# Black Holes

This video is about astonishing sinkholes in outer space called black holes.

For a short outline of the contents of this video, see the summary.

For a complete written record of the words in this video, see the transcript.

What would it be like to travel into a black hole? Take a look at this video simulation to find out:
https://youtu.be/eI9CvipHl_c

Physicist Leonard Susskind wrote an excellent book about black holes called The Black Hole War:
http://www.amazon.com/The-Black-Hole-War-Mechanics/dp/0316016411

For a detailed introduction to black holes, you might enjoy the classic book by Kip Thorne, Black Holes and Time Warps:
http://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/dp/0393312763

http://chandra.harvard.edu/xray_sources/supernovas.html

Black holes’ closely related cousins are neutron stars and pulsars. Learn more here:
http://imagine.gsfc.nasa.gov/science/objects/pulsars1.html

### Research Challenges

Newton’s law of gravity $F = Gm_1m_2/r^2$ tells us that gravity only affects objects that have mass. But light particles are massless. If light particles don’t experience any pull due to gravity, then what prevents them from escaping a black hole? (Hint: what does General Relativity say about light?)

If you fall into certain black holes, you will be ripped apart in a process called spaghettification. What does this process have to do with the ocean tides? Why do some black holes not cause spaghettification?

Once something enters a black hole, it can never return. Black holes continue to grow by eating anything coming near enough to them. But can black holes ever get smaller? Learn more about Hawking radiation answer to this question.

Searching for black holes is challenging since they ordinarily don’t emit any light. One way of identifying the existence of a black hole is through a phenomenon called gravitational lensing. How does gravitational lensing work and how can it be used to find black holes?

In addition to black holes, some physicists propose the existence of even more bizarre objects. See if you can separate fact from fiction regarding white holes and wormholes. How can conformal diagrams illustrate these ideas?