Top 10 Facts about the Black Hole

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If the universe were a fairy tale, then Black holes would surely be the perfect monsters! Dark, massive, destructive are generally not the characteristics held with high regard among the common folk. While the concept of black holes has revolutionised the world of quantum and astrophysics, it has equally enthralled people with its weird properties which however seem to go against the general laws of nature. In the words of Stephen Hawking, “It is said that fact is sometimes stranger than fiction, and nowhere is this more true than in the case of black holes.” Black holes have even fueled a large number of works of science fiction and movies. The Hitchhiker’s Guide to the Galaxy, Bobo’s Star by Glenn Chandler, The Fall of Reach by Eric Nylund, The City and the Stars by Arthur C. Clarke and Gateway by Frederik Pohl are some of those literary wonders. Black holes have also made their way into you drawing room through movies and TV shows like Star Trek, Treasure Planet, Battlestar Galactica, Doctor Who and Stargate SG-1.
Wikipedia defines a black hole as “a region of spacetime from which gravity prevents anything, including light, from escaping.” The term was originally coined in 1967 by John A. Wheeler, a visionary physicist and teacher who is also credited for the invention of the theory of nuclear fission, though the phenomenon was discover by Karl Schwarzschild way back in 1916. It was John Mitchell who actually first proposed the idea of ‘dark stars’ or object. Apart from the fiction, there are some very interesting facts associated with black holes as well that have continued to intrigue mankind for a very long time.

10.  It binds us all

The binding force behind the galaxies in space have always been a matter of question for scientists. It is now thought that most galaxies are held together by supermassive black holes at their centres, which cluster hundreds of solar systems around them. The gravitational force of the black holes actually helps in keeping the galaxies intact and the stars in their positions. It is also thought that maybe these black holes have helped the gas clouds cluster in to galaxies and form stars.  When galaxies collide, the central black holes form a binary system and become more massive. Black holes exist in abundance throughout the universe, holding the systems intact and together.

9.  Bridging the Gaps

bridging the gaps

Remember how The Enterprise travelled through the space in matter of seconds by creating a tunnel in time? Well, not just Star Trek, there have been wide mention of space travel using such tunnel called wormholes. Just the way anyone looking through Alice’s Looking Glass would be transported to a Wonderland, similarly it is believed that if one fell into a black hole, one might be sucked down a tunnel, called the “Einstein-Rosen Bridge” and shot out a “white hole” in a parallel universe! While it appears that a black hole sucks in everything and crushes it with its gravity, the concept of wormholes actually shows that it is just a form of interstellar efficient transport. Black holes may be seen as portals to the interstellar bridge that connect parallel universes, or even parts of the same universe, thus supporting the theory of Multiverse. In fact they may also be used as a means to travel in time according to the various theories that prevail in this field of quantum physics.

8.  A giant memory device

memory device

We all know that nothing, that enters a black hole, is accessible from the outside. But that does not necessarily mean that matter is lost inside a black hole or destroyed! Evidences have led scientists to believe that besides mass, charge, and angular momentum, information and unitary are also conserved inside a black hole. As Stephen Hawking puts it, “It is like burning an encyclopaedia. Information is not lost if you keep all the smoke and ashes, but it is difficult to read.” As a matter of fact, they can serve as giant storehouses of information that might actually flow from one world to another over time and space. They can thus help in knowing both the past and future! Black holes have existed since the inception of the Universe, which means, if the information inside a black hole is somehow accessible, it will open up a whole new dimension for scientists to ponder upon.

7.  Space Mapping

space mapping

Black holes are one of the brightest entities in the space, because of their constant cosmic activity as quasars. Also, they are abundantly scattered in space. The emissions from black holes are accurate markers in space, useful for making three dimensional maps of the universe. Since the stars are the main source of energy and mass for black holes, they are generally found very close to them. Almost every galaxy has a supermassive black hole at its centre and there are about 2.5 million black holes actively feeding in the space. So, if The Enterprise were really in our hands, there would surely have been a Columbus making some discoveries on his voyage across the sea of stars!

6.  Obesity

Black holes, just like human beings, can get annoyingly obese with time. Known as super-massive black holes, they are quite abundant in the galactic systems. A super-massive black hole might have begun as a normal black hole, weighing tens to hundreds of solar masses, but became more massive over time by the accretion of more matter from the galaxies. There is no limit to how small or how large a black hole can be. The more massive a black hole is, the more space it takes up. The majority of the mass growth of super-massive black holes is through rapid gas accretion, which can be observed as active galactic nuclei or quasars. They are also formed when two galaxies collide and smaller black holes at their centres form a pair and get merged. Most of the mass comes from the packing of large volumes of gases into a very small volume of the black hole. It is believed that these super-massive black holes play a pivotal role in preventing galaxies from growing bigger and more starry, by consuming the gasses, which are the raw materials for star formation!

5.  Once upon a Star

once a star

The origin of black holes actually trace back to stars. Stars are like giant nuclear fusion reactors, fueled by gases, mainly Hydrogen. As a star begins to run out of its fuel, it starts to collapse under its own gravity, forming a white dwarf or a neutron star. However, if the star is sufficiently massive, at least three to five times heavier than the Sun, the gravitational force cannot be balanced by the pressure of the internal gasses, causing the star to collapse to the size of a tiny atom, thus forming a black hole. The black holes we know about tend to fit into two size categories: “stellar” size are around the mass of one star while “super-massive” are the mass of several millions of stars. The big ones are located at the centres of large galaxies.

4.  Black is not dark

Black holes are invisible entities in space. However, they are not entirely dark, though the name suggests otherwise. Fireworks like scenes are often visible around black holes, when a gas gets pulled into one and burns bright due to the intermolecular friction cause by the strong gravitational forces of the black hole. It appears like a giant glowing spinning disk with the dark singularity of the hole at the centre. Black holes are also believed to emit photon particles and black body radiation, which was theoretically proved by Stephen Hawking. This can also cause spectacular effects in space. However, because of this radiation, black holes lose a part of their mass as energy, causing them to slowly shrink and evaporate with time. Perhaps, only the smallest black holes would have had time to evaporate significantly during the 14 billion years the Universe has existed.

3.  Falling into the abyss

falling into the abyss

Though the science fiction movies have made falling into a black hole, quite a spectacular event, it has a much harsher reality. If a person was supposed to describe his falling into a black hole, he would experience weightlessness in the beginning as he went into a free fall, followed by intense gravitational forces tormenting his body as he neared the centre. That is to say, if his feet were closer to the centre, then they would feel a stronger pull than the head, until his body is eventually stretched and then ripped apart. As he falls in he may observe distorted images as the light bends around him and he will also still be able to see beyond the black hole as light continues to reach him from the outside.

2.  Time will stop for everyone

time will stop for everyone

One thing that each one of us has grown up hearing is that “Time and Tide wait for none”. Well, not very true when it comes to black holes. Black holes have the ability to morph both space and time. For a person falling into a black hole across the event horizon, the outside world will seem to be in a fast forward motion. For an observer outside, the person will appear to fall into hole in a very slow motion, till the scene freezes and finally disappears from view. This phenomena, known as gravitational time dilation, is one of the very interesting facts about black holes. This is in synchronisation with Einstein’s Special Theory of Relativity, according to which a person on a space travel will age slower than his sibling on Earth.

1.  It really sucks

it really sucks

The most important thing that comes to mind when talking about black holes is its immense gravitational field. It is like a giant vacuum cleaner in space. The gravity in black holes is so strong that it tugs at space and time, slowing down time and stretching out space. If the universe were a giant sheet of rubber, then a black hole can be visualized as a pit into which things can just fall and get lost. Not even light, the fastest thing as per Einstein, can escape the clutches of a black hole! Black holes, hence cannot be seen in the dark space because it sucks in all the light around it. One of the drawbacks of this fact is that it makes time travel very difficult. It will perhaps not be incorrect to say that it is like a giant Bermuda Triangle in the interstellar space!

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I am an Electronics Engineering student at NIT Durgapur.

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