Black Holes & Hawking Radiation

Written By: Arman Momeni

Time is linear. Or is it?

We can observe the distinct separation between the past, present, and future. Time moves at the same pace in our lives. Dates are consistent reminders of the flow of time. However, time is the most deceptive idea in the universe. It is a paradoxical entity, contradicting itself, and while its flow may be linear, it is far from a steady-moving system.

In 1915, Albert Einstein followed up his theory of special relativity with the theory of general relativity. Einstein discovered that massive objects distort space-time (the three dimensions of space and the one dimension of time amalgamated in one continuum).

Picture space as a trampoline; if you set a large object in the center of the trampoline, the object presses down on the fabric and creates a dip. Now, if you were to roll a marble around the edge of the trampoline, it spirals inward towards the large object. This action is synonymous to the way that the gravity of a planet pulls at objects in space, or the way the sun pulls on planets.  

With the theory of general relativity, Einstein redefined gravity. It was no longer as much a force as it was curvatures in space-time. Gravity is a consequence, a by-product of mass. Bigger objects = larger curves = stronger gravity.

The theory of general relativity states that these warps in space-time not only affect gravity, but also affect time and the speed at which it flows. The stronger the gravitational field, the slower time moves. If someone were to be near a black hoe rather than residing on Earth, time would move far faster on Earth than near the singularity.

Black Holes:

Black holes are the epitome of Einstein’s theory, bringing gravity to its breaking point. As very dense collections of immense amounts of matter, black holes create unfathomable dips in space-time. Black holes contain such a strong force of gravity that not even light or electromagnetic waves have enough energy to escape. Once you are in a black hole, the velocity needed to escape its abyss is greater than the speed of light. Spoiler alert: it is physically impossible to travel faster than the speed of light.

Hawking Radiation:

Now, let’s delve deeper into one obscure aspect of black holes: Hawking radiation. But first, it is important to understand the structure of a black hole, including its infamous event horizon. The event horizon of a black hole refers to the exterior layer of a black hole. Once one passes this surface, the velocity needed to escape exceeds the speed of light, which means that one would be infinitely trapped in an endless abyss.

Hawking radiation refers to the radiation that is theoretically emitted from just outside the event horizon of a black hole. As its name states, Hawking radiation was proposed by Stephen Hawking in the late 20th century. Hawking stated that subatomic particles, such as photons or neutrinos, will arise naturally near the event horizon of a black hole. The strong nature of the event horizon will cause one particle to escape from the black hole while another particle, housing negative energy, will disappear into it.

When the particles of negative energy begin flowing back into the black hole, its mass begins to reduce until it eventually disappears, emitting a final, unsettling burst of radiation. But why is Hawking radiation significant? Hawking radiation, while hypothetical, describes the counterintuitive nature of a black hole. It proves that black holes have temperatures that are inversely proportional to their size/mass. In simple terms, Hawking’s theory shows that the smaller a black hole is, the hotter it will glow. Hawking radiation has never been observed, however it is heavily supported by the theory of general relativity and quantum mechanics.

If Hawking radiation is to be proven, it would show that black holes are able to emit energy and thus shrink in size. Black holes were originally thought to break the second law of thermodynamics, which related to entropy–the idea that the universe tends towards disorder. As black holes ultimately remove matter by sucking particles into their endless abyss, they were thought to lower the universe’s entropy, meaning that the universe would become more ordered. However, by showing that particles can effectively escape and black holes can emit radiation, Hawking’s ideology brings hope that monstrous, astonishing black holes do not go against the fundamental laws of physics.

Works Cited:

Britannica, T. Editors of Encyclopaedia (2023, December 22). Hawking radiation. Encyclopedia Britannica. https://www.britannica.com/science/Hawking-radiation

Staff, S. (2020, June 9). What is hawking radiation? https://www.sciencealert.com/hawking-radiation 

Freeman, L. (n.d.). What would happen if you fell into a black hole?. BBC Earth. https://www.bbcearth.com/news/what-would-happen-if-you-fell-into-a-black-hole