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

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In summary, the scenario of thrusting a million-mile-long stick towards someone's body poses the question of whether the stick would hit the person instantly or take a few seconds to reach them, given that nothing can travel faster than light. However, due to the fact that the stick is not a perfectly rigid object and is made up of atoms, any acceleration would propagate through the stick at the speed of sound of the material it is made of. This means that the push would take almost a day and a half to reach the other end. For further clarification, a FAQ on this topic is available for reference.
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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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  • #2
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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  • #3
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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1. What is a million-mile-long stick?

A million-mile-long stick is a hypothetical object that is one million miles in length. It is not physically possible for a stick to be this long, but it is often used as a thought experiment in science and mathematics.

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

If a person were to be poked with a million-mile-long stick, the force of the poke would be incredibly small due to the stick's length. It would likely have little to no effect on the person's body.

3. Would the stick break if I poked someone with it?

It is unlikely that the stick would break, as it is purely hypothetical and not subject to the laws of physics. However, if the stick were to be made of a material that could withstand the force of a million-mile-long poke, it would not break.

4. Could the stick cause damage if it were wrapped around the Earth and used to poke someone on the opposite side?

No, the force of the poke would still be incredibly small due to the stick's length. The Earth's atmosphere and the person's body would also absorb the force, making it even less impactful.

5. How does the length of the stick affect its poking ability?

The longer the stick, the less force it will have at the point of contact. This is because the force is spread out over a larger distance, making it less concentrated. Therefore, a million-mile-long stick would have a very small poking ability compared to a shorter stick.

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