HEAT IS ON

Ever since I was taught Newton’s Law of Gravitation at school, “Every particle in the universe attracts every other particle…….,” I had been wondering how the particles know of each other’s existence. The first prerequisite for attracting or being attracted is awareness of the other’s presence. So there must be something being exchanged among all particles of matter in the universe. Some scientists have suggested the existence of a force field around everything that exists; others have proposed the existence of gravitons. But as usual, they all missed the obvious.

Way back in the early 1960s I learnt about thermal radiation and heat transfer and came across the Stefan-Boltzmann Law of Blackbody radiation discovered in late nineteenth century. A black body is a hypothetic body that completely absorbs all wavelengths of thermal radiation incident on it. Such bodies do not reflect light, and therefore appear black if their temperatures are low enough so as not to be self-luminous. All blackbodies heated to a given temperature emit thermal radiation given by:

q = σ T4 A (1)

where

q = heat transfer per unit time (W)

σ = 5.6703 10-8 (W/m2K4) - The Stefan-Boltzmann Constant

T = absolute temperature Kelvin (K)

A = surface area of the emitting body (m2)

It was later modified for grey and colored bodies that were not black and for temperature of the environment or other bodies interacting with it. The final simplified equation of net heat transferred from one body to another is of the form:

q = ε σ Fh,c (Th4 - Tc4) Ac

where ε is the emissivity, F the form factor and h and c denote the hotter and colder temperatures.

I had found the answer to my long unresolved conundrum. Every object in the universe makes its presence felt by emitting thermal radiation, the intensity of which is proportional to the fourth power of its absolute temperature, and every object reacts to change in temperature of every other object in its sight.