Winter Solstice, the point at which the earth’s north pole is tilted directly away from the sun, is at 10:03am today (21 December 2025). You can see the 23.5 degree tilt clearly in this GOES West view:
It’s the shortest day of the year in the northern hemisphere and marks the beginning of astronomical winter and, conversely, the longest day in the southern hemisphere and beginning of summer. The north pole is 24 hour darkness, and south pole is in the sun continuously today, as can be seen in this view from Himawari 9 at the same time as the above GOES-West view…
But it’s not the date of the latest sunrise or earliest sunset! Here is a map for the US from the Naval Observatory showing the data of earliest sunset/latest sunrise:
Why is that? It’s because the earth’s orbit around the sun is not a perfect circle, but an ellipse. One of the quirks of our orbit is that we are actually closer to the sun than average right now. Perihelion, the point of closest approach to the sun, is on January 3rd this year at 147.1 million kilometers. Aphelion, the farthest, is on July 6th, at about 152.1 million kilometers. That 5 million km (3.1 million miles) makes a difference. Because we are closer, the earth is moving faster, so for the sun to get back to the same point in the sky is different (longer) than in July when the earth is farther from the sun and moving slower. Here’s a handy chart, from Brian Brettschneider at Brian B.’s Climate Blog.
It’s not the same for the northern or southern hemisphere because the tilt is opposite of the orientation of the orbital ellipse. You can explore this topic a bit more on Wikipedia or at Earth and Sky. The story of seasons, telling time, and figuring out the orbits of the Earth and other planets is really interesting and interwoven with that of mathematics, since a lot of modern math (including calculus) was invented in order to understand the motions of objects in the sky.
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This topic always proves disconcerting as I feel my brain attempting (failing) to rewire around the facts! Why is it colder if we’re closer to the Sun? What, on earth (pun intended), does the map with “No sunrise/sunset” telling me? Why does my brain NOT want to incorporate this information??? But thanks for trying to educate and offer information…as usual, the problem is me 🤣
It’s really “simple,” but takes some math. The change in energy received from the sun due to distance depends on the inverse square law, so the energy received per square meter at 152.1 million km is about 6.5% less than at 147.1 million. However, the energy received also depends on the angle of incidence – the angle between “straight up” and the tilt of the surface. That’s what causes the seasons – the tilt. At Frogmore, for example, On June 21st the sun is almost overhead, 81 degrees above the horizon at noon. Today, it will only top out at only 34 degrees above the horizon! The total energy received per square meter today is 44% less than in June! And “No sunrise/sunset” means 24 hours of darkness – the sun never gets above the horizon … just as in summer they have the “Midnight Sun” and the sun never goes below. Hope that helps!