Kilogram, ampere, kelvin and mole redefined

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Flemur
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Kilogram, ampere, kelvin and mole redefined

Post by Flemur »

A mole used to be a small burrowing insectivorous mammal with dark velvety fur, a long muzzle, and very small eyes. It's hard to improve on that, but maybe they redefined it with bigger eyes so it'd look cuter.

https://www.sciencedaily.com/releases/2 ... 115556.htm
The new definitions impact four of the seven base units of the SI: the kilogram, ampere, kelvin and mole; and all units derived from them, such as the volt, ohm and joule.
The kilogram -- will be defined by the Planck constant (h)
The ampere -- will be defined by the elementary electrical charge (e)
The kelvin -- will be defined by the Boltzmann constant (k)
The mole -- will be defined by the Avogadro constant (NA)
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Re: Kilogram, ampere, kelvin and mole redefined

Post by xenopeek »

Flemur wrote:
Mon Nov 19, 2018 10:53 am
A mole used to be a small burrowing insectivorous mammal with dark velvety fur, a long muzzle, and very small eyes. It's hard to improve on that, but maybe they redefined it with bigger eyes so it'd look cuter.
You must have skipped chemistry in school. In chemistry, mole is a unit for the amount of a substance. The statute of limitations has passed on when I last had these classes so don't ask me to explain it better :lol: (And I was more into physics and math anyway.)

Wikipedia has a more detailed writeup about the changes to the SI units: https://en.wikipedia.org/wiki/2019_rede ... base_units

As I understand it these SI units used to be defined by (inexact) artifacts—like in the example of the kilogram a piece of platinum called the "international prototype kilogram" kept in a Paris vault—and are instead now redefined to exact values. It all reads like a good thing.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by kenetics »

It's about time!
(Actually, time is already exactly defined by oscillations of a caesium atom.)
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Re: Kilogram, ampere, kelvin and mole redefined

Post by Flemur »

xenopeek wrote:
Mon Nov 19, 2018 11:29 am
You must have skipped chemistry in school.
I would have preferred to skip chemistry, but "They" made me take some on the way to a masters in physics.

But in any case, it would be nice if moles were cuter.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by Faust »

xenopeek wrote:
Mon Nov 19, 2018 11:29 am

You must have skipped chemistry in school. In chemistry, mole is a unit for the amount of a substance.
.......
That's about the size of it .

It's a method for specifying the number of units of a substance present ( be they molecules , atoms , ions )
without getting involved with the specific weight / formula weight of those entities ..... it "levels the playing field " for want of a better term .
Avogadro had a firm grip on that notion .

But these are absolutely miniscule adjustments being discussed , and nothing to lose sleep over :D

..... and I know there are other physics nuts on this forum :mrgreen:
" And so it goes " - Kurt Vonnegut
The modern reality and the satirical parody are rapidly converging .

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Re: Kilogram, ampere, kelvin and mole redefined

Post by Portreve »

Flemur wrote:
Mon Nov 19, 2018 10:53 am
A mole used to be a small burrowing insectivorous mammal with dark velvety fur, a long muzzle, and very small eyes. It's hard to improve on that, but maybe they redefined it with bigger eyes so it'd look cuter.
Someone needs to seriously gimp the heck out of a picture of a mole.
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Re: Kilogram, ampere, kelvin and mole redefined

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Re: Kilogram, ampere, kelvin and mole redefined

Post by Moem »

Flemur wrote:
Mon Nov 19, 2018 11:55 am
But in any case, it would be nice if moles were cuter.
How can you even say that? Just look at them! :o Aww. Don't you want to hug them?

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Re: Kilogram, ampere, kelvin and mole redefined

Post by Flemur »

Moem wrote:
Sun Dec 02, 2018 9:31 am
Flemur wrote:
Mon Nov 19, 2018 11:55 am
But in any case, it would be nice if moles were cuter.
How can you even say that? Just look at them! :o Aww. Don't you want to hug them?

Image
Awww. I wouldn't kill a mole but I might kilogram.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by MrEen »

kenetics wrote:
Mon Nov 19, 2018 11:32 am
It's about time!
(Actually, time is already exactly defined by oscillations of a caesium atom.)
That might change soon as well: https://www.universetoday.com/140712/a- ... could%20me

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Re: Kilogram, ampere, kelvin and mole redefined

Post by ajgringo619 »

Moem wrote:
Sun Dec 02, 2018 9:31 am
Flemur wrote:
Mon Nov 19, 2018 11:55 am
But in any case, it would be nice if moles were cuter.
How can you even say that? Just look at them! :o Aww. Don't you want to hug them?

Image
If I find out they're the ones digging up my yard, I'll be hugging them with a grenade! :twisted:
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Re: Kilogram, ampere, kelvin and mole redefined

Post by absque fenestris »

I am still looking for well-founded definitions of these widespread terms:
  • inch, foot & yard
    Anglo-Saxon drinking units
    and possibly the US dollar...
I know, historically it comes from Joachimsthal, body parts like fingers, hands and feets and estimates from some bartenders.

Is it also possible to be more precise?
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Re: Kilogram, ampere, kelvin and mole redefined

Post by catweazel »

Flemur wrote:
Mon Nov 19, 2018 10:53 am
A mole used to be a small burrowing insectivorous mammal
Image

Guaca mole.
"There is, ultimately, only one truth -- cogito, ergo sum -- everything else is an assumption." - Me, my swansong.

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Re: Kilogram, ampere, kelvin and mole redefined

Post by GS3 »

absque fenestris wrote:
Mon Dec 03, 2018 12:39 am
I am still looking for well-founded definitions of these widespread terms:
  • inch, foot & yard
    Anglo-Saxon drinking units
    and possibly the US dollar...
I know, historically it comes from Joachimsthal, body parts like fingers, hands and feets and estimates from some bartenders.

Is it also possible to be more precise?
I do not know what kind of definition you would want for a dollar other than unit of currency of the USA.

All the others are defined in terms of metric units. For instance, an inch is defined as 25.4 mm.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by absque fenestris »

...all the others are defined in terms of metric units. For instance, an inch is defined as 25.4 mm.
Schadenfreude: Napoleon is the winner - metric units...
About the Dollar:.. other than unit of currency of the USA. Yes. Just look for current price of recycled paper... :mrgreen:
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Re: Kilogram, ampere, kelvin and mole redefined

Post by Portreve »

xenopeek wrote:
Mon Nov 19, 2018 11:29 am
You must have skipped chemistry in school.
When I was in high school, from 86-90, Chemistry was not a mandatory class. In fact, you would have to have taken a couple other science classes first, and gotten through a lot higher level math classes than I ever took in order to get into it. Besides, if you weren't college-bound (and pursuing something science-related) is not likely to be of much use, anyway.

Moem wrote:
Sun Dec 02, 2018 9:31 am
Image
I must admit those are the cutest moles I've ever seen, Moem.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by xenopeek »

I was talking about what you may call middle school / junior high school (ages 12-14). In middle school we only had mandatory classes back then and chemistry was part of it IIRC. I got to select which classes to take in high school.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by notned »

They introduced moles to us by talking about volumes of gases. Once we could do that we could do anything.

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Re: Kilogram, ampere, kelvin and mole redefined

Post by Portreve »

xenopeek wrote:
Wed Dec 05, 2018 6:09 pm
I was talking about what you may call middle school / junior high school (ages 12-14). In middle school we only had mandatory classes back then and chemistry was part of it IIRC. I got to select which classes to take in high school.
I live in Florida. Our state educational results are towards to bottom of all states.

That said, things have changed over the years. We're still meh as far as educational quality is concerned, but we have upped our standards. I went to high school from 1986 - 1990, and when I enrolled, you needed four years of English, three of math, and two of science. By the time I graduated, I believe they'd upped the requirements twice, and so you had to have four years of all three.

I've never definitively been able to pin the cause down, but I have pretty significant comprehension and functional problems with math. It's actually kind of odd, since generally I'm pretty good at both abstract and analytical reasoning. I've always had problems keeping up with math class instruction, and when it comes to carrying out math problems (stuff above basic arithmetic) I can exhaust the number of things I can keep track of pretty easily, meaning I very quickly lose the plot, and with it the ability to understand or perform the problem. My range has increased with age, which leads me to believe there has been a cognitive stages of development component to it, but I still have issues.

In high school (9th - 12th grades) the highest I ever was able to complete was Algebra I. I had to drop out midway through Geometry because I just couldn't absorb and comprehend the materials. All throughout the K-12 process, especially from probably 4th or 5th grade on, I regularly struggled to be able to complete tests within the time allocated (50-60 minutes). In fact, where most students I knew took Pre-Algebra their first year of high school, I took General Math, followed by Pre-Algebra (which I failed and had to take in summer school), then Algebra I, which was all I was technically required to take, and I passed it with basically a C-. My idiot guidance counselor "suggested" I take Geometry, which as I already said I had to drop out before the teacher was forced to fail me. If I had been required to take higher level math classes, I don't know if I would have graduated from high school. I certainly would have been in there as an adult.

That is part of why I didn't pursue higher level science classes (apart from having no particular interest in them or need for them). I struggled to get through General Science and Biology I.
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Re: Kilogram, ampere, kelvin and mole redefined

Post by xenopeek »

I loved geometry :) The classes I finished high school with were statistics/probability, applied maths (covering algebra, functions, geometry, trigonometry and calculus), physics, chemistry, biology, economy and mandatory Dutch and English.

In college I had to take a year of advanced calculus and next a year of advanced algebra. That's when I considered I'd had enough maths :lol:
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