I have these questions: 1) Why must light always move along a geodesic line? What is the principle behind that? 2) A second question about spacetime: We mostly depict or imagine spacetime as a net of flexible fiber that extends everywhere as a plane as we see it.. As we are looking it, what exists above that plane or underneath it? Are there infinite such nets intertwined that take up and make up the whole spacetime? I guess that's only our picture for spacetime.. 3) Right after big bang it is believed that inflation occured with a speed far greater than speed of light. I know that this is said to be allowed by relativity since no information was transmitted with that speed. But everything is information and even the dimension of space and time that took up the "thing" that enclosed big bang can be considered as bits of information so the upper limit for speed should be applied. What is wrong? 4) And finally I want to ask about time dilation. For example the twin paradox. To sum it up, the one travels with great speed in space and after earth years he comes back young etc.. While his brother is old and everything has changed. But. We assign his speed with reference to the brother on earth (reference frame A which we consider still). But also, if we put a reference frame on the space traveler (B , which is moving with regards to A, but is still according to the traveler), he sees the brother on earth to be moving with the great speed, since speed is relative. But finally the traveler will be young and experienced time dilation and not the brother on earth! What happens???