Wednesday, May 18, 2022

Lāhainā noon, May 2022

Now that I'm back in the tropics again, I got to experience a uniquely tropical phenomenon today: at noon, the sun stood directly at the zenith overhead. In Hawaii, such days are known as “lāhainā noon” days, after a contest held by Bishop Museum in 1990 in which that was the winning entry. Briefly, as the Earth travels around the sun, the latitude at which it appears directly overhead (the subsolar point) varies from +23.5° on the June solstice to −23.5° on the December solstice. Points at those latitudes will see the sun reach directly overhead on just that one day, but points between the Tropics of Cancer and Capricorn will see the sun pass directly overhead twice a year. On the equator this happens on the equinoxes, then steadily closer to the solstices the further away you get.

Here in Hilo, at a latitude of +19.7°, the two lāhainā noon days are May 18 and July 24 (at least for 2022, it's possible the exact day could shift by one depending on e.g., whether it's a leap year). So this is the first one I've experienced since moving back at the end of September last year. For the next two months, roughly, the sun will appear north of zenith in the sky. Directly at lāhainā noon, however, shadows are cast straight down, so tall straight objects like flagpoles effectively have no shadow. I tried to get some photos, but there was a haze of clouds over the sun that made shadows very faint—I could make them out by eye, but they didn't really come out well on camera. I'll just have to wait for July to try again.

Oh, and if you're wondering about the name, it comes from the Lāhainā region on the island of Maui, which, being on the leeward side of the island, is prone to droughts. It can be translated fairly literally as “cruel sun.” Another, older, Hawaiian name for this phenomenon is “kau ka lā i ka lolo,” which has the humorous translation of “the sun rests upon the brain.” Anyway, that's all for now. Hopefully I'll be able to get some photos next time the sun comes around overhead. A hui hou!

Tuesday, May 17, 2022

Birthday #33

Another trip around the Sun, another birthday. The first one I've spent in Hilo since 2017, in fact. Which in itself is a birthday present. We finally got some belated winter rain for most of April and the beginning of May, but the weather's been really pleasant these past two weeks or so, with a mix of brilliant sunny days, enough clouds to keep it from getting too hot, and light showers.

This past weekend was AstroDay here in Hilo (also my 137th birthday on Mercury!), annual event where various observatories and astronomy-related organizations (like the UH Hilo astronomy department) set up tables in the mall and engage with the public. I've volunteered before both as an undergrad and with the JCMT, but the latest I would've done it would've been 2015, so it's been a while since I last participated. This time I was at the Gemini Observatory table with a few co-workers, and while it was rather draining (so many people!) it was also a really positive experience. It's nice to interact with a generally very supportive and interested public and engage in some outreach, and with the pandemic this was also my first chance to really work together with some of colleagues in person.

Anyway, I'm off to play board games with some friends as a birthday get-together this evening. Here's to many more birthdays in Hawaii!