So Thats How We Detect A Black Holes.......?

How to Detect a Black Hole🕳

One of the greatest scientist of our era prof. Stephen Hawking with Roger Penrose discussed the idea for defining a black hole as the set of events from which it was not possible to escape to a large distance. It means that the boundary of the black hole, the event horizon, is formed by rays of light that just fail to get away from the black hole. Instead, they stay forever, hovering on the edge of the black hole. It is like running away from the police and managing to keep one step ahead but not being able to get clear away.

How could we hope to detect a black hole, as by its very definition it does not emit any light? It might seem a bit like looking for a black cat in a coal cellar. Fortunately, there is way, since as John Michell pointed out in his pioneering paper in 1783, a black hole still exerts a gravitational force on nearby objects. Astronomers have observed a number of systems in which there is only one visible star that is orbiting around some unseen companion.

One cannot, of course, immediately conclude that the companion is a black hole. It might merely be a star that is to faint to be seen. However, some of these systems, like the one called Cygnus X-I, are also strong sources of x rays. The best explanation for this phenomenon is that the x rays are generated by matter that has been blown off the surface of the visible star. As it falls toward the unseen companion, it develops a spiral motion-rather like water running out of a bath-and it gets very hot, emitting x rays. For this mechanism to work, the unseen object has to be very small, like a white dwarf, neutron star, or black hole.

Now, from the observed motion of the visible star, one can determine the lowest possible mass of the unseen object. In the case of Cygnus X-I, this is about six times the mass of the sun. According to Chandrasekhar’s result, this is too much for the unseen object to be a white dwarf. It is also too large a mass to be a neutron star. It seems, therefore, that it must be a black hole.

There is much other evidence for black holes in a number of other systems in our galaxy, and much other bigger one in the center of other galaxies and quasars. One can also possibly say that there are black holes with a much smaller mass than our sun. Such black holes could not be formed by gravitational collapse, because their masses are below Chandrasekhar’s limit. Stars of this low mass can support themselves against the force of gravity even when they have exhausted their nuclear fuel. So, low mass black holes could form only if the matter were compressed to enormous densities by very large external pressures. Such conditions could occur in a very big hydrogen bomb. The physicist John Wheeler once calculated that if one took all the heavy water in all the oceans of the world, one could build hydrogen bomb that would compress matter at the center so much that a black hole created. Unfortunately, however, there would be no one left to observe it.

A more practical possibility is that such low mass black holes might have been formed in the high temperatures and pressures of the very early universe. A black hole could have been formed if the early universe had not been perfectly smooth and uniform, because then a small region that was denser than average could be compressed in this way to form a black hole. But we know that there must have been some irregularities, because otherwise the matter in the universe would still be perfectly uniformly distributed at the present epoch, instead of being clumped together in stars and galaxies.

so that's the arrow of time.......click to raed.......

The concept C, P, T(Time)

TIME??

 In his book, The Go-Between, L.P Hartley wrote, “The past is a foreign country. They do things differently there-but why is the past so different from the future?” why do we remember the past, but not the future?” in other words, why does the time go forward? Is this connected with the fact that the universe is expanding?

New Series

The laws of physics do not distinguish between the past and the future. More precisely, the laws of physics are unchanged under the combination of operations known as C, P, and T. (C means changing particles for antiparticles. P means taking the mirror images so left and right are swapped for each other. And T means reversing the direction of motion of all particles- in effect, running the motion backward.) The laws of physics that govern the behavior of matter under all normal situations are unchanged under the operations C and P on their own. In other words, life would be just the same for the inhabitants of another planet who were our mirror images and who were made of antimatter. If you meet someone from another planet and he holds out his left hand, don’t shake it. He might be made of antimatter. You would both disappear in a tremendous flash of light.

If the laws of physics are unchanged by the combination of operations C and P, and also by the combination C, P, and T, they must also be unchanged under the operation of T alone. Yet, there is a big difference between the forward and backward directions of time in ordinary life. Imagine a cup of water falling off a table and breaking in pieces on the floor. If you make a film of this, you run it backward, you will see the pieces suddenly gather themselves together off the floor and jump back to form a whole cup on the table. You can tell that the film is being run backward because this kind of behavior is never observed in ordinary life. If it were, the crockery manufacturers would go out of business.   

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The explanation that is usually given as to why we don’t see broken cups jumping back onto the table is that it is forbidden by the second law of thermodynamics. This says that disorder or in a scientific way we can say entropy increases with time. In other words, it is Murphy’s Law-things get worse (seriously get worse nowadays). An intact cup on the table is a state of a high order, but a broken cup on the floor is in a disordered state. One can, therefore, go from the whole cup on the table in the past to the broken cup on the floor in the future. But not the other way around.

Arrows of time...

The increase of disorder or entropy with time is one example of what is called an arrow of time, something that gives a direction to time and distinguishes the past from the future. There are at least three different arrows of time. First, there is a thermodynamic arrow of time the direction of time in which disorder or entropy increase. Second, there is the psychological arrow of time. This is the direction of time in which we feel time passes-the direction of time in which we remember the past, but not the future. Third, there is the cosmological arrow time. This is the direction of time in which the universe is expanding rather than contracting.

I know we shall argue the psychological arrow is determined by the thermodynamic arrow and that these two arrows always point in the same direction. If one makes the no boundary condition (assumption) for the universe, they are related to the cosmological arrow of time, though they may not point in the same direction. However, we shall argue that it is only when they agree with the cosmological arrow that why does disorder increase in the same direction of time as that in which the universe expands?

If you guys want me to explain all the arrows of time comment below……………………

the whole concept above is not written by me I just try to explain with the simplest form.

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So that happens if you fall into black holes

What you see if you observe a star collapse to form black holes

Amazing na watching a star from your home from your roof collapsing, in order to understand what you would see if you were watching a star collapse to form a black hole, one has to remember that in the theory of relativity there is no absolute time. Each observer has his own measure of time. The time for someone at a distance, because of the gravitational field of the star. This effect has been measured in an experiment on earth with clocks at the top and bottom of the water tower. Suppose an intrepid astronaut on the surface of the collapsing star sent a signal every second, according to his watch, to his spaceship orbiting about the star. At some time on his watch, say ten o’clock, the star would shrink below the critical radius at which the gravitational field becomes so strong that the signals would no longer reach the spaceship.

Watching Stars

His companions watching from the spaceship would find the intervals between successive signals from the astronaut getting longer and longer as ten o’clock approached. However, the effect would be very small before 9:59:59. They would have to wait only very slightly more than a second between the astronaut’s 9:59:58, signal and the one that he sent when his watch read 9:59:59, but they would have to wait forever for the ten o’clock signal. The light wave emitted from the surface of the star between 9:59:59 and ten o’clock, by the astronaut’s watch, would be spread out over an infinite period of time, as seen from the spaceship.

The time interval between the arrivals of successive waves at the spaceship would get longer and longer, and so the light from the star would appear redder and fainter and fainter. Eventually, the star would be so dim that it could no longer be seen from the spaceship. All that would be left would a black hole in space.

 The star would, however, continue to exert the same gravitational force on the spaceship. This is because the star is still visible to the spaceship, at least in principle. It is just that the light from the surface is so red-shifted by the gravitational field of the star that it cannot be seen. However, the red-shift does not affect the gravitational field of the star itself. Thus, the spaceship would continue to orbit the black hole. 

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The origin of black holes you must know...

Black holes..?

Black hole

What are black holes? Who first invented or discover them..? Let’s the adventure begins and find the answer to all these questions. As you all are my intelligent readers you must know the difference between discovery and inventions but if you don’t know I am here to help you, discovery means find out the things which already exist in nature & invention means to create a thing or you may be called as product or let’s say a gadget which does not exist in nature exactly what engineers did nowadays.

john wheeler

The term black hole is of very recent origin. It was coined in 1969 by the American scientist john wheeler as a graphic description of an idea that goes back at least two hundred years. At that time there were two theories about the light that you must be familiar with it. One assumed that light is a particle and other assumes that it is made up of waves.

don't take it seriously

the speed of light......

But now we know that both the theories are correct. By the wave/particle duality of quantum physics, light can be regarded as both a wave and a particle. Under the theory that light was a particle, one might expect them to be affected by gravity in the same way that cannon balls, rockets & planets are.

On this assumption, a Cambridge don, John Michell, wrote a paper in 1783 in the philosophical transactions of the royal society of London. In it, he pointed out that a star that was sufficiently massive and compact would have such a strong gravitational field that light could not escape. Any light emitted from the surface of the star would be dragged back by the star’s gravitational attraction before it could get very far. Michell suggested that there might be a large number of stars like this. Although we would not be able to see them because the light from them would not be able to reach us, we would still feel there gravitational attraction. Such objects are what we now call black holes because that is what they are black voids in space.

According to the theory of relativity, nothing can travel faster than light. Thus, if light cannot escape, neither can anything else. Everything is dragged back by the gravitational field. So one has a set of events, a region of space-time, from which it is not possible to escape to reach a distant observer. This region we what we now call a black hole. Its boundary is called the event horizon. It coincides with the paths of the light rays that just fail to escape from the black hole.    

labeled description of a black hole in the depth