8. The Ideal Gas Constant

Boyle discovered the relationship between the pressure and volume of a gas, and Jacques Charles and Joseph Gay-Lussac discovered the relationship between volume and temperature. To obtain the required data, Gay-Lussac took a hot-air balloon to an altitude of 23,000 feet. The results of Boyle, Charles and Gay-Lussac could be combined to show that in a fixed quantity of a gas, temperature was proportional to the product of pressure and volume. The constant of proportionality is known as the ideal gas constant.

7. Absolute Zero

It's easy to make heat but producing cold is a much more difficult task. Pressurization enabled scientists like Michael Faraday to liquefy oxygen, hydrogen and helium. That brought us to within a few degrees of absolute zero. But heat is also motion, and a technique of slowing down atoms by using lasers has enabled us to come within millionths of a degree of absolute zero, which we now know to be slightly more than –459 degrees Fahrenheit. Absolute zero falls in the same category as the speed of light. Material objects can get ever so close, but they can never reach it.