# What would happen if someone broke the "Grand Kilogram" **URL:** \ **Category:** Factual Questions\ **Created:** [July 2, 2016, 3:31pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923 "2016-07-02T15:31:21Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [July 4, 2016, 6:28am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/21 "2016-07-04T06:28:19Z")
> [@bump](#): > > That was what I was going to ask- why not have it defined in terms of some fundamental constant, instead of as a specific object? Fundamental constants are also set by a consortium of national metrology institutions and the resolution of the defined constants are usually on par with existing measurement ability and eventually become the bottleneck of measurement uncertainty as technology advances. This is the reason they are periodically redefined. For example, if there is a constant called Bump’s constant and it is set at 1.23, it is not that the actual constant is 1.230000000000000, it’s that it is only known to two decimal places. It could actually be 1.230… or 1.239… or anything in between. So if you have a unit that you measure that is defined by frequency \* bump’s constant, you are really limited in how accurate that measurement is by the resolution of the constant regardless if you can measure frequency to a part in 10^13. ---
**Author:** ![PotatOS](https://avatars.discourse-cdn.com/v4/letter/p/85e7bf/32.png) [@PotatOS](https://boards.straightdope.com/u/PotatOS)\ **Post date:** [July 4, 2016, 6:33am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/22 "2016-07-04T06:33:26Z")
It would be a good thing. > [@nate](#): > > There is a big meeting coming up either this year or next, I can’t remember off-hand, where the the SI system will be redefined, I think the goal is to attempt to relate every unit back to fundamental constants and/or the second as time can be measured accurately to like 13 decimal places or something. As discussed in [this video](https://www.youtube.com/watch?v=ZMByI4s-D-Y), the official kilogram is losing weight, simply from erosion (and possibly decay of some isotopes? I didn’t re-watch it). Earlier systems for measuring temperature relied on some specific physical thing like “the ambient temperature in the deepest chamber of King Tut’s tomb”, and it’s pretty obvious why that’s a problem and we ended up switching to other systems. Treating one property of a specific physical object as a fundamental constant presents some major problems (even if it has copies, which are not perfectly consistent, despite our best efforts). Having to visit a certain location to calibrate your instruments is not least among them. It’s real pretty, but breaking THE kilogram into a million pieces would force science to improve a little bit faster. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [July 4, 2016, 8:27am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/23 "2016-07-04T08:27:49Z")
Isn’t the kilogram defined as the weight of 1000 grams, were a gram is the weight of a cube of water, one centimeter per side? A 10x10x10 cm cube of water should be usable as a reference kilogram. ---
**Author:** ![PotatOS](https://avatars.discourse-cdn.com/v4/letter/p/85e7bf/32.png) [@PotatOS](https://boards.straightdope.com/u/PotatOS)\ **Post date:** [July 4, 2016, 8:36am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/24 "2016-07-04T08:36:11Z")
No, the kilogram is the only base SI unit with a prefix. Historically, you’re right, but check out [this video](https://www.youtube.com/watch?v=ZMByI4s-D-Y). ---
**Author:** ![Adoschtinad](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Adoschtinad](https://boards.straightdope.com/u/Adoschtinad)\ **Post date:** [July 4, 2016, 10:34am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/25 "2016-07-04T10:34:22Z")
> [@Mangetout](#): > > Mass murder. > [@velomont](#): > > I guess the perpetrator would be a serial kilo. Hoooly shit you guys kilo’d it ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 4, 2016, 2:03pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/26 "2016-07-04T14:03:22Z")
> [@](#): > > Quoth **Sage Rat** : > > Isn’t the kilogram defined as the weight of 1000 grams, were a gram is the weight of a cube of water, one centimeter per side? A 10x10x10 cm cube of water should be usable as a reference kilogram. Water with what proportion of deuterium vs. regular hydrogen, and O-18 vs. O-16? At what temperature? Under what pressure? Yes, that was the basis for why the standard was chosen as it was, and it’s good enough for many purposes, but it’s not good enough to be the standard for all measurement. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 4, 2016, 3:29pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/27 "2016-07-04T15:29:43Z")
Um…OP cites the thread which this one is a _spinoff of_–and it’s not a prepositional grammar thread. It’s about the status, use, fact of, whatdoyoucallthis and whatdoyoucallthat of weight and mass. Yes, coppers! Come get me! I’m junior modding the fuck out of this thread! Top of the world, Mom! ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [July 4, 2016, 3:57pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/28 "2016-07-04T15:57:32Z")
From wikipedia, the summary of proposed [changes to the SI](https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_base_units): There will still be the same seven base units (second, metre, kilogram, ampere, kelvin, mole, and candela). Of these, the kilogram, ampere, kelvin and mole will be redefined by choosing exact numerical values for the Planck constant, the elementary electric charge, the Boltzmann constant, and the Avogadro constant, respectively. The second, metre and candela are already defined by physical constants and it is only necessary to edit their present definitions. The new definitions will improve the SI without changing the size of any units, thus ensuring continuity with present measurements. ---
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [July 4, 2016, 4:17pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/29 "2016-07-04T16:17:31Z")
The original was once made. I assume we could figure out how to make another! ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [July 5, 2016, 6:06am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/30 "2016-07-05T06:06:25Z")
> [@Chronos](#): > > Water with what proportion of deuterium vs. regular hydrogen, and O-18 vs. O-16? At what temperature? Under what pressure? One can assume that these values could be set so that they match the current weight. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [July 5, 2016, 6:48am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/31 "2016-07-05T06:48:55Z")
Wasn’t it in the plans to replace it with a silicon sphere sized to a mind numbing degree of precision? The idea being to change the standard kilogram to an exact number of silicon atoms represented to the best technical ability in said sphere. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 5, 2016, 10:49am UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/32 "2016-07-05T10:49:20Z")
Wait, they’re re-defining the mole as well as the kilogram? Does that mean that they’re abandoning the relationship between the mole and the gram, or that they’re redefining the atomic mass unit? ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [July 5, 2016, 1:26pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/33 "2016-07-05T13:26:35Z")
> [@Chronos](#): > > Wait, they’re re-defining the mole as well as the kilogram? Does that mean that they’re abandoning the relationship between the mole and the gram, or that they’re redefining the atomic mass unit? From the Wikipedia article: > [@](#): > > One consequence of this change is that the current defined relationship between the mass of the 12C atom, the dalton, the kilogram, and Avogadro’s number will no longer be valid. One of the following must change: > the mass of a 12C atom is exactly 12 dalton > the number of dalton in a gram is exactly the numerical value of Avogadro’s constant > > The draft SI brochure assumes the first will remain true, which would mean that the second will no longer be true. The molar mass constant, while still with great accuracy remaining equal to 1 g/mol, will no longer be exactly equal to that. ---
**Author:** ![Mogle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mogle/32/12021_2.png) [@Mogle](https://boards.straightdope.com/u/Mogle)\ **Post date:** [July 5, 2016, 7:29pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/34 "2016-07-05T19:29:09Z")
> [@Sage\_Rat](#): > > One can assume that these values could be set so that they match the current weight. Problem is, the Pascal is a derived unit that depend on the kilogram, so you couldn’t specify the pressure without first defining the kg. ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [July 5, 2016, 7:58pm UTC](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923/35 "2016-07-05T19:58:14Z")
Read a fascinating book some time back about the histories of various measures - from the king’s foot, to each town having its marketplace standard, to the physical representations and beyond. As I recall, solids simply decay - or erode as an earlier poster said. Not significant unless you are attempting to measure with this extreme degree of accuracy. And such things as dust, or oil from one’s hands, could throw it off. When the meter was in metal, it needed to be at a constant temp or it would expand/contract… Not sure if it was that or another book on the subject, that said the meter was originally calculated incorrectly, due to one of the teams of French surveyors fudging their data. Fascinating stuff. [Previous page](https://boards.straightdope.com/t/what-would-happen-if-someone-broke-the-grand-kilogram/758923.md?page=1)