Not many things can mystify the mind like black holes do. When examined in depth, black holes aren’t all that confusing, in fact in some cases, black holes can be incredibly helpful! Thanks to the discoveries of physicists, we have a pretty good hold on what black holes are, and how they function, and how they affect our own galaxy. First, though, one must know the basics of the physics that we apply to black holes.
Gravity is the essence of black holes. Gravity is a well-known force, as it has an enormous effect on the earth and everything on it. Whether you are conscious of it or not, gravity is constantly working on you. When you jump, it is what pulls you back down to earth, but even after you’ve landed, gravity’s force is still applied. For example, you need to use a chair to keep you up when sitting because if not gravity would pull you to the ground. This goes for all objects on and around the Earth. The factors that affect the force of gravity are the universal gravitational constant, the mass of said planet and the radius of said planet. Therefore, the gravitational force is different on each planet, not taking into account that distance between planets which also effects their gravitational pull on each other. The force of gravity on earth is equivalent to about 9.8 meters per second squared. That is equal to the acceleration at which objects are pulled back down to earth. As a more advanced way of thinking of gravity, Tia Ghose defines it in What Is Gravity as: “the consequence of the fact that matter warps space-time.”
Now that there is a general understanding of what gravity actually is, lets examine how gravity works within a black hole and what a black hole actually is. Black holes form by the death of stars. When they die, most stars will just form white dwarfs, but the largest of stars will become black holes. A star’s lifetime is dependent on the chemical composition within the star’s core. All stars are made up of different molecules that fuse together to create new molecules. The energy from these fusions work against the star’s massive gravitational pull and keep the star alive. At some point, though, these molecules fuse to form iron and that fusion does not give off enough energy to hold up against the gravitational pull. Then gravity takes over the star and creates white dwarfs, but it is not the same case for supermassive stars. These stars will quite literally go out with a bang, exploding, releasing all the fiery strength in less than a second before gravity takes over, leaving behind nothing but their stellar core. The remnants of the star will then collapse in on itself, thus creating a black hole.
Black holes are essentially invisible on the black canvas of the universe, but their intense gravitation pull and their effect on the stars around them give away their location. Though these elusive beings are depicted as a huge danger to the universe, and to our own planet, there is no need to be alarmed. As National Geographic explains in Black Holes 101, “if our sun was suddenly replaced by a black hole of similar mass, our planetary family would continue to orbit unperturbed, if much less warm and illuminated.” Our own milky way is out of the way of danger of any impending black holes.
The physics that we apply to black holes are governed by Einstein’s field equations. These equations stem from Einstein’s theory of general relativity. Through extensive calculation of these formulas, we discover that a “black hole,” isn’t a hole at all, but rather a singular point of such large gravitational pull. This pull is so strong that no object within the event horizon could ever gain enough velocity to escape its gravitational force. The event horizon is, as the author of What is a Black Hole explains, “the last distance from which light can escape the pull of the black hole. Inside the event horizon, everything, including light, must move inward, getting crushed at the centre.” Some theorize that a black hole could be used as a worm hole if entering only the event horizon in just the right way.
This is because the gravitation pull of black holes is so intense that it even warps spacetime. Every mass in space slightly alters spacetime, almost like a dent. Think of spacetime as elastic, the heavier the object, the more of a dent it makes. Planets like earth make a small dent, but it is nothing in comparison to that of a supermassive black hole. This effect can be visible, Robert Britt describes an example of this in Einstein’s Warped View of Space Confirmed, “In observations of activity around black holes in 1997, researchers noted that gasses spiraling into the black hole wobbled, or precessed, like a top.” Unusual motions can also be seen of light when entering a black hole. Picture the spacetime continuum again like that elastic, but with parallel lines that remain parallel until they curve around the black hole. Light curves with those lines around the hole until it is out of its immediate gravitational reach, but if the steam of light happens upon a parallel line that essentially “touches” the black hole, it will disappear into the darkness.
As stated before, though black holes can sound very intimidating, there is nothing to fear. It is common knowledge that the milky way has its very own supermassive black hole at its center, and studies suggest that there are thousands more joining it. Nell Greenfieldboyce states in Center of Milky Way Has Thousands of Black Holes, Study Shows: “Their calculations show that there must be several hundred more black holes paired with stars in the galactic center, and about 10,000 isolated black holes.” These entities though, do not negatively affect the earth because we are lightyears away from their event horizons, and essentially out of danger.
Over the past decades, scientists have made incredible strides researching black holes, and there is plenty more to come. No one can really know what is to come of further black hole research, but scientists are diving further into the idea of wormholes and harnessing them for the use of time travel. Using Einstein’s rules of general relativity, many have theorized the existence of entities called “white holes.” A better explanation is given by Jessica Krall and Jessica Felhofer in The Future of Black Holes,” The idea of wormholes first came from the idea of white holes. The equations of general relativity have an interesting mathematical property: they are symmetric in time. This means that you can take any solution to the equations and imagine that time flows backwards rather than forwards, and you will get another valid solution to the equations. If you apply this rule to the solution that describes black holes, you receive a white hole. Since a black hole is a region of space from which nothing can escape, the time-reversed version of a black hole is a region of space into which nothing can fall. So, just as a black hole sucks things in after they pass the event horizon, a white hole would spit these things out.” The future of black holes is more than promising and could mold the future of not just this planet, or the milky way, but the future of the entire universe. That is completely dependent, though, on the idea that all we know about black holes today is correct.
“Black Holes.” Physics For Idiots, physicsforidiots.com/space/black-holes/.
“Black Holes, Explained.” What Is a Black Hole?, 25 Sept. 2018, http://www.nationalgeographic.com/science/space/universe/black-holes/.
Ghose, Tia. “What Is Gravity?” LiveScience, Purch, 3 June 2013, http://www.livescience.com/37115-what-is-gravity.html.
Greenfieldboyce, Nell. “Center Of The Milky Way Has Thousands Of Black Holes, Study Shows.” NPR, NPR, 4 Apr. 2018, http://www.npr.org/sections/thetwo-way/2018/04/04/599437677/new-study-shows-the-center-of-the-milky-way-has-thousands-of-black-holes.
Britt, Robert Roy. “Einstein’s Warped View of Space Confirmed.” Space.com, Space.com, 8 Mar. 2016, http://www.space.com/456-einstein-warped-view-space-confirmed.html.
Krall, Jessica, and Jessica Felhofer. “The Future of Black Holes.” The Future of Black Holes, http://www.felhofer.com/blackholes.htm.