Althouse: Waxing gibbous.

January 31, 2026

Waxing gibbous.

The full moon rises this afternoon, at 3:42 p.m. here in Madison, and it won't set until 7:17 a.m., but we think tomorrow will be very cloudy, so we wanted to see the near full moon today, and the setting time was 6:40 a.m.

Do you understand why the setting times are 37 minutes different on 2 consecutive days? The sunrise times on those 2 days are only 2 minutes apart, 7:14 and 7:12.

The video above is from Meade, and that's me in the corner at the beginning, capturing this:

19 comments:

dbp said...: The sun rise and sunset times change because of the tilt of the earth as we orbit the sun. The moon rise and moon set times change, because the moon orbits the earth.; 1/31/26, 9:32 AM
Original Mike said...: "Do you understand why the setting times are 37 minutes different on 2 consecutive days? The sunrise times on those 2 days are only 2 minutes apart, 7:14 and 7:12."

Because the moon is revolving around the Earth. It moves a little over 10 degrees in the sky (i.e. against the background stars) every day.; 1/31/26, 9:34 AM
Ann Althouse said...: Grok: "The Sun's position changes very gradually relative to the stars — only about 1° per day eastward — because Earth orbits the Sun once per year. This causes sunrise and sunset times to shift by just a few minutes daily (mostly due to the changing seasons and Earth's axial tilt affecting the ecliptic's angle with the horizon). Near the end of January in Madison (latitude ~43°N), the daily change in sunrise is small, as you observed (only 2 minutes).

"The Moon, however, orbits Earth much faster: it moves about 13° eastward per day relative to the stars (completing one orbit in ~27.3 days sidereal, or ~29.5 days for phases). Because of this, the Moon lags behind Earth's rotation by roughly 50 minutes on average each day. In other words, if the Moon were fixed relative to the stars, it would rise/set at the same solar time daily — but it isn't, so moonrise/moonset times drift later by about that amount on average."; 1/31/26, 9:42 AM
Howard said...: "The angle of the dangle is directly proportional/equal to the heat of the meat."; 1/31/26, 9:55 AM
Peachy said...: A lot of solar and planetary goodies on tap for 2026.
Nice photos. I like the hill-top vantage point. That looks like just above the university.; 1/31/26, 10:07 AM
Original Mike said...: Observatory Hill. Would have been a thrilling observing site before the advent of electric lights.; 1/31/26, 10:19 AM
Meade said...: Thanks Peachy, that spot is just about smack dab in the center of the UW campus.; 1/31/26, 10:23 AM
Smilin' Jack said...: Sometimes the white horses pulling Selene’s chariot get a bit tired, that’s all. No big deal. Don’t listen to all that impious nonsense about orbits and such—remember what happened to Socrates when he questioned the gods.; 1/31/26, 10:36 AM
Narr said...: Almost, Howard.

The angle of the dangle is proportional to the heat of the meat and the mass of the ass.

Yes, I'm thirteen at heart.; 1/31/26, 10:49 AM
Rustygrommet said...: I like the top one.

Narr
Ain't we all.; 1/31/26, 12:31 PM
Yancey Ward said...: The difference between sidereal month and the synodic month (full moon to full moon) are different because the Earth has moved in its orbit about the Sun between full moons.; 1/31/26, 12:51 PM
Narr said...: "Ain't we all."

Till the last moment.; 1/31/26, 3:19 PM
Iman said...: Waxing gibbous? Try waxing gibbons. Be ready for a shock.; 1/31/26, 3:24 PM
Meade said...: EUELL be shocked.; 1/31/26, 3:29 PM
Yancey Ward said...: I imagine Meade's joke would be an enigma to anyone under the age of 55.; 1/31/26, 4:16 PM
Meade said...: An enigma wrapped in a stalk stock of wild asparagus.; 1/31/26, 4:27 PM
campy said...: Moonset times change because of climate change, which is caused by MAGA fascists driving gas-guzzling trucks and SUVs. Once the Decent F*cking People take over and Impeach Drumpf, they will restore things to the way Holy Mother Gaia intended.; 1/31/26, 5:48 PM
Mason G said...: "An enigma wrapped in a stalk stock of wild asparagus."

That tastes like a pine tree?; 1/31/26, 10:45 PM
Mason G said...: "which is caused by MAGA fascists driving gas-guzzling trucks and SUVs."

And cow farts. You forgot the cow farts.; 1/31/26, 10:46 PM