May 4, 2010

Black Holes

Filed under: Essays,Uncategorized — unwriter1 @ 4:12 pm
Tags: , , ,

Aptly named because they are not easily seen due to their melding with the darkness of space but yet as a hole, it’s a slight misnomer. A simple description.

Stars do eventually run out of fuel. When that happens they expand outward greatly. Our own star, the sun, will, in a few billion years, expand out beyond Pluto then collapse back into a very small dead star. Increase the size to almost twice that of our sun and it will collapse into a neutron star. But, a star twice the size of the sun will expand then implode into a black hole.

By definition, a black hole is a very small version of itself that has a gravity field from which nothing can escape, including light. The death of these stars is a supernova explosion. A black hole is not very dense. One a billion times the size of our sun will have a mass only about twenty times that of air. In other words, matter that is squished into nothing but quarks, is not very massive. The tidal force, the force that pulls objects in, is stronger for small black than for larger ones.

Once past the event horizon (beyond which nothing escapes), the tidal force takes over.

“The tidal force at the event horizon is smaller for larger black holes: you would get torn to shreds far outside a black hole the mass of our sun, but at the event horizon of a billion solar mass black hole the tidal force would only be a millionth of an ounce!”

“Strange Facts About Black Holes

• Light bends so much near black holes that if you were near one and looking away from the hole, you would see multiple images of every star in the universe, and could actually see the back of your own head!

• Inside a black hole the roles of time and radius reverse: just as now you can’t avoid going into the future, inside a black hole you can’t avoid going in to the central singularity.

• If you stood a safe distance from a black hole and saw a friend fall in, he would appear to slow down and almost stop just outside the event horizon. His image would dim very rapidly. Unfortunately for him, from his point of view he would cross the event horizon just fine, and would meet his doom at the singularity.

• Black holes are the simplest objects in the universe. You can describe one completely by just its mass, spin rate, and electric charge. In contrast, to completely describe a dust mote you’re have to specify the position and state of all of its atoms, taking at least $10^{16}$ numbers!

• As Hawking discovered, black holes can evaporate, but only very slowly. Even one the mass of a mountain will last for ten billion years, and one the mass of the Sun will only evaporate after 1067years. “

Finding black holes isn’t easy, but one may suspect an area where one would expect to see a star and only find a black spot. They can be seen, so to speak, also when in a binary system as there will be a stream of matter being sucked out of one half of the set.

This is a brief overview of what a black hole is. For more information, google the source in the footnotes or just google black holes.



  1. You are far too intelligent for me. I never knew there was so much to know about black holes. Up until now I just figured a black hole was the thing that swallowed up what I was looking for at the moment. 🙂

    Interesting post.

    Comment by Ginger Simpson — May 4, 2010 @ 5:27 pm | Reply

  2. Very interesting post on a topic of great interest to me. Thanks, I learned some things this morning …

    Comment by theoldsilly — May 5, 2010 @ 7:13 am | Reply

  3. As you approach the speed of light, time slows down until it finially stops all together. As you approach an ever increasing source of ultimate gravity, the same thing happens, in that time keep slowing down to a halt.

    Thus, if you are falling into a black hole, you can never fall all the way, as time will halt before you finish your journey!

    Comment by Clark — January 7, 2011 @ 10:14 pm | Reply

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