IAU redefinition of the astronomical unit

New Scientist: Sizing up a new measuring ruler for the solar system

The IAU has voted to change the definition of the astronomical unit. It is now defined as being exactly 149597870700 metres, and the symbol has been changed to "au" rather than "AU".

Why not exactly 150 mln

I get the redefinition by why the change in capitalisation? It will be hard at first to get used to that...

tommi59 wrote:

Why not exactly 150 mln

Probably to avoid changing the definition of AU too drastically.

Hmmm apparently the IAU has been recommending the use of "au" since before this announcement, e.g. the IAU style manual (1989) (pdf)

The International Bureau of Weights and Measures on the other hand recommends "ua", see BIPM: Table 7 "Non-SI units whose values in SI units must be obtained experimentally"

So I suspect everyone will utterly ignore it and continue to use AU capitalised as before...

Maybe they thought AU was to close to their abbreviation? Sounds silly, but there was a little blow-up between the World Wildlife Foundation and the World Wrestling Federation...the latter ended up changing to WWE.

-M-