**B R Sitaram**

Here are the answers to last month’s questions.

**Q 1. I mentioned in the March 2019 issue of Teacher Plus that a calendar has to repeat after every 28 years (and also mentioned the smaller periodicities of 6 and 11). What is the first time in the future when this periodicity will break and why?**

A. This pattern will break at the end of this century. The pattern depends on the fact that we have a leap year every four years, but that is not true for the year 2100: 2100 is divisible by 4 but will not be a leap year! 2000 was a leap year, but 1700, 1800, 1900, 2200, 2300, etc. are not leap years!

**Q 2. Look at the list of words given below. All of them stand for “Mother”. Matru (Sanskrit), Mata (Hindi), Mater (Latin), Mutter (German), Moeder (Dutch), Match (Russian, pronounced with a long ‘a’), Madre (Spanish), Maika (Croatian), Mother (English), Modir (Icelandic), ….You can make similar lists for Father, Brother, Sister, etc. The question is, what conclusion can you draw from the above list?**

A. These words clearly show that these languages have a common origin – the Proto Indo-European language (PIE for short). It is believed that PIE was spoken somewhere in the Asia Minor region, around the Black and Caspian seas and the people migrated to Europe, Iran and India, founding the language groups like Teutonic, Slavic, Indic and Iranic.

**Q 3. What great discovery, which completely changed the way objects were portrayed in a drawing or painting, was made by artists and mathematicians working together and when?**

A. The discovery was that of perspective, which showed how a sense of depth could be introduced in a drawing or painting. The basic idea of perspective is that the farther away an object is from a viewer, the smaller it appears. This makes parallel lines that are going away from a viewer appear to meet at a point. The idea of perspective originated in the drawings of Ghiberti and was given a mathematical foundation by the work of Filippo Brunelleschi, Toscanelli and Alberti. Artists like Leonardo da Vinci and Durer even made machines that could help artists create perspective drawings!

**Q 4. I have a magic formula for reducing weight. It takes effect instantly and the effects last as long as you live, with no chance of regaining the lost weight. What is my magic formula?**

A. The answer is simple: just jump from a tower! While in free fall, you are weightless (your weight becomes 0!). The taller the tower, the longer you will be weightless! Of course, this formula has two drawbacks: first, you are unlikely to survive the jump and second, there is no point in losing weight: you need to lose mass!

### Questions for this month

- Why will 2100 not be a leap year? After all, 2100 is divisible by 4!
- Newton’s law of gravitation says that the apple falls to the ground because of the force of gravity. The law is supposed to be universal, so should apply to the moon too. How come the moon does not fall to the ground?
- Some of you might remember from your school days that a calorie is the amount of heat required to heat 1 g (or 1 ml) of water by 1 degree Celsius. A typical cup of coffee would be made with 200 ml of water and you would have heated it by at least 50 degrees Celsius, so you would have used 50 x 200 = 10,000 calories. Weight watchers will remember that an adult is supposed to consume about 2000 calories a day. How come our body can do so much of work with just 1/5 the energy required to make a cup of coffee? Or is it really that we hardly do any work?
- Many Indian books claim that Aryabhatta was the first scientist to state that the Earth was round. What historical fact, taught in most curricula and found in most Indian textbooks on Science or Geography, shows that this claim is absurd?

Send in your answers and comments to zeal.qotw@gmail.com.