Depends on their response to wavelengths at rest, including IR (for blueshift) and UV (for redshift)

So I looked it up and the mass change is actually positive, about 1 part per billion per year. Not evaporation but adsorption.

Duh. Do you think they’d change the value significantly? But now it’s actually constant and changes to that piece of metal will change nothing.

The pound has been defined as 0.453 592 37 kg since 1959, having relied on the slightly evaporating Parisian etalon for 60 years. You have no moral high ground.

The kilogram is no longer defined as the mass of the Paris etalon. Now it’s defined so that Planck constant ℎ = 6.62607015 × 10⁻³⁴ kg m²/s, where 1 s is 9 192 631 770 oscillations of ¹³³Cs and 1 m is how long light travels in 1/299 792 458 s in vacuum.

500M MT

Stacking metric prefixes. That’s how big the problem is. And a (metric) ton is a million grams. 500 Eg (exagrams) to 1 Zg (zettagram). You don’t get these numbers even with data volume! (edit: yes, on a global scale)

Edit: apparently “MT” is not metric megaton but metric ton. Fuck whoever abbreviates in non-standard ways. https://www.nayuki.io/page/common-mistakes-when-using-the-metric-system