## Tuesday, November 29, 2011

### It's That Time of Year Again

It's that time of year again.  The holidays are here, and you can't flip through the channels without eventually hitting a Christmas special.  We watched Miracle on 34th Street yesterday, and I was struck by the scene at the end where all the mail addressed to Santa gets shipped to the courtroom where Kris Kringle is on trial. One of the clerks in the mail room says "there must be about 50,000" letters to Santa Claus that they have to get rid of.  How many letters get delivered to the court room?

In the movie, 21 duffel bags full of letters are brought in and dumped on the judge's desk.  Judging by how the men carry the bags, they certainly weigh between 2 and 200 lbs, so we can reasonable assume there are about 20 lbs of letters to Santa in each bag.  According to the United States Postal website, a standard letter weighs less than 3.5 ounces.  Assuming a 1 ounce letter, we can easily compute the number of letters delivered,

# of letter = (21 bags) × (20 lbs/bag) × (16 ounces/lb) / (1 ounce/letter)
= 7000 letters.

At about 7000 letters, the mail clerk was correct to within about an order of magnitude.  Not too shabby.

Fermi Lives at Harwoon Union

It's been a busy semester.  A couple of months ago, I received a very nice email from Lisa Therrien and several other teachers at Harwood Union Middle School in Duxbury, VT.  Apparently Fermi fever is catchy, because Ms. Therrien is teaching her students how to make order of magnitude estimates.  I got invited to listen to several of her students describe their estimations over Skype.  It was a very enjoyable experience, and I can truly say that Harwood Union Middle School has some very creative young mathematical minds.  I only wish more teachers incorporated this style of thinking into their math and science classes.

Estimation as a Skeptic's Tool

In addition to Harwood Union School, I also got invited to speak for Ann Arbor Science & Skeptics in October.  It was a great group, and we discussed how estimation can be used as a skeptic's tool. Here's a few of the cool estimates that were suggested by the group:
• How much hair throughout the entire world is grown in one day? (Enough to cover about 10 square miles.)
• What was Forrest Gump’s average speed as he ran across the country? (About 5 cm/s.)
• If the Sun disappeared, how quickly would the temperature drop on Earth? (About 0.1°C per century if you’re talking about the average temperature of the whole Earth, or about 20°C per day if you’re talking about just the surface temperature.)
The only downer of the trip for me was that I had to admit my secret shame.  I, physicist Aaron Santos, have never actually read a Carl Sagan book.  It's a problem that I will hopefully be remedied in the near future, but for now, feel free to throw your rotten tomatoes.