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Re: Order of magnitude estimation



R.W.Tarara wrote:

energy output of over 12 MJ. As to why it costs so much to eat, I guess if
we could injest coal or natural gas, we could 'fuel' ourselves a lot
cheaper. There is much more time, effort, and cost involved in growing and
processing our normal food-stuffs than to 'mine' the fuels of commercial
electrical energy.

Rick

I'm convinced R.Tarrach had this answer in mind when he was writing that text.
I guess it is intended just to provoke the student, to make him question
what he seees or knows: is that reasonable? is it what I expected?. To show
him that many times a simple and easy calculation may give a useful insight
into a given problem. Just like many other "fermi" questions.

Any way, although that may be a trivial example, I think there is a second
reading, namely to question the stablished system itself. Of course, this
takes us anywhere, but to a physics thread. So,better if you forget it.

What to you think are the value of such a questions? Do you give them
a special attention (f.i. dealing one or two days with such a questions)?

Regards,
M.A. Santos
msantos@etse.urv.es