Are the black holes really black or invisible?

 

The blackest paint available on the market today is called Black 2.0. So the reason this appears black is that all visible light is coming in and getting absorbed by the black paint, and almost no visible light is returning to your eyes. So when the photoreceptors in our eye see a spot that has no light coming from it, it just is an absence of a signal. And so it appears black to us lack is the absence of color or the absence of any light. But what does invisible mean? Well, invisible doesn't mean the absence of light, it just means that you don't notice that something is there. So for example, Carol syrup and glass have about the same refractive index. And so light travels through it at about the same speed. And so that means that they bend light about the same, which means that any light coming through from the background gets bent about the same way. And so that means when you stick to glass and caramel syrup, it becomes invisible.  So the glass invisible simply because it lit the background glass through at the same rate as the liquid that it was in. And also it bent the light the same way that the liquid bent the light, so we cant tell it is there.                                                                                                      So for something to be invisible, it doesn't mean that there's no light getting to your eyes. There's a lot of light getting to your eyes, and it's all coming from the background. Talking about what a black hole, it is made of matter, just like anything else that you can touch and feel in the universe. But a black hole is a little bit different because it's been compressed very tightly. So with any large object in space, like the earth, two main forces are competing against each other. The first force is gravity, which is always pulling and compressing everything together is the only force that's always attractive. So gravity is always pulling everything together. But the electromagnetic force on the electrons around the molecules and atoms are always repelling each other. So it kind of comes into a balance, gravity pulls everything together, and then the electromagnetic force pushes everything apart, and it stays like that. But because the more mass you have, the more gravity you have from every particle pulling each other together, it means that you can reach a critical point. And that critical point means that there's a point when you get enough mass packed together, that the gravity can overcome the electromagnetic repulsion of the atoms and molecules. And so if you pack enough mass together, then gravity will just keep pulling on and pulling on and pulling on it until the electrons get closer and closer together. But there's a problem because, in physics, there's a rule that states that two electrons can't be in the same state in the same location at the same time. And so if you try to pack electrons together, they can't do it. And so they exert pressure called degeneracy pressure. And that's what a white dwarf is. And so white dwarf is when the gravity has balanced with the degeneracy pressure of the electrons in a star. And so it stops collapsing. But then if you pack even more mass into it, the gravity keeps pulling it closer and closer together so that eventually the electrons come so close to the protons and the atoms that they interact with the protons. And when an electron and a proton get close enough together, it can form a neutron. And so if you get enough mass together, it comes close together due to that strong force of gravity, then now all the atoms with their protons, neutrons, and electrons just become this sea of neutrons. And this is called a neutron star. And it's extremely dense, but it's not a black hole yet, and a neutron star supported about the same way that a white dwarf is because there's a rule in physics that also says that two neutrons can't be in the same state at the same time in the same location that exerts an outward pressure that keeps the neutron star from collapsing on itself. But then if you pack even more mass onto it, not even the neutron degeneracy pressure can keep the star from imploding on itself, and it becomes a black hole. So basically any star after it explodes into a supernova. If the core leftover is 2.5 times larger than the mass of our Sun, it will have enough mass to collapse into a black hole. And so a black hole is a singularity. One single point where all mass all matter in the entire star has collapsed into one single point because there's nothing that can hold it back after it collapses tighter and tighter together. because gravity gets stronger and stronger, the closer the particles are together. And so once masses collapse into a black hole, there's absolutely nothing that can escape from the inside of the black hole to the outside world. Not even light So not only can its light, not escape from the black hole, but any light that's coming from around the black hole will also fall into the black hole and be absorbed into it.

Are black holes black? Well, by our definition, does a black hole absorb all visible light? Well, yes, it does. Not only does it absorb all visible light, but it gives off no light whatsoever, no visible light, no infrared light, nothing. So a black hole is the blackest black possible in the universe. So there's a certain radius around a black hole called the event horizon. And this is the radius around the black hole, in which if something passes, it cannot return from the black hole. And so basically, there's this sphere around the black hole called the event horizon, from which no light can escape, and all light going into it is absorbed. So even though the mass of a black hole is contained in a singularity, meaning an infinitesimally small point, the event horizon has a definite diameter, and that's the part that appears black.

One of the first ways they were able to test Einstein's theory of relativity is by watching how the sun bent the light from a distant star. Well, a black hole is black, and a black hole can be invisible depending on what's behind it. If an Earth is behind the black hole, then obviously you can see the black hole, but if there's nothing behind the black hole to see the black, then all you see is black on a black background, and then the black hole is invisible. So a black hole is black, and sometimes it's invisible depending on what's behind it, everyone.