Hi guys. I'm currently taking a break after mugging all those lengthy SS notes. Recently my obsession towards relativity has grown. I've grown more curious towards how this spacetime curvature according to Einstein creates what we feel as the mysterious force - gravity. Finally I kinda understood thanks to a certain website. Here's how it works.
Imagine a universe with 2-d spacetime (yes i noe there's supposed to be more dimensions to spacetime but for simplicity's sake we make it 2d)
As shown in the diagram , there's 1 dimension of time(vertical axis) and 1 dimension of space(horizontal axis). The red thick line represents a planet moving through time. The blue line represents a small object, eg. an apple, moving through time also. However, this diagram is flawed because it doesn't show the curving of time. It only shows the curving of space. As a result, the path of the apple moving through time is parallel to the path taken by the planet - implying that the apple is not influenced by the planet's gravity.
This is a more accurate diagram of the curving of spacetime. Similar to what is shown above, the thick red line is the path taken by the planet and the blue line is the path taken by the apple. However, notice that the path of the apple is curved towards the path of the planet. The geodesic(straightest path traveled on a curved surface) of the apple is such that the apple moves closer to the planet in spacetime and eventually comes in contact with it. This means that what we feel as gravity is actually the natural movement(in other words geodesic) of our bodies through the curved surface of spacetime due to the presence of a large object i.e the earth. Isn't it amazing that Einstein came up with something as elegant as this to explain gravity? Even Sir Issac Newton, the man who discovered gravity, is unable to explain how gravity actually works. Ponder over it. I wonder how einstein conveyed the idea of spacetime curvature in the language of mathematics. Just too profound for a layman like me.
