Even sound needs silence in order to be sound. — Honore de Balzac.

IN the earlier parts of the series, “Astronomical parlance”, we acquainted ourselves with some of the very basic terminology involved in this business. Every item in our everyday lives has words peculiar, or particular to that item. These are known as their idiom. Take for example a shirt, a very common actor in life. A shirt has a collar, button holes, cuffs, a pocket, etc. The car has wheels, a steering, the gear system, the engine that drives them all.

Just like them astronomy has its terms, and these terms, or the idiom are different from those used in, say, botany, zoology or medicine. So it is important for you to take note of the terminology employed in astronomy. We shall call them the idioms of astronomy. The same words are employed elsewhere in life but with slightly different meaning.

So far, we have learnt a few of the very basic idioms, for instance, albedo (the ratio of light reflected by Earth to that received by it from the Sun and other sources). When studying a relatively new body in space, scientists study the albedo of that body to determine how far from the nearest star it is. Then they want to know how much of the light it reflects back into space, from the amount it actually receives upon its surface. That conclusion will also give them general information about the material available on the surface of that body, including gases and minerals, if any, and in what quantity. Let us get on with the day’s business now.

Angstrom: Angstrom is a unit of length used for measuring extremely tiny amounts. One is equal to one hundred-millionth (10 raised to the power of minus 8) of one centimetre. Named after Swedish physicist Anders Angstrom, the unit is specially used to specify radiation wavelengths at a very high frequency end of electromagnetic spectrum. It is also the unit of distance because the diameter of most atoms is from one to four angstroms. One angstrom is equal to 100 trillionth of one metre, four billionth of one inch, (approximately) or about one millionth the diameter of a human hair! Interesting, isn’t it?

Antimatter: Each of the family of particles that make up all matter has a counterpart, or mirror image called an antiparticle. Antimatter is composed of antiparticles. The existence of antimatter is a subject of theoretic conjecture, not absolute reality. But the matter cannot be left at that. Even though the only known example of antimatter are the particles created when sub-atomic particles are smashed together in an accelerator/collider and then they too do not last long. As soon as antimatter encounters its equivalent matter, the two

mutually annihilate, or destroy themselves, converting both back to energy.