Wednesday, June 25, 2008

Einstein and bicycles

"I thought of it while riding my bicycle", is reputedly what Albert Einstein said about his Special Theory of Relativity.

Another Einstein quote - "Life is like riding a bicycle. To keep your balance, you must keep moving" -says something of the physicist's depth of intuition for bicycling. While a student at Munich University in Bavaria, he would tour by bicycle. And while at Princeton University during the early 1950s, Einstein was often seen on his bike. (The above image is not from Princeton, but from Santa Barbara, CA.)

So, it's really not too big a stretch to call Einstein a bike commuter, although the communities he lived in were more compact than our urban sprawl of today, and so perhaps the word "commuter" was less relevant. Einstein was irrefutably a cyclist. What was the attraction that bikes held for him? My own personal theory is that, being a theoretical physicist, he was compelled to run the numbers. And, running the numbers, he couldn't in good conscience use a car on a regular basis.

Here are the numbers, by the way:

1. The modern automotive internal combustion engine (ICE) machinery is 10% efficient. That is, 10% of the chemical energy in the fuel gets turned into kinetic energy (energy of motion) where the rubber meets the road.

2. Since the ratio of car mass to passenger mass for a single passenger vehicle is roughly 15 : 1, the overall efficiency of a car system (its ability to move your carcass down the road) is 0.10 x 1/15, or somewhat less than one percent. Say 2/3 of 1 percent. Multiply this by the number of passengers.

So, good rule of thumb, a car is 1% efficient. Incredible, isn't it?

How about a bike? Well, most studies show overall efficiency of a bike system (depending on rider technique) to be in the 18 - 25% range. This sounds pretty bad until you compare it to an automobile system!

So when you ride your bike, you're (let's say) 20 to 30 times as efficient as an automobile. Think of yourself getting 600 to 900 miles per gallon.

Not too shabby.

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