Wikipedia:Reference desk/Archives/Science/2022 September 15
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September 15
[edit]Symmetrical variant of Kröger–Vink notation
[edit]Does any variant of Kröger–Vink notation exist where v and i are replaced by the same symbol? Besides making the symmetry of a Frenkel pair more obvious (e.g. NaØ + ØNa), this would also emphasize how crystals with a specific point defect fell on a continuum between two crystal structures. (For example, AFAICT a body-centered cubic crystal with vacancies in half the cell centers would be the same as a simple cubic crystal with interstitials in half the cell centers.) This in turn, I'd think, could lead to insights about how one structure might be transformed into the other through compression, injection and ventilation of gases, and/or annealing. NeonMerlin 09:36, 15 September 2022 (UTC)
Most-partiality of solar eclipse
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Assuming no change to local time zones or DST rules, at what local time during the solar eclipse of May 11, 2040 will the sun be most obscured in Melbourne? And is it likely to be obscured to the extent that someone looking at the Sun with appropriate protective equipment (e.g. eclipse glasses) will be able to notice it at all? This image makes it look like the eclipse will happen here from 0240 to 0450 UTC, which translates to 12:40-2:50PM under our current time zone and DST rules, but I don't know how to figure out when the sun will be most obscured, let alone how much. 175.39.61.121 (talk) 22:22, 15 September 2022 (UTC)
- The degree of occlusion as a function of time is almost perfectly symmetric around the maximum, so it will occur halfway between 02:40 and 04:50 UTC, at about 03:45 UTC. One should then see a substantial bite taken out of the Sun using suitable viewing equipment (which could be a pinhole camera obscura). In no way will it be spectacular; if one doesn't know an eclipse is happening, it may pass unnoticed. --Lambiam 23:35, 15 September 2022 (UTC)