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Hawking Radiation

by Sherry Li

Stephen Hawking discovered hawking radiation in 1974. In simpler terms, hawking radiation describes particles formed by black holes’ boundary and implies that black holes have temperatures that are inversely proportional to their mass. It is said that hawking radiation is this dim light that slowly drains the energies of a black hole. Over time, a black hole will emit so much hawking radiation that it disappears.

Stephen Hawking

Born on January 8th, 1942, the legend died on March 14th, 2018. He was born exactly 300 years after Galileo Galilei who was one of Hawking’s biggest inspirations. Although he was a late developer, he already had started speculating about the origin of the world at a young age. After debating with his father, they compromised on Natural Sciences as his major for Oxford. However, while he was still an undergraduate, Stephen started becoming clumsy, and even tying his shoelaces became difficult. At the age of 21, he was diagnosed with motor neuron disease which slowly erodes muscle control. After publishing his book The Large Scale Structure of Space-Time, he started doing research and found that black holes emit heat. This was later known as hawking radiation. Although he was told he only had two years left in 1962, he was able to live until 75 and contribute to many of the biggest scientific discoveries. He’s a very prominent figure and a role model for many people.

Black Holes

A black hole is a certain place in space where gravity pulls so much that even light can’t get out. The gravitational pull is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because light can’t get out, people can’t see black holes. In 2019 the EHT (Event Horizon Telescope) released the first-ever image of a black hole at the center of the supergiant elliptical galaxy M87, located in the Virgo constellation.

Black holes can be large or small but even the small black holes can contain a large amount of matter. Scientists believe the first black holes formed when the universe began. Although black holes can’t be seen, scientists can examine the effects of the strong gravity on the other stars and gas around the black hole to determine if it’s there. There are many conspiracy theories about the black hole but it’s confirmed that earth won’t fall into a black hole since there isn’t any close enough. Even if there was a black hole with the same mass as the sun, the earth would just orbit the black hole since it would have about the same gravity as the sun. But rest assured, the sun will never turn into a black hole because it’s not large enough.

Hawking Radiation

In 1974, Hawking demonstrated that the event horizon of a black hole isn’t absolute. Due to quantum indeterminacy, he proposed that black holes emit a tiny amount of light now known as hawking radiation. He believes that if the mass of a black hole is M solar masses, it should glow like a blackbody with a temperature of 6 × 10-8/M kelvins. Many ideas were built upon this and his equation in the picture above. If hawking radiation is real then black holes must also follow the laws of thermodynamics. It’s an idea proposed by Jacob Bekenstein which physicists have built on and have shown that there is a set of laws for black holes known as black hole thermodynamics.

However, there’s much controversy about this proposition. If a black hole eventually disappears, all of the information about the things it gobbled up in its lifetime disappears forever. The problem is that this isn’t possible according to quantum mechanics. Quantum mechanics states that information can never be destroyed. This is the black hole information paradox. Then scientists used studies to show that objects that fell into a black hole leave imprints on the black hole’s gravitational field which, in theory, preserves at least some of those objects’ information. There are still many things to be discovered about black holes and hawking radiation.


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