Astronomers Fix the Astronomical Unit

gbrumfiel writes "The Astronomical Unit (AU) is known to most as the distance between the Earth and the Sun. In fact, the official definition was a much more complex mathematical calculation involving angular measurements, hypothetical bodies, and the Sun's mass. That old definition created problems: due to general relativity, the length of the AU changed depending on an observer's position in the solar system. And the mass of the Sun changes over time, so the AU was changing as well. At the International Astronomical Union's latest meeting, astronomers unanimously voted on a new simplified definition: exactly 149,597,870,700 meters. Nobody need panic, the earth's distance from the sun remains just as it was, regardless of whether it's in AUs, meters, or smoots."

Comments

Re:let's not waste significant digits!

[icebike]

you'd think they could have rounded up to 150 gigameters.
if politicians can be SD-conservative, why can't astronomers? we all know that significance is precious and rare...

Interesting point.
If you are going to pic arbitrary number, why not pick an easy one?

I suspect there is a desire to keep all past references to AU meaningful within a small margin of error, so as to not have to translate any written works.
The difference between the new arbitrary number and the prior imprecise one is probably infinitesimally small for the scale of reference AUs are use for.

Rounding it up almost half a million kilometers (quarter million miles) maybe not so much.

I suspect that since it was imprecise in the first place, and used for almost nothing except astronomical reference, preserving existing references in the literature was more important than the ease of writing it down.