Hello. I thought I understood special relativity very well, but that’s the trouble when you don’t research anything and just here bits and pieces then fill in the gaps yourself. Something was bothering me when it dawned on me that my understanding of it includes an aether and I know the universe shouldn’t. I’m taking a logical wrong turn somewhere and I can’t pin it. I‘ve understood the concept for about four years but thought that time would slow to half rate at half the speed of light because for every action there is an equal and opposite reaction, so the faster you move though space; the slower you move through time, all relative to the speed of light. So your total speed through space-time should remain constant ( C ). So if you move and half the speed of light through space; you move at half the speed of time relative to someone who remain stationary in your original world line. I’m here because I found out that assumption is wrong. In the twin paradox; you travel around for a bit, very fast and come back visibly younger than your twin. This very much implies an aether. There not both older relative to the other. Maybe they’re separated by the fact that freely moving motion is always relative but acceleration/deceleration isn’t? That still implies an aether. One (the one that ages slower) was moving through space “faster” than the other after all relativistic factors are a taken into account? If not, why not? Edit: Length changes as well! Space-time as a whole contracts. So is it just length are all three spatial dimensions. In a straight line presumably it would be one dimension but that doesn’t seem to fit very well. In four dimensional space-time in which they are interchangeable, it doesn’t seem right that two dimensions change relative to the rest of the universe and two don’t. Edit2: Apparently length contraction appears differently for different observers. So if that’s true, both observers measure the same amount of time dilation, that is to say; they both observe the other moving through time slower than themselves, e.g. at half speed while moving at three quarters of light speed (zero from their perspective of course). But they see length contraction differently, so if one sees the space between them as lengthened relative to them, then the other observes contraction of space, again implying an aether as a distinction is made as to which one is actually moving. That doesn‘t ring true. Time and space are merely different aspects of the same thing, like matter/energy, isn’t that the whole point? Why would they behave differently? I’m clearly missing something here. Edit3(I‘m not rewriting it because it will probably be less clear): With the acceleration/deceleration thing: It should mean there’s no distinction between the two. Acceleration in one direction is deceleration in the opposite direction if there’s no aether. Is that right? If there the same thing because there’s no absolute rest then how can one twin be older than the other? Hold on, there’s no distinction between which of two objects is moving, but if there is a change in their velocity relative to each other then there is a distinction between which one made that change, and that one will be the young twin, right? That means that time is moving at the same rate for both (but not from their perspective because the other is moving away from them both, so each will see the other moving through time slower them themselves) while they are consistently moving away from each other at the same speed and the only real time dilation that accurse is during acceleration/deceleration. It has nothing to do with velocity?