Black Holes: Gateway to Another Dimension, or Ghosts of Stars’ Pasts?
There are many different beliefs and myths when it comes to black holes. Some insist that they don’t exist because they’re invisible to the human eye, or that a black hole will simply consume all of the matter in the universe. Both notions are false.
Black holes do exist within the universe, and, despite their name, they’re not actually empty holes. Black holes consist of a huge amount of densely packed matter, meaning that they have a lot of mass condensed into a very small area. The mass density of these black holes creates a gravitational pull so strong that not even light can escape it. Because of this, black holes are invisible to the human eye, which gives them their name. This is also why we don’t know what a black hole truly looks like.
So, if we can’t actually see them, how do we know they exist? Scientists are not quite sure what secrets lie inside of a black hole, but the indicator to its existence lies beyond its boundary. The boundary of a black hole is known as the event horizon, the escape velocity of which being the speed of light. This means that in order to escape a black hole after passing through the event horizon, the velocity of matter trying to escape must surpass the speed of light. However, Albert Einstein’s theory of special relativity dictates that the speed of light within a vacuum is the same regardless of the speed at which an observer is travelling, and, therefore, nothing in the universe, regardless of frame of reference, can surpass the speed of light. In layman’s terms: do not, under any circumstances, fall into a black hole, because you are definitely not getting out.
Many wonder what would actually happen if you were to fall inside of one of these mysterious space voids, though, and fantasy and science fiction open our minds to the crazier interstellar possibilities. Would you pass through a time warp or get transported to an alternate dimension? The answer: no. Although theories like wormholes, hypothetical connections between widely separated parts of the space-time continuum, with each end being a black hole, are consistent with Einstein’s theory of relativity, it is extremely unlikely that they exist.
We know that nothing can pass back through the event horizon of a black hole, and, therefore, all signs of its existence must lie beyond the boundary. One of the biggest tells to the existence of black holes is the emission of electromagnetic waves in the form of radiation. We know that nothing can be truly emitted from a black hole, as previously stated, but Stephen Hawking proposed an argument that meshes quantum mechanics with theories of relativity. His argument, now known as Hawking radiation, speaks about how pair production, the process in which a particle and its antiparticle are created from a photon or other neutral boson particle, can occur just outside of the event horizon. It is possible, then, that the positive of the pair escapes and is viewed as electromagnetic radiation, while the negative of the pair succumbs to the intense gravitational pull of the black hole and passes through the horizon.
The idea of Hawking radiation, among other methods, including the gravitational lens effect and mass estimates from orbiting objects, allow scientists to detect the presence of black holes. Smaller black holes, though, are very difficult to detect. These small black holes, known as stellar mass black holes, have a mass anywhere from 10 to 24 times that of our sun. Scientists believe that these kinds of black holes are formed when a large enough star (at least 3 times the mass of the sun) dies in a supernova explosion, where the core of the star collapses in under a second, leaving behind densely packed matter. While these are very difficult to detect, scientists believe that anywhere from ten million to as many as one billion of these stellar mass black holes exist within the Milky Way alone, simply based on the number of stars out there that are large enough to produce them.
On the other end of the mass spectrum are supermassive black holes. These black holes are millions or even billions of times as massive as the sun, and astronomers believe that one lies at the center of virtually every galaxy. At the center of the Milky Way lies Sagittarius A* (Sgr A*), about 27,000 light-years away from Earth with the mass of around four million suns, detected by watching its effects on nearby stars and gas using radio telescopes. These supermassive black holes are the subject of one of the most recent machine learning ventures.
Scientists are beginning to turn to machine learning to finally reveal what a black hole actually looks like. A team of researchers at MIT have developed a new computer algorithm to help construct the first true image of a black hole. To get an idea of how difficult this task is, MIT team leader Katie Bouman equates the feat to “taking an image of a grapefruit on the moon.” Presently, the largest radio telescope in the world has a diameter of only 1,000 feet, or around 0.3 kilometers. In order to capture an image of Sgr A*, one would need a radio telescope with a diameter of 10,000 kilometers, virtually impossible given that the Earth’s diameter is only 13,000 kilometers.
Naturally, this is impossible. However, Bouman’s team plans to use machine learning to compile data from various radio telescopes across the globe, essentially turning the planet into one giant radio telescope. This new algorithm, called Continuous High-resolution Image Reconstruction using Patch, or CHIRP for short, can sift through the noise and irrelevant data collected from the different observatories. The meaningful information from the “global radio telescope” that has been identified will then be pieced together, and CHIRP will, in theory, be able to interpret the patterns present in the data and help construct a coherent image of a black hole, almost as if completing a jigsaw puzzle while still missing many pieces.
If successful, CHIRP will grant us the first ever true image of a black hole. Furthermore, it will provide insight as to whether or not Albert Einstein’s theories of general and special relativity accurately predicted the properties and behavior of black holes. Only time will tell, but we very well could be one step closer to uncovering the secrets that black holes are hiding deep beyond the event horizon.
Written by Rachel Weissman, Edited by Jack Vasquez & Alexander Fleiss