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Light and Blackholes

  1. Jan 17, 2015 #1
    Well read a post long ago about light

    My questions are:

    If light has no mass then how can it be suck in a black hole?

    What exactly is redshifting?

    What do polarizing glasses do?
  2. jcsd
  3. Jan 17, 2015 #2


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    In Einstein's theory of general relativity, gravity is not a force but a curving of spacetime.

    Light follows straight lines (properly called geodesics) through curved spacetime which toward the black hole.

    As for 'what is' questions, well, Wiki is a good primer.


  4. Jan 17, 2015 #3
    Thanx but don't quite get it "what is" questions perhaps you could simplify it.

    (Also that what are the children forum and is it okay for a 7th grader like me).
  5. Jan 17, 2015 #4
    Assume a Badminton net tightly spread parallel to floor and above the floor.Assume it as flat space-time without force of gravitation.Now put a 1kg iron ball on it,it bends down a little to create slope around it like toilet .This is curvature of space time.
    Now another smaller ball will go towards bigger ball due to curvature.
  6. Jan 17, 2015 #5
    I really appreciate your answer but I also need to know about redshifting and polarizing
  7. Jan 17, 2015 #6


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    I am beginning to suspect that this is for homework. We won't do your work for you.

    Read the articles. See if you can make sense. If you're not sure, tell us what you can and we'll try to help.
  8. Jan 18, 2015 #7
    Maniac, just type in" What is the red shift? " into Google and then read.Easy as eating pie.
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