@Background Pony #608C  
But we’d perhaps need a pony to represent platinum, since the prototype meter bars are made from a platinum/iridium alloy, ditto for the kilogram.

Does this mean that Applejack is International Prototype Pony?

@Parcly Taxel  
Nice!

@SeraphimDawn See my comment earlier.

@Parcly Taxel
 
Normal the metal is pretty scarce on this planet. What is it used for? I know it’s a very dense metal. Beautiful even.

@SeraphimDawn Indeed. Because of its unusually high abundance in a particular stratigraphic layer, we can be sure that an asteroid impact caused the mass extinction that killed off the sauropods.

Doesn’t this metal occur more in asteroids?

@Rdobet  
@Barhandar  
P.S. Also, absolute constants are fine and dandy, but most prototypes still will be purely physical items, calibrated to match the constant-derived values only at first iteration, same way we’re still running Newtonian mechanics unless the precision is insufficient.

@Rdobet  
And then someone finds out how to change that…

@Questionmarktarius  
https://derpiboo.ru/936570

@Parcly Taxel  
Well, sad as it is. It’s at least better than units be defined on something absolutely constant.

Yay, finally the table continues!

(hurr deep I can’t brain today)…
 
Iridium - Periodic Table of Videos

@Registered Anon Left in the storage archives.

@Parcly Taxel  
What do you mean by “left to the winds”? Chucked out or something? I figured at least some of them were put on display or something. I’m sure something similar will happen with the kilogram prototypes.

@FredMSloniker There were thirty metre bars made and handed out to national standards institutes like NIST. Some of them were put on display after the first replacement of the definition by a krypton wavelength standard, like the original one in the BIPM, while others were just left to the winds.

@Questionmarktarius  
Yes, but the question is, what did they do with them? Chuck them in the trash? Put them on display?

@Registered Anon  
Those beams didn’t cease being metres. They just ceased being the metre.

@Parcly Taxel  
I’m just curious what will happen to the International Prototype Kilogram (And the national prototypes) once the Planck standard comes into effect. I realize they will no longer define the kilogram (And will just revert back to being cylinders of platinum and iridium). I know the meter was also defined in terms of a physical prototype until it was redefined in terms of the speed of light, but I don’t know what happened to those. Maybe some of the prototypes will be put in museums.

Platinum/iridium objects have possibly the highest resistance to physical and chemical corrosion, which is why the kilogram is still defined by a cylinder of this alloy in Sèvres. Quite a shame, since in 2016 or so the SI committee will replace this with a Planck constant-based definition.
 
The element’s crustal abundance is very low in most places because the remainder sank into Earth’s core during its formation. Except, of course, the K-T boundary - the strongest evidence for the asteroid that extincted the dinosaurs.

@Questionmarktarius  
New headcanon: Derpy, lead poisoning?

I don’t think Derpy has sowed up yet.
 
Must be saving her for lead.

@Registered Anon  
It’s also used for tips of fountain pens and ink nibs, due to the long amount of time it takes to wear down combined with fortunately small quantities required. Which means the previous picture (osmium’s, with the pen) would fit here much better.

Only Applejack could make sitting on a girder look cute.