As the tittle says, I am constantly hearing about spacetime, which I sort of get (it’s a 4D space, with 3 spatial and 1 temporal axis) and curvature, which I do not get. What is curved in spacetime? When we say geodesics, what are they representing? I am getting the feeling that it is something like the spatiotemporal distance between two events that is being modified, but what does it mean in physical terms? Is it even physical, since two observers can disagree in almost everything, except the order of casually linked events?
Or I am thinking it too much, and it’s only a model of interpreting observation that only approximates complex reality up to a point?
In: 5
[Here](https://www.youtube.com/watch?v=MTY1Kje0yLg) is a good visualization of curvature. Spacetime is a like a sheet of textile and the mass of object will curve it which will change their trajectory.
Obviously it’s a analogy and it can be hard to really understand for people. It’s not something you can see or touch, it’s outside of the human experience.
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