Notices
Results 1 to 5 of 5

Thread: Energy transfer faster than speed of light?

  1. #1 Energy transfer faster than speed of light? 
    New Member
    Join Date
    Jun 2012
    Posts
    3
    Hello, new member here.

    I know the answer to both questions is no. Just want to know the why.

    Assuming a suitable material was invented. A piston ten light minutes long sitting in space.
    One end is pushed. Is the transfer of energy from one end to the other faster than light?

    Also, a piston swung in an arc. If it was long enough and enough force was applied could the
    end exceed the speed of light (like a laser appears to)?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator Janus's Avatar
    Join Date
    Jun 2007
    Posts
    2,216
    In the first case, the transfer will be slower than light, at the speed of sound for the material of the piston. And no, it is not possible to have a material for which the speed of sound is greater than than of light.

    The same is true in the second case also. When you swing the piston at your end, it takes time fro the movement to travel the end, the piston will twist into a spiral. You eventually will reach the maximum stress it can handle and it will break apart. Even if you could avoid this, the amount of energy needed to move the end of the piston approaches infinity as the end of the piston approaches the speed of light. That means that the amount of energy you must exert at your end also approaches infinity, and that you will always be short of the energy needed to reach light speed at the end of the piston.


    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


    Edit/Delete Message
    Reply With Quote  
     

  4. #3  
    New Member
    Join Date
    Jun 2012
    Posts
    3
    Hello Janus,
    Thank you for your reply. I understand the second reason, but not the first. I am a bit confused as to where the speed of sound comes into play. For the sake of argument if the piston was steel and 6100 metres long and I push one end, are you saying there will be a delay of one second before the other end moves. (That the transfer of energy is limited to the speed of sound through a given material?) Sorry if I'm talking rubbish.
    Reply With Quote  
     

  5. #4  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,795
    Quote Originally Posted by befuddled View Post
    Hello Janus,
    Thank you for your reply. I understand the second reason, but not the first. I am a bit confused as to where the speed of sound comes into play. For the sake of argument if the piston was steel and 6100 metres long and I push one end, are you saying there will be a delay of one second before the other end moves. (That the transfer of energy is limited to the speed of sound through a given material?) Sorry if I'm talking rubbish.
    There is no perfectly rigid material that will move at one end when you push the other end. What happens is that pushing the rod causes a pressure wave to travel along the rod. The speed of this pressure wave is the speed of sound.
    Reply With Quote  
     

  6. #5  
    New Member
    Join Date
    Jun 2012
    Posts
    3
    Thank you,

    I finally get it.
    Reply With Quote  
     

Similar Threads

  1. Faster Than the Speed Of Light?
    By Westerhouse in forum Astronomy & Cosmology
    Replies: 37
    Last Post: May 31st, 2012, 12:44 PM
  2. Faster than the speed of light
    By RJC in forum Physics
    Replies: 10
    Last Post: May 30th, 2012, 05:35 PM
  3. Is it possible to go faster that the speed of light?
    By lanceschroederl@yahoo.com in forum Physics
    Replies: 31
    Last Post: February 27th, 2011, 04:38 AM
  4. Faster than the speed of light?
    By treats in forum Physics
    Replies: 26
    Last Post: December 23rd, 2010, 06:53 PM
  5. Faster than the speed of light
    By tenniskettle in forum Physics
    Replies: 30
    Last Post: October 18th, 2010, 04:27 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •