Ever since I was a young child and viewed the Disney movie Black Hole (1979) starring actors Maxmilian Schell, Yvette Mimieux, and Ernest Borgnine to name a few, I was deeply curious or trapped like light is within this phenomenon. This movie left an impression on my mind. I was fascinated with the concept of whether a black hole existed or not. Little did I know at that time that scientific great minds had already been working on the dynamics behind this particular cosmic activity for years.
The idea of a body so massive that even light could not escape was first put forward by John Michell in a letter written to Henry Cavendish in 1783 of the Royal Society. The first use of the term “black hole” in print was by journalist Ann Ewing in her article “Black Holes’ in Space”, dated 18th January, 1964 and then the first man to coin the term in a lecture he gave in 1967 was John Wheeler. A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping. Albert Einstein’s theory of general relativity (1916) predicts that a sufficiently compact mass will deform spacetime to form a black hole. The boundary of the region from which there is no escape is called the event horizon. The event horizon is a boundary in spacetime through which matter and light can only pass inward towards the mass of the black hole. This deformation becomes so strong at the event horizon that nothing can pull away from it. An effect that was defined by Albert Einstein in 1907 which is called gravitational time dilation is where an object that is falling into a black hole appears to slow down to an observer as it approaches the event horizon versus an object that is further away from the gravitational pull. At the same time, all processes on this object slow down, for a fixed outside observer, causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, the object becomes so dim that it can no longer be seen.
Black holes are formed by gravitational collapse of astronomical objects such as stars which collapse at the end of their life cycle. Supermassive black holes of millions of solar masses may form. There is a general consensus that supermassive black holes exist in the center of most galaxies. There are on one end countless stellar mass black holes that are peppered throughout our Universe as the result of remnants of massive stars that are 10 to 24 times as massive as the Sun and then we have on the other end of the spectrum what you call supermassive black holes that are millions, if not billions, of times as massive as the Sun.
Scientists can’t directly observe black holes with telescopes that detect x-rays, light, or other forms of electromagnetic radiation. Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as light. If there are other stars orbiting a black hole, their orbit can be used to determine its mass and location. Such observations can be used to exclude neutron stars. Also, if a black hole passes through a cloud of interstellar matter, for example, it will draw matter inward in a process known as accretion.
In this way, astronomers have identified a supermassive black hole of about 4.3 million solar masses in the core of our own Milky Way Galaxy. X-ray emissions from the double-star system Cygnus X-1 and other recent precise measurements points towards evidence that there is a black hole existing there. Astronomers have also found convincing evidence for a supermassive black hole in the galaxy NGC 4258, the giant elliptical galaxy M87, and several others. Scientists verified the existence of the black holes by studying the speed of the clouds of gas orbiting those regions.
Black holes act as an ideal black body as it reflects no light. Stephen Hawking in 1974 provided a theoretical argument for black body radiation or Hawking radiation to exist within black holes. Black body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body) held at constant, uniform temperature. A black-body at room temperature appears black, as most of the energy it radiates is infra-red and cannot be perceived by the human eye.
There are three internal parameters that are important concerning a black hole which are total mass, charge, and angular momentum. It appears that information concerning these three parameters is only conserved and that all other information about an object entering a black hole is lost. This brings about the black hole information paradox. The black hole information paradox results from the combination of quantum mechanics and general relativity. It suggests that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state. This has brought about controversy because it violates a commonly assumed tenet of science-that in principle complete information about a physical system at one point in time should determine its state at any other time. If the material entering the black hole were a pure quantum state, the transformation of that state into a mixed state of Hawking radiation would destroy information of the original quantum state. This presents a physical paradox.
Stephen Hawking Kip Thorne
This annoyed many physicists, notably John Preskill, who in 1997 bet Hawking and Kip Thorne that information was not lost in black holes. In July 2004, Stephen Hawking published a paper presenting a theory that quantum perturbations of the event horizon could allow information to escape from a black hole which would resolve the information paradox and he conceded his bet. What are your thoughts about information that enters a black hole? Do you think it burns up and disintegrates slowly according to Hawking radiation or do you believe the holographic principle that the information can be retrieved or encoded on the surface of the event horizon? I believe that information is never lost.
After reading this article, do you believe that black holes exist? I feel strongly that they do exist. A physics professor, Laura Mersini-Houghton at UNC-Chapel Hill in the College of Arts and Sciences is still not convinced that they exist. She has submitted a paper to ArXiv, an online repository of physics papers that is not peer reviewed, offering by exact numerical solutions that they do not exist due to a star losing too much mass when it collapses under its own gravity and then it cannot form a black hole due to lack in density. What are your thoughts about these being in existence in our Universe?