Chapter 2: Into the Vast Darkness

What is a Black Hole?

Wikipedia says, "A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole."

How is a Black Hole formed?

A black hole can be formed by the death of a massive star. When such a star has exhausted the internal thermonuclear fuels in its core at the end of its life, the core becomes unstable and gravitationally collapses inward upon itself, and the star’s outer layers are blown away. The crushing weight of constituent matter falling in from all sides compresses the dying star to a point of zero volume and infinite density called the singularity.

Choose your Adventure!

Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or "stuff," in an object.

At the simplest level, there are three kinds of black holes: stellar-mass black holes, supermassive black holes, and intermediate-mass black holes. So if you jumped into one, your exact fate might depend on which sort of black hole you choose.

The first kind of black hole is called "stellar." Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar-mass black holes in Earth's galaxy. Earth's galaxy is called the Milky Way.

The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.

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A Fun Fact!

Could a Black Hole Destroy Earth?

Black holes do not go around in space eating stars, moons, and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.

Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now. The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.

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Spaghetti

If you were free-floating in space near a stellar-mass black hole that wasn’t feeding on anything, your only hint that it exists might be the gravitational magnification, or “lensing,” effect it could have on background stars.

But as you flew closer to this strange spot, you’d be stretched in some directions and squished in others, a process that scientists call spaghettification. This is because the black hole's gravity compresses your body horizontally while pulling it like taffy in the vertical direction. If you jumped into the black hole feet first, the gravitational force on your toes would be much stronger than that pulling on your head. Each bit of your body would also be elongated in a slightly different direction. You would literally end up looking like a piece of spaghetti!

So, as you fell into a stellar-mass black hole, you probably wouldn’t worry much about the existential mysteries you might be able to unlock on "the other side." You’d be as dead as spaghetti-shaped doornail hundreds of miles before you hit the singularity.

Even if you were still alive, you’d have to travel faster than the speed of light in order to escape. But as we know, nothing in the known universe can do that.

With that in mind, it's possible (although unlikely) that if humans survive long enough to pioneer advanced space travel technology, we might be able to visit a black hole up close. And if we do, maybe we'll even toss a few probes into the black hole to test what happens at the event horizon.

Unfortunately, because nothing can escape the event horizon, not even information, we’ll never be able to know for certain what goes on when matter (in this case you) reaches the point of no return. So, even if you do find yourself with the opportunity to take a cosmic cliff dive into a black hole, for safety reasons, you probably should resist the urge. 👽