I'm aware I'm raising a topic which must have been discussed several times, but I couldn't find anything specific to my question. So... Let's assume the universe began from a big bang, which seems for sure. Since then the universe expanded, and it's currently growing. One question, which leaves me sleepless at night is: inside what is the universe expanding ? Ok, the answer is: into the nothingness. I doubt there is someone out there who has a faint idea of what a "timeless and spaceless" nothing is. My first objection is that the verb "to expand" requires an outside, otherwise we should use another verb. The idea of expansion into nothing is senseless to me. But move on. Something else makes me sleepless. If the universe began from a singularity (the big bang), there must be a boundary, and a center. I am more keen to the idea of centerless universe, but since nothing travels faster than light, everything must be within a certain distance from the big bang point, wherever it is. Otherwise, what does it mean that "we cannot look further than 13 billions light years away" ? I point my telescope to a star, then to a further star, and so on. I cannot see any star further than 13 billion l.y. away. So there is a final star. Where am I wrong ? If there's no center, every star is the last star. Something tell me that we are playing with concepts we don't understand at all. Probably the whole notion of measure loses it's meaning. I dunno. I want my sleep back.