Spacetime

Space, time, energy and mass are all the same entity.
It is not like energy is filled in space, but rather that energy is the space.

• Einstein field equations do not represent energy curves space, but rather describes the spatial curvature of energy.

[Doubts]

"A straight line connecting two points in space represents the shortest distance between them.

But a straight line connecting two points in spacetime represents the longest distance between them."

"Because if you had a clock, your average speed would be higher when travelling in the zigzag path, and hence your clock will run slower, and the time measured will be slower. On the other had, when travellling in a straight line, your average speed will be as low as possible, and hence the time your measure will be more. This is due to time dilation."