Name: carol a jackson
Date: Around 1995
What is the smallest measurement (anything smaller than a millimeter)?
You mean the smallest distance we can measure? Practically speaking, it is
probably around 1 Angstrom. This requires very special techniques however
(scanning tunneling microscopes for example). 1 Angstrom is 10 million
times smaller than a millimeter. 1000 times smaller than a millimeter is a
micron, which is the sort of scale used in manufacturing computer chips and
is about as small as you can see with normal light microscopes.
There are measurements smaller than 1 Angstrom - 1 picometer is 100 times
smaller, and 1 femtometer (also known as a fermi) is 100,000 times smaller,
and is about the size of an atomic nucleus. But there are not any technolo-
gies available to practically do anything on that kind of length scale, so
the smallest useful scale is about an Angstrom.
It depends upon what you mean by the word "measurement". We say that we
measure distances down to a small fraction of a fermi in some physics
experiments, but the concept of "measurement" means something completely
Take a ruler and measure the distance across a kitchen table. That
PROCESS gives you a meaning for "distance", right? OK, here is one that I
give my physics students: What do you mean by the "distance" from here to
the moon? I promise you that nobody is going to make that "measurement" by
using the PROCESS that you used to measure the "distance" across the kitchen
table. So the meaning has completely changed.
For more about this topic, find the book "The Logic of Modern Physics,"
by Percy Bridgman. It is an old book, but his ideas are important to all
modern scientists. That is why I keep a copy on my library shelf.
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Update: June 2012