A quick word on units: As I noted in the lecture, while the units that much of the world uses (meters, seconds, and kilograms) are the most rational, there are still places--like America--that make use of miles and feet. And, when it comes to the speed of light, we saw in class (and you'll verify below) that using feet happens to make life a little easier. The bottom line: Don't be beholden to any particular set of units. Be able to work with any units, and freely translate from one set to another. Here's a little practice:
Approximating the speed of light as 186,000 miles/second, calculate the speed of light in feet per nanosecond (ft/ns), where a nanosecond is one billionth of a second.
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