xkcd’s table of approximations

Randall Munroe’s xkcd has a table of slightly wrong equations and identities.

The table gives that the number of seconds in a year is 754 = 31640625 or (using the “RENT method”) 525,600 × 60 = 31536000. (This refers to the song Seasons of Love, which features the number of minutes in a year prominently in its lyrics.) I’ve always been partial to “pi seconds is a nanocentury” (attributed to Tom Duff), which gives π × 107 for the number of seconds in a year, but you have to know π for this to be useful.

Also, while I’m on the subject: it’s easy to remember that the circumference of the Earth is 4 × 107 meters, or 40,000 kilometers; the meter was originally defined to be one ten-millionth of the distance from the North Pole to the equator through Paris. Call this C, or 2πr. The surface area of the Earth is therefore 4πr2 = C2/π, which works out to (1.6/π) × 1014 square meters; may as well let π = 3.2 for the moment and call that 5 × 1013. Munroe gives 698, which I suppose has some amusement value.

Advertisements

3 thoughts on “xkcd’s table of approximations

  1. I’m pretty sure I’ve previously told you my favourite of these: π” = 8 cm (correct to .25%), which turns out to mean that metric hat sizes (where the granularity is centimetres of circumference) move in exact lock step with English hat sizes (where the granularity is eights of an inch of diameter).

  2. Shopping locally for what you are buying from a reputable person who can be taken at high speeds.
    Keep in mind that expectation is a google kind of yearning.
    9m A collection of cars a 1924 silver Rolls-Royce Ghost, originally built for the US military in
    1943 – before being loaded onto the boats one by one.
    Version 3 end of the movie that also contains a handful of the villagers have cars the rest travel on horse-drawn
    carts or bicycles. But, he said in the Bergen google Record interview.

    road scholar italy

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s