Caoimhín's Content

In the last piece, I mentioned that we are coming up to the equinox. We are at least now closer to the coming equinox than we are to midwinter. If we were to move back into the recent past, back to midwinter, we’d see the Sun come down to its lowest noon high point. Moving forward into this year, the maximum height at noon would go up, and the Sun is still rising at this time of year. Moving further ahead past the equinox the Sun keeps rising, and then continuing up to its highest point for mid summer.

I mentioned in a past piece, much farther back, that this rising and falling traces out a shape in the sky, called the analemma. I have written about the analemma and the analemma from the equator in particular, so you can go back to those pieces if you would like. I will go through the view from the equator quickly, and exactly at the equator, 0 degrees in either direction, seems to be written as 0 degrees north The exact equator gets called north, which feels unfair. Maybe south-slash-north if you’re exactly at 0 degrees, or 0 degrees N/S, would be more fair. If you are in fact at the equator with the Sun right at it’s highest at noon, it will be around the equinoxes. The Sun will reach its furthest south for the northern midwinter and then it will come up across the zenith of the sky and reach its furthest north for the northern midsummer. At the equator, the Sun is actually at its highest, it’s closest to the middle of the sky, around the equinoxes. The Sun will be at its lowest either at midsummer or at midwinter, depending on what side of the equator you are and what you call your seasons. This low of course is still very high, higher than the highest point for far northern or southern latitudes. It’s a very different view when you’re at the equator. For places at or near the equator on certain days of the year, usually close to the equinoxes, the Sun is directly overhead. This can happen at other times for other locations on Earth as well.

I think we might as well start by hopping to the Sun, and looking back at the Earth from there. We’ll put ourselves bang on the Sun’s equator, and get rid of the “ground” or anything else that might get in the way. We’re going to find the Earth, which should be right above the Sun’s equator in some direction. If you are on Earth and you are in between the two tropics, the Tropic of Cancer and the Tropic of Capricorn, then you will have the Sun directly overhead at some point of the year. This is really all the tropics are, anywhere within 23.4 degrees of the equator. Looking back at the Earth from the Sun, whatever’s in the middle of our viewpoint is directly under the Sun, called the subsolar point. As the Earth turns, it makes a huge track across the Pacific, cutting across some of the Caribbean, across Africa, across the Middle East, and back into the Pacific. We’re seeing it a little north due to the northern summer date’s we’re viewing. Coming back into the Pacific a little, Hawai’i would be back here somewhere in the middle of the Pacific. In the Stellarium view I’m using it seems to be under the clouds, which seems odd, I don’t usually think of Hawai’i as a cloudy place. Hawai’i is in the tropics, within the Tropic of Cancer and the Tropic of Capricorn. I often forget which one is the top one or the northernmost one, it’s the Tropic of Cancer. Hawai’i is just south of the Tropic of Cancer and so it is one of those places where on certain days of the year when the Sun is directly overhead.

Coming back to Earth, we will head to Mauna Loa in Hawai’i. This is only 19 degrees north, so very close to the equator. We’ll come up to having the Sun in the middle of the sky, at least halfway between east and west, at noon but not yet the highest noon. There is a day of the year where the Sun is directly overhead for people who are in Hawai’i. It isn’t at it’s highest for the equinox, moving back in time a little bit, the Sun varies between being its farthest south for midwinter, and it really is in the south because we’re so close to the equator. It will come up to the zenith and then continue right up to its “highest”, or furthest north, point in the sky somewhere around northern midsummer. We’re in the northern part of the tropics, so it’ll come to its highest on two dates closer to midsummer. These are around May and July, but they vary depending on the island. For this, southerly, island, they are around the 18th of May, at least it was the 18th in 2001, and July 24th. Thanks to the time zones, it doesn’t happen exactly at 12 o’clock, it’s actually a little further ahead, around 12:20. For 2025, it also seems to be at the zenith on the 18th of May, but it does vary for different years, similar to midsummer.

This is Lahaina noon, it is the highest noon because it is when the Sun is directly overhead. Lahaina or Lāhainā in Hawai’ian, is one name for it as its occurrence in Hawai’i particularly well documented and observed. Lahaina noon doesn’t itself mean the highest noon, it means the Cruel Sun, because this is terrible. You can’t really get any shade unless you have something directly above you, any straight standing object that’s directly under the Sun like this isn’t going to cast a shadow. You can’t stand next to a house or a wall and get shade because the wall isn’t going to cast a shadow to the side, it would only cast a shadow straight down. An umbrella would work if you had an umbrella, or a parasol I suppose, directly over your head, then you could get protection from the cruel Sun. The Sun really beats down on your brains when it’s directly overhead, from what I’ve heard at least.

Of course the highest noon happens anywhere in the tropics, which covers many places. There is a time when the Sun passes directly overhead for Mecca, the Muslim holy site, the most holy site in the Islamic faith. At about 21 degrees north, it is a but further north, and has its subsolar day around the 28th of May and 16th of July. This is an an especially interesting thing, not because if the Sun is directly overhead, there will be no shadow for that location, but because for anywhere else the Sun will cast a shadow. Heading to the exact coordinates, we will come forward to daytime. We are already on what should be approximately be the right date, in Stellarium we are on what looks like the 27th of the 5th in 2025. Thanks to time zones again, at almost 12:30 is when the Sun is directly overhead for this particular location on the Earth, if the Sun is directly overhead, there will be no shadow cast by any straight upright object directly at this location. If you’re a few degrees to the west, or to the south, or to the north or to the east, there will be a shadow. As long as you know what time the Sun is directly overhead for this exact location, then you can use a stick and its shadow to point in its direction. By measuring the length of the shadow, you can work out how far away you are as well, as long as you know the length of the stick and a few other things, but how far away you are doesn’t matter too much, all that matters for this particular measurement is the direction.

So if you want to know where Mecca’s location is from your location, all you need to do is set up a stick at the time where it would be noon for it, allowing for time zones, and the opposite direction of that stick’s shadow is the direction of Mecca. The shadow will point away from the location where the Sun is at its highest point, so you’ll know if you’re to the east or the west, the north or the south, and it’s pretty accurate. This is useful if for any reason you need to know where this specific location is, if you need to face this direction a few times a day perhaps, then knowing that there is a date where you can locate it using the Sun and its shadow is very useful. Of course you could do the same for Hawaii if you wanted to know exactly where Hawaii was relative to you. All you’d need to do is erect a pillar, set up a stick on the correct date, and measure the shadow, it’ll point you in the right direction.

Another interesting thing, a further interesting point which I mentioned in the past article where I talked about the analemma, is how this relates to calendars. The solar calendar is very useful if you’re in the northern or southern hemisphere because you will have the summer when the Sun is high, the winter when the Sun is low. However, if you’re at the equator, the solar calendar isn’t quite as useful because summer and winter are just the extreme point of the Sun in opposite directions, and the equinoxes are whenever it’s roughly overhead. A lunar calendar can be even more useful if you’re on the equator, so a lot of cultures along the equator use a lunar calendar, including the Islamic religious calendar. However, when the Sun is directly overhead, that’s decided by the solar calendar. Here in the north where we use a solar calendar, we don’t know exactly what date will have a Full Moon in advance on unless we go and calculate it, because the solar calendar and the lunar calendar don’t line up. If you use a lunar calendar, then you’ll need to do specific calculations to figure out what day to the Sun will be directly overhead, because it will vary greater in a lunar calendar than it would in a solar calendar.

These are just a couple of interesting things about where the Sun is and how it looks when it gets directly overhead. I will hopefully talk about the sublunar point soon, but I wanted to get this piece on the subsolar point out before I talk about the sublunar point. There is a sublunar point as well, however it is far more variable, the Moon goes around us a lot quicker than we go around the Sun. I hope you found these strung together tidbits as interesting as I did. If you did then make sure to like this article and subscribe to this website and my YouTube channel if you’d like to see more. Hopefully I’ll see you back here next time.