The autumn equinox is the day Earth's axis leans neither towards the Sun nor away from it. In 2026 it falls on 23 September. The word means "equal night", and most of us were taught that day and night are exactly the same length on that date. It is almost true. Count the minutes in Oslo and the day comes out longer — and the further north you live, the more minutes you have left over.
The equinox is not the day when light and dark are equal.
Two things cheat. The first is an agreement: sunrise is timed from the instant the upper edge of the Sun's disc breaks the horizon, not from its centre, and sunset runs until the last edge vanishes. That hands us half a Sun extra at each end of the day.
The second is the air. The atmosphere bends sunlight on its way down, the way a spoon looks broken in a glass of water. So we see the Sun rise before it has cleared the horizon, and we still see it after it has dropped below. The air lends us minutes of light that, strictly speaking, are not there.
The tilt is also the reason seasons exist at all — not distance. Earth is closest to the Sun in January, in the depths of the northern winter.
Try it at home: the orange and the torch
You need an orange, a wooden skewer, a torch, a marker and a dark room.
- Push the skewer through the orange. That is the axis.
- Draw a line around the middle. That is the equator.
- Stand the torch on the table. That is the Sun.
- Hold the orange at a slant, keep the slant pointing the same way, and walk slowly around the torch.
- Stop where both ends of the skewer catch the same light. The boundary between lit and dark now runs straight through both ends. That is the equinox.
Notice how sharp that boundary is on the orange. On the real Earth it is not — the air smudges it, and the leftover minutes hide inside the smudge.
What happens if you hold the orange perfectly upright, with no tilt, and walk the whole circle again?
Questions worth wondering about
Where on Earth are day and night almost equal all year round?
If the air bends sunlight, what exactly are we looking at the moment the Sun "rises"?
What would seasons look like on a planet lying on its side, axis pointing straight at the Sun?
The equinox passes without anyone noticing — just a boundary line sliding through two poles at once, out in the dark. And it decides that it will already be night when you get home in November.
Next time the Sun comes up, it is not really there yet. Look at it a little longer than usual.
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