An internal combustion engine and any physical variable star, including a Cepheid, are heat engines. For example, in a diesel engine, when the working substance is compressed, it is ignited. At the same time, the pressure rises sharply and compression is replaced by expansion. With the expansion and subsequent exhaust, the gas temperature decreases. After that, the process is repeated. A similar process takes place in physical variable stars. When the star contracts, the interior overheats and the pressure of the star’s matter increases, the star begins to expand and lose energy. After that, the star contracts again. The role of the valve is played by a layer of doubly ionized helium, which, when the star contracts, increases the opacity and thereby leads to overheating of the star, and during expansion, on the contrary, increases the transparency and contributes to its cooling.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.