What would happen if a poked someone with a million-mile-long stick?

  • Level: Undergrad 
  • Thread starter Thread starter CYP450
  • Start date Start date
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 2K views
CYP450
Messages
29
Reaction score
0
Suppose I was holding the end of a million-mile-long stick and the other end was an inch from another person's body. If nothing can travel faster than light, then what would happen if I thrust the stick forward? Would it hit the person right away or would it take a few seconds to?
 
Physics news on Phys.org
The stick is not a perfectly rigid object. There is no such thing as a perfectly rigid object - relativity forbids it.

The stick is made of atoms. Any acceleration at one point in a stick propagates through the stick at the speed of sound of whatver material it is made of. If the stick were made of diamond, its speed of sound would be about 8 miles/s. So your push would take almost a day and a half to reach the other end.
 
Last edited:
We have a FAQ on this topic.

https://www.physicsforums.com/showthread.php?t=536289

Please read it and see if it makes sense to you.
 
Last edited by a moderator: