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

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SUMMARY

The discussion centers on the physics of thrusting a million-mile-long stick towards another person. Due to the principles of relativity, the stick cannot be perfectly rigid, and any force applied at one end propagates through the material at the speed of sound specific to that material. For example, if the stick is made of diamond, the force would take approximately 1.5 days to reach the other end, as the speed of sound in diamond is about 8 miles per second. This highlights the limitations imposed by the speed of light and the non-rigid nature of materials.

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  • Understanding of relativity and its implications on physical objects
  • Knowledge of material properties, specifically the speed of sound in different materials
  • Familiarity with basic physics concepts related to force and motion
  • Awareness of the limitations of rigid body assumptions in physics
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  • Research the speed of sound in various materials, including metals and polymers
  • Explore the implications of relativity on rigid body motion
  • Study the FAQ on the physics of non-rigid objects and their behavior under force
  • Examine real-world applications of these principles in engineering and material science
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This discussion is beneficial for physics students, educators, and anyone interested in the fundamental principles of motion and material properties, particularly in the context of relativity and non-rigid bodies.

CYP450
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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?
 
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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.
 
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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.
 
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