I have a very basic question about the relativity of simultaneity (damn that's a mouth full). So basically rule no. 1 would be that it's all relative right? In the example of the ladder thought experiment it's shown that because of "Lorentz length contraction" a ladder which is bigger than a garage can from one viewpoint fit into said garage and from another viewpoint not fit. Am i understanding it so far? And all of this is because there are two separate references of observation, the aforementioned frames in this thread. In the first reference frame the observer is together with the ladder moving through the garage and the other reference is a dude looking at them from the other opposite house. Right? OK first of all i'm a bit confused about the "Lorentz length contraction". Is this an actual literal contraction or is it just an illusionary one? If it's a literal one, how does that happen on purely physical basis? What does speed have to do with how long something is? I would think that the length of an object has an absolute value, no matter how it is perceived from different observers. If it's not a literal contraction and it just depends on the observer then the whole argument becomes useless so i'm just going to assume that physics claims an actual contraction. So how does that happen physically? And why is the contraction experienced differently by different observers?