An Earthling’s Guide to Black Holes

Welcome, earthlings, to the place of no return — a region in space where the gravitational pull is so strong, not even light can escape it. This is a black hole. It’s OK to feel lost here. Even Einstein thought the concept was too bizarre to exist. But fear not: This is just your mind thinking. So let’s get started.
  1. The black hole is a hungry beast.
    It swallows up everything too close, too slow or too small to fight its gravitational force — even light. With every planet, gas, star or bit of mass consumed, the black hole grows. At the edge of a black hole, its event horizon, is the point of no return. Stay far away from the event horizon, because that’s where the hole pulls in light. And nothing is faster than light. At the event horizon, everything enters the black hole.
  2. Pretty much everything we understand about how the universe works, depends on the black hole.
    Someone is wrong, or we have to admit that earthlings still aren’t equipped to understand the universe. The firewall paradox calls to question the most definitive theories of science. Albert Einstein, Joseph Polchinski or Stephen Hawking, or none, everything we know about the universe could change if we could know for certain what happens to information inside a black hole.
  3. If you fell into a black hole, it’s not clear how you would die.
    The question of how you would die inside a black hole is probably the biggest debate in physics right now. It’s called the firewall paradox. Based on the math in Einstein’s 1915 General Theory of Relativity, you would fall through the event horizon unscathed before gravity’s force pulled you into a noodle and ultimately crammed you into singularity, the black hole’s infinitely dense core.
  4. There's another possibility, though.
    In March 2012, Dr. Joseph Polchinski and his team pitted Einstein against quantum theory, which posited that the event horizon would become a blazing firewall of energy that would torch your body to smithereens. (If you want to take a minute to look around and appreciate your existence, go ahead. We'll wait.)
  5. Then again, both theories could be wrong.
    So the physicist Stephen Hawking said last January. Black holes aren’t what we thought they were. There is no event horizon, and there is no singularity. They’re just different. According to Dr. Hawking, at the edge of a black hole, you would scramble and leak out into the cosmos as “Hawking radiation.” (We explain this more here:
  6. Shifting gears: Black holes can sing.
    In 2003, an international team discovered the longest, oldest, lowest note in the universe — a black hole’s song. Although it is too low and deep for humans to hear (it's a B flat note that's 57 octaves below middle C), the note appeared as sound waves that moved out from explosive events at the edge of a supermassive black hole in the galaxy NGC 1275. The notes stayed in the galaxy and never reached us, but we couldn’t have heard them anyway.
  7. Those "songs" could help maintain galaxies.
    The “songs” of black holes may be behind a declining birth rate of stars in the universe. In clusters of galaxies such as Perseus, the home of NGC 1275, the energy these notes carry is thought to keep the gases too hot to condense and form stars.
  8. Actually, black holes may control the size of a galaxy.
    Astronomers think that the energy that forms when galactic masses swirl and heat up around a black hole shoots out in X-ray beams that fuel quasars, supermassive black holes that are actively chomping down gas at the centers of distant galaxies.
  9. Astronomers have evidence for black holes in nearly every galaxy in the universe.
    There are so many black holes in the universe that counting them is impossible. Nearly every galaxy (of the 100 billion or so other galaxies visible from Earth) shows signs of a black hole. Supermassive black holes — a million to a billion times more massive than our sun — exist only in the center of a galaxy. At the center of the Milky Way, 26,000 light-years from Earth, scientists are hoping to make an image of what is believed to be our own supermassive black hole.
  10. Black holes are stellar tombstones.
    Literally. In July 1967, a network of satellites recorded an explosion of gamma rays coming from outer space. Today, scientists believe that the gamma ray burst is the final breath of a dying star and the birth of a stellar-mass black hole.
  11. Stars become black holes when they start to lose fuel.
    It starts when a massive star runs out of fuel to power itself. As the star begins to collapse, it explodes. The star’s outer layers spew out into space, but the inside implodes, becoming denser and denser, until there is too much matter in too little space. The core succumbs to its own gravitational pull and collapses into itself, in extreme cases forming a black hole.
  12. To find the darkness, follow the light.
    Because light can’t escape a black hole, seeing what’s inside it is impossible. Getting a picture of a black hole’s edge is difficult, and getting a clear picture is an event. Actually, it has never been done. Scientists suspect black holes when their tools detect high-energy radio waves. (Generally, if there is a lot of energy with a massive core at the center of a galaxy, the core is probably a black hole.)
  13. A black hole is not forever.
    Quantum effects suggest that a black hole will evaporate — eventually. It would take many times the age of the universe for a black hole to fully evaporate.