So far a lot has been said about the English, German and Dutch astronomers but very little about the contributions of the French astronomers or astrophycists. Although their say in fields as diverse as medicine, avionics, automobile, education and mechanics are exemplary, and the world owes them a heavy debt for that, it goes without saying that what follows next will amply substantiate that the indomitable Frenchmen of yore were no spring chickens. Their contribution to the changing world was enormous.

Laplace, Pierre-Simone De: Mathematician and astronomer, La Place (1749-1827) founded mathematical formula for the formation of the universe and the first theory for the tides, also mathematically. By redoing Newton’s equations, he established that the Solar System is very stable.

His other notable contributions are related to mathematics, which is not in the ambit of our present discussion. But his innovative treatment of problems relating to astronomy and mechanics popularised the new ideas in Europe, which were confined to the elite thus far. He also developed the Metric system of measurement which is the primary system inthe world today.

Latent heat: Every budding astronomer must know about heat as much as possible. This will help you understand planets, our Sun, other stars, galaxies, et al, how they deal with the ‘spare’ heat, as well as their interiors and even their atmospheres. It will also help you understand the inter-galactic, inter-stellar voids and even the ultimate possibility of life around a particular star, and whatever possibility of life there is on other celestial bodies.

Latent heat is the heat released when matter undergoes a change of phase, for instance from liquid to solid or from gas to liquid phase. An example is the process of evaporation, which absorbs a large amount of heat. When water reaches boiling point, its temperature does not rise further. The additional heat is boiled away. In other words, it evaporates.

When we freeze, or melt anything, it also involves heat -- the loss of heat in the first case and addition of temperature in the second. This process invloves latent heat.

Louis Leakey: The Leakey family is inevitable when it comes to talk about the evolution of humans beings. The family of anthropologists worked in the Olduvai Gorge in Tanzania.

Their discoveries tended to prove that humans probably evolved in Africa and then spread all over. It goes to the credit of the Leakeys to have dated human existence back 3.75 million years. They have made several astounding discoveries, many of which have been disputed by other scientists.

The younger Leakey, Richard, found a complete 1.5 million years old human skeleton in 1976. It was of homo erectus, the first human who is thought to have stood and walked straight on two legs instead of all fours. The raging controversy has lasted since the early 1970s in which some of the hard work of the Leakeys under harsh conditions has been hotly contested by others --- as often happens in the world of science.

However, the Leakey family enjoys a unique place of eminence in the world of science, despite whatever controversy. To them goes the credit of tracing the roots of humanity.

Light year: A light year is a measure of distance, not of time. This unit is in universal use of astronomy and cosmology because distances in outer space are so vast that measuring them in miles or kilometres would be meaningless and unwieldy.

Light travels slightly more than 186,000 miles per second. At such a fantastic speed, it takes about 1.5 seconds to reach from the moon to Earth (distance 238,000 miles). Light travels in 8 1/2 minutes from the Sun to the Earth (93 million miles). About 4 1/2 years to travel from the nearest star to the Solar System (not counting the sun).

Hence light travels a mind-boggling six trillion miles in a year, that is six followed by 12 zeros, that’s how much one light year is. There are other distances even greater than that, for which other units are employed.

The writer is an astronomer formerly employed by PIA, and can be reached atastronomerpreone@hotmail.com

Published in Dawn, Young World March 11th, 2017