Hypothesis: Tugging from the Sun to Earth Faster than Light?

  • Thread starter BenWillcox
  • Start date
In summary, the idea of a solid rod extending from Earth to the sun and someone tugging on it at the other end, causing the person on Earth to feel the pull instantly, is not possible due to the limitations of relativity. The speed of light is the maximum speed at which information can travel, and therefore there is a limit on how rigid an object can be. This is why white dwarfs collapse into neutron stars and everything collapses into black holes.
  • #1
BenWillcox
2
0
I thought of this today...

Suppose a solid rod of diamond (so there would be no slack) existed that extended from Earth to the distance of the sun. For example, someone at a location the distance of the sun away would be holding one end of the rod, while the other end would be held by a person on earth. IF the person at the distance of the sun tugged on the rod, would the person on Earth feel a pull instantly? If light takes 8 minutes to travel from the sun to earth, couldn't the kinetic energy of this tug be felt by the person on Earth at a rate faster than the speed of light?

Of course none of this is possible and obviously isn't true, but I'm wondering why this wouldn't occur faster than the speed of light.

Thanks,

Benjamin Willcox
 
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  • #2
Hi Ben
welcome to PF :)

what is your reasoning as to why would you even think the pulse along the rod would travel faster than light ?Questions along these lines pop up quite regularly here. the other variation is someone striking one end of a very long rod.

cheers
Dave
 
  • #3
Thanks for your reply Davenn, I don't understand what you mean by pulse. Here is a picture I drew up to help explain it better:
Untitled.jpg
 
  • #4
The is no such thing as a perfectly rigid object. The other end of your diamond rod would always move at much less than light speed. The bulk modulus is the property that defines rigidity of an object. The bulk modulus of a diamond is only about twice that of aluminum.
 
  • #5
Neutron stars represent the upper limit for rigidity of materials in the universe. In fact, limiting the speed of sound to c actually gives the basis for calculating the maximum theoretical mass of a neutron star - re: http://arxiv.org/abs/astro-ph/0011107
 
  • #6
BenWillcox said:
Thanks for your reply Davenn, I don't understand what you mean by pulse. Here is a picture I drew up to help explain it better:View attachment 47177

yup I knew what you meant :)

by pulse I mean, when the rod is pulled, pushed or hit at one end there is going to be a pulse of that motion that moves along the rod towards the other end.

even for a rigid material like diamond, over any significant distance, its still going to exhibit an elastic deformation along its length. This is something that is valid even when looking at the Earth as part of solid Earth geophysics, on a small scale rock acts very solid but on large scale it quite happily deforms elastically.

So when you pull on one end of your rod its going to produce an extensional elastic deformation (if pushed or hit it will produce a compressional pulse) that will travel as a pulse along the length of the rod

And I would suggest that the speed of that pulse is substantantially less than the speed of light.
Maybe some one else may know the formula /maths for worthing that speed out ??
not in my field of expertise

hope that helps you visualise what is happening

cheers
Dave
 
  • #7
BTW, that speed is the speed of sound.
 
  • #8
russ_watters said:
BTW, that speed is the speed of sound.

Thanks Russ

I suspected that was the case, but wasnt sure so didnt post

Dave
 
  • #9
We have an FAQ on this question https://www.physicsforums.com/showthread.php?t=536289 [Broken]
 
Last edited by a moderator:
  • #10
Thanks Ryan

didnt know that one existed

D
 
  • #11
davenn said:
yup I knew what you meant :)

by pulse I mean, when the rod is pulled, pushed or hit at one end there is going to be a pulse of that motion that moves along the rod towards the other end.

even for a rigid material like diamond, over any significant distance, its still going to exhibit an elastic deformation along its length. This is something that is valid even when looking at the Earth as part of solid Earth geophysics, on a small scale rock acts very solid but on large scale it quite happily deforms elastically.

So when you pull on one end of your rod its going to produce an extensional elastic deformation (if pushed or hit it will produce a compressional pulse) that will travel as a pulse along the length of the rod

And I would suggest that the speed of that pulse is substantantially less than the speed of light.
Maybe some one else may know the formula /maths for worthing that speed out ??
not in my field of expertise

hope that helps you visualise what is happening

cheers
Dave

what if you could extend that rod to the nearest galaxy moving away from us due to metric expansion of space :confused: does it stop that weird phenomenon
 
  • #12
hitchiker said:
what if you could extend that rod to the nearest galaxy moving away from us due to metric expansion of space :confused: does it stop that weird phenomenon

It would probably be stretched by the two galaxies rushing away from each other, then broken when it can't take any more, I'm guessing.
 
  • #13
BenWillcox said:
If light takes 8 minutes to travel from the sun to earth, couldn't the kinetic energy of this tug be felt by the person on Earth at a rate faster than the speed of light?

Of course none of this is possible and obviously isn't true, but I'm wondering why this wouldn't occur faster than the speed of light.

Because relativity puts limits on how rigid an object can be. Since information can't travel faster than light, there's a limit on how stiff an object can be.

This is why white dwarfs collapse into neutron stars. Once the electrons start moving at the speed of light, they lose stiffness, and the star collapses. This is also why everything collapses to black holes. Once you compress anything to the point where things are moving near the speed of light, it also loses stiffness and things collapse.
 

1. How does tugging from the Sun to Earth faster than light work?

The hypothesis suggests that the Sun's gravitational pull on Earth could potentially travel faster than the speed of light. This would mean that the Sun's "tug" on Earth would be felt instantaneously, rather than taking the 8 minutes it currently does to travel at the speed of light.

2. What evidence supports this hypothesis?

Currently, there is no scientific evidence to support this hypothesis. The speed of light has been consistently measured and confirmed by numerous experiments, and there is no known mechanism that would allow for faster-than-light travel. Without evidence, this hypothesis remains purely speculative.

3. What would be the implications if this hypothesis were proven to be true?

If this hypothesis were to be proven true, it would fundamentally change our understanding of physics and the laws of the universe. It would require a complete overhaul of our current understanding of the speed of light and how it affects the dynamics of the solar system. It could also potentially open up new possibilities for space travel and communication.

4. How is this hypothesis being tested or researched?

As of now, there is no known research or experiments specifically aimed at testing this hypothesis. However, scientists continue to study the speed of light and its effects on the universe through various experiments and observations. If evidence were to arise that supports this hypothesis, it would likely spark further research and experimentation.

5. Are there any potential flaws or criticisms of this hypothesis?

As with any scientific hypothesis, there are potential flaws and criticisms. One major criticism is that it goes against our current understanding of physics and the laws of the universe. It also lacks any substantial evidence to support it. Additionally, the concept of faster-than-light travel is highly controversial and has been debated among scientists for decades. Until there is concrete evidence to support this hypothesis, it remains highly speculative and unproven.

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