Life Cycle of Black Holes

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  • 0:09 Black Holes - Myth vs. Reality
  • 1:12 How a Black Hole Forms
  • 3:02 Little and Big Black Holes
  • 3:49 Lesson Summary
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Lesson Transcript
Instructor: Amy Meyers

Amy holds a Master of Science. She has taught science at the high school and college levels.

Learn about black holes, their myths and their reality. Learn how black holes form after stars undergo supernovae and create singularities. Discover how big black holes grow, how scientists find black holes and where black holes are located in the universe.

Black Holes - Myth vs. Reality

Black holes - they are what you think, and they aren't. There are a lot of general misconceptions about black holes. First of all, our sun will never become one - it just isn't big enough. Black holes aren't giant vacuum cleaners sucking matter out of space, we cannot detect black holes visually, and time travel is not possible by falling into them.

Scientists have theorized about the existence of black holes since way back in the 1700s. It wasn't until Einstein's work on general relativity in the early 1900s that scientists had support for the relationship between gravity and light. Further work was performed by other scientists, and it was 1967 when a physicist named John Wheeler first publicly used the words 'black hole.' Although these scientists couldn't see a black hole, they theorized its existence from the effect of the black hole's gravity on everything around it.

How a Black Hole Forms

A star collapses when it runs out of fuel, causing its density to become greater.
Star Collapse

Black holes form from stars of a specific size at the end of their life. A smaller star, like our sun, forms a white dwarf at the end of its life. A medium-size star ends its life as a neutron star. A huge star, many times bigger than our sun, becomes a black hole.

When a star runs out of fuel in its core, it collapses and its density becomes greater. When a star starts big enough, it will collapse, making its density very strong, nearly infinite. Density is defined as mass divided by volume; this means that the more massive something is but the less space it takes up, the more dense it is. Picture the sun collapsing and becoming so dense that the entire sun fits into an area the size of New York City.

The density in a black hole is so strong that not even light can escape it. In doing so, the star creates what is known as a singularity. A singularity is an infinitely dense point of zero volume. Have you ever seen them crush a car at the junkyard? They squish it down from a huge volume to just a little flat pancake. This is essentially what a singularity is, only even more so - a huge volume of matter that is squished into an itty-bitty, zero-volume point.

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