The swan was seen as a traditional symbol of beauty and grace in ancient Greece, and was sacred to Aphrodite. The swan was also sacred to Apollo, the god of music (among other things), in Greek mythology. At the time, the people believed that the swan sang a sweet and beautiful song when people died.
For example, in case of monatomic gas it is just a kinetic energy of motion of atoms of gas as measured in the reference frame of the center of mass of gas. In case of molecules in the gas rotational and vibrational energy is involved.
kinetic energy the energy of motion. nuclear energy energy that can be liberated by changes in the nucleus of an atom (as by fission of a heavy nucleus or fusion of light nuclei into heavier ones with accompanying loss of mass). potential energy energy at rest or not manifested in actual work.