Black Holes

Black Holes

Black Hole Discovery History

Described at least theoretically as far back as 1783 by Henry Cavendish, the postulate that the gravitational pull could be so high that even light could not escape was proposed. Subsequently reinforced by other scientists and by observations of relatively large black spheres devoid of any stars but surrounded by stars of some density otherwise, two explanations were proposed – that simply nothing existed there, albeit in a spherical region; or there was something there which was massive and appeared dark. It took a leap of an educated guess that since our ability to perceive an object typically depends upon light, that very light absence could actually be occurring.

Einstein, in 1915, noted that gravity affects light. Work by Schwarzschild, then Lorentz, then Chandrasekhar, then Oppenheimer found that the sphere (with radius known as the Schwarzschild radius) limited light escape, could be modeled with a single point, and had three characteristics – had mass, angular momentum, and electrical charge. John Wheeler subsequently called the phenomenon a “black hole” in 1967 in a lecture, and Ann Ewing used it first in print in 1964. Characteristics of a black hole were further elaborated upon by Stephen Hawking in the 1970s and beyond.

 

Present-Day Understanding of Black Holes

The “no-hair theorem” states that a black hole, upon achieving a stable formation, has three qualities – mass, charge, and angular momentum; these allow indirect measurement of the black hole. As far as physical properties, one could envision that if a telescope saw a dark sphere in an area where stars and other objects occurred with certain density, three characteristics simplify an understanding of the black hole – event horizon (where the black hole’s boundary may be such that light below this boundary cannot escape its gravitational pull; Schwarzschild radius (R = 2*MC/e^2), which defines this sphere; and the concept of the singularity which is a model of a point of conversion of the imploding star. The cause of the star’s implosion is theorized to be that normally, gravity does provide a force towards the center of mass, but the electrochemical activity counteracts this imploding force – however, in exceptionally large stars, e.g. defined as a unit of 3-4 solar masses (mass of the sun, about 2 nonillion kg or 333,000X the mass of earth). Achieving this critical gravity, with no “fuel” left in active particles as a star, implosion begins with black hole formation – per the Tolman-Oppenheimer-Volkoff limit.

Interesting subsequent theories since shown to be proven include the concept of small amounts of gas escaping as vapor (proposed by Hawking), an influence on the remainder of stars either drawn towards the black hole or moving in a circular pattern around it given the force of the angular momentum of the black hole. Hence, we are able to observe what is happening as a result of the massive black hole, rather than seeing into the black hole with light which is impossible.

 

Future Ideas based upon Black Holes

The above discussion is obviously very basic, based upon what has been described and put in layperson’s terms, but there are considerable implications which are take-away points. These include an insight into the space-time continuum, where theoretical equations presently predict that time at some level either slows down or stands still within the occurring black hole. This has created controversy obviously, and while the case may be one of perspective of a “person in the black hole” vs. “an observer on the outside of the black hole,” it is a problem that in many ways resembles the special relativity problem of Einstein (and likely involves it, to some extent).

Further insight may be gained from superior visualization, e.g. from telescopes such as Hubble or ones that travel farther from earth. Despite a layperson’s presentation of the topic that has been found to pervade modern-day science fiction, the reality may be even more strange in this case than fiction.

 

(Information above has been acquired from numerous sources, including www.science.nasa.gov, www.wikipedia.org, and www.science.nationalgeographic.com, among others)