Can a Hypothetical Perfectly Rigid Body Transmit Forces Faster than Light?

[etriad]

Sorry in advance if this is a ridiculous question, but I've always wondered about this.

Let's say we could create a wire in space away from any gravitational affects. Make the wire 2 light seconds long, for example. If we pulled on one end, when would the effects be felt on the other end? I'm assuming that we could create a zero-stretch material (maybe a very bad assumption).

 

[Doc Al]

I'm assuming that we could create a zero-stretch material (maybe a very bad assumption).

Yes, that's a bad assumption.

Read this: Can I send a signal faster than light by pushing a rigid rod?

 

[tiny-tim]

welcome to pf!

hi etriad! welcome to pf!

Sorry in advance if this is a ridiculous question, but I've always wondered about this.

Let's say we could create a wire in space away from any gravitational affects. Make the wire 2 light seconds long, for example. If we pulled on one end, when would the effects be felt on the other end? I'm assuming that we could create a zero-stretch material (maybe a very bad assumption).

at least 2 seconds later …

the wire is mostly empty space: the molecules in it are bound together only by electromagnetism, and electromagnetic effects can't travel faster than light

 

[etriad]

Thanks for the link.

 

[sardar]

I can assure you that there is no such thing as a "ridiculous" question when it comes to understanding the laws of physics. In this case, the concept of a rigid body and the speed of light are both fundamental principles in physics, and it is important to understand how they relate to each other.

First, let's define what we mean by a rigid body. A rigid body is an object that maintains its shape and size, even when subjected to external forces. This means that all points on the object move together and maintain a constant distance from each other. In reality, there is no such thing as a perfectly rigid body, as all materials have some degree of flexibility or elasticity. However, for the purpose of this discussion, we can assume a hypothetical material that is perfectly rigid.

Now, let's consider the speed of light. According to Einstein's theory of relativity, the speed of light is the maximum speed at which all matter and information can travel in the universe. This means that no object or signal can travel faster than the speed of light.

So, what happens when we try to apply a force to a rigid body that is 2 light seconds long? Well, first of all, it is important to note that the concept of a "wire" implies a one-dimensional object, while the speed of light is a measurement of velocity in three-dimensional space. Therefore, it is not possible to directly compare the two.

But, for the sake of argument, let's assume that we have a material that is capable of maintaining its rigidity over a distance of 2 light seconds. If we were to pull on one end of this material, the force would propagate through the material at the speed of sound, which is much slower than the speed of light. This is because sound waves travel through the vibration of molecules, while the speed of light is a fundamental property of the universe.

In summary, the effects of a force on a rigid body would be felt at the other end of the material at the speed of sound, not the speed of light. This is due to the fundamental differences between the properties of a rigid body and the speed of light. I hope this helps to clarify your question.