Thursday, February 26, 2015

Lessons in Time

The other day I was microwaving some food to heat it up. Ten seconds seemed like forever. I was actually able to do several other things while I waited. The microwave has changed my perception of time in some ways. nanoseconds As I thought about that I remembered the first time I heard Grace Hopper speak.

One of her favorite stories was about explaining to an admiral why there was a delay in satellite transmission. She used a wire “nanosecond” to demonstrate. Light travels about 11 3/4 inches in a nanosecond. She would show the wire and explain that there were a lot of nanoseconds between the ground and the satellite.

Later in her career Admiral Hopper used to show off packets of picoseconds. She got the little packets in the cafeteria where they were already labeled with the letter P.

I am I am sure many others use the nanosecond story to help explain to our students why smaller computers are faster computers.  I’m thinking about adding the microwave story to my toolkit as well. Some times that we think are very fast in the abstract are actually very slow in reality. Once you realize that 10 seconds is not instantaneous and that you can actually accomplish other things during that time you realize that parallel operations can make better use of the time available. Ten seconds to you and I can be a long time. A nanosecond is a long time to a computer. Even, these days, a picosecond is a long time for a computer. We’ll see how that goes over.

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