Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

More Curious Questions

  1. Aug 19, 2008 #1
    The first two are theoretical. Please excuse grammatical and spelling errors.

    If you had a spaceship at the edge of the universe, and this spaceship could travel faster than the universe is expanding, what would happened if you tried to travel outside its boarder? Would you crash into the boarder like a brick wall?

    If you had a satellite one light year away, that had amazing video capabilities so much so that when pointed at the earth you could see people moving. And somehow you were able to access this video feed faster than the speed of light, would this be a mechanism for looking into the past?

    I heard that black holes are much like the concept of a mathematical singularity. The center (if you will) of a singularity is a point. Are the center of black holes points (in the Euclidean sense "that which has no part") or does the center have some substance.
  2. jcsd
  3. Aug 19, 2008 #2


    User Avatar

    Staff: Mentor

    This is a very common question here. The question is flawed because the universe has no edge.
    Well, I guess. I suppose the tooth fairy could exist too if we decide to just say she exists. I'm not sure what the point of such questions is...
    I'm not sure if that is really known, but perhaps someone else has some insight...
  4. Aug 19, 2008 #3


    User Avatar
    Science Advisor
    Gold Member

    The image you received from the satellite would be 2 years old [earth time].
  5. Aug 20, 2008 #4


    User Avatar
    Science Advisor

    He's talking about accessing the video feed with an FTL signal, so I think the images would be 1 year old. However, Diffy, if you just let the sattelite beam the signal back to Earth, then the video would be one year old. OTOH, if the sattelite were in LEO, you could just wait a yearto watch the film. Any stored video image is a way of looking into the past.

    he cventer of a BH is indeed believed to be a singularity, so named because it is a single point is spacetime. I have my doubts about this conclusion, but the maintream seems to use this as the model, at least when describing Black Holes to the laity.
  6. Aug 20, 2008 #5
    Thanks all,

    I really love this stuff, I wish I could take some classes to learn more. Do you know if there are any astronomical jobs one could be qualified for with a PhD in Mathematics? What would they entail?
  7. Aug 20, 2008 #6
    A black hole singularity is most often not a point. Stars spin and thus have a property called angular momentum. Angular momentum cannot be lost or destroyed. A point cannot exhibit rotation and cannot therefore have angular momentum. Roy Kerr realized this and solved Einstein’s field equations for a spinning singularity, now called a Kerr Ring Singularity. The mass of a spinning star collapses into a thin ring with the diameter of the Planck scale and zero height, i.e., a space with zero volume.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook