03 Invariants of the theory of relativity, space-time intervals
Today, I’d like to talk about space-time intervals. In the theory of relativity, space-time intervals can be thought of as 'four-dimensional length'. In 2-dimensions, length means the line-segment above the paper. And in 3D, the length is the length of the bar inside the three-dimensional space. The main stage of relativity is the fourth dimension. Here, the fourth dimension has nothing to do with the fourth dimension of mystery novels ! The main tool used to talk about relativity is the Lorentz transformation. This Lorentz transformation is essentially a mix of time and space. The theory of relativity is based on two basic ideas. The second is the constancy of the speed of light. The invariants that emerge from relativity come mostly from the constancy of the speed of light. This means that the speed of light in a vacuum is always constant regardless of the speed of the light source. This "always constant" is directly related to other invariants of rel...