← Everything Everywhere Daily: History, Science, Geography & More
Everything Everywhere Daily: History, Science, Geography & More
Black Holes (Encore)
00:14:58
Learn about the most powerful objects in the universe
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Gary Arndt
The following is an encore presentation of Everything Everywhere Daily. Gravity is the weakest of the fundamental forces of nature, yet if you have enough of it, it can create the most powerful thing in the known universe, a black hole. The very idea of a black hole didn't really exist until the early 20th century, and now they are regularly found by the world's most powerful telescopes. As much as we know about them, there is even more we don't know and probably will never know. Learn more about black holes, what they are, and how they work on this episode of Everything Everywhere Daily. This episode is sponsored by Quince. Finding the perfect gift can be pretty overwhelming. This year I found the perfect spot for timeless gifts made from premium materials. So you gotta check out Quince. Quince lets you treat your loved ones and yourself to true quality at an affordable price. I got a cotton fisherman throw blanket from Quince and I literally use it when I am writing many of the episodes for this podcast. I also have some Turkish cotton bath towels from Quince that I absolutely love. By partnering directly with top factories and cutting out the cost of the middleman, Quince passes the savings on to you. Quince is also on the nice list. They only work with factories that use safe, ethical and responsible manufacturing practices and they use premium fabrics and finishes for that luxury feel in every piece. Gift Luxury this holiday season without the luxury price tag. Go to quince.com daily for 365 day returns plus free shipping on your order. That's quinc.com daily to get free shipping and 365 day returns. Quince.com Daily this episode is sponsored by Butcherbox. You've probably heard me talk about how ButcherBox only sells 100% grass fed grass finished beef, but what exactly is that and why does it matter? 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When I say that gravity is the weakest of the fundamental forces in nature, it might come as a surprise to you. After all, gravity is what causes us to fall down, and it's why the planets revolve around the sun. However, consider this. If you pick up an object, you can counter the entire gravitational force of the planet Earth with just your arm. Technically, there is a gravitational attraction between any two objects. However, for the most part, it's extremely weak. The gravitational attraction between two people, for example, is so weak that it can barely be measured. Gravity is a fundamental property of mass. And the thing is, you can just keep piling up mass to get more and more gravity. The gravity we experience on Earth is defined as 1G or 1 gravitational equivalent. Let's say you landed on a planet with twice the gravitational force of Earth or two GS. You would definitely notice that something was different if you weighed 150 pounds or 68 kilograms on Earth. It would be like walking around with that weight on your shoulders all the time. Movement would be difficult, and even simple falls would potentially break bones. At 3G, even simple movement would be difficult for all but elite athletes. The Icelandic strongman Hafthor Bjornsson once set a world's record by taking five steps with a 1,430 pound log on his shoulders. That would be the equivalent of walking in a 4.6g environment. At 5g's, it would be difficult for any human to stand up from a seated position, and breathing would become almost impossible. At 10 GS, taking even a single step would break bones. Assuming you could even take a step at 90 g's, your bones would be crushed by gravity alone. 5 or 10 g's might be beyond the ability of humans to withstand. But cosmically speaking, it's nothing. Stars can accumulate an enormous amount of mass. Our sun is huge compared to Earth. But there are other stars in our galaxy that have a mass over 250 times that of our Sun. When a star reaches the end of its life and can no longer produce fusion, the heat which expanded the star outward starts to disappear and gravity causes it to collapse. Now, depending on the original mass of the star, it might collapse down to what is known as a white dwarf. A white dwarf can have the mass of our sun, but be the size of Earth. A teaspoon of matter from a white dwarf star would weigh 15 tons, or the equivalent of three elephants. The only thing which stops a White dwarf from collapsing further is something known as electron degeneracy pressure. This is when quantum effects in the individual atoms are the only thing that are fighting gravity. This, however, has a limit. In particular, it's known as the chandrasekhar limit. At 1.4 solar masses, electron degeneracy pressure can no longer continue to withstand gravity. Gravity will cause all the individual atoms to collapse, and the electrons will merge with protons. The result is called a neutron star. A neutron star is like one massive atomic nucleus. It's the forces within the atomic nucleus, in particular neutron degeneracy pressure, that are now the only thing holding back against gravity. Whereas a white dwarf is something about the mass of our sun the size of a planet. A neutron star could be of similar mass, but only a few kilometers across. But what if we keep piling more mass onto a neutron star? Then what? Eventually, it reaches a point where nothing we know of can withstand the gravity, and then it becomes a black hole. When I mean that nothing can withstand the gravity, I do mean nothing can withstand it. There are no physical forces and no objects that we know of that can escape the gravity of a black hole. Light can't even escape, which is why they're known as black holes. In a black hole, most of what we know about reality simply falls apart. A planet or a star has a radius, a size we can measure. A black hole doesn't have a size. There is no size, no matter how small that it could be, because gravity would always crush it even smaller. Black holes are often called singularities. For this reason. Their size would be shrunk down to a mathematical point. Instead, a black hole has what's known as an event horizon. Anything within the event horizon can never escape. Moreover, it can't communicate with anything outside of the event horizon. In many episodes, I'll talk about something which was at least considered centuries before it came into being. In the case of black holes, the first person who considered such a body was the English clergyman John Mitchell in 1784. However, it really wasn't until the theory of relativity explained by Albert Einstein that people began to take the implications of such extreme gravity seriously. For decades, a black hole was simply a theoretical object. Nobody was sure if they really existed or if it was something that just went weird with the equations once mass reached a certain point. The debate ended in 1971 with the discovery of Cygnus X1, the first black hole, which was discovered. Now, at this point, you might be wondering if a black hole doesn't emit or even reflect any Light, Then how can it be detected? While you can't see a black hole directly, you can observe the stuff around it. Because of their high gravity, black holes will often have an accretion disk around them that spins quite rapidly. This disk is usually the source of x rays or other wavelengths of light that are emitted. Since the discovery of Cygnus X1, there have been a steady stream of black holes which have been discovered. And one of the biggest findings is that there is a supermassive black hole at the center of most galaxies. Known as an active galactic nucleus, or agn. These can sometimes produce an incredible amount of energy around their accretion disks. And they're the source of energy for quasars. Supermassive black holes are hundreds of thousands to billions of times more massive than our Sun. The largest black hole which has been discovered to date is at the center of the galaxy Holm, 15A 700 million light years from Earth. It's believed to have a mass equivalent to 40 billion times that of our Sun. Something this massive is believed to have been created through multiple collisions with other galaxies and mergers with other black holes. When a black hole merges, it's an infrequent event, but the most gravitationally impactful event in the universe. In 2015, the LIGO gravitational observatory, on which I've done a previous episode for the first time, measure the gravitational waves from a black hole merger. While very large astronomical black holes are what capture the attention of astronomers, in theory, a black hole can be of any mass. If you condense the mass of any object enough, you can, again, in theory, create mini or micro black holes. To create this type of black hole, you would need an enormous amount of energy. Such conditions may have existed just after the Big Bang, or they also might exist inside of a particle accelerator. When the Large Hadron Collider opened in Europe, there was a small group that didn't want it to open because they were afraid it might create micro black holes that would destroy the Earth. Their fears, it turned out, were unwarranted for several reasons. First, the Large Hadron Collider would need to be about 35 times more powerful to even theoretically create a micro black hole. Second, even in theory, micro black holes would only last for a tiny fraction of a second before they evaporated. Both micro black holes and the method by which they would evaporate were first proposed by the greatest black hole theorist of all time, Stephen Hawking. Hawking proposed the idea that black holes could disappear over time due to something called Hawking radiation. According to Quantum mechanics particles and antiparticles can be created spontaneously from vacuum fluctuations. Normally, these particles and antiparticles quickly annihilate each other, Returning their energy to the vacuum. However, if this process occurs near the event horizon of a black hole, One of the particles can be drawn into the black hole while the other escapes. This creates a net energy loss from the black hole. And the escaping particle is observed as Hawking radiation. The rate of Hawking radiation emission Is inversely proportional to the mass of the black hole, meaning that smaller black holes emit more radiation than larger ones. In the case of micro black holes, they would vanish almost instantly. The threat of micro black holes also has to do with a misunderstanding of how black holes work. Black holes do not suck things into them. A black hole created by a few subatomic particles Would still have the gravitational attraction of a few subatomic particles. And the event horizon of such a tiny black hole would be even smaller. Black holes are just sources of gravity. They're not omnidirectional space vacuum cleaners. For example, let's assume that our sun was instantly turned into a black hole with the same mass as the Sun. What would happen to the Earth and the other planets in the solar system? The answer is, for the most part, nothing. They would continue to orbit the new black hole just as they do the Sun. Because it would have the same mass. It would be a whole lot darker, but the orbit of the planet wouldn't change. Albert Einstein famously showed that mass and energy were equivalent in his famous equation E mc2. One of the implications of this is that it's theoretically possible to create a black hole by just using energy. If enough energy could be concentrated in one spot, it could form what is known as a Kugelblitz. A Kugelblitz would have an event horizon and would be indistinguishable from a regular black hole. I'll end with one of the most challenging questions regarding black holes. The black hole information paradox. According to the principles of quantum mechanics, information is never truly lost, but rather is encoded in the state of a system. However, according to general relativity, any matter that falls into a black hole is considered irretrievably lost as it's trapped behind the black hole's event horizon and cannot be observed from the outside. This creates a paradox as it suggests that information can be lost in violation of the principles of quantum mechanics. Resolving this paradox has been a major question in theoretical physics. And the best guesses as to the answer lie in the previously mentioned Hawking radiation. Black holes are at the forefront of theoretical physics because in them everything we know about the universe ceases to make sense. We can never peer into a black hole or send a probe into one to gather data. Black holes have an important part to play in the creation of galaxies, and might even be part of the solution to the riddles of dark matter or dark energy. Nothing that we know of or at this point can even theoretically think of can beat a black hole. And that is why black holes are, and always will be the most powerful thing in the universe. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Benji Long and Cameron Keever. I want to give a big shout out to everyone who supports the show over on Patreon, including the show's producers. Your support helps me put out a show every single day and also Patreon is currently the only place where Everything Everywhere Daily merchandise is available to the top tier of supporters. If you'd like to talk to other listeners of the show and members of the Completionist Club, you can join the Everything Everywhere Daily Facebook group or Discord server. Links to Everything are in the show. Notes.