Scientists Reveal What’s Actually Inside a Black Hole

Sure! Here’s a sanitized version of the transcript, with any sensitive or inappropriate content removed:

—

Imagine a powerful entity from which nothing can escape. Now imagine that this entity is invisible, has the ability to freeze time, and can stretch your body as thin as spaghetti. This may seem like a terrifying nightmare, but such entities exist in our universe. They are called black holes. Join us as we journey through the cosmos to understand what black holes are, how they form, and why they could lead to the destruction of everything as we know it.

Before diving into the science behind black holes, we need to discuss what a black hole is and how they form. This will provide the foundation for understanding what happens to matter and energy that fall into a black hole. Simply put, a black hole is a region of space where matter is packed so tightly together that its gravitational force becomes stronger than any other force in that part of the universe. This means that if anything, including light, gets close enough to a black hole, there is no escaping its gravitational pull, and it will be drawn towards the center, known as the singularity. This is where the gravity of a black hole is most intense.

We will go more in-depth into the different parts and aspects of black holes, but for now, it’s important to know that the singularity is where matter is compressed into an infinitely tiny point, and everything we know about time, space, and reality breaks down. The second part of the black hole we need to define is the event horizon. This is the boundary around the black hole where it becomes impossible to escape the gravitational pull produced by the singularity, as the velocity needed to break free exceeds the speed of light. Since the laws of physics tell us that nothing can move faster than the speed of light, there is no hope of exiting the black hole once an object goes past this point.

The first person to describe a black hole was John Michell in 1783. Michell was considered a brilliant scientist at the time. However, his ideas eventually fell into obscurity since the math and understanding of physics necessary to explain how a black hole works wouldn’t be invented for another century and a half. In 1915, Albert Einstein came up with his theory of general relativity, predicting the existence of black holes based on the equations he developed. At this point, the scientific community was divided on whether such a powerful source of gravity could actually exist. But as cosmologists and mathematicians began to investigate the universe using Einstein’s equations, it became clear that black holes were indeed theoretically possible.

Then, in the early 1970s, British astronomers Louise Webster and Paul Murdin at the Royal Greenwich Observatory and Thomas Bolton, a graduate student at the University of Toronto, independently announced that they had discovered an invisible massive object orbiting a star over 6,000 light-years from Earth. The celestial body was emitting massive amounts of X-rays, but the source of the radiation could not be seen. The astronomers named the mysterious object Cygnus X-1, which would eventually be regarded as the first black hole ever to be observed by scientists.

It’s worth mentioning that a light-year is a measurement of distance and not time. When scientists use the term light-year, they are talking about the distance light travels in one Earth year. Since light always travels at the same speed, one light-year is approximately 5.88 trillion miles or 9.46 trillion kilometers. This means that 6,000 light-years is around 30,000 trillion miles.

Let’s now discuss how these incredible marvels of space actually form. Even though we know the basic properties and physics of black holes, there is still a lot that scientists have yet to uncover. We know that most black holes are formed when a large star goes supernova and collapses in on itself. In the middle of stars, elements are being forced together in a process called fusion. Initially, the hydrogen in a star fuses together to form helium. After the star uses up all of its hydrogen, helium begins to fuse into carbon; this process continues until the fusion of elements starts to produce iron and nickel. At that point, the fusion process no longer releases energy, instead requiring an input of energy to keep going. This causes the star to cool, leading to the outward forces of pressure slowly dropping. When this pressure drops to a low enough level, gravity takes over, and the star collapses in on itself in a matter of seconds, resulting in a supernova explosion. In order for a star to go supernova, it must have a mass approximately three times greater than our sun. Once these massive stars spew their elements across the cosmos, all that remains is an infinitely dense point in space; this is how a black hole is born.

However, the collapse of stars cannot account for every black hole in the universe, and this is where scientists are stumped. It’s not entirely clear where some of the largest black holes in our cosmos came from. In December of 2004, astronomers observed flashes of light coming from a series of gamma-ray bursts. The data collected suggested that these flashes were the “afterglow” of a gigantic explosion that resulted from a black hole and neutron star colliding. This event resulted in a significantly larger black hole forming, which confirmed that black holes are not only created by the collapse of massive stars, but much larger black holes can be born from cosmic collisions.

The largest black holes in the universe can be found in the center of galaxies and are known as supermassive black holes. Even though scientists know these are the most massive and densest black holes in our universe, they still don’t know exactly how they were formed. We’ll look more closely at each type of black hole to better understand what makes them different from one another and hopefully gain more insight into where they came from.

But before we do this, let’s address some common misconceptions about these cosmological entities. Black holes are not the same as wormholes. Sci-fi stories often include wormholes that can take space travelers from one part of a galaxy to another in a matter of minutes. This is very important when writing exciting plots because no one would watch a show or read a book depicting a crew traversing the cosmos at light speed and arriving at their destination hundreds of years after they left. Wormholes fix this narrative problem as, theoretically speaking, they can be used as a kind of space shortcut by almost instantaneously folding space-time.

The way this could work is that two points in the universe could be connected by a tunnel that has an entrance in one region of space-time and an exit hundreds, thousands, or even millions of light-years away. To visualize this better, let’s say you were a small insect on a piece of paper and wanted to get from one end of the paper to the other. Under normal circumstances, you’d need to crawl across the entire page to get to your destination, which could take a very long time. However, if the goal is to get from one edge of the paper to the opposite edge and we fold the paper in half, you would only have to take a few steps to reach your destination! This is similar to how a wormhole might work in our cosmos.

Unfortunately, black holes do not do this because they are completely different phenomena than wormholes. Instead, if you entered a black hole looking to take a shortcut between two points in space, you would be drawn into the singularity and crushed under its immense gravitational force. As far as we know, there is nothing on the other side of a black hole; once you pass the event horizon, you are drawn into the darkness with no way to escape.

Another common misconception is that black holes are the vacuum cleaners of the universe, sucking up anything and everything into them as they move through space. In reality, black holes don’t suck anything in. Instead, objects only fall into black holes when they are put on a trajectory that brings them too close to a black hole’s gravitational pull. Entire stars, solar systems, and galaxies orbit black holes in the same fashion that the planets of a solar system orbit their star. Due to our universe’s chaotic nature, things are always being knocked into black holes. For example, Sagittarius A, the black hole in the middle of our Milky Way Galaxy, is constantly consuming stellar dust, celestial bodies, and stars.

Some interesting and destructive phenomena can occur depending on what falls into the black hole. As some objects are ripped apart and consumed, they release huge amounts of energy and matter that are hurled across the universe. This can lead to a phenomenon known as relativistic jets, which shoot gamma radiation at near the speed of light out from a black hole, affecting anything in their path, including stars and planets.

Typically, astronomers classify black holes into three categories: stellar-mass, supermassive, and intermediate-mass. There are no exact parameters set for each class, and there are black holes that straddle the line between two groups. In fact, scientists are constantly reassessing and shifting the boundaries of each black hole type; relatively recently, a fourth category called primordial black holes has been added.

Let’s examine each one to get a better understanding of the diversity within these phenomena and how it affects the science that goes with them.

**Stellar-mass black holes.** Not all stars that go supernova end up as black holes. Depending on the mass of the star, it might not have enough matter to create a singularity and instead just ends up as a neutron star. Neutron stars are super dense celestial bodies that have enormous amounts of gravitational pull but not enough to form a black hole. A star needs to be around 20 times more massive than our sun to turn into a stellar-mass black hole rather than a neutron star when it goes supernova. Stellar-mass black holes can continue gaining mass as more matter falls into them. Since we cannot directly observe black holes, the only stellar-mass black holes that we know of are paired with stars. The black hole pulls gas and matter from the nearby star, which forms into a disk around the event horizon. The gas becomes superheated and begins to produce X-rays, giving this type of interaction the name X-ray binaries. We know of around 50 suspected stellar-mass black holes in our Milky Way galaxy alone. However, there are likely many more stellar-mass black holes left to be discovered, as scientists believe there might be as many as 100 million in our galaxy.

**Supermassive black holes.** Astronomers have found that practically every large galaxy in the known universe has a supermassive black hole at its center. Unlike stellar-mass black holes that have a mass dozens of times greater than that of our sun, supermassive black holes have a mass of hundreds of thousands to billions of times larger than our sun. These are enormous entities that exert an immense amount of gravitational pull on the solar systems in the center of galaxies. Sagittarius A, the supermassive black hole at the center of our Milky Way Galaxy, is approximately 4 million times the sun’s mass. However, this is relatively small compared to the black holes at the centers of other galaxies. Take Holmberg 15A, a galaxy that lies around 700 million light-years from our own. Its supermassive black hole is at least 40 billion solar masses, or 40 billion times more massive than our sun. Again, scientists are not entirely sure how these gigantic black holes came to be, but it likely had to do with multiple larger black holes colliding and combining their mass while also consuming huge numbers of stars, planets, and space debris. It’s hypothesized that some of these black holes formed in the first few billion years after the Big Bang when the most massive and hottest burning stars went supernova. It has been suggested that since these types of stars burned through their fuel and exploded so quickly, sending their stellar remnants across the cosmos, the resulting black holes had a head start on gaining mass.

**Intermediate black holes.** Since there was such a big gap between stellar-mass black holes and supermassive black holes in terms of size, scientists created a third classification known as intermediate black holes to fill in the gap, which covers black holes with a mass of over 100 times that of our sun to tens of thousands of times the mass of our sun. Intermediate black holes have already consumed large amounts of matter and may have even combined with other black holes, but they are not yet large enough to be considered supermassive. Over time, as intermediate black holes devour more and more matter and continue to collide with other black holes, their mass could become large enough to bump them into the next category of supermassive black holes. Interestingly, scientists are still debating whether any intermediate black holes have actually been discovered. Theoretically, intermediate black holes should be fairly common in the cosmos, as stars are dying and going supernova all the time, resulting in stellar-mass black holes forming. Since the universe isn’t stagnant, each stellar-mass black hole will eventually begin to consume nearby matter and anything that crosses into its domain, starting the evolution from a stellar-mass black hole to an intermediate black hole. The fact of the matter is that intermediate black holes are likely lurking in the darkness of space and don’t have accretion disks or neighboring stars to help scientists locate them. They are also not quite massive enough to exert their gravitational influence in a noticeable way, such as with supermassive black holes, which again makes them hard to locate. Regardless, astronomers are still on the hunt for these bridges between stellar-mass and supermassive black holes.

**Primordial black holes.** The final classification that scientists use for black holes is primordial black holes. These are black holes that formed seconds after the Big Bang. It’s believed that as the universe was born from the original singularity, some of the matter might have been hot and dense enough to immediately form black holes. Scientists theorize that these very early black holes could have had masses that ranged from 100,000 times less than a paper clip, making them micro black holes, to 100,000 times more than the mass of our sun. After the Big Bang, the universe quickly cooled, and the formation of primordial black holes ended. These black holes would have already been consuming matter and growing hundreds of millions or even billions of years before the first stellar-mass black holes were formed from stars going supernova. To be fair, primordial black holes are only hypothetical, as scientists believe that our universe is around 13.7 or 13.8 billion years old, and there is currently no way to know what happened moments after the Big Bang. Some cosmologists have proposed the idea that primordial black holes—and all black holes, for that matter—might have a lifespan and, due to quantum mechanical processes, may eventually evaporate out of existence if there isn’t enough matter around them to consume. Smaller black holes are predicted to evaporate more quickly than larger ones, but either way, the remnants of many primordial black holes may have disappeared from existence long ago.

Let’s now dissect black holes even further and examine the inner and outer workings of these cosmological mysteries. But first, let’s discuss something that must be on everyone’s mind: what would happen if you were to fall into a black hole? Since no one has fallen into a black hole yet, scientists have to theorize what would happen, but using the laws of physics, we know that some astonishing things would occur if you crossed the event horizon.

Let’s start with spaghettification. This is the technical term for what would happen to you or anything else that fell into a black hole and was pulled toward its singularity. Imagine you were floating towards a black hole. You’re feeling just fine until you start closing in on the event horizon, where gravity is so intense that nothing, not even light, can escape. As you get closer to the singularity at the center of a black hole, the gravity becomes more and more intense. The problem is that this happens extremely quickly; there are massive differences in how gravity acts across every centimeter of your body. For a few seconds, your feet are being pulled toward the center of the black hole quicker than the top of your head. Your body would begin to stretch. This might feel good for a split second. It would straighten your spine and stretch your muscles. However, as you approach the event horizon, the gravitational pull becomes so intense that it would literally stretch your body out into a thin noodle shape. This is where the term spaghettification comes from. So, from your perspective, you would survive until part of your body approached the event horizon, and a few seconds later, you would be gone as your body stretched into a thin shape.

However, things get even stranger for someone who is watching you fall into a black hole from far away. As you approach the event horizon and gravity increases, time seems to slow down. To the observer, you would seem to be moving so slowly that it’d be hard for them to tell if you were moving at all. In fact, once you hit the event horizon, you would seem to stop moving completely. This means that to an outside observer, you would appear to be alive just before the event horizon practically forever because it would take many of their lifetimes before your body would pass beyond that point and disappear into the singularity of the black hole. Eventually, you would just disappear from the observer’s perspective, but it’d take a very, very long time. This all has to do with perspective and what Albert Einstein called “relativity.” Basically, the more gravity there is, the slower time moves for you than someone who is observing you where there is less gravity. So, if you were to fall into a black hole, you would be spaghettified, frozen in time, and destroyed all at once, depending on what perspective you were viewing the interaction from.

Needless to say, things get really strange the closer you get to a black hole. Even though the masses of black holes are all different, the anatomy of a black hole, regardless of size, is essentially the same. A black hole only possesses three basic properties, which limits how different any two black holes can be from one another. These three distinguishing properties of black holes are mass, spin, and electrical charge. Let’s see how these three properties impact how a black hole interacts with our universe.

As mentioned before, the event horizon is the boundary around the black hole where the velocity needed to escape the gravitational pull exceeds the speed of light. The very fact that nothing, including light, can escape the black hole once it reaches the event horizon means there is no way for an outside observer to see or know what happens past that point. The only way to definitively solve the mystery of what happens inside a black hole is to pass the event horizon and observe what happens before you are turned to spaghetti and crushed. However, any intrepid astronaut who embarks on this journey in the name of science will not be able to send a signal out of the black hole, so whatever is seen in the milliseconds before death will only be known to the person who has passed the event horizon, which kind of defeats the purpose of entering a black hole for science.

Even though black holes themselves don’t emit or reflect any light, astronomers can see where the event horizon is. This is because any object that is pulled into a black hole will seem to freeze in time just before the event horizon due to gravity’s effect on relativistic