Why does Space-Time curve and more importantly, why and how does Space and Time come together to form a “fabric”?
In: Physics
Oh, that’s all.
The notion of a fabric and curvature are mostly just tools to help us wrap our heads around it. These physical theories are basically just mathematical models of how things actually work. In the case of general relativity (GR) the models predict pretty accurately.
The concept of curvature comes from an extrapolation of something we can understand well. If you take a piece of fabric and pretend it’s infinitely thin, it becomes a 2 dimensional surface embedded in a 3 dimensional space. You can bend and deform it. But if you were a 2 dimensional creature on that surface, it would just appear to be a flat plane, because you have no way to observe a 3rd dimension. An object moving along that fabric would twist and turn in ways you couldn’t understand. But to us 3 dimensional creatures looking at the fabric we can see the bends and deformations. To us it’s obvious why the object is moving in the way it is.
Gravity works similarly. Objects in space bend in the presence of a gravitational object – the moon orbiting the earth. But how does it do that? There’s nothing ‘pulling’ the moon to the earth – no particle we can see, no string, etc. Well, if we consider that our 3 dimensional space may be bending and deforming in 4 dimensional frame, in ways we can’t see and understand, we can visualize how that might work – that just like putting a weight in our 2d fabric distorts it and therefore distorts the path of objects traveling on it, without any obvious interaction of particles, string tying them together, etc. Massive objects do the same to 3d space. The earth distorts 3d space causing the moon to orbit it.
Is it an actual distortion? Don’t know. Doesn’t really matter, either. What matters is that the model works well enough that we can predict things we previously couldn’t. Further, and this is a sign this is a good model, it predicts things we’ve never seen. When we discover one of those things, it serves as good evidence that the model is valid. Distortion of light around the sun, gravitational lensing, time dilation in a gravitational field, etc. are all things the theory predicted that weren’t observed until later.
So, mainly it’s a way of conceptualizing a physical effect in a way that allows us to understand the interaction between these objects without seeing an exchange of information between them (particles, etc)
Latest Answers