As the summer solstice was last night (23:59 20 June 2008 UTC; 7:59 pm EDT on the 20th locally), today, the twenty-first of June, is the first full day of summer in Earth's northern hemisphere. And a few days earlier, on the 18th, the Moon was full.
So have you seen it lately? The full or near-full moon, that is? The full moon rises around sunset, and it's usually pretty noticeable.
You may not have. As noted above, we're near extrema of both the Sun and Moon. The Sun at the summer solstice is as high as it gets in the sky. The full Moon's path in the sky is about as low as it gets -- the full Moon's path is, in a rough sense, out of phase with the Sun's. (I'm not going to get into why this is, but please do note that I say "full" here.) And with the full Moon's path being so low, it's also much shifted to the south.
You've probably noticed the other side of this phenomenon. Think of full moons you've seen when it's getting cold -- say late fall and early winter: November, December, and January. They were way up high in the sky, weren't they? And the Sun's path is very low, which is why it's locally -- hemispherically, in a sense -- cold then.
If you'd like to look for the moon, now a few days past full, Weather Underground's Durham, N.C. information gives a local rising time tonight of 10:57 pm. That's on an artificial horizon with no hills or trees. It's also south of southeast -- way farther south than we're used to. Depending on your horizon to the southeast, it may be midnight or later before you see the moon come up.
Today, 5 January 2008, is the day of latest sunrise for most people living in Earth's northern hemisphere. The days have been getting longer since the winter solstice, because the time of sunset has been getting later faster than the sunrise has been getting later. But starting today, the sun rises earlier. The sequence of days of interest near the winter solstice is: day of earliest sunset, winter solstice, perihelion, day of latest sunrise.
Interestingly, the oddity of these days not occurring when we think they should is a partially artificial problem: If we defined noon as the time when the sun is highest in the sky, latest sunset and earliest sunrise would occur on the solstice.
Today, 3 Jan 2008, is the day of perihelion for the Earth: the day the Earth is closest to the Sun. Earth's orbit is so close to circular that perihelion and aphelion (and their concomitant changes in insolation) have no apparent effect on the Earth's weather.
The winter solstice is tonight, at approximately 1:10 am EST 22 December (6:10 am UDT 22 December 2008). That will make tonight the longest night of the year. The solstice marks the beginning of winter. The Sun will trace its lowest paths through the sky today and tomorrow. The days will start to lengthen after the solstice, becoming equal length with night on the first day of spring. They will continue to lengthen until the summer solstice, when nights are at their shortest.
The solstice occurs at a particular instant: at the time when the Earth reaches a particular point in its orbit. So for our friends on the U.S. west coast, the solstice actually happens on the 21st, at 10:10 pm PST.
Today, December 7th, is the day of earliest sunset for virtually everyone in the Northern hemisphere. You'd think that would coincide with the Winter Solstice and concomitant shortest day, but because of asymmetries in the earth's orbit, it doesn't.
The days will continue to get shorter until the Solstice, which this year is on 22 December at 1:10 UTC (22 December, 6:10 am EST). After the Solstice, the days will start to lengthen, but the sun continues to rise slightly later each day until about the 5th of January. 5 January is approximately the date of latest sunrise. After then the sun starts to rise earlier each day.
This and other useless trivia are on my Google-based Anti-Calendar. There's a button in the sidebar for the Anti-Calendar in the "Stuff" section. You can use that to add the Anti-Calendar to your set of Google calendars if you want. Or you can view a less interesting version of it directly.
And, for some bizarre reason, I know four people who have birthdays today. Happy birthday to three of them.
The autumnal equinox is tomorrow -- Sunday -- at approximately 5:54 am EDT (23 September 9:54 UT). Summer will be over, and fall (or autumn, as the folks across the pond would say) will begin. Day and night will be of approximately equal length on that day.
The moon will be full on Wednesday, the 26th; by most folks' reckoning, that full moon will be the Harvest Moon. I hope to get up a post about moon names by then, but I've been trying to get one up for a couple months, and haven't done it yet. We'll see.