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B Regarding Aspects of the Speed of Light and Space

  1. May 6, 2017 #1
    It's generally understood that nothing can be accelerated up to the speed of light, and that nothing can surpass it. That being said, the expansion of space itself can exceed this "universal speed limit," as the Universe is expanding so fast that light can't catch up to it. Regarding the properties of light and Einstein's works on relativity, what mathematical aspects permit space to exceed the speed of light? What makes it seemingly exempt from the restriction of not being able to travel past the speed of light?
  2. jcsd
  3. May 6, 2017 #2


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    Staff: Mentor

    The distance to objects far away can increase faster than the speed of light. This is not an actual velocity, as it does not involve the motion of objects.

    The speed of light is a limit for the motion of objects.
  4. May 6, 2017 #3


    Staff: Mentor

    Space isn't a material. It doesn't have a velocity. Velocity has units of length/time, but the expansion of the universe is in units of 1/time, so it is not a quantity that can be sensibly compared to the speed of light.
    Last edited: May 6, 2017
  5. May 8, 2017 #4
    Indeed. I wasn't sure what was meant by
    This makes sense. I wasn't sure what was meant by space expanding faster than light. From our perspective, at a set velocity i.e.
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