Cheap but decent Mini Tape Measure

[Simon Williams 3Participant @simonwilliams3]

What Schrodinger failed to take into account is that cats can walk through walls. Cat owners (now there's an oxy-moron) have known this since pre-history, and Douglas Adams documented it.

Simon

[John FlackParticipant @johnflack59079]

Belatedly, I believe the official yard measurement Ia a metal strip located in Trafalgar Square, London.

Perhaps if an official measurement strip was considered necessary why upon metrication is the new metric official, presumably metre equivalent not provided? Or has the site been located elsewhere??????

[pgk pgkParticipant @pgkpgk17461]

The international prototype metre.. several of which exist and are distributed globally. I suppose it makes the french feel important

**LINK**

[John FlackParticipant @johnflack59079]

Please define 'A prototype metre'……………………..

[Jon GibbsParticipant @jongibbs59756]

Posted by Michael-w on 12/01/2017 12:07:13:

I hate that Schrodinger's cat idea, it's just stupid,

Michael W

…which was the whole point of course and why Schrodinger came up with it in the first place.

To illustrate what he saw as the strange nonsense when quantum mechanics is applied to real world physical things.

…and as Richard Feynman said… "If you think you understand quantum mechanics, you don't understand quantum mechanics."

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Jon Gibbs on 12/01/2017 11:55:06:

Posted by Michael Gilligan on 11/01/2017 23:47:18:

Posted by Jon Gibbs on 10/01/2017 11:40:52:

Yes but the most splendid irony IMHO is that the inch is now defined in terms of the metre

Now contemplate that the metre is ultimately defined in terms of time. **LINK**

http://www.bipm.org/en/publications/si-brochure/metre.html

So where does that put that most sacred of all units [the speed of light]

… Think about it …

MichaelG.

I think I'm missing your insight here. I have tried to think about it – honest

.

Jon,

My 'problem' with this is roughly as follows:

• The 'speed of light in vacuo' is taken to be a fundamental constant.
• but speed is measured in metres per second
• and the metre is defined in terms of the second
• so our fundamental constant is expressed something very close to a circular definition

… Does not compute.

MichaelG.

[Jon GibbsParticipant @jongibbs59756]

Posted by pgk pgk on 12/01/2017 12:59:25:

I suppose it makes the french feel important

It's a strange person IMHO who begrudges anyone credit for having a good idea.

[Michael GilliganParticipant @michaelgilligan61133]

oPosted by John Flack on 12/01/2017 13:04:16:

Please define 'A prototype metre'……………………..

.

I presume your request is directed to pgk, but, as I'm here …. this quote from his link seems to suffice:

[quote]

A challenge of the newly formed International Bureau of Weights and Measures (Bureau international des Poids et Mesures, BIPM) in Paris was to construct international prototypes for the metre and kilogram and to distribute national copies for members of the Metre Convention. For the kilogram, it was agreed that the new prototype should be made from an iridium-platinum alloy. The 10% iridium/90% platinum alloy was chosen because of its high density, corrosion resistance and stability.

[/quote]

MichaelG.

[Jon GibbsParticipant @jongibbs59756]

Posted by Michael Gilligan on 12/01/2017 13:12:49:

• The 'speed of light in vacuo' is taken to be a fundamental constant.
• but speed is measured in metres per second
• and the metre is defined in terms of the second
• so our fundamental constant is expressed something very close to a circular definition

… Does not compute.

MichaelG.

Ahh, thanks but surely there's no circular argument if you go back to the definition of the second…

9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

…and a metre is distance travelled by light in a vacuum in 1/299 792 458 of that time.

So it's defined from the Caesium atomic standards used in GPS and is simply the distance covered by light in a vacuum in 30.663319 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

…that's not circular to me.

Jon

Edited By Jon Gibbs on 12/01/2017 13:26:25 – Ooops factor of 10 out!

Edited By Jon Gibbs on 12/01/2017 13:53:11

[John FlackParticipant @johnflack59079]

But the prototypes were deposited in 1880……….to check a metre do I have to check the speed of light????

All I want to do is make sure a round bit fits into a round hole!!!!!!! No wonder there are those who prefer Imperial.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Jon Gibbs on 12/01/2017 13:25:15:

…that's not circular to me.

Jon

.

Thanks for your view … I will think on it.

No-one else seems interested.

MichaelG

[Harry WilkesParticipant @harrywilkes58467]

Posted by Michael Gilligan on 05/01/2017 18:36:42:

If it's this model **LINK** https://www.thetapestore.co.uk/stanley-fatmax-2m-keyring-tape-measure-1-33-856

that certainly looks a bargain, Neil

Thanks

MichaelG.

Don't know if it was a bargain Michael but I purchased one from the link and it came to today and I have to say I'm most pleased with it

H

[richardandtracyParticipant @richardandtracy]

Posted by Simon Williams 3 on 12/01/2017 12:36:24:

What Schrodinger failed to take into account is that cats can walk through walls. Cat owners (now there's an oxy-moron) have known this since pre-history, and Douglas Adams documented it.

Simon

They can certainly get through shut & locked doors. One of ours has perfected the art of opening our kitchen fanlight and going through it in such a way it latches itself closed after he's done it. Had us baffled for years how he got out until he did it in front of us.

Regards,

Richard

[Jon GibbsParticipant @jongibbs59756]

Posted by John Flack on 12/01/2017 13:55:44:

to check a metre do I have to check the speed of light????

All I want to do is make sure a round bit fits into a round hole!!!!!!! No wonder there are those who prefer Imperial.

Well yes if you need to check the metre to within a few atoms but for most practical purposes the atmospherically controlled standard metres will continue to be close enough for us.

…but you seem to have overlooked the fact that the yard, inch, pound and pint are all defined from the equivalent metric quantities these days.

…but if you insist on denying the supremacy of the metre I suppose you could go back to first principles and define the inch as the distance covered by light in a vacuum in 0.778848302 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom 

Edited By Jon Gibbs on 12/01/2017 14:28:34

[pgk pgkParticipant @pgkpgk17461]

Posted by John Flack on 12/01/2017 13:55:44:

But the prototypes were deposited in 1880……….to check a metre do I have to check the speed of light????

All I want to do is make sure a round bit fits into a round hole!!!!!!! No wonder there are those who prefer Imperial.

You'll need a round standard for that. The limits if Pi should do….

[maurice bennieParticipant @mauricebennie99556]

At what temperature should this be carried out ?????

[Jon GibbsParticipant @jongibbs59756]

Posted by maurice bennie on 12/01/2017 15:30:25:

At what temperature should this be carried out ?????

A smidge above 0K…

**LINK**

[Neil WyattModerator @neilwyatt]

Posted by Michael Gilligan on 12/01/2017 13:12:49:

Posted by Jon Gibbs on 12/01/2017 11:55:06:

Posted by Michael Gilligan on 11/01/2017 23:47:18:

Posted by Jon Gibbs on 10/01/2017 11:40:52:

Yes but the most splendid irony IMHO is that the inch is now defined in terms of the metre

Now contemplate that the metre is ultimately defined in terms of time. **LINK**

http://www.bipm.org/en/publications/si-brochure/metre.html

So where does that put that most sacred of all units [the speed of light]

… Think about it …

MichaelG.

I think I'm missing your insight here. I have tried to think about it – honest

.

Jon,

My 'problem' with this is roughly as follows:

• The 'speed of light in vacuo' is taken to be a fundamental constant.
• but speed is measured in metres per second
• and the metre is defined in terms of the second
• so our fundamental constant is expressed something very close to a circular definition

… Does not compute.

MichaelG.

Second is defined in terms of the vibration of the ground state of a caesium atom.

Metre is therefore a derived unit from the speed of light and the vibration of the caesium atom.

You don't need to measure the speed of light in m/s second use it to derive the metre, just use an atomic clock to measure how far the light travels in one second, then use that distance as your standard to define the metre as a fraction of it.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Neil

… Maybe I'm getting there [albeit very slowly]

This from Wikipedia, makes some sense:

The number of fundamental physical constants depends on the physical theory accepted as "fundamental". Currently, this is the theory of general relativity for gravitation and the Standard Model for electromagnetic, weak and strong nuclear interactions and the matter fields. Between them, these theories account for a total of 19 independent fundamental constants. There is, however, no single "correct" way of enumerating them, as it is a matter of arbitrary choice which quantities are considered "fundamental" and which as "derived". Uzan (2011) lists 22 "unknown constants" in the fundamental theories, which give rise to 19 "unknown dimensionless parameters", as follows: … < etc. >

MichaelG.

https://en.m.wikipedia.org/wiki/Physical_constant

Edited By Michael Gilligan on 12/01/2017 18:30:26

[Another JohnSParticipant @anotherjohns]

Posted by Neil Wyatt on 12/01/2017 17:57:33:

Metre is therefore a derived unit from the speed of light and the vibration of the caesium atom.

IIRC Caesium was chosen because it only has 1 electron on its outer shell, and the atom itself is large (making a good target for the MASER used to "excite" it), but one has to grab the atoms whos' electrons have an incorrect spin before photons are counted, as the two different spins cause the electron jumps to be not the same.

Neil – I think you should just stick to whatever tape measure you have handy, and not bother with the rest!

JohnS.

[Flying FiferParticipant @flyingfifer]

Or use a bit of string !!!

[pgk pgkParticipant @pgkpgk17461]

Posted by Jon Gibbs on 12/01/2017 13:15:58:

Posted by pgk pgk on 12/01/2017 12:59:25:

I suppose it makes the french feel important

It's a strange person IMHO who begrudges anyone credit for having a good idea.

the history of the 'invention' and development of the metric system and credit for that is a different matter to the politics surrounding its implementation and where to store the reference standards.

Indeed its a very strange person who has no sense of humour and enjoys sniping at others

[V8EngParticipant @v8eng]

Posted by Jon Gibbs on 12/01/2017 15:51:48:

Posted by maurice bennie on 12/01/2017 15:30:25:

At what temperature should this be carried out ?????

A smidge above 0K…

I am very pleased to see that we are getting back to proper Model Engineering terminology.

[Gordon WParticipant @gordonw]

My understanding of all this is from reading Measuring the meridian- J Verne and watching the Big bang theory.

[Neil WyattModerator @neilwyatt]

I'm just eyeing my tape measure suspiciously wating for it to cry 'Vive l'Empeurer' and try to wrap it's metric tentacle around my neck…

Neil

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