There's no complicated geometry or number theory this time, just multiplication. Urban sophisticate Ezra Klein preaches the virtues of the Roku Netflix box for the 20% of Americans with high-speed Internet connections. Klein notes that "One of the effects of $200-a-barrel oil will be that anything that can possibly be transported electronically will be." That's close, but not quite right: anything that can be transmitted electronically cheaply will be.
But is it cheaper to have users download movies than pay business class postal rates? This provides a convenient excuse to do some multiplication.
- Suppose a DVD case is 5"x5"x.25". How many DVDs fit into a single 40'x20'x10' shipping container?
- each DVD contains 4.7 gigabytes of data. What is the total storage capacity of a container full of DVDs? (Note: the abbreviations beyond giga- are terabyte (1000 gigabytes), petabyte (1000 terabytes) and exabyte (1000 petabytes).
- Suppose that freight moves at an average speed of 50mph. How many seconds does it take for freight to travel from Bellingham, WA, to Key West, FL?
- Divide the result from #2 by the result from #3. This gives you a
measurement in the form of bytes per second. What is the bandwidth of a
shipping container full of DVDs across the country? Is this faster or
slower than most consumer-grade broadband connections? What if we used Blu-ray discs instead, which contain 50 GB worth of data?
- Suppose the per-mile costs of freight is $3.50 (I did A Google and came up with $3.25, so we'll highball it). What is the cost per megabyte of shipping a container full of DVDs across the country? 5a: A consumer-grade broadband connection of 5 megabits per second, running full-tilt all the time, would yield a cost of $0.0006 per megabyte. Which is cheaper?
I will leave finding the actual numbers an an exercise to the reader, but the bottom line is that sending dense physical storage by mail is significantly faster or cheaper than using broadband, even with oil at $200, $300, or $1,000 per barrel.
