Does the Relativistic Speed of Soap Bubbles Affect Their Shape?

Click For Summary

Discussion Overview

The discussion revolves around the effects of relativistic speeds on the shape of soap bubbles, particularly focusing on whether their spherical shape is maintained when observed from a moving frame of reference. The conversation touches on concepts from relativity, surface tension, and energy minimization, exploring both theoretical implications and philosophical interpretations.

Discussion Character

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

Main Points Raised

  • Some participants assert that soap bubbles are spherical due to the principle of least-area for enclosing a volume, but question how this principle applies in relativistic frames.
  • One participant suggests that while a soap bubble may appear spherical when moving at relativistic speeds, it could be perceived as rotated and flattened due to light delay effects.
  • Another participant draws a parallel between soap bubbles and wooden meter sticks, discussing how energy considerations affect their shapes and questioning why traditional calculations fail in moving frames.
  • There is mention of the Terrell-Penrose effect, which relates to how objects are perceived at relativistic speeds, but its implications for mass are questioned.
  • One participant introduces a speculative idea about spacetime being composed of tiny bubbles and discusses the implications of spacetime's behavior under relativistic effects.

Areas of Agreement / Disagreement

Participants express differing views on how relativistic effects influence the shape of soap bubbles, with no consensus reached on the implications of these effects or the relevance of the least-area principle in moving frames.

Contextual Notes

The discussion includes references to complex theoretical concepts such as surface tension, energy minimization, and relativistic effects, which may not be fully resolved or agreed upon among participants.

Mueiz
Messages
188
Reaction score
0
It is well known that the shape of soap bubbles is spherical because of the fact that a sphere is the least-area way of enclosing a given volume .
If we look to a soap bubble from a frame of reference that move at relativistic speed relative to the bubbles, then ,as a result of length contraction, we will see that the diameter of the bubble in the direction of our speed is decreased by gama factor...so the shape of the bubble is no longer spherical.
What is the reason that the least-aeea method is not successful in moving frames?
 
Physics news on Phys.org
Mueiz said:
It is well known that the shape of soap bubbles is spherical because of the fact that a sphere is the least-area way of enclosing a given volume .
If you can say why "least-area" is relevant in the normal situation, you'll have your answer.
 
Hurkyl said:
If you can say why "least-area" is relevant in the normal situation, you'll have your answer.

If you give an answer it will be more useful than your If
can just two minutes be enough to answer a question in relativity you seem to be influenced by time dialation:biggrin:
 
Last edited:
Mueiz said:
It is well known that the shape of soap bubbles is spherical because of the fact that a sphere is the least-area way of enclosing a given volume .
If we look to a soap bubble from a frame of reference that move at relativistic speed relative to the bubbles, then ,as a result of length contraction, we will see that the diameter of the bubble in the direction of our speed is decreased by gama factor...so the shape of the bubble is no longer spherical.
What is the reason that the least-aeea method is not successful in moving frames?

I wonder if you are aware the soap bubble will still actually look spherical, but rotated as it flies by at near c. If you carefully take light delay into account, you can derive that bubble is flattened in your frame, but that is not what you would see.

I don't know how that affects your issue.
 
A soap bubble minimizes its area because it has an energy due to surface tension that is proportional to its area.

Similarly, a wooden meter stick has a certain shape that minimizes its energy. Stretching or compressing it relative to its equilibrium length of one meter requires an input of energy. We could then ask why the usual way of computing its equilibrium length fails in a moving frame. In theory, you could calculate the behavior of the wood using a description of its electrons and nuclei in terms of QED, and the result would be as expected from SR. There is a discussion of this in W.F.G. Swann, "Relativity, the Fitzgerald-Lorentz Contraction, and Quantum Theory," Rev. Mod. Phys., 13, 197 (1941). Of course, QED didn't exist in 1941, and even today it's not practical to compute the properties of wood using QED, but Swann discusses the general physical interpretation of this sort of thing.

This kind of thing leads to the same philosophical and interpretational issues as Bell's spaceship paradox:
http://en.wikipedia.org/wiki/Bell's_spaceship_paradox ,
http://math.ucr.edu/home/baez/physics/Relativity/SR/spaceship_puzzle.html

I don't think any of this is trivial or obvious. Bell famously got a majority of physicists in the Cern cafeteria to make the wrong prediction about the spaceship paradox. Ohanian discusses this in Einstein's Mistakes on p. 283 and, in my opinion, gets it totally wrong -- but it does show that there can be controversy among people who are well versed in SR and have thought deeply about these issues.
 
Last edited by a moderator:
Mentioning soap bubbles makes me think that you are referring to the theory that says that space itself is made up of tiny bubbles. Spacetime dialates so that objects in it always travel at the same speed less than light.

Spacetime itself wouldn't have to be under the affect since it wouldn't be able to dialate so that an object traveling in it and the spacetime itself would also measure the same speed for light. So, space itself is immune to relativistic effects and has been said to be able to travel FTL itself. We will never have to worry about spacetime measureing the speed of light incorrectly as it warps to insure that everything else measures it at the same speed.
 
PAllen said:
I wonder if you are aware the soap bubble will still actually look spherical, but rotated as it flies by at near c. If you carefully take light delay into account, you can derive that bubble is flattened in your frame, but that is not what you would see.

Ahhh, the Terrell-Penrose effect. Yes, however that should have no effect on the gravitational or interial mass, yes?

GrayGhost
 

Similar threads

  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 26 ·
Replies
26
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 25 ·
Replies
25
Views
8K
  • · Replies 18 ·
Replies
18
Views
5K
  • · Replies 75 ·
3
Replies
75
Views
7K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K