http://www.facebook.com/ScienceReason ... Physics (Episode 5): Thermodynamic Temperature. --- Please SUBSCRIBE to Science & Reason: • http://www.youtube.com/Best0fScience • http://www.youtube.com/ScienceTV • http://www.youtube.com/FFreeThinker --- What is the temperature of outer space? way out there between galaxies ... where there is only about one hydrogen atom per cubic meter? Can an individual atom be hot or cold? Can it even have a temperature? It sounds a little silly to say an atom is 27 degrees Fahrenheit or something. PARTICLE TEMPERATURE: But temperature is really a measure of the motion energy of an atom if the atom is motionless then it is at zero Kelvin. Now it can never be really motionless so it can never be at exactly zero Kelvin. And it moves pretty fast pretty fast as the temperature rises. At a tiny fraction of a degree above absolute zero, (700 nK (1 nK = 10?9 K)) the atom is already moving at about 1 centimeter per second. For subatomic particles the energy is often measured in MeV or GeV. An electron with 1 GeV of energy is moving close to the speed of light. And that corresponds to a temperature of ... 11 thousand billion kelvins. AVERAGE TEMPERATURE: For a collection of atoms or molecules like a gas or a crystal lattice, the temperature of the collection is just the average temperature of the group. But of course because of collisions and interactions at the molecular level, a group of atoms or molecules will distribute the total motion energy pretty evenly among the individuals in the collection. HEATFLOW: And if two or more systems are brought together, some motion energy from the hotter system will flow to the colder system until they are both at the same temperature. When you measure your body temperature using a thermometer, your body cools down a tiny bit and the thermometer heats up until the two are at the same temperature. Then reading the thermometers temperature also reveals your body temperature since the two are the same. PRESSURE AND VOLUME: If we take a quantity of gas and enclose it in a container, the individual molecules in the gas constantly bang into the walls of the container creating a pressure on the walls. We can do three different things to increase the number of wall-collisions: -- Increase the number of atoms in the container by adding more gas. -- or increase the motion energy of the atoms already in the container by heating the gas. This makes them go faster and increases the number of times that each atom hits the wall. -- or we can make the container smaller decrease the volume so that individual atoms have shorter distances to go to collide with the wall. This leads directly to the ideal gas law relating temperature, volume, pressure, and quantity of gas: p = nRT/V Snuck that one in on you didnt we :) --- The Cassiopeia Project - making science simple! The Cassiopeia Project is an effort to make high quality science videos available to everyone. If you can visualize it, then understanding is not far behind. • http://www.cassiopeiaproject.com .