BLACK HOLES

What is a black hole? "It is a hole in spce, it just sucks everything in" Why is it called black hole? "Ummm..."

Well, there was a little twist in that... Black hole is black because it "sucks" everything, even light itself can't escape. Black hole is not a hole like a hole in the ground. It is a 3D hole, you might think it that way. Enough with the holes already! Hole, hole, hole...

First we must know how black holes are born, before we can dwell into what this mysterious object is. Black holes are somewhat beasts of the universe, they can consume anything from planets to galaxies. They dominate the universe and are at center stage in shaping the cosmos. Black holes are remnants of dead stars, they are born in the most violent event in the universe, a supernova (hypernova) explosion. When a star much, much bigger than our Sun dies, the core of the star can no longer hold up against its own gravity and it collapses. When a supermassive star starts to fuse iron at its core, the star is doomed. So, the core collapses, and a black hole is born. The new black hole starts to devour the star from inside out, this all happens in a millisecond. Even before the rest of the star knows what has happened. The mini black hole devours mass equal to millions of Earths in a second and starts to choke, releasing a gamma ray burst. Gamma rays are the most powerful and energetic form of radiation. They cause the star to go supernova, exploding with the power and brightness of billions of stars. Outshining even entire galaxies, what remains, is a black hole.

Black hole can have the mass of billions of suns in a very compressed space. This is why black holes are so dangerous, bacause of gravity. On Earth, gravity keeps us on the ground and in space it holds planets orbiting stars and so forth. But, in the case of black holes, the gravity goes into overdrive, it becomes superstrong. The more massive the object is, the more gravity it has according to the Newtonian concept of gravity. General relativity and quantum mechanics, say that, it is also the volume in which the mass is compressed, the density and the mass that dictates the effect it causes. 

The reason why we can not see them directly (why they are black) is because the gravity near the black hole is so strong that sucks in even the photons (light) and doesn't let them out. Because of that nothing reflects back for us to see beyond the event horizon. Event horizon is the point of no return, it is not a physical line or anything, it's where the gravity is so strong it's impossible to get out. The misconception here is that, everything is sucked in no mather what. Yes, everything is sucked in if it gets too close. You can think it this way, it's the same thing, if an asteroid gets too close to Earth. Earth's gravity "sucks" in the asteroid. But, our Moon is far enough so that it orbits Earth and is bound to Earth's gravitational field. It's the same thing with black holes, there are even stars orbiting black holes. Most galaxies have supermassive black holes in the center, they help to form galaxies and somewhat gravitationaly hold them together.

The gravity of a black hole is so strong that it even slows down time itself and everything that is sucked in is spaghettified. All the matter that falls in to a black hole goes to the singularity. It is a point in the center of a black hole, with density that infinite as well as the size of it. No one can know  for certain. Black holes seem to break the rules of physics, there are so much mass in a indesimal point that there can only be theories.

How do we know then that there really are black holes out there? The matter that falls in to a black hole is heated up and cause the matter to form a accretion disc around the event horizon. This heated  matter sends of infrared as well as x-ray radiation. So, eventoug we can't see in to a black hole, we still can see the event horizon and how matter behave near a black hole. The gravitational effect that a balck hole causes, for example in the center of our own galaxy, to the stars orbiting it are clear. Only a black hole could cause the supermassive stars to travel millions of kilometers per hour and to orbit seemingly nothing. 

There are alos theories that black holes are the gateways to other dimensions, universes and that they could be wormholes to different parts of the universe. I say that, no one can know, it is impossible to go into a black hole and find out. The obstacles are overwhelming to say the least. What we know for certain is that they are out there. No doubt about it, but everything else is somewhat blurred, as is the space around the singularity.

Artist rendering of a black hole. Picture from Cosmology.com