Like in this demonstration: https://youtu.be/MTY1Kje0yLg?si=tohjaO8JBmt7IpWo
The movement of two objects is explained using Einstein’s theory of objects in space bending the fabric of space to cause one object to move in relation to another.
My question is what makes up the “fabric of space” that is being bent? As in the example of the linked video, what in space makes up what that blue fabric represents?
In: 3
There is no “fabric”. It’s just an analogy which is easier to visualize than the underlying mathematics, though spacetime does dip under mass (sometimes so steep that light can’t get back out), it seems to be stretched by “dark energy” and suitably large collisions can send out ripples.
Newton had a similar analogue for his description of gravity, in that objects attract each other based on their mass and distance. Newton didn’t actually believe that everything was connected by invisible force lines, but everything behaved *as if they were.*
You should watch [this video](https://www.youtube.com/watch?v=wrwgIjBUYVc) because the one you linked is an analogy that explains gravity by using gravity (that funnel is shaped tha way because Earth’s gravity pulls the objects down).
To answer your question, there is no material in the “fabric” of spacetime, and what’s curved or deformed is the actual dimensions (x,y,z,t).
The mention of fabric is a metaphor. The way I understand it, the demonstration you linked is a 3d representation of the effect of gravity by looking at a 2d example of space. Meaning don’t look at it from the side, you need to look at it from directly above to see the motions at play. The stretch of the fabric is the representation of the effect of gravity.
Another way to put it is, without gravity an object in motion travels in a straight line. Gravity causes space to curve, so the object in motion is still traveling in a straight line, but the path is bent without a direct force applied to the object.
Einstein called the metaphor a “crutch”. At best it’s a mental aid. At worst it locks people into thinking of relativity that might not be ontologically correct. Einstein still thought about gravity as a real force, not a property of geometry. Also, Einstein was wrong about a lot of things, so maybe he was wrong in his thinking about this too.
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