You left me two notes on this questioning statements I made. I’m not sure if you have other issues with my explanation of relativity.
The first was this one:
My statement is absolutely correct. If “we” are in a Lorentz frame K, and “a person” is in a Lorentz frame K’ accelerated near to the speed of light relative to one another, “we” will see “a person” slow down. The person will also see us slow down. This one effect of time dilation.
The second issue you had was with my statement on length contraction, something about observers having to compare notes. For the life of me I cannot retrieve that note from medium. It seems to have disappeared.
The statement I made is absolutely correct. The issue with length contraction is that it has to do with how you do the measurement. Consider an observer in a Lorentz frame K observing on in K’ such that K’ contains a ruler that is accelerated to a significant fraction of the speed of light such that the ruler’s length is in the direction of motion. The ruler will experience a Lorentz contraction in the direction of motion. In order to measure that contraction, however, you must measure the distance between the front and back of the ruler simultaneously, which is not typically how we measure things. Instead, we observe things based on light that arrives at our eyes (or instruments) simultaneously. That light, however, will not have left the front and back of the ruler simultaneously because its motion. Because of this fact, we do not observe length contraction, but an effect called Terrell rotation. In this effect, we will observe the object at its normal length but rotated. This, however, is because of a precise cancellation of length contraction by the lack of simultaneity in the measurement.
I hope these explanations allay your concerns. If you have any other, feel free to drop me a note. I’m always happy to discuss relativity.