Gas laws 1662 Robert Boyle studied the relationship between volume and pressure of a gas of fixed amount at constant temperature. He observed that volume of a given mass of a gas is inversely proportional to its pressure at a constant temperature. Boyle's law, published in 1662, states that, at constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system is always constant. It can be verified experimentally using a pressure gauge and a variable volume container. It can also be derived from the kinetic theory of gases: if a container,
Thermodynamics of the universe the temperature formula_22 as well, and is therefore proportional to formula_23. As the universe expands it cools down, so formula_22 depends on formula_9 as well. In fact, since the energy of a relativistic particle is inversely proportional to its wavelength, which is proportional to formula_9, the energy density of the radiation must be proportional to formula_17. From this discussion it is also obvious that the temperature of radiation is inversely proportional to the scale factor formula_9. Plugging this information to the Friedmann-Lemaître-Robertson-Walker equations of motion and neglecting both the cosmological constant formula_29 and the curvature parameter formula_30, which is justified