words – a black hole.
Scientists have since built on these theories, confirming that Einstein, Schwarzschild, and others were right time and time again. However, trying to explain the concept to the public is a completely different matter. People in general like to know what something looks like, and the rules of a black hole make it really difficult to answer that question.
But in 1979, French cosmologist Jean-Pierre Luminet found a way to do this using theories and equations that determine how gravity pulls objects into a black hole, such as cosmic space (which turned out to be a rather complex process). Contrary to the public’s impression that a black hole is a giant galactic vacuum cleaner, the black hole simply exerts the force of gravity, nothing more, nothing less. And if you haven’t figured it out yet, gravity is very complex.
When Luminet began creating its image of a black hole, it used equations to predict how the light itself would be affected by passing near the black hole. His result showed a small ring of light around a completely black circle. He then figured out how space dust might affect the appearance of its orbit around the black hole, what might happen if the black hole itself is spinning, and other complications. He then used a 1970s-era computer to print a simulated image.
In his paper, he suggested that this image could accurately represent, among other black holes, “the supermassive black hole whose existence in the core of M 87 has recently been suggested.”
In April 2017, a massive project led by Harvard astronomer Shep Doeleman scanned the skies around M87 using telescopes around the world. They then spent two years analyzing the data and creating an image:
(Event Horizon Telescope)
In conclusion, we can say that Luminet did a pretty good job.
Resources:
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