International Prototype Kilogram Losing Weight: The Untold Story

Background: The kilogram is the only SI base unit that is defined in relation to a physical object (the International Prototype Kilogram, or IPK) rather than in terms of fundamental physical properties. Recently it was discovered that the IPK had mysteriously lost mass when compared to copies that are otherwise identical. The following story may shed some light on the IPK's recent weight loss.

International Prototype Kilogram Hospitalized

International Prototype Kilogram: 
image courtesy of wikimedia commons

The International Prototype Kilogram (credit).

PARIS — The International Prototype Kilogram (IPK) has checked itself into a hospital, citing “extreme exhaustion,” a spokesperson for the Système International d'Unités (SI) said. The unnamed spokesperson, speaking on the condition of anonymity, would not reveal the condition of the IPK or the name of the hospital, added “the unrelenting schedule and awesome responsibility has taken its toll on the IPK and resulted in a state of extreme exhaustion for which it needs time to recuperate.”

Sister copies of the IPK, kept in an environmentally-controlled vault in the Bureau international des poids et mesures (BIPM), voiced their concern. “She has not looked very well lately; she lost almost 50 micrograms of mass and we've all been a bit worried,” said an IPK copy who gave her name as Jeannette.

The replica known as K20, designated as the primary mass standard in the US, was more critical. “‘Extreme exhaustion’ my [deleted]. Everyone knows of the heavy-duty partying lifestyle that the IPK indulges in. She could use a little time in rehab. She may be made of platinum and iridium, but that doesn't mean she's indestructible.”

The SI spokesperson discounted the claims made by K20. “Any claims of substance abuse by the IPK are totally without merit. The fact is, it has been working at defining the standard for the kilogram constantly since 1889 and that schedule would tire anybody.”

Another source at the BIPM speculated that talk of redefining the kilogram in terms of fundamental physical constants may have contributed to the IPK's illness.

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