by 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 proposals about gravity. It took until 1964 for scientists to even suggest they had spotted one, and it was only in 2019 that astronomers were able to capture the now famous photo of the supermassive black hole at the center of the galaxy M87, the first real image of it. black hole.
Having said that, Christopher Nolan’s impressive film “Interstellar”, which features a black hole in particular, was released in 2014. So, even if he prefers to avoid CGI, Nolan had no choice but to use computers to creating the film’s black hole. And it could only do that because there is a long tradition of generating images of a black hole, as far back as 1979.
The universe, as it happens, loves the following rules. The entire history of physics – really all of science – can be summed up in one sentence: the attempt to figure out what the rules of the universe are. Scientists define these rules using mathematical equations. So all you had to do to create an image of a black hole was plug those equations into a computer and let it spit out a result. How hard could it be? Extremely difficult, as it turns out, because the first problem was figuring out the equations in the first place.
For a long time, scientists understood gravity as it was formulated in 1687 by Isaac Newton: Every object in the universe exerts a force on every other object in the universe, and that force is proportional to the product of the masses of the objects (how there’s enough stuff) and inversely proportional to the square of the distance between the centers of the elements. In simpler terms, larger objects and shorter distances create more gravity.
And then Einstein came along and made everything much more complicated. As it turned out, there were a few cases where the theory of gravity didn’t perfectly predict what was going on. Although Newton was able to describe the force that created gravity, he was never able to determine what happened to that force – he gave us the “what” but not the “how” and “why. ” Einstein’s theories built on the work of Newton and other physicists to fill that gap, and by doing so, they solved some of the situations where Newton’s theory broke down.
In 1905, Einstein revealed his theory of special relativity, which was based on two ideas: firstly, that the laws of physics do not change as long as you move at a constant speed, and secondly, that the speed of light is always in a vacuum, no matter what. If you’ve ever heard of “space-time” or the “space-time continuum,” this is where it comes from. For the speed of light to always remain the same, both time and duration must change, sometimes in unexpected ways (famously, time dilation). This strange connection between physical space and time is a crucial part of how our universe works.
For the next 10 years, Einstein worked to find out if he could fit gravity into his theory of space-time, which is what general relativity did. To grossly oversimplify, every object in the universe physically bends the space-time field, changing the path of any object that passes near it. According to Einstein’s theory, we see that the change in trajectory is gravity, and that nothing, even light, is immune.
Shortly thereafter, some physicists, such as Karl Schwarzschild, noted a potential problem: What if an object had such a mass that it could distort space-time so much that could even light, the fastest object in the universe, escape? Well, when light is absorbed into something, our eyes see that object as black. And this black object would have to be absurdly dense, so dense that its center might appear to create a small hole in the fabric of space-time.
In other words – hold on, the words exactly the same in fact – black hole.
Scientists have built on these theories ever since, proving Einstein, Schwarzschild and others right time and time again. However, trying to explain the concept to the public is a different matter altogether. In general, people like to know what something looks like, and black hole rules make answering that question extremely difficult.
But in 1979, French cosmologist Jean-Pierre Luminet found a way to do it using the theories and equations that confirm how gravity pulls things like cosmic space into a black hole (a rather messy process, as it happens). Contrary to popular belief of a black hole being a giant galactic vacuum cleaner, a black hole is nothing more than the force of gravity, nothing less. And gravity, in case you haven’t picked up already, is very complicated.
So, when Luminet set out to create its image of a black hole, it used equations to predict what effect light itself would have on approaching the black hole. Its result showed a small ring of light around a circle that was completely black. Then, he figured out how the orbit of the space dust around the black hole might affect its image, what would happen if the black hole itself were rotating, and other complications. And then, he used a 1970s era computer to print a simulated picture.
In his paper, he suggested that this image could accurately represent, among other black holes, “the recently proposed supermassive black hole in the nucleus of M 87.”
In April 2017, a massive project led by Harvard astronomer Shep Doeleman scanned the sky around M87 using telescopes around the globe. They then spent two years analyzing the data and creating an image:
(Event Horizon Telescope)
Overall, it’s safe to say that Luminet did a pretty good job.
Sources:
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