NASA E/PO, Sonoma State University, Aurore Simonnet
Black holes are the only objects in the universe that can trap light by sheer gravitational force.
Scientists believe they are formed when the corpse of a massive star collapses in on itself, becoming so dense that it warps the fabric of space and time.
And any matter that crosses their event horizons, also known as the point of no return, spirals helplessly toward an unknown fate.
Despite decades of research, these monstrous cosmological phenomena remain shrouded in mystery.
They're still blowing the minds of scientists who study them. Here are ten reasons why:
Randy Astaiza contributed to an earlier version of this post.
NASA/CXC/M.Weiss
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 neighbor, a black hole.
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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 in 1915. From Schwarzschild's work came a term called the Schwarzschild radius, a measurement of how small you'd have to compress any object to create a black hole.
Long before this, British polymath John Michell predicted the existence of "dark stars" so massive or so compressed that they could possess gravitational pulls so strong not even light could escape; black holes didn't get their universal name until 1967.
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Black holes have this incredible ability to literally stretch you into a long spaghetti-like strand. 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, they will become increasingly more attracted as they inch closer to the center of the black hole. The closer they get, the faster they move. But the top half of your body is farther away and so is not moving toward the center as fast. The result: Spaghettification!
