# fermi problem

### Size of 91,000 documents

Here is a quick one. One of the big news stories recently was this regarding WikiLeaks and the release of the Afghan War Diary. There could be tons of things to discuss regarding this - but I am not going to do that. The first thing that struck my mind was "over 91,000 documents". That seems like a lot. If each one of these documents were printed on one page, how big would the stack of paper be? I could just estimate this - fermi-problem style. But instead, I thought would use a stack of paper. Here is a pack of 500 sheets of paper. Opening it, I can measure the thickness: How thick…

### An estimation problem for math teachers

You thought I was going to talk about a problem that math teachers could use, didn't you? Well, maybe math teachers can use this. (note: when I say "teachers" I really mean "learning facilitators") It all started when I read this valedictorian speech from Erica Goldson. Here is part of it: "I am now accomplishing that goal. I am graduating. I should look at this as a positive experience, especially being at the top of my class. However, in retrospect, I cannot say that I am any more intelligent than my peers. I can attest that I am only the best at doing what I am told and working the…

### Could cars slow down the Earth?

Time for another Fermi problem. There was a recent story in Science News that talked about the effects of the Chilean quakes on the Earth's rotation. The basic idea is that some ginmourmous amounts of rock moved closer to the Earth's center. Since the angular momentum of the Earth is conserved, the angular rotation rate would increase. The estimated change of the day was by about 1.26 microseconds. Could all the cars in the USA be used to change the rotation of the Earth? Well, I shouldn't have phrased the question that way. Of course 1 car technically is all you need to change the…

### How many people to review youtube videos?

There was a Buzz Out Loud episode in the not-to-distant past where the discussion of youtube came up. I can't remember the exact details, but the main point was that it would be impossible for google (the owners of youtube) to review all of the videos that were submitted. And here is my calculation. How much would it cost google a year to do this? First, I need to pick some variables (and I will first do this symbolically - then you can put in your own values if it makes you happy). Submission Rate (s): This is how many minutes of video are submitted each minute (so the units would be…

### Physics and the movie UP - floating a house

I haven't seen the Pixar Movie "Up" yet, so don't spoil it for me. I have, however, seen the trailer. In my usual fashion, I have to find something to complain about. There is this scene where the old man releases balloons out of the house. What is wrong with this scene? Also, would that be enough balloons to make the house float? Here is a shot of the balloons coming out of the house. Ok, I was already wrong. The first time I saw this trailer I thought the balloons were stored in his house. After re-watching in slow motion, it seems the balloons were maybe in the back yard held down…