Black hole is a term that has been heard by many people in different physics fields. However, only few people know the real meaning of black hole. Black hole issue has been surrounded by several questions including what it really is, when and how black holes are formed, is it possible for researchers to view black hole and what ‘event horizon’ is in relation to black hole. Speculations have emerged due to these questions including arguments of scientists who favor the vision and existence of black hole.
Black hole refers to a theoretical body that general relativity equations predict. Gravitational activities cause a star with significant mass to collapse. Subsequently, the entire or most of the mass of the star compresses to form a small space area. According to scientists, the collapse is followed by infinite curvature of space-time. Space-time curvature hinders everything including light from seeping from an event horizon. This is also called a boarder (Frolov, 1998).
People have always debated on the occurrence and existence of black holes because nobody has ever observed them directly. They are only favored by the argument that their effects have projections that match their observations. Nevertheless, alternative theories exist. Among the notable theories include the Magnetospheric Eternally Collapsing Objects (MECOs). This theory attempts to exemplify the scientific observations.
However, most alternate theories eliminate space-time singularity’s existence that is found at the center of the black hole. Nevertheless, the argument of most scientists favor the explanation of black hole by stating that it is a viable explanation that attempts to elaborate what happens (Hooft, 1985).
Black holes issue is not something new. Debates that can be traced to as early as 18th century touched on this issue. At this time, some people proposed that light was attracted by super-massive objects. The inclination of another light theory called Newtonian Optics was towards perceiving and treating light as simple particles.
John Michell wrote an article in 1784 forecasting an entity whose radius was 500 times the radius of sun despite their density being the same but the sun being able to attain an escape velocity which can be equal to that of light. According to Michell, the entity could become invisible. Nevertheless, not many people were interested in such a theory at that time. Eventually, the theory was forgotten during the 20th century.
The light theory quickly replaced this theory becoming prominent in the 20th century. Both theories are now out-phased. While referencing them in regards to the contemporary physics, scientists call them ‘dark stars’ as a way of distinguishing them and the black holes of the modern science (Frolov, 1998).
Black holes’ concept became prominent after the 1916 Albert Einstein’s publication of general relativity. Karl Schwartzchild, a physicist wasted no time before coming up with a solution to Einstein’s equation of the spherical mass. This is commonly known as the Schwartzchild metric. The results of this solution were unprecedented. The character of the term used in expressing the radius eventually became disorienting. For some radius, zero seemed to be the denominator. This factor made mathematical calculations impossible or extremely complicated. Nevertheless, the approach aimed at shedding light on the black hole concept.
Over time, many people supported the black hole theory. The deduction of Subrahmanyan Chandrasekhar, a prominent physicist was that stars with solar masses of 1.44 and above ought to collapse on experiencing general relativity. The view of another physicist called Arthur Eddington was that some properties had the ability to avert a collapse. Through personal ways, evidence has been found to show that both physicists were right.
Theory’s development was also influenced significantly by Robert Oppenheimer, a physicist. In 1939, Robert forecasted a supper-massive star with the ability to collapse and create a unique ‘frozen star’ not just in mathematics’ perspective but a natural perspective. His prediction was that this collapse would cause a slow down leading to a freezing time within the juncture when it would cross Schwartzchild radius (Rs).
According to the physicist, the light that would emerge from this star would undergo a red shift at the Rs. Nevertheless, the belief of several scientists is that this is a trait that Schwartzchild metric has because of its nature which is majorly symmetrical. Their view is that this collapse would naturally not occur in actuality since asymmetries are prevalent in most light stars that have been identified so far (Hooft, 1985).
In 1967, almost a half of a century following the Schwartxchild Radius’ discovery, Stephen Hawking and Roger Penrose provided a prove that showed that general relativity caused black holes. Their work further showed that the collapse could not be averted in any way. Pulsars discovery enhanced this while enabling John Wheeler to use the word black hole during a lecture that was in the late 1967. Hawking radiation’s discovery has been incorporated in the subsequent researches which prove the ability of black holes to emit radiation.
Speculation about black hole is another issue. Theorists and researchers who want to challenge the concept are associated with this speculation. An accord that is almost universal exists in the modern world. This accord is about black holes’ existence. Nevertheless, it has always been impossible for scientists to agree on the black holes’ actual nature.
Several unanswered questions concerning black holes’ nature exist. The belief that is held by some individuals is that materials that are lost in the black holes can reappear elsewhere in the universe. They argue that this is similar to wormhole’s case. Significant developments have also been made about the concept of black holes. Hawking radiation is one of the most prominent developments introduced by Stephen Hawking, a British physicist in 1974.
Hawking radiation refers to a theoretical projection whose focus is the explanation of thermal properties relating to the concept of black holes. Black holes are considered to have gravitational fields that are very powerful and these enable them to draw matter and energy. Jacob Bekenstein tried to explain the theory more by suggesting that the entropy of black holes should be well-defined. This resulted in thermodynamics’ development for black hole which incorporates energy emission. Hawking radiation was eventually developed and this has remained influential in black holes studies (Hooft, 1985).
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Frolov, V. V. P., & Novikov, I. D. (1998). Black hole physics: basic concepts and new developments (Vol. 96). Springer.
Hooft, G. (1985). On the quantum structure of a black hole. Nuclear Physics B, 256, 727-745.