Friday 13th - friggatriskaidekaphobia

May 13th is a Friday and Friday the 13th is considered unlucky! The fear of Friday the 13th is known as friggatriskaidekaphobia.

Have you ever wondered how those are possible in a year? It is simple math..

Here is a table to show how the 13th of every month is distributed based on which day the year starts.

13th of every month - the year starts on Day 1

If a year starts on Day 1, the distribution of the 13th would be as above. There is a 13th in every column.. what does this mean? If the year starts with a Friday (i.e. Day 1 is a Friday), there will be only 1 Friday the 13th that year. There can't be a year without at least one "Friday the 13th".

The maximum number of "Friday the 13th" would occur on Day 2 which means that Day 1 should be a Thursday i.e. the year should be a Thursday.

For a leap year, the distribution would be slightly different and as follows

13th of every month in a leap year - the year starts on Day 1

In a leap year, the maximum number of "Friday the 13th" would occur on Day 6 which means that a leap year starting on Sunday would have 3 of them.

An interesting article is available on EarthSky.org

1. Telescope - Let's calibrate!

The Milky Way as seen from the La Silla Observatory (Source: Wikipedia)

If there was one thing that has baffled humankind and its imagination the most over several thousands of years, it would undoubtedly be the night sky and the star dust that we all are made of. Starting from the ever changing shape of the dominant moon to the dots that can be joined to form all sorts of shapes (from a crab to a microscope). Don't forget the occasional dropping of the stars!

Isn't it interesting to know that our lives are driven by these objects which are several thousands or millions or trillions of kilometers away? They are also the inspiration for several stories across the world. If we were to prepare a "list of commons" of all civilizations across the world, 2 things would be definitely there on the list - firstly, the human being and second, the study of night sky by the human being (and it wouldn't be an exaggeration).

The Moon - most commonly seen object in the sky (Source: Wikipedia)

The Telescope series will help us improve the understand those little dots and spheres better. So let's calibrate our telescopes for the ride!

Each article of this series is drawn from several sources and they will be highlighted here.