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Main Boards => News and Articles => Topic started by: ninthace on 18:02:12, 17/06/20

Title: British Definition of the Metre Amended.
Post by: ninthace on 18:02:12, 17/06/20
For those of us who walk in metres, I bet you missed this one:


The Weights and Measures Act 1985 has been amended to include a revised definition of the metre.
See http://www.legislation.gov.uk/uksi/2020/586/article/2/made
To save you the trouble the revised definition is as follows:


"for which the symbol "m" is used, is the SI unit of length, defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m/s, where the second is defined by taking the fixed numerical value of the caesium frequency ΔvCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s↑-1."


So now you know.  And for those of you who still walk in imperial - an inch is defined as 2.54 cm so you are walking in metric even if you didn't know it  O0
P.S.  If you are on a diet a kilogram is now:


“for which the symbol “kg” is used, is the SI unit of mass, defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 x 10↑-34 when expressed in the unit J s, which is equal to kg m2 s↑1, where the second is defined by taking the fixed numerical value of the caesium frequency ΔvCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s↑-1.”


Isn't science wonderful?  :)

Title: Re: British Definition of the Metre Amended.
Post by: pleb on 19:30:13, 17/06/20
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Title: Re: British Definition of the Metre Amended.
Post by: SteamyTea on 21:20:38, 17/06/20
Now explain, in clear English, why the derived units i.e. newton, pascal, joule
Are capitalised when abbreviated i.e. N, Pa, J.
But written in lower case when in long hand i.e. newton, pascal, joule.
Eventhough they are named after real people i.e. Newton, Pascal, Joule.


And why is the kilogram the odd one out?  It should be the gram.
Title: Re: British Definition of the Metre Amended.
Post by: GnP on 21:46:40, 17/06/20
Thanks for the heads up . !!

I just don`t know how I missed that . O0
Title: Re: British Definition of the Metre Amended.
Post by: Mel on 23:35:13, 17/06/20
Can I have some of what you're drinking Mr N?  Might help me understand that better  :D
Title: Re: British Definition of the Metre Amended.
Post by: ninthace on 01:06:18, 18/06/20
Can I have some of what you're drinking Mr N?  Might help me understand that better  :D
It still does not explain how my out and back walk today was further in one direction than the other.  Perhaps I had a duff batch of caesium.  ;)
Title: Re: British Definition of the Metre Amended.
Post by: Bigfoot_Mike on 06:25:19, 18/06/20
Is it only the British versions of the metre and kg that are defined in this way? Am I a different height and mass if I travel abroad? If so, what happens to me while in transit, or does that depend on the nationality of the carrier?
Title: Re: British Definition of the Metre Amended.
Post by: SteamyTea on 07:59:30, 18/06/20
Is it only the British versions of the metre and kg that are defined in this way? Am I a different height and mass if I travel abroad? If so, what happens to me while in transit, or does that depend on the nationality of the carrier?
The French use it, so you are safe there.
Title: Re: British Definition of the Metre Amended.
Post by: richardh1905 on 08:45:30, 18/06/20
I struggle to see what this has to do with walking.  ::)
Title: Re: British Definition of the Metre Amended.
Post by: ninthace on 09:56:38, 18/06/20
Is it only the British versions of the metre and kg that are defined in this way? Am I a different height and mass if I travel abroad? If so, what happens to me while in transit, or does that depend on the nationality of the carrier?
Yet again, I think it is a case of HMG catching up with the rest of the world so I think your dimensions in transit will be ok, provided you travel at a sensible velocity.
Title: Re: British Definition of the Metre Amended.
Post by: Bigfoot_Mike on 18:58:50, 18/06/20
I struggle to see what this has to do with walking.  ::)
The distance we walk and the mass we carry are now different.  :)
Title: Re: British Definition of the Metre Amended.
Post by: SteamyTea on 21:21:22, 18/06/20
The distance we walk and the mass we carry are now different.  :)
Or the same, but described differently.
Title: Re: British Definition of the Metre Amended.
Post by: GoneWest on 08:11:29, 19/06/20
Or the same, but described differently.


Indeed. It's all relative, after all.
Title: Re: British Definition of the Metre Amended.
Post by: myxpyr on 16:00:37, 19/06/20
Well, I always know how many miles I've walked. Why would I want to know how many kilograms I've walked? ;D O0
Title: Re: British Definition of the Metre Amended.
Post by: ninthace on 16:28:27, 19/06/20
Well, I always know how many miles I've walked. Why would I want to know how many kilograms I've walked? ;D O0
Depends on if you can walk fast enough - the faster you walk, the heavier you get.   O0
(https://www.physlink.com/education/askexperts/Images/ae388c.gif)
 
Title: Re: British Definition of the Metre Amended.
Post by: myxpyr on 16:49:41, 19/06/20
 ???
Title: Re: British Definition of the Metre Amended.
Post by: Mel on 17:07:59, 19/06/20
......- the faster you walk, the heavier you get.   O0
 


Does that theory work in reverse?  :D



Title: Re: British Definition of the Metre Amended.
Post by: ninthace on 18:24:59, 19/06/20

Does that theory work in reverse?  :D
In theory yes - if you can come to a dead stop relative to the universe, but you had better be good at holding your breath as you would  have to leave the earth behind  ;)   
Title: Re: British Definition of the Metre Amended.
Post by: Cooksbridge Monkey on 18:34:10, 19/06/20
In theory yes - if you can come to a dead stop relative to the universe, but you had better be good at holding your breath as you would  have to leave the earth behind  ;)
Here's something to try next time you're in a lift. Before it starts going down bend your knees slightly. Then, as soon as it starts going down, straighten your knees suddenly. For a micro second you should be weightless O0
Title: Re: British Definition of the Metre Amended.
Post by: Bigfoot_Mike on 20:10:39, 19/06/20
Here's something to try next time you're in a lift. Before it starts going down bend your knees slightly. Then, as soon as it starts going down, straighten your knees suddenly. For a micro second you should be weightless O0
.. but you would still have the same mass.
Title: Re: British Definition of the Metre Amended.
Post by: Bigfoot_Mike on 20:13:11, 19/06/20
Depends on if you can walk fast enough - the faster you walk, the heavier you get.   O0
(https://www.physlink.com/education/askexperts/Images/ae388c.gif)
 




Not only do you get heavier, but your length also decreases. Does this mean that faster walkers are denser than slower walkers?  :)  PS how did you get the formula to appear? I can’t get the equivalent for length to show.
Title: Re: British Definition of the Metre Amended.
Post by: ninthace on 20:52:33, 19/06/20
Not only do you get heavier, but your length also decreases. Does this mean that faster walkers are denser than slower walkers?  :)  PS how did you get the formula to appear? I can’t get the equivalent for length to show.
You mean?
(https://wikimedia.org/api/rest_v1/media/math/render/svg/37ae2718b3d30ba8c8f9019bedde2e289f1f3b28)
We know a poem about that don't we boys and girls?


There was a young man called Fisk
Whose fencing was exceedingly brisk
So fast was his action
The Lorentz contraction
Reduced his rapier to a disk


(With apologies to Fitzgerald)
P.S.  You can work wonders moving equations around if you copy them as images Mike