Aether wind vs Einsteins 2nd postulate

[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.)

Homework Equations

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!

 

[SammyS]

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.

 

[jakepeck]

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?

 

[collinsmark]

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.

 

[SammyS]

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?