To escape the Earth’s gravitational influence you need to have a certain escape velocity (even if you are the superman), you must fly up towards space with approx. 40,320 km/h, however, a speed of 42.1 km/s is required to escape the Sun’s gravity (and exit the Solar System) from the same position. But what if Earth decides that it won’t let you go, ever? For that to happen the gravity must be so strong that you will not be able to escape into space, no matter what.
A Black Hole is an impeccable example of a powerful gravitational influence so strong that even light can’t escape. The velocity of light in vacuum is 299,792 kilometers per second, imagine the forces required to stop light from escaping. A black hole is formed when space-time deforms by a sufficiently compact mass, as predicted by the theory of general relativity. The boundary of this deformed region from which no escape is possible is called as Event Horizon. So, a black hole doesn’t reflect light right? Thus, we can call it an ideal black body. According to quantum field theory in curved space-time, event horizon emits Hawking radiation with the same spectrum as a blackbody of a temperature inversely proportional to its mass. Hawking radiation is blackbody radiation that is predicted to be released by black holes, due to quantum effects near the event horizon. It is named after the physicist Stephen Hawking. This temperature is on the order of billionths of a Kelvin for black holes of stellar mass, making it essentially impossible to observe.
A simple steady black hole has mass but no angular momentum or charge and is known as Schwarzschild black hole named after Sir Karl Schwarzschild.The “No-escape” factor is true only near a black hole’s horizon but far away from it(outside) gravitational field is same as that of an object with same mass as that of the black hole.
The event horizon is named so because the events that happen inside it towards the hole, are not observable.For an outside observer (say, your friend) such event has never happened,it goes undetectable because the outside observer receives nothing that could be detected. Another interesting effect that takes place near a black hole is gravitational time dilation.The farther the clock is away from the gravitational source, faster the time passes. Gravitational time dilation has been experimentally measured using atomic clocks on airplanes. The clocks aboard the airplanes were slightly faster than clocks on the ground. The effect is significant enough that the Global Positioning System’s artificial satellites need to have their clocks corrected. This final correction is even added to an I Phone (thanks to Sir Steve Jobs). But for the observers falling into the black hole (say yourself), the clock appears to tick normally.
Moving towards the center of a black hole (chills), there is the region where space-time curvature becomes infinite and that is called as a gravitational singularity. At this point the quantities that are used to measure the gravitational field of a celestial object become infinite. At this place, the normal laws of space-time are not applicable.
Rotating black holes are surrounded by the regions of space-time where nothing can stand still known as Ergosphere. According to general relativity, any rotating mass will tend to drag along space-time surrounding it.
The man himself, Sir Einstein, thought that the formation of a black hole is not possible and that the angular momentum of collapsing particles would stabilize themselves at one point. This led to the dismissal of all the research for many years. However, a few determined and crazy men continued to believe that black holes were physical objects and soon, by the end of 1960’s, they influenced others that formation of an event horizon is possible. After that, according to Penrose, the singularity will form within.
Our universe may have emerged from a black hole in a higher-dimensional universe, propose a trio of Perimeter Institute researchers.Conventional understanding holds that the big bang began with a singularity – an unfathomably hot and dense phenomenon of space-time where the standard laws of physics break down.(phys.org)
Though black holes are believed to primarily be formed by gravitational collapse, but there are even more crazy ways which may lead to the formation of a black hole.
Well ,I believe that black holes are the most beautiful mysteries no matter they are formed by “deformed” space-time.They love the Universe more than anything else because they never let anything go away.
A fall that never ends
As the space-time bends
At the unknown another side
Through the darkness
When the time glides….
- Jaskaran Singh
(Featured Image credits – fabianoefner.com)