Wednesday, January 6, 2016

general relativity - How can the diameter of the universe be so big, if nothing can go faster than light?



The following are facts of the prevailing cosmological model.





  1. The age of the universe is about 13.772 billion years.




  2. Nothing with mass can exceed the speed of light.




  3. The diameter of the observable universe is 28.5 gigaparsecs, i.e. 93 billion light-years.





How could two particles never exceeding 186,000 miles per second ever end up farther than 27.544 ± light years apart? Is it possible to explain this seeming contradiction in a way that appeals to reason and doesn't require a pencil and paper?



Answer



Lets assume you have to explain the truth without any complications to your friend.


Firstly, give your friend some introduction and draw some analogy between physics terms and some nicer terms.


"Space is like a piece of cloth, a fabric which can stretch. There are some godly powers, forces which keep stretching the space fabric (the cloth) continuously. Light always moves along the fabric of space like a super fast worm."


Now ask your friend to be the god by holding two diagonally opposite corners of a cloth and ask him to stretch it quickly (faster than the worm). After stretching, tell him that light still continues to move along the fabric at the speed of light being oblivious to all the stretching magic which happened.


Ask him if the distance between his two hands has increased. Also, ask how far the worm has travelled during the process...


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