87 FAQs about BLACK HOLES at the Astronomy Cafe

Additional Online Resources (ca April 2000):

Computer Models and Simulations: Into the Cosmos

Trip to a Black Hole plus general information: Robert Nemiroff

Basic black hole Primer: Jillian's Guide to Black Holes

 Back to the Astronomy Cafe - 365 of the most popular questions since 1996. Over 1 million page requests!

Beginner:

  1. What is a black hole?
  2. Are black holes now considered to be 'proven' real objects in the universe?
  3. Is there really a black hole in the center of the Milky Way?
  4. Where are the best candidates for black holes?
  5. How big and hot can black holes get?
  6. What happens to matter when it falls into a black hole?
  7. If you stuck your hand into a black hole what would happen?
  8. How do astronomers study black holes when they can't see them?
  9. How do black holes form?
  10. Can black holes really suck things up?
  11. Could a black hole absorb enough mass to become a Big Bang?
  12. What kinds of visual distortions would you see near a black hole?
  13. If the front of a spaceship crosses the horizon of a black hole in a matter of seconds, what does the back of the spaceship see that is still outside?
  14. Could a galaxy ever collapse into a black hole?
  15. We can bring information back from the center of a hurricane, why not a black hole?
  16. Who coined the term 'black hole'?
  17. Do black holes ever get full?
  18. What is on the other side of a black hole?
  19. Do black holes grow?
  20. Can a star clog a black hole that is swallowing it?
  21. Will the black hole at the center of the Milky Way eventually eat all the matter in our galaxy?
  22. Do black holes die if they are not fed?
  23. Can you name some naked eye stars that will turn into black holes eventually?
  24. How does a black hole make room for all the stuff it sucks up?
  25. Can one black hole form inside another?
  26. What is on the other side of a black hole?
  27. How much can a black hole weigh?

Intermediate:

  1. Do the jets of gas in some galaxies have anything to do with rotating black holes?
  2. If nothing can escape a black hole, why do they still emit x-rays?
  3. What is the maximum possible rotation speed of a black hole?
  4. What do worm holes have to do with black holes?
  5. Has the existence of worm holes been demonstrated yet?
  6. What is an event horizon?
  7. Does the matter that falls into a black hole come out as another Big Bang?
  8. Do black holes really emit anything?
  9. Is it true that a star never 'freezes' when it passes through the event horizon, and that this is an illusion?
  10. Shouldn't black holes all be spinning infinitely rapidly because practically everything in the universe rotates?
  11. If you could survive a trip into a black hole, what would you see?
  12. Can black holes trap gravity waves?
  13. Is it true that the matter inside a supermassive black hole is not as dense as inside a stellar-sized black hole?
  14. What exists between the event horizon and the singularity in a black hole?
  15. As seen from far away, can anything ever fall inside a black hole?
  16. Why is it that black holes can't expand but the universe can?
  17. What would happen if a black hole passed through a worm hole?
  18. What are worm holes?
  19. Why does Stephen Hawking say that black holes are not black?
  20. What shape does a rapidly rotating black hole have?
  21. How do white holes work?
  22. Can light orbit a black hole just outside its event horizon?
  23. Could black holes really be gateways to other dimensions or universes?
  24. Is the edge to a black hole a smooth one, or is it a sharp boundary in space?
  25. Are black holes left over from supernovae?
  26. How can you use black holes for time travel?
  27. Can nuclear fusion happen near a black hole?
  28. For a black hole the size of our solar system, could you avoid its singularity?
  29. Do you actually see the ghost image of a star suspended just outside a black hole forever?
  30. What is space 'doing' near the event horizon of a black hole?
  31. Does general relativity fail inside black holes?
  32. Do the central black holes in galaxies represent the remnants from single first generation stars?
  33. Is Cygnus X-1 a proven black hole?
  34. Is there a limit to how much mass a black hole can absorb?

Advanced:

  1. What is the latest on black holes?
  2. What happens when a black hole and a white hole collide?
  3. Where does matter go after it is squeezed through a Singularity?
  4. What happens when two black holes collide?
  5. Will we ever be able to use wormholes for travel?
  6. What are the variables that enter into the formula for the Schwarschild Radius of a black hole?
  7. If a black hole's pull is faster than the expansion of the universe,will a new Big Bang happen?
  8. How can the force of gravity escape a black hole?
  9. Do tidal gravitational forces near a singularity distort the shapes of fundimental particles?
  10. Why can gravity be 'seen' from a black hole but not light?
  11. How do we know that Einstein's equations actually work just inside a black hole's event horizon?
  12. How does a black hole actually loose mass through Hawking Radiation?
  13. Can black holes really form if it takes an infinite time for matter to fall inside its event horizon?
  14. Do evaporating black holes produce gamma ray bursts?
  15. Are the Planck conditions reached inside a black hole?
  16. How do gravitons get out from inside a black hole to make the gravitational field of the black hole?
  17. Why do small black holes exert a stronger tidal force than big black holes?
  18. How is it possible for time to change inside a black hole?
  19. What is the importance of black holes to cosmology?
  20. Is information about what fell into a black hole stored on its event horizon?
  21. What happens to time as you pass through an event horizon and approach the singularity?
  22. What is a ring singularity?
  23. Can one black hole form inside another?
  24. Can a concentration of energy in a small region of space produce a black hole?

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