8th February 2016 - Page 6 of 14

8th February 2016

At what rate does the earth spin?

The earth spins or rotates on its axis every day. It takes 24 hours to rotate once on its axis. To calculate the rate of rotation, the circumference of the earth at the equator, which is 25,000 miles, is divided by the total time taken per rotation, which is 24 hours. The value comes to be approximately 1,000 miles per hour or 1,600 km per hour, which is equivalent to covering the distance between Delhi and Mumbai in 52 minutes (approx.)—quite a high speed indeed.

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8th February 2016

How pure are Olympic gold medals?

The Olympic gold medals are mostly made of silver, not gold. Only six grams, or 0.19 ounce, of gold is required to coat the medal. The medal itself is made of 92.5 per cent or 550 grams of pure silver. The medals are usually circular with a diameter of a minimum of 60 mm and a thickness of a minimum of 3 mm. These speciﬁcations are as per the Olympic Charter. The last time a pure gold medal was awarded in the 1912 Olympics in Sweden.

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8th February 2016

Another purpose for domestication of ‘pigeons’

Pigeons have been domesticated since ancient times to carry messages. They used to travel several miles to deliver messages. Even today, pigeon posts exist that serve the military in many countries. Pigeons have also been domesticated for a sport called ‘pigeon racing’. The racing is timed, and it has been found that the competing pigeons can ﬂy up to 1,750 km a day.

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8th February 2016

Evaluate the sum of the angles of a spherical triangle

A spherical triangle is formed on the surface of a sphere by three arcs. When the magnitudes of the three angles are added, they have a value that is greater than 180°, which is the value for the sum of three angles of a normal triangle.

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8th February 2016

What is ‘Triskaidekaphobia’?

‘Triskaidekaphobia’ is a word that arises from the greek tris meaning three, and deka meaning ten, i.e. thirteen, and phobia meaning fear. Triskaidekaphobia thus means the fear of the ‘number thirteen’. In western culture, the number thirteen is often associated with ill luck. Many hotels in the western countries have no thirteenth ﬂoor, and many streets are avoided being given the number thirteen.

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8th February 2016

What is space-time curvature?

Space and time are woven together to form a fourth dimension called ‘space-time’. The ‘curvature’ is a geometric property of space- time. Einstein identiﬁed this property while he was working on his General Relativity theory. The curvature of space-time is directly related to the energy and the momentum of any matter or radiation. A standard way to illustrate this idea is to place a bowling ball (representing a massive object such as the sun) onto a stretched rubber sheet (representing space-time). If a marble is placed onto the rubber sheet, it will roll towards the bowling ball, and may even be put into ‘orbit’ around the bowling ball. This occurs, not because the smaller mass is ‘attracted’ by a force emanating from the larger one, but because it is travelling along a surface which has been deformed by the presence of the larger mass. In the same way, gravitation in Einstein’s theory arises not as a force propagating through space-time, but rather as a feature of space-time itself. According to Einstein, your weight on earth is due to the fact that your body is travelling through warped space-time.

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