Skip to main content
Physics

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

8
  • $\begingroup$ Kyle in your second paragraph you said that light travels 15 billion light years in 10 years, but i didn't get that and you said its because of relativity but there are many things in relativity and excatly what part of relativity are you talking about? Please edit your answer and explain me better of what you are talking about in second paragraph. Hope you give a better answer. :) $\endgroup$ Commented Apr 23, 2015 at 17:18
  • $\begingroup$ @Bhavesh hopefully that's clearer? $\endgroup$ Commented Apr 23, 2015 at 17:21
  • 1
    $\begingroup$ @Bhavesh Simply put, imagine A and B are two points that are 5 billion light years apart. A photon travels from A to B in 5 billion years. But then the universe suddenly expands to twice it's size, the distance between A and B is now measured to be 10 billion light years. The light travelled from A to B (which we measure as 10 billion light years apart), taking only 5 billion years to do so. $\endgroup$ Commented Apr 23, 2015 at 18:03
  • 2
    $\begingroup$ @Bhavesh The light only traveled 10 billion light years, but the point where the light originated is 15 billion light years away by the time the light from it has traveled that far. The intervening space expanded, making the distance larger. $\endgroup$ Commented Apr 23, 2015 at 18:04
  • 1
    $\begingroup$ @Bhavesh that's the idea, yes. The "sudden" doubling in size is not realistic, it is more gradual throughout the travel of the photon, but it's the same idea. The space already passed is growing behind the photon (of course so is the space ahead). $\endgroup$ Commented Apr 24, 2015 at 2:27