Talk:Astronomical unit

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• Astronomical unit SVG.svg

Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 03:23, 14 October 2025 (UTC)

SIGFIGs

Any discussion of the recent change in SIGFIGs? I think I agree with it, but it would be nice if it was discussed. Gah4 (talk) 11:26, 5 February 2026 (UTC)

Are you referring to my recent revert of an anonymous edit? Johnjbarton (talk) 17:14, 5 February 2026 (UTC)

Yes. One is that I don't understand what {{convert}} does with sigfig=100, but it doesn't seem to give 100. In general, I am against excessive sigfigs, though for quantities that do have useful precision, I like to see it. Gah4 (talk) 09:49, 6 February 2026 (UTC)

Convert changes large sigfig values to be no more than 14 which experiment a long time ago showed matched what {{#expr}} does. Johnuniq (talk) 10:03, 6 February 2026 (UTC)

The standard is exact so in principle one could use infinite significant figures. The way one accomplishes this in the 21st century is to use the exact value in computer programs with appropriate precision arithmetic. No one doing precise work will type in a converted value with many significant figures.

In spirit the exact value reflects experimental results at 12 or maybe 13 significant figures. (It meaning and thus accuracy are not close to that I think). So I think 12 is a good value for the list. Alternatively we can delete the conversion table absent a source. Johnjbarton (talk) 17:35, 6 February 2026 (UTC)

And even more, there is no WP requirement that sigfigs reported agree with the source. But yes, users should compute the appropriate approximation needed, in unit systems that don't have a nice conversion. Gah4 (talk) 23:55, 6 February 2026 (UTC)

Experts writing computer programs will enter the exact value, or to as many significant figures as the precision of the chosen variable type will hold. If the value is represented as a floating point, there will be some more imprecision when the decimal value is converted by the computer to binary. If stored as an integer, the decimal to binary conversion will not affect the precision. Jc3s5h (talk) 17:41, 7 February 2026 (UTC)

Earth ~1au~ Mars

not to scale but the image https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Astronomical_unit_svg.svg/500px-Astronomical_unit_svg.svg.png leads me to believe that we (Earth) are ~ 1 AU distant from Mars. What do you think ~2026-23443-44 (talk) 16:04, 16 April 2026 (UTC)

I think it is true a bit less than twice a year since Mars takes longer than a year to orbit the Sun. Johnjbarton (talk) 17:12, 16 April 2026 (UTC)