length expansion

  Symmetry is beautiful and intuitive. Symmetry is efficient and economical. And symmetry is an important principle that exists in the base of nature. And symmetry in relativity is very important. When we often say symmetry, we think of the symmetry of a figure. We call it line-symmetry or point-symmetry, where the left and right are the same or symmetric about a certain point. A Human is line-symmetrical, and the virus of the regular icosahedron is point-symmetrical. Fig. 1 Line-symmetric human body Fig 2. Point-symmetric virus But symmetry in science is a bit different from the symmetry of geometry. It is called symmetry, even though it is not symmetrical about any line or point and does not change for a particular action. This is what we call symmetry when we have made a certain action on a physical object and it has not changed. The symmetry is summarized as follows. Types of symmetry In relativity, symmetry and conservation are also very...

     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...