Falling into The Unknown : Black Holes

#astrophysics #space #blackholes #einstein

The time has come to tackle the most feared of the heavenly bodies, Black Holes. Like almost everything in nature they have different properties, sizes, masses and characteristics.

A Black Hole is formed when the internal pressure of a star is insufficient to resist the objects own gravity. Our Sun is kept in Hydrostatic Equilibirum due to the fusion of Hydrogen to Helium exerting outward and gravity pushing inward, keeping the Sun spherical. For the beginning of Black Hole formation, gravitational collapse wins the duel and the core of the star continues its collapse faster than fusion can push it outward. 

A Black Hole causes such extreme curvature of spacetime that light cannot escape from its grasp. Escape velocity in physics is the minimum speed needed to escape from a massive body. To demonstrate, the escape velocity to get off Earth’s surface is 11.2km per second. The escape velocity of the Sun is 618 km/second. The Escape Velocity of a Black Hole is faster than the speed of light. So that is at least 299,792,459 km/second. 

As the escape velocity is faster than light, we can’t view the actual hole directly but black holes can emit particles in the form of Hawking Radiation eventually causing them to evaporate. This can take around 10 to the 92nd power of years to happen. Black Holes can form an accretion disk of matter around them that is visible. This can be debris of a Star that strayed too close to the Black Hole and was destroyed.

One Kilometer faster than the speed of light. The higher the mass of the black hole, the faster speed we need to travel to escape from it. 

So I would like to clear up some misconceptions about Black Holes that commonly exist. Firstly, Black Holes are not cosmic vacuum cleaners hurtling through the universe at random sucking everything into them. Black Holes are situated at the centre of most Galaxies, even our own galaxy The Milky Way. Our Black Hole is Saggitarius A* with 4 million times the mass of our Sun and a diameter of 44 million KM. A Black Hole is only dangerous if you get too close to it and fall in. 

Black Holes have properties such as mass, electric charge and spin. The two main types of Black Hole are a Stellar Mass Black Hole and a Supermassive Black Hole. Stellar Mass black holes can be 10/20 times the mass of the Sun and Supermassive Black Holes much larger – many millions and billions the mass of our Sun. 

The Black Hole fits within General Relativity. The mass of the Black Hole causes phenomenal curvature of Spacetime. A much larger dent in the fabric of the cosmos.

 So what would happen if you fell into a Black Hole? As you fall downward due to curvature path around the Black Hole you would reach The Event Horizon. At this point space and time break down. The singularity is the centre of the Black Hole, the area of infinate curvature and density. Crossing the event horizon is the point of no return – you are going into the Black Hole and nothing in the natural or supernatural world is going to save you. Sorry. 

As you fall, at a certain point the force on your feet would be millions of times the force on your head. This will make you stretch infinately into the width of a subatomic particle before swirling into the hole. In physics this process is called, wait for it, Spaghettification. Look it up. I promise I didnt make that up. 

Credit : The Inquisitor

So what if someone else is watching you fall into a black hole? General Relativity states that time slows the closer you get to a centre of mass. The closer to the Black Hole you fall, the slower you travel to someone watching you. So at the point of infinate density and curvature of the singularity, time breaks down. Time effectively stops to an observer. So if I were standing on the Earth, watching you fall into a Black Hole – technically you would be falling – FOREVER. The Event Horizon in a Black hole is the last place where we can assign a “when”.

If you are inside the Black Hole, assuming you miraculously survive, all of time would pass you by. All of it. Very creepy! 

Jude Morrow.

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