Effects of Space-Time Hypothetical Thought Experiment

  • Context: Graduate 
  • Thread starter Thread starter madsam
  • Start date Start date
  • Tags Tags
    Effects Space-time
Click For Summary

Discussion Overview

The discussion revolves around a hypothetical thought experiment involving a very long cylindrical material, approximately 100,000 km in length, that is rotated in deep space. Participants explore the implications of this scenario on time, space, and physical properties, particularly when the outer edge approaches relativistic speeds. The conversation touches on concepts from both special and general relativity, as well as the structural integrity of materials under extreme conditions.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that as the cylinder spins, the outer edge would experience relativistic effects, potentially leading to time dilation and increased mass.
  • Others argue that the covalent bonds of the material would fail at much lower speeds than suggested, making the experiment impossible.
  • A participant introduces the concept of a "C-Lock effect," suggesting that a point would be reached where further acceleration becomes impossible, akin to encountering an impenetrable wall.
  • There is a discussion about the lack of a truly rigid body in relativity, which complicates the thought experiment.
  • Some participants mention the idea of frame dragging and time travel associated with infinitely long rotating cylinders, though there is uncertainty about the specifics of this model.
  • Questions arise regarding the method of rotation and the forces applied to the cylinder, with some seeking clarification on how the rotation is initiated.
  • One participant notes that the upper limit on angular velocities differs depending on the position along the cylinder, suggesting that relativistic effects would complicate the dynamics of the system.

Areas of Agreement / Disagreement

Participants express a range of views, with some agreeing on the impossibility of the experiment due to material limitations, while others explore the theoretical implications of the thought experiment without reaching a consensus on its feasibility or outcomes.

Contextual Notes

Limitations include assumptions about material properties under extreme conditions, the definition of rigidity in relativity, and the unresolved nature of the proposed "C-Lock effect." The discussion also highlights the complexities of applying both special and general relativity to the scenario.

Who May Find This Useful

Readers interested in theoretical physics, particularly those exploring concepts of relativity, hypothetical scenarios in space-time, and the implications of extreme physical conditions on material properties.

madsam
Messages
4
Reaction score
0
Hypothetical thought experiment;
What would happen if you created a very long cylindrical material, eg 100 000km long and took it into deep space. Here you rotate one side of it so the tube is spinning in a large circle with radius 100 000km, ignoring friction and gravity.

Once it is spinning, the outer edge will spin faster that the inside as it has a greater distance to travel and is doing this in the same time etc.

If the object was sped up to travel 50-99% the speed of light*, time and space would bend in order for the outer edge to speed up to allow the edge to spin faster, without exceeding the speed of light.

I suppose that the mass of the outer side would increase while time would slow down, and the object would begin spiraling in on itself, in the same way spaghetification occurs in a black hole, however I am not entirely sure

What would appear to occur for a person with a frame of reference;
a. A stationary observer
b. An observer standing on the inner edge of the circle
c. A person on the outside edge of the circle (Moving closer to the speed of light)

Also, i know that to move an object near the speed of light requires and infinite amount of energy, however technically your not moving the outer edge, but instead it is being pulled along by the particle bonds. Would you then still require vast amounts of energy in order to increase the objects speed?

This isn't a homework question, it's just something i thought of and has puzzled me for a fair few days, as well as those around me. So if you guys could help with some input, it'd be great.

* The speed, whilst still a relatively high value, may not be necessary to answer the question as long as the outer edge of the object is moving faster at near speed of light.
 
Last edited:
Physics news on Phys.org
madsam said:
Also, i know that to move an object near the speed of light requires and infinite amount of energy, however technically your not moving the outer edge, but instead it is being pulled along by the particle bonds. Would you then still require vast amounts of energy in order to increase the objects speed?

The co-valent bonding between atoms of the material would be ripped-apart far below the speed you suggest, resulting in a catastrophic fragmentation.
In other words, this "experiment" is impossible.
 
pallidin said:
The co-valent bonding between atoms of the material would be ripped-apart far below the speed you suggest, resulting in a catastrophic fragmentation.
In other words, this "experiment" is impossible.


Like i said, thought experiment, its the same sort of question as holding a mirror up while traveling at the speed of light, and seeing whether or not you would have a reflection.
If the material wasn't ripped apart and could withstand the forces, what would happen then?
 
madsam said:
If the material wasn't ripped apart and could withstand the forces, what would happen then?

Well, a very special condition would occur. The system would "lock". That is, further acceleration becomes impossible, as if an invisible, impenetrable wall is encountered.
 
It's rather interesting that you should bring this subject up.

The "C-Lock effect", as I call it, has tremendous potential, but as yet I have not been able to devise an actual, real-world physical experiment to express and validate the phenomenon.

Too much structural stability problems. I've come to the tentative conclusion that a macroscopic C-Lock is not possible.
 
Last edited:
madsam said:
Hypothetical thought experiment;
What would happen if you created a very long cylindrical material, eg 100 000km long and took it into deep space. Here you rotate one side of it so the tube is spinning in a large circle with radius 100 000km, ignoring friction and gravity.

Once it is spinning, the outer edge will spin faster that the inside as it has a greater distance to travel and is doing this in the same time etc.

There is no such as a rigid body in relativity.
pallidin said:
The "C-Lock effect", as I call it, has tremendous potential, but as yet I have not been able to devise an actual, real-world physical experiment to express and validate the phenomenon.

Can you give a reference for this?
 
An infinitely long rotating cylinder is a hypothetical model for time travel via frame dragging...
 
George, I coined the term. As far as I know there is no specific reference to it apart from my own.
 
madsam said:
Like i said, thought experiment, its the same sort of question as holding a mirror up while traveling at the speed of light, and seeing whether or not you would have a reflection.
It's not at all the same sort of question. There's nothing in relativity that suggests that the mirror would break or anything like that, but the existence of an absolutely rigid body is in direct violation of the postulates of relativity.

madsam said:
If the material wasn't ripped apart and could withstand the forces, what would happen then?
You'd have to be more specific. You haven't even explained how you intend to get it rotating. Are you pushing every part of it at once, or are you applying a force to the stationary end of it? I'm also curious about if you really want this treated as a GR problem (including the curvature and frame dragging effects caused by the motion of a massive cylinder) when there's enough interesting stuff going on in the SR version (mass--->0) of this problem.

The upper bound on the set of possible angular velocities is different for a point near the "outside" endpoint of the cylinder than for a point near the "inside" endpoint. So it seems clear that if the cylinder is turned by gently applying torque to a small part near the "inside" endpoint, the cylinder will bend. The initial bend would propagate through the cylinder and straighten it out, if it wasn't for the relativistic effects. What relativity adds is that it will get more and more bent as the angular velocity of the part near the inside endpoint is increased. The internal forces in the cylinder will also make it more and more difficult to increase the angular velocity further.
 
Last edited:
  • #10
Naty1 said:
An infinitely long rotating cylinder is a hypothetical model for time travel via frame dragging...
I think that cylinder is supposed to rotate around it's symmetry axis, and this one is meant to be rotated in different way. (But I'm not 100% sure about either statement).
 

Similar threads

High School Traveling through space at zero km/s
  • · Replies 11 ·
Replies
11
Views
1K
High School Thought Experiment: Behavior of shadow of object moving at speed c
  • · Replies 14 ·
Replies
14
Views
2K
High School Rotating disc: tidal relativity across surface of disc
  • · Replies 14 ·
Replies
14
Views
1K
High School A thought Experiment in Time Dilation
  • · Replies 31 ·
2
Replies
31
Views
3K
High School True static equilibrium and effects on time
  • · Replies 25 ·
Replies
25
Views
3K
High School Traveling outside of the Earth's atmosphere
  • · Replies 27 ·
Replies
27
Views
2K
High School Ride Gravitational Waves to Increase Speed?
  • · Replies 6 ·
Replies
6
Views
2K
High School Experience Travel on a Photon: Hitch-Hiker's Guide to the Universe
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad A question about the speed of light and electromagnetism
  • · Replies 51 ·
2
Replies
51
Views
5K
Graduate Rotating Disk Method to Attain Light Speed?
  • · Replies 40 ·
2
Replies
40
Views
2K