An intriguing question came to mind: Scenario: A ship that has it's inner walls painted blue say something like the base blue used in computer graphics [hyperlinks], zips past you at 0.8c, what colour do the walls appear to be from our RF?
mainly because then the colour is a product of the light eminating from a ship that has a v =0.8c Maybe we can modify the scenario by painting the outside the same blue as the inside and compare the difference [if any] If the inside of the ship was rectagular with the length towards it's vector would the forward inner wall be a different colour to the other inner walls to the 1] ships observer and 2] to the RF observer? Just curious.......
it does not make any difference. 1. ships observer would not notice any difference as he is at rest (or co-moving) with ship's walls. 2. The orientation of walls does not make any significant difference in velocity between observer and the ship. To the observer the ship's color after blue-shift would be UV.
Try a different slant on this...Just a thought…. If the leading inside wall of the box were to be painted blue and there was a mirror on the inside trailing wall, then the beam of light leaving the mirror and heading forward would remain blue.
Why blue-shift instead of red-shift due to "transverse doppler"? I would have thought blue-shift during the "approach" phase, redshift during the "transverse" instant, and then more extreme red-shift during the "depart" phase. If the resulting UV frequency during approach is outside of the visible spectrum, wouldn't the ship appear black? Same question if the walls were originally red: If the red-shift during departure were to result in an IR frequesncy outside of the visible spectrum.
I'm not sure I agree with this, which is a shame, because it would be neat if it was true. The observer looks at a mirror on the trailing wall, and sees an image of the leading wall. How is the light from the image of the leading wall different from the light from the real trailing wall? It appears just like the trailing wall, only farther back (like a wall trailing along behind the ship). I would think the light from the image wall and the real wall would both be blue-shifted as the ship approaches.
You guys need to specify which frame you're in when you make these statements. Are you in the box looking at the wall/mirror? Or are you observing it from the outside? From inside the box, the reflected light is unchanged. It's the same frequency of blue. From outside the box, you can only observe the front wall as it receeds from you (you are behind the box) or the reflected light as it comes toward you (you are in front of the box). Yes?
I'd agree with that. My comments about blue-shift and red-shift were from the reference frame of the relatively 'stationary' observer (who is watching the ship move past).
But the mirror is co-moving with the leading wall so the incident blue light is not red-shifted but remain blue. the reflected blue light will be blue-shifted to UV.
This is where it gets weird. I think we all agree that we (the observers) are standing in front of the box. Imagine the box has a hole in the front leading edge such that you can view a mirror placed on its trailing internal wall. The box is painted inside and out in the colour blue (except for the mirror. If the box is stationary relative to us, we must agree that all colours look blue. But as the box moves quickly towards us, the outside leading edge changes colour because it is blue-shifted, hence, we see UV. Agreed? But this is the trick, the light leaving the front internal leading wall is emitted backwards (and hence red-shifted relative to the observer) towards the mirror. Normally, we would NEVER have the privilege of observing such light, but in this case we have a mirror. The mirror is also travelling relative to the observer and has the effect of “correcting” the already shifted light back to blue. Result….the internal front leading edge looks blue regardless of relative velocity. What do you think guys?
the interesting thing is we can not see UV so does the wall disappear or is it just black? Obviously the wall isn't going to disappear.....xcing xcling xcling [x- files] ......or it it? :m: Please Register or Log in to view the hidden image!
actually I think it is a very valid question: If the walls colour is shifted to UV what do we actually see? The wall still exists yes? But it's not reflecting visable light and it's not just absorbing light ....so.....hmmmmmmm
Yes, the light leaving the front internal leading wall is red-shifted relative to the stationary observer, not to the mirror which is co-moving with the leading wall. as such the mirror simply reflects back the blue light. If a mirror is stationary behind the moving box then you are right. That is not the case here.
Hmmm, I'm sure you're wrong here, but let me think about it. First you say "Yes, the light leaving the front internal leading wall is red-shifted relative to the stationary observer" So, the mirror (relative to the observer) will correct this red-shift back to blue, won't it? Please Register or Log in to view the hidden image!
The blue light emitted by leading wall looks red-shifted to the stationary observer. For the observer, the moving mirror should receive the blue-shifted red-shifted light. For the mirror, no-shift, its blue light all the way from the wall. Don't try to confuse me with your confusion of frames. Please Register or Log in to view the hidden image!
No it doesn't because it's travelling backwards and is thus impossible to EVER see. "blue-shifted red-shifted light." hahahaha Think about it. You agree that the light leaving the front internal wall is red-shifted relative to the observer. Agree? So a reflection of this red-shifted light (relative to the observer) will be blue-shifted by an object (the mirror) travelling toward the observer. Hence, back to blue. Please Register or Log in to view the hidden image! Please Register or Log in to view the hidden image! Please Register or Log in to view the hidden image!
OMG, this is nothing but similar when the ship is moving away from the observer, you don't imagine properly?? I was laughing ROF while typing this exclusively needed for you. Yes, but you only 'discovered' that the observer cannot see. Please Register or Log in to view the hidden image! It is red-shifted for the observer because the emitting wall is moving towards the observer. For the observer, the moving mirror recieves the 'blue light'. The observer understands what the mirror would recieve. what? blue light. its BLUE light. back to blue, ofcourse.
