Evangelista Torricelli invented the barometer. Torricelli also introduced a law (Torricelli's law) that states the speed of efflux (v) of a fluid through a sharp-edged hole at the bottom of a tank filled to a depth (d) is the same as the speed that a body would acquire in falling freely from a height (h).
Robert Boyle created Boyle's law. This law states that the absolute pressure and volume of a given mass of confined gas are inversely proportional, if the temperature remains unchanged within a closed system.
Daniel Bernoulli laid the basis for the kinetic theory of gases and applied the idea to explain Boyle's Law.
Joseph Priestley discovered oxygen. Other significant contributions Priestley made were his study of electricity and his discovery of the conductivity of water and metal. Priestly founded Unitarianism.
John Dalton created Dalton's law, which states that the total pressure exerted by a mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases. John Dalton also had an atomic theory which states that elements are made of small particles called atoms. Atoms of the same element have the same proporties and atoms of different elements have different proporties. Atoms can't be subdivided, created, or destroyed. Atoms of different elements combine in simple whole-number ratios to create compounds. In chemical reactions atoms are combined, separated or rearranged.
Jacques Charles created Charles's law. This law states that at a constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature on the absolute scale. He had the idea to put hydrogen in ballons so they would float.
Amedo Avogadro created Avogadro's law. This law states that under the same conditions of temperature and pressure, equal volumes of gases contain the same number of molecules.
Albert Einstein created the theory of relativity. This theory stated three things. The measure of various quantities are relevant to the velocities of the observers. Space and time should be considered together in relation to each other. The speed of light is nonetheless invariant, the same for all observers. This was his most famous theory. Einstein also theorized about wormholes, modern quantum theory, and cosmology.