# Aether wind vs Einsteins 2nd postulate

• jakepeck
In summary, the light would move faster in the direction of the aether wind and slower in the opposite direction, and would scatter uniformly in all directions at the same speed. Relativity and differences in perspective would play a role in determining when light would return to the observer.
jakepeck

## Homework Statement

Imagine yourself seated at the center of a spherical shell of radius 3 X 10^8 meters the inner surface being diffusely reflecting. A source at the center of the sphere emits a sharp pulse of light, which travels outward through the darkness with uniform intensity in all directions. Explain what you would expect to see during the three second interval following the pulse under the assumptions that,

a) there is a steady aether wind blowing through the sphere at 1000km/s
b) there is no aether and Einstein's second postulate holds
c) discuss the relationship of this thought experiment to the Michelson Morley experiment.

(Hint: Think about the time it would take for light to reach the parts of the spherical shell in different directions relative to the direction of the aether wind.)

N/A

## The Attempt at a Solution

a) the light would move faster towards the direction of the aether wind and slower in the opposite direction
b) the light would scatter uniformly in all directions at the same speed
c) relativity and differences in perspective?

Please help me and let me know if I'm not understand the question fully or missing something major.

Thanks!

Hello, jakepeck. Welcome to PF.

So, what would you expect to "see"? (you being at the center of the sphere.)

I suppose, that your seeing is aided by having some instrumentation so you can determine at what time light returns from various directions, and what intensities from those directions.

I outlined what I expected I would see in the OP, I'm just not sure if its completely right or I'm leaving something out. I don't think the light would return because the inner surface is DIFFUSELY reflective, therefore the light would scatter upon hitting the outside of the inner surface.

Any help? Or was my original answer correct?

jakepeck said:
I outlined what I expected I would see in the OP, I'm just not sure if its completely right or I'm leaving something out.
a) the light would move faster towards the direction of the aether wind and slower in the opposite direction
b) the light would scatter uniformly in all directions at the same speed
Don't forget that you can't observe/detect light instantaneously at a distance. The light needs to hit your eyes in order for you to see it. Try to consider the paths that the light must travel in order to eventually hit your eyes (with you being at the center). What's the minimum time in each case, after the initial, sharp pulse of light, that you would be able to see a reflection (via the light bouncing back and hitting your eyes or instrumentation at the center)? In the case of the aether being present, what is the minimum time in the direction of the wind, and also in a direction perpendicular to that? I think that's what SammyS was hinting at.
I don't think the light would return because the inner surface is DIFFUSELY reflective, therefore the light would scatter upon hitting the outside of the inner surface.
The fact that the reflection is diffuse doesn't necessarily mean that you would see nothing forever after. The fact that it's diffusely reflective does make a difference, but it doesn't necessarily mean that you will see nothing at all.

If the sphere had a mirror finish, you would have to consider the angle of incidence, angle of reflection at various locations of the sphere. It's likely that light would return to you in the center only from a few limited regions of the sphere. The fact that the surface is diffuse means that some light will return to you from all portions of the sphere. The underlying question is: Will light return from all portions simultaneously? If not, from which regions will light return first? ... from which regions last? What is the maximum time difference?

## 1. What is the difference between Aether wind and Einstein's 2nd postulate?

The Aether wind theory states that there is a medium called "aether" that fills the entire universe and electromagnetic waves travel through it. On the other hand, Einstein's 2nd postulate states that the speed of light in a vacuum is constant and independent of the observer's frame of reference. This means that the speed of light is the same for all observers, regardless of their motion or the motion of the source emitting the light.

## 2. How does the Aether wind theory relate to the concept of absolute rest?

The Aether wind theory suggests that there is a state of absolute rest, where the aether is at rest and not affected by any motion. This implies that there is a preferred frame of reference, which contradicts Einstein's theory of relativity. In contrast, Einstein's 2nd postulate states that there is no absolute rest or preferred frame of reference, and all motion is relative.

## 3. Can you provide evidence for or against the Aether wind theory?

There have been numerous experiments conducted to test the existence of the aether, but all have failed to provide conclusive evidence. The famous Michelson-Morley experiment in 1887 showed that the speed of light was the same in all directions, regardless of the Earth's motion through the aether. This result was inconsistent with the predictions of the Aether wind theory. Additionally, the theory was unable to explain the phenomenon of aberration of starlight, which showed that the Earth's motion did not affect the speed of light.

## 4. How does Einstein's 2nd postulate impact our understanding of time and space?

Einstein's theory of relativity revolutionized our understanding of time and space. It showed that space and time are relative concepts and are intertwined in what is known as spacetime. This means that an observer's perception of time and space is dependent on their frame of reference and the relative motion between them. Einstein's 2nd postulate, along with his theory of relativity, forms the basis of modern physics and has been consistently supported by experimental evidence.

## 5. Is the concept of aether still relevant in modern physics?

No, the concept of aether is no longer considered relevant in modern physics. The Aether wind theory has been disproven by numerous experiments, and Einstein's theory of relativity has provided a more accurate and comprehensive understanding of the universe. The idea of aether is now considered a historical concept and is no longer used in scientific discussions or theories.

• Special and General Relativity
Replies
3
Views
1K
• Special and General Relativity
Replies
29
Views
2K
• Special and General Relativity
Replies
5
Views
2K
• Special and General Relativity
Replies
57
Views
4K
• Introductory Physics Homework Help
Replies
4
Views
2K
• Introductory Physics Homework Help
Replies
9
Views
2K
• Introductory Physics Homework Help
Replies
2
Views
2K
• Introductory Physics Homework Help
Replies
5
Views
3K