Ok, maybe I'm starting to get it, maybe not. I think the answer is that the photons emitted inside the train are carrying the same relative kinetic E as the passengers at either end of the train, so there is no shift in wavelength holding c constant.
But consider the platform observer...
1. So in the example where the lightning is simultaneous at both ends of the car, if the car is in motion won't the an onboard observer in the middle see a shift? (yes we need windows for this)
2. "Doppler shift reflects relative motion between emitter and receiver." I'm ok with that for...
Ok, if that is the correct answer, can you help me get my head around it?
I am thinking the sensor at the back of the car is moving towards the photons coming from the light, and the sensor at the front of the car is moving away from them. So why wouldn't there be redshift/blueshift...
To avoid confusion, I'm talking about:
"A flash of light is given off at the center of the traincar just as the two observers pass each other. The observer onboard the train sees the front and back of the traincar at fixed distances from the source of light and as such, according to this...