I have specific questions about Lorentz transformations specifically about length contraction.
Why does length contraction only occur in the direction of travel, (not in all directions) when approaching the speed of light?
From an outside observer's perspective watching an object traveling close to the speed of light, why does the obsever notice the object contract?
These Ideas are accepted by physicists, but for 1 I don't understand how they know that length contraction is in only one direction without they themselves being in the reference frame of someone or something traveling close to the speed of light.
For 2 Let's say that I'm driving in a car 5 meters long and I'm driving on a road that has white markers on it. Where the markers are in one line and each marker is 5 meters apart from the next one and the line of markers is parallel to my direction of travel. At normal speeds I would observe that at a given moment one marker would line up with back of the car and the next marker would line up with the front of the car (the car occupies 1 marker space). So now if I were to travel at speed such that my Lorentz factor is 2. I see one of two cases. In the first case I don't observe any change in myself or my car and I observe a length contraction of 2. Meaning that I would see a change in my environment not in myself or my car. So I would now observe that at a given moment the car would take up the length of 2 marker spaces. Therefore an outside observer would then see the car expanded by a factor of 2 not contracted. In the second case I do notice a change in myself. I contract with the space so things look very wierd in my perspective, Everything has contracted by a factor of 2 in the direction of travel. So my arms, my legs, the carseat, the hood of the car, etc. has all shrunk by a factor of 2. However because the road has shrunk by the same amount as the car, I take up only one marker space. Therefore an outside observer would not see any change in the length of me or the car. So in both cases the car doesn't contract from an outside observer's perspective.