![]() The size of an event horizon of a black hole depends on the gravity, so really the event horizon is a sphere surrounding the black hole. That distance defines a sphere around an object: anyone on that sphere’s surface would feel the same gravity from the object at the center. This means that anyone at a given distance from a massive object - say, a million kilometers - would feel the same force of gravity from it. The gravity you feel from an object depends on two things: the object’s mass, and your distance from that object. And they’re definitely not funnel shaped. So if someone says a black hole has zero size, you can be all geeky and technical and say, not really, but meh. That’s one one-hundred quintillionth the size of a proton. If the Universe itself prevents you from measuring it, you might as well say the term has no meaning.Īnd how small is a Planck Length? Teeny tiny: about 10^-35 meters. In fact, the term "real size" doesn’t really mean anything at this kind of scale. The actual physics is complicated, but pretty much when the collapsing core hits this size, even if we could somehow pierce the event horizon, we couldn’t measure its real size. A Planck Length is a kind of quantum size limit: if an object gets smaller than this, we literally cannot know much about it with any certainty. It’ll eventually reach a size called the Planck Length, a unit so small that quantum mechanics rules it with an iron fist. Because it’s wrong.Īt some point, the collapsing core will be smaller than an atom, smaller than a nucleus, smaller than an electron. That really bugged me, as you can imagine… as well it should. Smaller, smaller… and when I was a kid I always read that it collapses all the way down to a geometric dot, an object with no dimensions at all. It will continue to collapse, and the gravity increases. But our math in these situations is pretty good, and we can at least apply them to the collapsing core, even when it’s smaller than the event horizon. We can’t see in, and it sure enough isn’t gonna send any info out. What happens to the core? The actual mass that collapsed? Like I said above, to the collapsing core, its clock keeps ticking, so it sees itself collapsing all the way down to a point, even if the event horizon has some finite size. I decided she had a point (HAHAHAHAHA! A "point"! Man, I kill me), and made sure that when I wrote about the event horizon versus the black hole itself I was making myself clear. I was writing about black holes in my previous job, and we got in a fun discussion over just what we meant by black hole: did we mean the object itself that collapses down to a mathematical point, or the event horizon surrounding it? I said the event horizon, but my boss said it was the object. So OK, they’re small, but how small are they? Sure, the mass is important, but sometimes it’s the little things that count. Now, I could explain why they have such strong gravity, but you know what? I’d rather let this guy do it. OK, so now you know what one is, and how they form. Any event that happens inside it is forever invisible. The region around the black hole itself where the escape velocity equals the speed of light is called the event horizon. And since nothing can escape, well, read the quotation at the top of the page. That means that nothing can escape the gravity of this object, not even light. At some point, if the core is massive enough (about 3 times the mass of the Sun), the gravity gets so strong that right at the surface of the collapsing core the escape velocity increases to the speed of light. So the star’s heart collapses while the rest of it explodes outwards (this is the Cliff’s notes version for more details on the process - which is way cool, so you should read it - check out my description of it ).Īs the core collapses, its gravity increases. This sets off a shockwave, blowing up outer layers of the star, causing a supernova. The core runs out of fuel, and collapses. The most common way for a black hole to form is in the core of a massive star. ![]() OK, first, a really quick primer on black holes. It’s not their mass, it’s their size that makes them so strong. ![]() Mind you, this list is nowhere near complete: I could have picked probably 50 things that are weird about black holes. And if you do, then feel free to leave a comment preening about your superior intellect. Regular readers will know a few of these since I’ve talked about them before, but I’m hoping you don’t know all of these. So below I present ten facts about black holes - the third in my series of Ten Things You Don’t Know (the first was on the Milky Way the second about the Earth ). Since it’s Halloween this seems appropriate … and my book Death from the Skies! just came out, and there’s lots of ways a black hole can destroy the Earth. Allow me to be your tour guide to infinity.
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