length expansion

Today, I would like to introduce a way to check relativistic effects in a narrow laboratory. Relativistic effects are usually hard to see in the lab. It is difficult because it requires an incredibly fast speed. But there is a way. Initially, experiments were conducted using excited hydrogen atoms. What we are going to do today is look at Walter Kündig's method. The basic method of Kündig is as follows.  [Walter Kündig, “Measurement of the Transverse Doppler Effect in an Accelerated System”, Phys. Rev. 129, 2371(1963)]  Walt K ü ndig 's Experimental Devices   It uses a device that turns quickly like a centrifuge. It measures the frequency of light emitted from the source by placing the source in the middle and the absorber at the edge. The story of the experimental device is not important, but please read the literature if you are interested in learning about that.   The e xperimental results are interesting. The Doppler Effect was k

Hello!   Today I would like to introduce ‘ the submarine paradox of Supplee ’  which appears in the theory of relativity. In 1989, Supplee raised questions about relativistic buoyancy. Picture a submarine floating in the sea. This submarine does not sink or float , so w e can say that we have ‘neutral buoyancy’.       Suppose this submarine is now running fast. Suppose you are running at a relativistic speed, ignoring the resistance of water. This is a very important topic for black hole research. Understanding the situation of paradox is simple. Suppose a person on the bottom of the sea observes this submarine. The submarine shrinks in length because it runs at relative speed. However, as the mass increases the density also increases. If so, a submarine cannot maintain neutral buoyancy and must inevitably sink. As shown in the picture below.   Now let's take a look at the position of the crew on the submarine. The crew on b