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Name: carol a jackson
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1995


Question:
What is the smallest measurement (anything smaller than a millimeter)?


Replies:
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.

asmith


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 different.

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.

jlu


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