3. The Black Holes Basics

3. The Black Holes Basics
An illustration of what a black hole with an accretion disk may look like based on modern understanding. The extreme gravitational fields create huge distortions in the hot matter and gas rotating forwards the black hole.

After having an overview of Supernova and Neutron Stars; The Black Holes Basics is the ideal next step in understanding the greatest marvel of nature.

Albert Einstein’s Perspective

Einstein whose theories of general relativity and special relativity really inform the basis of understanding of black holes at a fundamental level. Famously he used his intuition for all kinds of things he imagined; he would ride on a beam of light or ride in a windowless elevator. He had these thought experiments that would do to help his thinking about the universe and through his intuition he would come to these great conclusions.

Yet even so he did not believe that black holes were real when they popped out of his equations. Einstein was really quite an intriguing person and was a real sort of hold out when he came up with the most radical theories that completely transformed our understanding of the universe.

One can describe the entire universe on his contents and so on his general theory of relativity, reworking gravity but when the implications of his theories were worked out; he often didn’t like the implication. He didn’t like the idea of an expanding universe. It was a natural consequence of Einstein’s field equations but he didn’t like that. Why? Because he was emotionally attached to the idea of fixity of a steady universe.

It was very disorienting to think of the universe as expanding. Likewise the reason he didn’t like black holes first of all because he never expected so. The black hole solution which is the gravity of a very compact mass. How intense it is and how it deforms the space around it is an exact solution. It’s a simple exact solution to his very complex equations.

He never imagined there would be a simple solution so that was a surprise but then it was what this solution was as we’ll see later on there are many different ways of thinking about a black hole. What is called a singularity?

The Black Holes Basics

Black Hole is a place where all the known laws of physics break down and he did not like that. It’s sort of aesthetic reasons almost that he didn’t like it but eventually he got around There are lots of entities that we are happy to believe they exist. Whose existence we infer only indirectly.

The Black Holes Basics we infer their presence indirectly as with dark matter. There are lots of entities that we are used to in life but we need incontrovertible evidence. Today we really know quite well; not just that they exist but also many of their peculiar properties. We actually see evidence for their peculiar properties.

There are different definitions of black holes and can answer those in different ways and depending on how you answer them maybe that gives a kind of different window upon their behavior or understanding of them or how they manifest in the universe. Similarly we don’t really see them directly and so there are obviously ways that we can study them.

Historic Path to The Black Holes Basics

There’s different conceptions of what a black hole is. In the big scheme of human history it’s a very new idea and it’s so radical. It was not easily accepted so one of the first people to really come up with the idea was Chandra Shikhar an Indian Astrophysicist in 1935 actually had worked it out. He was in Cambridge England at Trinity College. He worked it out that the end state of some stars would be a very compact dense objects.

When he presented this at the royal society and Arthur Eddington one of the famous Astrophysicists of the day refuted it because he didn’t like these peculiar properties of Black Holes. Nobody wanted to believe they existed; so it took till about the 1960s when the first evidence of the end states of stars appeared.

Seeing the Black Hole

There are different kinds of courses depending on the birth mass of the star and so when they discovered one of the possibilities; they knew that could exist really became real as in observationally. The part of the reluctance is because of peculiar things as objects are so enigmatic. This is what so seductive about them.

There are a bunch of different ways to think about The Black Holes Basics and scientists hit a wall which way they think feel slightly illuminated. One way to think about it is the kind of strength of gravity that they exert. For example in a black hole the gravity is so intense that not even light can escape which is why they’re called black holes

The way to intuitively think about it is for example; if we launch a satellite from the earth to escape the gravity of the earth we need a rocket. We need to blast out at a velocity of about 11 kilometers per second. If you can imagine that gives you a sense of sort of the strength of earth’s field.

Event Horizon

For a black hole that speed to launch anything with is the Cosmic Speed. The speed of light and of course nothing material get that close to the speed of light. So that’s one way to think about it. Carl Schwarzschild was the person who right after Einstein announced his theory of general relativity. He was fighting in World War-I in the trenches once he heard about the lecture. He worked it out; got the solution of the black hole which is sort of the intense gravity.

He mapped out the shape of space around a black hole and this was radius; an odd weird radius region around the black hole that is also called the Event Horizon. This is the point of no escape. Black hole has this boundary called the Event Horizon and anything that makes it in including light cannot make it back out so it’s the point of no return.

If the earth were to have the kind of gravity that a black hole does; all of us everything on earth would have to be crunched to the size of a Penny; everything including all of us right now talking everything. Another way to think about black holes is that they are the end states of stars.

The Black Holes and Neutron Stars

If the birth mass of a star to be about eight times that of the sun or above then after finishing its life cycle exhausting all its fuel it will actually explode and end its life as a black hole. Neutron stars are intriguing and just packed with neutrons and a black hole is just much more compact and so a neutron star is basically like a big giant neutron. It’s a star the size of a city or something like that. Relatively speaking a The Black Holes Basics, it is much denser than a neutron star and it has this peculiar property of having an event horizon. One of the fundamental contributions that Einstein made is this profound way in which he was able to link mass, the shape of space and motion. He sort of showed that geometry or the shape of space is defined by the distribution of masses.


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