0:00 Look around you. Where are you? Where is this place you are occupying? Somewhere in a room, maybe in a city on a continent on a planet orbiting a star in a galaxy among billions. But… where is all of that? While this may feel like a daft question, it turns out that the concept of an absolute position is something humans made up. In a nutshell, the universe is a big bag of space that has things in it. If someone removed all these things, the stars and planets and black holes and dust,
0:32 there would just be empty space left. In empty space, the concept of having a position loses all meaning. Empty space is uniform, the same everywhere. The space we occupy is not like a stage under our feet. We can't mark specific points, or staple something to spacetime as an anchor. Without things there is no position. We are really ever only at a position in relation to something else. Which also means that things we take for granted, like up and down are actually relative too.
1:06 Ok, let us fill the universe up with things again and try to find out where you are, right now. Relative to everything else. Let us start this video at a familiar place and then get increasingly weird. From your perspective the world is seemingly flat and you can move in 3 dimensions. It's what physicists call a 'frame of reference' - the perspective you have of the universe and how you see things
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