Tag Archives: si units

Absolute Unit(s)

This makes me abnormally excited. I don’t know what it is with me and the SI units, but I dig ‘em, man.

And let’s be honest: I searched “kilogram” and read every related bit of info that came up, ‘cause the kilogram is my bro.

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*screeches in metric*

So y’all know I love the SI units, right? Hell, the “kilogram” tag on this blog is used frequently enough that it shows up in the “Tags” list on my front page.

Well, another closely-related thing I love are the SI prefixes. These are things like kilo or nano or yocto (which got its own blog a while back) that precede a unit and indicate either a multiple (like “kilo” suggests a thousand times something) or a fraction (like “milli” suggests a millionth of something) of the unit. Kilogram, nanosecond, millimeter, etc.

That kinda stuff.

Well, I guess four new prefixes have been proposed for the next levels of super big and super small: ronna and ronto for 1027 and 10-27 respectively, and quecca and quento for 1030 and 10-30, respectively. If they’re approved, they’re set to be officially put into place in 2022, making them the first prefixes approved since 1991.

And that is way too cool.

(I love the prefixes and I’m not sorry.)

 

HEAVY NEWS

It’s official! The definition of the kilogram (and a few other units) is being changed next May. Specifically, our buddy the kilogram will now be defined using the Planck constant as opposed to Le Grand K, the physical object that has been the kilogram since forever.

Very cool. Kinda sad, though. The kilogram will still be my favorite SI base unit, even though some of its uniqueness is being stripped away for more precision. Not that that’s a bad thing, but still…

My heart, she pounds

More kilogram news, people! It looks like our favorite non-conforming SI base unit is finally going to join the popular crowd and get defined by a physical constant rather than a physical object. It sounds like discussions are going to take place this year and a formal vote will take place next year.

Do you know how cool that is? We could possibly see a re-definition of the kilogram. A more precise definition.

That is seriously huge.

*breaks down your front door* HAVE YOU HEARD THE LATEST NEWS ABOUT THE KILOGRAM??

I’ve done a couple of posts about the kilogram, and if you’ve read any of them (or have done any reading about the SI units at all (‘cause that’s a common interest, right? (I mean, I can’t be the only one (…right?)))), you know that the kilogram is the only one of the basic seven measures that is still defined by a physical object rather than a calculation or constant.

Specifically, the mass of the kilogram is defined by an egg-sized alloy of platinum and iridium. This little dude sits beneath not one but three glass bell jars ion a climate-controlled, hermetically sealed room in Paris. Why? Because it’s the object that defines the kilogram, meaning that it is the benchmark against which all other kilograms are compared. So if it changes weight—due to dust or residue or moisture—the kilogram itself changes weight. In fact, it’s so important that the kilogram remains unchanged that it is only removed from its prison every 40 years in order to compare it to other similar replicas that are stored around the world.

These issues with the physical copy are the main reasons why scientists wish to define the kilogram with something that is an inherent standard in nature—like the speed of light or the wavelength of photons. For quite some time, physicists have been considering using the Planck constant as part of the definition of the kilogram. Specifically, the Planck constant could be used in conjunction with Einstein’s E = mc2 equation in a way that could determine mass solely through physical constants. However, no one has yet been able to actually measure the Planck constant to a level of precision that would surpass that of using the physical kilogram as the standard.

However, based on the current pace of progress, physicists suspect that they might be able to redefine the kilogram in terms of the Planck constant by as early as 2018, rendering Le Grand K, as the physical kilogram is known, obsolete.

Crazy, huh? Check out the article here!

I have nothing else today, sorry

Nate’s been catching me up on my Marvel movies (and by “catching me up” I mean “showing me all the Marvel movies ‘cause I’ve seen zero of them on my own”), which has gotten me thinking about that idea I had awhile back: a group of superheroes based on the seven base SI units: meter, kilogram, second, ampere, Kelvin, candela, and mole. The villains, of course, would have to be a group of people based on the Imperial units, like the foot, the pound, the gallon, etc. I think I’ve blogged about this before, but I’ve been thinking about it a lot recently. I think it would be pretty entertaining.

Also: spring break is next week! That means the semester is almost half over. That’s scary.

In This Blog: Wikipedia Gets Sassy about the Kilogram

I’ve talked about the kilogram quite a bit on here, but I want to revisit it a bit. Mainly because of Wikipedia’s sassy little remark about the International Prototype Kilogram (IPK).

The other six base SI units (second, meter, ampere, Kelvin, mole, and candela), which used to be based on physical artifacts, are now defined in terms of physical constants for precision’s sake. For example, the meter was originally defined as 1/10,000,000 of the meridian through Paris between the North Pole and the Equator. It is currently defined as the distance travelled by light in a vacuum in 1/299,792,458 of a second.

Only the kilogram remains to be redefined in this new, more precise way.

The IPK itself is a small little cylinder of platinum/iridium and is stored in Sèvres, France. It is the internationally recognized artifact that is defined as having a mass of exactly one kilogram. So it is, in essence, the kilogram.

800px-CGKilogram

But of course, there are copies of it. Sèvres holds three; other nations have national prototypes. And that’s where things get interesting.

Wiki: “By definition, the error in the measured value of the IPK’s mass is exactly zero; the IPK is the kilogram. However, any changes in the IPK’s mass over time can be deduced by comparing its mass to that of its official copies stored throughout the world, a process called ‘periodic verification.'”

“Beyond the simple wear that check standards can experience, the mass of even the carefully stored national prototypes can drift relative to the IPK for a variety of reasons, some known and some unknown.”

And what does this drift look like? the IPK itself is the line at zero denoted with the K. The other lines represent the mass changes in various national prototype kilograms.

Prototype_mass_drifts

Well, hell. And the IPK itself, Wiki notes, may be changing as well (and likely is), though it is still the “base” against which every other national prototype is compared.

Yup, humans have been to the moon but can’t figure out how to keep the kilogram constant. I find that hilarious.

But here’s where I lost it when reading this article:

“The magnitude of many of the units comprising the SI system of measurement, including most of those used in the measurement of electricity and light, are highly dependent upon the stability of a 134-year-old, golf ball-size cylinder of metal stored in a vault in France.”

Ooooh, Wiki…a bit of attitude, eh?

My mom can attest to the fact that I laughed about this for like 10 minutes straight.

(all pics from Wiki’s Kilogram page)

TWSB: Weighty Matters

Happy Birthday, Stephen Hawking!

Woah, I had no idea he was in his 70’s. He’s like 40 years old in my mind for some reason.

I’m not going to BS my way through this and attempt to describe in any significant detail some of Hawking’s major discoveries and theories, so instead I’ll just post something that’s sciency but pretty much totally unrelated to Hawking. ‘Cause I’m dumb.

Anyway. The KILOGRAM!

The kilogram intrigues me. It’s my favorite SI unit. Of the seven basic SI units, it’s the only one still based on a physical object. The blog post actually started my This Week’s Science Blog series was, in fact, about the kilogram. At that time I’d read an article detailing how several of the actual “copies” of the kilogram—that is, the various chunks of metal that all once weighed exactly the same—have been damaged/broken over the decades, resulting in different countries’ kilograms all being defined as slightly different weights.

But now, scientists have discovered that several copies of the kilo have gotten heavier due to surface contamination in the form of carbon and mercury. The actual gain is no more than tens of micrograms, but that’s a big deal considering that things like radioactive materials are often restricted by weight. A few more micrograms of radioactive substance could mean a lot in some situations.

Scientists hope to “clean” the kilo using ozone and ultraviolet light, which would, according to research, not harm the actual metal. But a better solution according to many would be to actually redefine the kilogram based on some law of nature rather than a physical object—something that has been accomplished for the other six major SI units.

Hang in there, kilogram…your day of reckoning is coming!

Gives new meaning to “dropping a few kilos”

I’m thinking of having a weekly science-related blog, how does that sound for everyone? Such a plan will probably only last a month or so at most, but I like plans, so deal with it.

In the spirit of this new installation.  (Edit: apparently the LA Times hates direct links to their articles; sometimes this link works and sometimes it just goes to a list of articles. If it does this, just ctrl + F “kilo,” that should bring you there. It’s a worthwhile article to read).

When I get a new cat (because it’s inevitable at some point in my life, though I don’t dare let another living feline in the same house with Annabelle), I’m naming him Kilogram 20.

“…at least six copies of the kilogram have been lost or damaged over the years from war, clumsiness or other reasons.” That’s insanely funny. Haha, I guess on the bright side we can say the SI is “losing weight.”

Today’s song: So Rich, So Pretty by Mickey Avalon