#thebigbang

What do they look like?

Scientists can’t actually see black holes like other space objects like stars and planets. They are invisible, but interact with and influence the space around them, which can be detected. When looking at a black hole, you are essentially looking at the event horizon. Anything crossing this needs to travel faster than the speed of light to escape, so you see a black sphere reflecting nothing. However, sometimes material will ricochet off the event horizon instead of being drawn into the black hole. Radiation can’t escape gravitational pull once it crosses the event horizon, so it’s difficult to spot one in isolation. However, stellar black holes are most easily located in X-ray binary systems, where gas from a companion star is being pulled into them. X-rays are made by this gas which is heated up as it spirals towards the black hole via an orbiting structure. Astronomers can also measure a black hole’s mass, (a stellar black hole typically having between 2 and 20 solar masses), by observing its gravitational effect on the companion star.

What would happen if you fell into one?

The simple answer to this is that you would die. A black hole is a singularity surrounded by a barrier (the event horizon). Enthrallingly, we don’t know what the singularity is. It is important to note that black holes don’t suck things up. If we swapped our sun for one, for example, the only consequence would be us freezing to death.

If someone were to go near one and you were watching them from a distance, they would seem to slow down as they approached the event horizon. At some point they would appear to freeze in time, slowly turn red and disappear. If you were the one falling into it, you would see the universe in fast forward, kind of like seeing into the future. 

One theory states that you would die quickly. Black holes curve space so much that once you pass the event horizon, there is only one possible direction to go in. A black hole’s mass is so concentrated that at some point even tiny distances of a few centimetres would mean that gravity acts with millions of times more force on different parts of your body. Your cells would be torn apart as your body stretches until you become a hot stream of plasma, one atom wide. Another theory claims you would die quicker than this. Very soon after you cross the event horizon, you would hit a firewall and be killed instantly.

How soon you die depends on the mass of the black hole. For example, a smaller one would kill you before you entered its event horizon whereas you could travel inside a supermassive black hole for a while. This is because the further away from the singularity you are, the longer you live.

Hawking radiation

To end the terror of this article, I will talk about a process that eventually destroys black holes altogether. Hurrah! This process is called Hawking radiation, and isn’t accepted under classical mechanics. 

The theory starts with the fact that empty space is not actually empty but is filled with virtual particles (particles or interactions with inordinately short lifetimes) popping into existence and obliterating each other again. When this happens on the edge of a black hole, one of the virtual particles will be drawn into it and the other will escape and become a real particle. This causes the black hole to lose energy. It happens slowly to begin with, but quickens as the black hole gets smaller. When the black hole has the mass of a large asteroid, it radiates at room temperature (20ºC) and when it has the mass of a mountain it radiates at around the heat of our sun (6000ºC). In the last second of its life, it radiates away with the energy of billions of nuclear bombs in a colossal explosion. This process is sluggish and the biggest black holes we know of could take up to a googol years to evaporate. On a sad note, when the last one dies, nobody will be around to witness it. The universe will have become uninhabitable long before then. On the other hand, this gives us the time period of all of human existence and whatever type of consciousness that comes after that, to work out what black holes really are. 

References for part 1 and 2:

Katherine Blundell, Black Holes: A Very Short Introduction

www.amazingspace.org

www.astronomy.swin.edu.au

www.hubblesite.org

www.newatlas.com

www.space.com

Thank YOU to whoever made this. Sharing because Colin Firth eyegasms.