Stephen Hawking and Black Holes

Quoted from Wikipedia to substantiate what I want to convey :) and information I knew from the Book Brief History of Time and some High school Knowledge

Stephen Hawking is a Theoretical Physicist and is the President of Royal Society (Newton's held this Post at his time).He has a motor neuron disease (ALS) and communicates to the world about his views and ideas about physics through a speech generating device. He was paralyzed at the age of 21 when he fell down from stairs to hit his head. The "Brief History of Time" is his book regarding Black Holes. He has held many honorary positions and was awarded the Presidential Medal of freedom (The highest Civilian Award in US)

Black Holes

As quoted from Wikipedia- :)

Hawking's work with Brandon Carter, Werner Israel and D. Robinson, strongly supported John Wheeler's no-hair theorem – that any black hole is fully described by the three properties of mass, angular momentum, and electric charge. Following analysis of gamma ray emissions, Hawking suggested that after the Big Bang, primordial miniature black holes were formed. With Bardeen and Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics. In 1974, he calculated that black holes should thermally create and emit subatomic particles, known today as Bekenstein-Hawking radiation, until they exhaust their energy and evaporate.

A black hole is a region in space where gravitational field is so high (Mass is high) that even light cannot escape. Black hole has a point Event Horizon that marks the point of no return. The theory of General Relativity (Albert Einstein formula E = MC 2) has led to the studies about Black Holes. The black hole is formed from stars like sun which dies with a massive collapse at the end of their life cycle. A Black Hole continuously absorbs tremendous mass from surroundings and grows. It just swallows stars from nearby that come to it due to gravitation pull and super massive Black Holes are formed. In particular, there is strong evidence of a black hole of more than 4 million solar masses at the center of our galaxy, the Milky Way.

The idea of a body so massive that even light could not escape was first put forward by geologist John Michell in a letter written to Henry Cavendish in 1783 of the Royal Society:

If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of 500 to 1, a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light, and consequently supposing light to be attracted by the same force in proportion to its vis inertiae, with other bodies, all light emitted from such a body would be made to return towards it by its own proper gravity.

—John Michell

Chandrasekhar limit

Subramaniam Chandrasekhar calculated that (Now called as Chandrasekhar limit 1.4 solar masses) beyond this limit a star would collapse. But a white dwarf slightly more massive than the Chandrasekhar limit will collapse into a neutron star.

Oppenheimer and his co-authors interpreted the singularity at the boundary of the Schwarzschild radius as indicating that this was the boundary of a bubble in which time stopped.

"Wow"

When an object falls into a black hole, any information about the shape of the object or distribution of charge on it is evenly distributed along the horizon of the black hole, and is lost to outside observers. The behavior of the horizon in this situation is a dissipative system that is closely analogous to that of a conductive stretchy membrane with friction and electrical resistance—the membrane paradigm. This is different from other field theories like electromagnetism, which do not have any friction or resistivity at the microscopic level, because they are time-reversible. Because a black hole eventually achieves a stable state with only three parameters, there is no way to avoid losing information about the initial conditions: the gravitational and electric fields of a black hole give very little information about what went in. The information that is lost includes every quantity that cannot be measured far away from the black hole horizon, including the total baryon number, lepton number, and all the other nearly conserved pseudo-charges of particle physics. This behavior is so puzzling that it has been called the black hole information loss paradox.

Event horizon

The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine if such an event occurred

To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.^[46] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.

Singularity

At the center of a black hole as described by general relativity lies a gravitational singularity, a region where the space time curvature becomes infinite

Observers falling into a Schwarzschild black hole (i.e. non-rotating and no charges) cannot avoid being carried into the singularity, once they cross the event horizon. They can prolong the experience by accelerating away to slow their descent, but only up to a point; after attaining a certain ideal velocity, it is best to free fall the rest of the way. When they reach the singularity, they are crushed to infinite density and their mass is added to the total of the black hole. Before that happens, they will have been torn apart by the growing tidal forces in a process sometimes referred to as spaghettification or the "noodle effect".

 It also appears to be possible to follow closed time like curves (going back to one's own past...Oh my God!!!) around the Kerr singularity, which lead to problems with causality like the grandfather paradox. It is expected that none of these peculiar effects would survive in a proper quantum mechanical treatment of rotating and charged black holes.

Grandfather paradox. :)

The paradox is this: suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension the traveler himself) would never have been conceived. This would imply that he could not have travelled back in time after all, which means the grandfather would still be alive, and the traveler would have been conceived allowing him to travel back in time and kill his grandfather. Thus each possibility seems to imply its own negation, a type of logical paradox.

Considering the exotic nature of black holes, it may be natural to question if such bizarre objects could exist in nature or to suggest that they are merely pathological solutions to Einstein's equations.

But whatever it is I liked the idea of turning your time back at Kerr Singularity. I think beyond the time when earth or Universe was born can be experienced if someone falls in a Black Hole.

These are theoretical calculations :).

Also to note :Stephen Hawking didn't believe in Philosophy and was an atheist.

In his early work, Hawking spoke of God in a metaphorical sense, such as in A Brief History of Time: "If we discover a complete theory, it would be the ultimate triumph of human reason – for then we should know the mind of God.

Hawking writes, "The question is: is the way the universe began chosen by God for reasons we can't understand, or was it determined by a law of science? I believe the second." He adds, "Because there is a law such as gravity, the Universe can and will create itself from nothing.

:(

He didn't believe in Heaven and afterlife :(

Also he believed in extra terrestrial life or Aliens

Hawking has indicated that he is almost certain that alien life exists in other parts of the universe, "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like". He believes alien life not only certainly exists on planets but perhaps even in other places, like within stars or even floating in outer space. He has also warned that a few of these species might be intelligent and threaten Earth. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans," he said. He has advocated that, rather than try to establish contact, humans should try to avoid contact with alien life forms. At a George Washington University lecture in honor of NASA's fiftieth anniversary, Hawking discussed the existence of extraterrestrial life, believing that "primitive life is very common and intelligent life is fairly rare".

Now when Science and Philosophy compete with each other let's take some rest... :)