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NIST to redefine the kilogram based on a fundamental universal constant

washingtonpost.com

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Re: NIST to redefine the kilogram based on a fundamental universal constant

#71

Post by jasonwatkinspdx »

cpr wrote: post #42

An interesting (banned) TEDx talk by Rupert Sheldrake, one part on the changing "fundamental constants", starting here: https://youtu.be/JKHUaNAxsTg?t=591 The other parts are a bit "woo" and I'm sure would be laughed at by the HN crowd. But his points about fundamental "constants" changing, and the metrologists' dogmatic (really, anti-scientific) response, are worth pondering.

Just in case folks are unaware, this is the parapsychology guy that believes the following:

> Sheldrake's morphic resonance hypothesis posits that "memory is inherent in nature" and that "natural systems, such as termite colonies, or pigeons, or orchid plants, or insulin molecules, inherit a collective memory from all previous things of their kind" ... Sheldrake proposes that it is also responsible for "telepathy-type interconnections between organisms". His advocacy of the idea encompasses paranormal subjects such as precognition, telepathy and the psychic staring effect as well as unconventional explanations of standard subjects in biology such as development, inheritance, and memory.

The reason his TED talk was pulled is because he's a crank, and the entire talk is a confused defense of pure BS.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#72

Post by tankenmate »

astrodust wrote: post #61
sanxiyn wrote: post #3

> Scientists don't know whether the BIPM prototype is losing mass, perhaps because of loss of impurities in the metals, or if the witnesses are gaining mass by accumulating contaminants. Can we stop this nonsense? It would be a big problem if it were true, but it isn't. It's the later (contamination weight gain) and we have fairly good understanding of what's going on. For example, see https://phys.org/news/2013-01-k…

Do they account for potential variations in gravity where they've been doing the measurements? Given how ridiculously sensitive the equipment is the position of the moon probably has an impact on the readings they're getting.

Balance scales work independently of gravity, both sides of the scale are equally affected.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#74

Post by hluska »

ramshorns wrote: post #34
kiernanmcgowan wrote: post #11

The kilogram is not the only unit that will be redefined based on universal constants. The seven base units[0] will transition to being based on elementary charge and the Planck, Boltzmann, and Avogadro constants[1]. [0] https://en.wikipedia.org/wiki/SI_base_unit#Seven_SI_base_uni... [1] https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_ba...

Four of the seven physical constants used to define the seven base SI units will change, so a bunch of physical constants that currently have exactly defined values will start being subject to measurement uncertainty. So μ_0 will no longer be exactly 4π × 10^-7 H/m, k_C = 1/4πε_0 will no longer be exactly 8,987,551,787.3681764 N m^2/C^2, and 1 mol of carbon-12 will no longer have a mass of exactly 12 g.

I don't actually know what any of that means (this is either impostor syndrome or I'm just dumb), but it reminds me of why I love Hacker News so much.

Now to Google to figure out what the heck you just said...:)

Re: NIST to redefine the kilogram based on a fundamental universal constant

#75

Post by spiralganglion »

Jyaif wrote: post #49
ramshorns wrote: post #34

Earlier quoted context omitted.

Four of the seven physical constants used to define the seven base SI units will change, so a bunch of physical constants that currently have exactly defined values will start being subject to measurement uncertainty. So μ_0 will no longer be exactly 4π × 10^-7 H/m, k_C = 1/4πε_0 will no longer be exactly 8,987,551,787.3681764 N m^2/C^2, and 1 mol of carbon-12 will no longer have a mass of exactly 12 g.

Why can't they update the Avogadro constant and keep having 1 mole weight 12g of carbon 12?

And for that matter, isn't it a bit frivol to call it a constant, if it's based on something mutable? Perhaps "the Avogadro number" would be a more appropriate name.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#76

Post by undersuit »

randlet wrote: post #57
GCA10 wrote: post #48

Earlier quoted context omitted.

I was about to argue that the illegal drug trade might be a counter-example, but haven't they gone metric, too?

Even if they did use the imperial system, no drug dealer is going to care about a change in the 8th decimal place of the definition of the pound.

Carfentanil is LD50 at 0.05mg. Don't be Bill Gates, 640KB is not enough for everyone and the 8th decimal of the pound is a lethal dose of Carfentanil.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#77

Post by randlet »

undersuit wrote: post #76
randlet wrote: post #57

Earlier quoted context omitted.

Even if they did use the imperial system, no drug dealer is going to care about a change in the 8th decimal place of the definition of the pound.

Carfentanil is LD50 at 0.05mg. Don't be Bill Gates, 640KB is not enough for everyone and the 8th decimal of the pound is a lethal dose of Carfentanil.

I stand corrected! Thanks.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#78

Post by analog31 »

amptorn wrote: post #69
grondilu wrote: post #23

Earlier quoted context omitted.

Slightly off-topic, but looking at the temperature section in your second link reminded me of the latest video from Linus Tech Tips[1] where he gets bashed for using the expression "degrees Kelvin". Personally, I don't see the problem. Since a kelvin is a hundredth of the difference between boiling and freezing temperatures of water, there is a notion of scale so the term "degrees" makes sense. 1. https://www.youtube…

Yes, in the same way that a half-marathon is 13 degrees mile long.

The half-marathon is a race that commemorates the Greek soldier who ran halfway from Marathon to Athens after the Battle of Marathon.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#79

Post by analog31 »

ZeljkoS wrote: post #13

Interesting fact: this is important for US too, because pound is defined as exactly 0.45359237 kg ( https://en.wikipedia.org/wiki/Pound_(mass)#Current_use )

Indeed, all of the US units are defined in terms of metric standards. There is no standard inch.

Re: NIST to redefine the kilogram based on a fundamental universal constant

#80

Post by analog31 »

slim wrote: post #30

It does not make sense, practically. So they'll be using a balance with multiple moving parts made of multiple minerals that have to be precisely calibrated with margins of error adding up, instead of a simple platinum cylinder? Although, it makes sense politically

I wouldn't say politically, but I'm sure that scientific aesthetics play a role. There are people who have devoted their careers to the development of fundamental standards. We search for the next digit of h, for the same reason why we search for the Higgs particle -- because we're curious.

A better kilogram might not have a practical use right away, but it might in the future, if for instance we want to do things like look for time dependent variations in the physical constants, tiny departures from existing theories of mechanics, etc.

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