Black holes are the only objects in the universe that can trap light by sheer gravitational force.
They’re thought to be what anchors galaxies — some of the largest objects in the universe.
And what happens past their event horizon, also known as the point of no return, can only be speculation since we will never get a chance to see it with our own eyes and live to tell the tale.
Despite decades of research, these dynamic cosmological phenomena are still shrouded in mystery. They’re still blowing the minds of scientists who study them and here are ten reasons why.
Randy Astaiza contributed to an earlier version of this post.
Some think that black holes are like cosmic vacuums that suck in the space around them when, in fact, black holes are like any other object in space, albeit with a very strong gravitational field.
If you replaced the sun with a black hole of equal mass, the Earth would not get sucked in -- it would continue orbiting the black hole as it orbits the sun, today.
Black holes look like they're sucking in matter from all around, but that's a common misconception. Companion stars shed some of their mass in the form of stellar wind, and the material in that wind then falls into the grip of its hungry neighbour, a black hole.
Einstein didn't discover the existence of black holes -- though his theory of relativity does predict their formation. Instead, Karl Schwarzschild was the first to use Einstein's revolutionary equations and show that black holes could indeed form.
He accomplished this the same year that Einstein released his theory of general relativity, 1915. From Schwarzschild's work came a term called the Schwarzschild radius, which is a measurement of how small you would have to compress any object to create a black hole.
In theory, any object can become a black hole if you compress it to a small enough space because when you compress it, you make it more dense, giving that object a stronger gravitational pull.
For example, if you shrunk Earth down to the size of a peanut, it would be dense enough to form a black hole. Different objects must be shrunk down to different sizes -- it's the radius of a the sphere you would have to compress the object down to in order to get a black hole that the Schwarzschild radius refers to.
It might sound crazy that black holes could spawn new universes -- especially since we're not sure other universes exist -- but the theory behind this is an active field of research today.
A very simplified version of how this works is that our universe today, when you look at the numbers, has some extremely convenient conditions that came together to create life. If you tweaked these conditions by even a minuscule amount, then we wouldn't be here.
The singularity at the center of black holes breaks down our standard laws of physics and could, in theory, change these conditions and spawn a new, slightly altered universe.
Black holes have this incredible ability to literally stretch you into a long strand akin to a piece of spaghetti. Appropriately, this phenomenon is called 'spaghettification.' Look it up.
The way it works has to do with how gravity behaves over distance. Right now, your feet are closer to the center of Earth and are therefore more strongly attracted than your head. Under extreme gravity, say near a black hole, that difference in attraction will actually start working against you.
As your feet begin to get stretched by gravity's pull, it will become increasingly more attracted as it inches closer to the center of the black hole. The closer it gets, the faster it moves. But the top half of your body is not as far away and so is not moving toward the center as fast. The result: Spaghettification!
Black holes don't just consume material. They also spit it out.
This surprising discovery was first predicted by Stephen Hawking in 1974. The phenomenon is called Hawking radiation, after the famous physicist.
Hawking radiation disperses a black hole's mass into space and over time will actually do this until there is nothing left, essentially killing the black hole. This is why Hawking radiation is also known as black hole evaporation.
Black holes can generate energy more efficiently than our sun.
The way this works has to do with the disk of material that orbits around a black hole. The material that is nearest to the fringe of the event horizon on the inner edge of the disc will orbit much more quickly than material at the very outer edge of the disc. This is because the gravitational pull is stronger near the event horizon.
Because the material is orbiting and moving so rapidly, it heats up to billions of degrees Fahrenheit, which has the ability to transform mass from the material into energy in the form what is called blackbody radiation.
To compare, nuclear fusion converts about 0.7% of mass into energy. The condition around a black hole converts 10% of mass into energy. That's a big difference!
Scientists have even proposed that this kind of energy could be used to power black hole starships of the future.
Picture space as a stretched rubber sheet with criss-crossing grid lines. When you place an object on the sheet, it sinks a little.
The more massive an object you put on the sheet the deeper it sinks. This sinking effect distorts the grid lines so they are no longer straight, but curved.
The deeper the well you make in space, the more space distorts and curves. And the deepest of wells are made by black holes. Black holes create such a deep well in space that nothing has enough energy to climb back out, not even light.
Stars throughout galaxies form within gas clouds. However, these gas clouds first need to cool to create the conditions that ignite star formation.
Supermassive black holes at the center of galaxies emit large amounts of high-energy particles in the form of blackbody radiation. These high-energy particles will heat up these gas clouds around them, preventing them from cooling, and ultimately stifling star formation.
The only difference between a black hole and our sun is that the center of a black hole is made of extremely dense material, which gives the black hole a strong gravitational field. It's that gravitational field that can trap everything, including light, which is why we can't see black holes and why they get their name.
If you shrunk our sun down to where it was only 3.7 miles across, then you would have compressed all of the mass in our sun down to an incredibly small space, making it extremely dense and also making a black hole.
You can turn anything into a black hole, in theory. In reality, we only know of one way that can produce a black hole and that is the gravitational collapse of an extremely massive star -- 20 to 30 times more massive than our sun.
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