Gary’s Q&A

Listener question & Gary’s response · Transcript passage

Jesus Chan asks Hello Gary, greetings from South Texas. Does temperature mean the same thing at different scales? Can a single atom or a tiny system even have a temperature the way a cup of coffee does?

The short answer is not really.

Temperature is a macroscopic property—meaning it’s defined for systems with a large number of particles, like gases, liquids, or solids. In essence, temperature is a measure of the average kinetic energy of the particles in a system.

A single atom can’t really be a liquid, solid, or gas. These states of matter exist with respect to how they behave with other atoms or molecules. By the same token, the notion of temperature loses meaning when you refer to a single atom or molecule.

That being said, experiments have been done on the laser cooling of individual atoms. This is done to achieve temperatures near absolute zero. Likewise, scientists also talk of the temperature of particles shortly after the Big Bang.

So, A single atom has kinetic energy, but temperature isn’t just about a single particle’s energy—it’s about the distribution of energies across many particles.

So, I’d say no, an atom can’t have a temperature like a cup of coffee, but I’m guessing there are others who would disagree. It really is mostly a matter of definition.