Black Holes - Explained

Many people like are curious about Black Holes and what they actually are, and how we know they exist.

So let me explain.

Firstly a Black hole is formed when a star 10 times bigger than the sun has used up all of it fuel in the nuclear fusion process. Infact the heat and radiation pressure that the star produces through fusion is usually balanced by the force of gravity acting inwards. This is called Hydrostatic Equilibrium, it is what makes a star have a spherical form. But when the star can not produce enough pressure outwards to balance the gravity, then the star becomes a Super Nova.

The remanant is either a Neutron star or a Black Hole. Let there be light...... Well, no, darkness.

The word hole, can also be misleading, the Black Hole is not a 2-D hole, like a circle but in fact is Spherical.

The actual physical remain of the star is compressed into a single point, a singularity. Not even the smallest dot because a dot still has a dimension, but a pure zero point.

A fraction of the mass of the star has been compressed to infinite denisty at the heart of the black hole, and it is this fundamental principle that gives the Black Hole its famous characteristics.

The Spherical hole you imagine is actually the boundary where inside the hole light can no escape, the force of gravity inside the boundary is so strong that the escape velocity is bigger than the speed of light. The escape velocity is the speed that an object or particle must reach in order to escape the gravitational field of the planet or star.

On the outside of the hole light can escape but is strongly distorted.

If you fell into a black hole feet first your feet would be attracted and accelerated to the black hole at a greater rate than your head, so you would be stretched like spaghetti.

Gravity chages how Space-Time behaves, a famous preposition of Einstein. The stronger the gravitational field the faster times flows in comparison with a weaker field. This is a big subject so just accept this as it is, if you want to know more look at general relativity.

So if some people have seen Interstellar, some of the crew go close to the black hole and they are away from the mother ship for about an hour, but the crew left on the ship can waited two years. This is a secnario that can occur.

People want to know if the Sun can become a Black Hole, well it can't due to it's total mass, when it dies there will not be enough gravity to force the singularity of a Black Hole. The Sun will turn into a Red Giant and swallow the Earth and then eventually shrink into a White Dwarf which is just a big Diamond, untill the finally loses its's heat and becomes a cold brown dwarf not visible but by most telescopes.

However if the Sun suddenly turned into a Black Hole, it would consume the earth, the mass wouldnt change and hence neither the gravity, the orbits would remain the same, just we wouldn't have light. Black Holes only consume bodies that get to close, just like the earth attracts asteroid, its a similar mechanism.

Hope you enjoyed. Any questions, write them in a comment.

MadMac