The Science of Measurement

I refer to physics as the science of measurement because when we practice this elegant science we are always taking things from a given perspective or most specifically from a point of reference.

In his book Relativity, Albert Einstein pondered about a scenario in which he was sitting on the platform of a depot watching a train go by. As he watched the train go by he noticed that there was a man in the train looking out the window directly at him. Einstain's question became..."Which one of us is moving?" It had occurred to Einstein that as he looked at the man in the train going by it appeared that the train was moving. But as he considered the facts he realized that the man in the train could have said the same thing. So, I now pose the question. Which man is moving, Einstein on the platform or the man in the train?

The first gut response to this query is to say 'hey, wait and minute...any first grader knows that the train is moving.' Well then, if it is so easy then prove it. Then someone will say 'but everything is moving in the universe so they are both moving...it's a dumb question'. Again, I say prove it. Then someone else says 'do you think someone is spinning the world around under the train?' As you can see this idea sparks a very active discussion.

There is no way to prove which one of the two men is moving without first defining a point of reference. This then makes it easy for Einstein to say "from my perspective the man in the train is moving." So if Einstein on the platform is defined as the point of reference then the motion of the train can be validated and measured. The man on the train can do the same thing. By defining himself as the point of reference he can validate and measure Einstein's motion.

I hope this can help you understand that all physical entities dealing with motion and dynamics are relative to a point of reference and this makes them measurable. This is why I call physics the science of measurement.

Here are some thoughts for discussion:

• Is it really all that important to analyze a measuring device in order to express your measurements in the proper number of significant figures?
• What is a significant figure?
• What about when you are using your calculator and and you get an answer that is expressed in about nine figures...can you just use all nine or so figures...doesn't the calculator give only valid ssignificant figures...afterall, it is a very modern device?
• What about the numbers themselves...are they O.K. to use by themselves or do they require a unit of measure? If so, what purpose does the unit of measure serve?

Comment on these thoughts as you respond to this blog. When you are finished read some of the responses of your peers and comment on one of them. Keep it cool and sign only your first name.