Thinking Science: Using well-defined terms.

The important point is that I can derive the length of a meter without knowing the length of a meter beforehand. I explained how in the first post on the previous page.

If I can count vibrations in Cesium-133 and experimentally measure the distance light travels in this time... I can accurately calculate the length of a meter.

Do you accept this?

The important point is the fact that the definitions of the speed of light and the meter are circular and your subterfuge with your own definition of the term doesn't negate the fact.

I am trying to have an informative discussion (rather than a silly argument).

I wish you you either accept my explanation, or explain your problem with it.

InfraBlue is demonstrating the problem with imprecise language. I think the problem is the phrase "circular definition". I think we disagree on what it means.

If I say...

1. An hour is defined as 1/24th of a day.
2. A day is defined as 24 hours.

These aren't circular definitions. They are really the same definition. Neither is incorrect. Mathematically speaking, they are both setting the relationships between hours and days. The reason that this works is that these words can have multiple definitions which allow you to derive the length of an hour or a day through "experimental" means.

Why do you wish that I or anyone would accept your explanation that's based on your own definition of the term "speed of light" when it is incorrect?

Your example doesn't apply since the argument isn't about different ways of defining the term "speed of light." It's about the circularity of the one definition—which isn't the one of your invention—of the term "speed of light."Clearly, you've demonstrated that you do not understand the meaning of circularity. What's more, your understanding is further muddled by your use of your own definitions.

I assert that The speed of light is the distance travelled by light per unit time.

You don't accept this. I gave you a link explaining how speed is measured. You didn't accept it (or maybe you didn't accept that the "speed of light" is actually the speed... of light). I think that is our disagreement. Let's leave it there.

This shows the problem with using imprecise language to reason about scientific terms.

Your assertion doesn't address the definition of "the speed of light," which is what my argument is all about.

Your straw man argument about your assertion is moot.

The story about how science landed on this definition of a meter is an interesting one.

In Isaac Newton's time, a meter was defined as "1 millionth of the distance between the equator and the north pole". They couldn't measure this that accurately... but then again they didn't have very accurate clocks either at that time. If one person's meter was a little different than someone else's meter, it could be worked out. I don't... but I imagine that people used "reference meters".

As science advanced and clocks got better and measurements in general were more accurate, the definition of the meter based on the Earth no longer worked (for one thing, the changes by a slight amount depending on where and when you take the measurement). So they invented the "reference meter" in the late 1880s. This was an actual bar of metal. From time to time, they would cut a bar that was the exact same length, and these copies were copied and you got a bunch of "meters" that were all pretty much the same size.

At this time scientists were making more and more accurate measurements about the speed of light. In 1867 the value for the speed of light was 299,910 plus or minus 50 meters.

By 1972 we got down to a value of 299,792.4574 plus of minus 1/1000 of a meter. This was still measured using the reference meter bar, but it became ridiculous. It is very slight, but any metal expands and contracts based on tiny changes in temperature pressure... this level of accuracy for the speed of light is greater than the accuracy of the metal reference bar.

It was in 1983 that scientists decided to fix the speed of light. Any new measurements would make the meter more accurate.

Before, we had a reference meter which we used to calculate the speed of light. Now we have a reference speed of light which we use the calculate the length of a meter. Either way, the value can be established by experiment.

Once you understand this change in 1983, it makes perfect sense.

(I don't know if this explanation is better than mine).

https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html#:~:text=Since%201983%20the%20metre%20has,light%20exactly%20299%2C792.458%20km%2Fs.

The term "metre" (meter) wasn't defined "in Isaac Newton's time" - simply, because only on July 11, 1792 8nearly 60 years after Newton's death) the 'Académie des Sciences' made the first ever definition: Nous fixons l'unité de mesure à la dix-millionième partie du quart du méridien et nous la nommons mètre. ("We fix the unit of measurement at the ten millionth part of the quarter of the meridian and call it metre.") Source



Woodcut dated 1800 illustrating the new decimal units which became the legal norm in France on 4 November 1800, five years after the the metrical system was first introduced. In the captions, each one of these six new units is followed by the old French unit in brackets: the litre, the gram, the metre, the are (100 square metres), the franc, and the stère (1 cubic metre of wood). Source

Interesting Walter.

I was wrong about the meter in Newton's time. I just looked it up, they had feet and inches in Newton's time. These measurements were defined in terms of body parts. The meter was an advance!

I should add feet and inches to my explanation, and say the meter was "just after Newton's time".

Thanks.

The metric system came about during the French Revolution, it was part of the age of reason.

They tried to do the same thing with the calendar but it didn’t catch on.

I thought most college graduates knew that, but even when it’s a subject you know, and a thread you’ve started you still end up pulling ‘facts’ out of your arse.

It’s like you’re a mission to prove you’re a ******* idiot.

Hi Izzy

That’s no excuse.

Don’t post when you’re off your tits is a good rule of thumb for people like you.

Well, even that wouldn't accurate.

Metre (meter) is actually the French term "mètre" (The word "mètre" had already been used in the French language for more than a century in compound words such as thermometer (1624) or barometer (1666) (thermomètre resp. baromètre.)

So instead of adding just 'feet' and 'inches' you better had used the units of measurement in France before the French Revolution.
[One of Charlemagne's units of measure - the pied du Roi (the king's foot) remained virtually unchanged for about a thousand years By the time of the revolution, the number of units of measure had grown to the extent that it is almost impossible to keep track of them, especially, if you look over the French border e.g. to Germany - perhaps that's why we learn such at school.]

The metre is part of the decimal numeral system ...



... and decimal numerals were taught in Germany already in the early 16th century.

I am scientist/engineer, not a historian (as you can see ).

I did a little checking after you corrected my historical inaccuracy. Apparently Newton did refer to "feet" in his writings (he was English). He used a bunch of other units for length including the apparent size of Jupiter.

Standardizing the meter was pretty important once we started to advance in the field of Physics.

You don’t acknowledge making **** up about Newton.

I’m no scientist, but I still don’t feel the need to make **** up about the periodic table or cosines.

That’s the difference, there’s no shame in not knowing something, but there is in making crap up.

We all know Newton was English. He appeared on the ‘new’ pound note.

Not only but especially there, correct work must be done.

Newton wrote in Latin and used the Paris inch/foot. (The Paris inch is longer than the English inch and the Vienna inch, although the Vienna inch was subdivided with a decimal, not 12 lines.)

My point was about the definition of the term "meter" and how it was defined through its various stages in history. I retract the phrase "In Newton's time". This phrase was clearly wrong.

I made another mistake. There was period of time where the length of a meter was defined by a wavelength that I forgot about.

I believe the basic narrative is correct. It each stage they had a way to define the length of a meter that corresponded to a physical measurement. As science progressed, they adapted to allow for more precise measurement. Science relies upon well-defined terms.