Physical · the experiment

Farthest in July

Earth is closest to the Sun in January and farthest in July — the exact opposite of what "distance makes the seasons" would predict. This page went up on 6 July 2026, the very day Earth reached aphelion, its greatest distance from the Sun all year, in the middle of northern summer.

Nearly everyone, asked why summer is hot, reaches for the intuitive answer: the Earth must be closer to the Sun. It isn't. When it's summer in New York, London, and Tokyo, the Earth is at its farthest point of the entire orbit. The real cause is the 23.4° tilt of Earth's axis — and you can prove it below by switching each effect off and watching which one the seasons actually depend on.

Here is the whole argument in one move. Uncheck Axial tilt: the tall seasonal curve collapses onto the thin dashed line. That dashed line is everything the changing distance does by itself — a faint ripple of a few percent that, for the Northern Hemisphere, is strongest in January, the depth of winter. Now re-check the tilt and uncheck Elliptical orbit instead, pretending Earth circles the Sun at a fixed distance: the seasonal curve barely flinches. One switch controls the seasons. The other barely matters — and points the wrong way.

Why the tilt does so much

The tilt changes sunlight two ways at once, and they compound. In your summer, your hemisphere leans toward the Sun, so the noon Sun climbs higher — its rays strike the ground closer to straight-on instead of smearing across a slanted surface — and the day is longer, so that stronger sunlight falls for more hours. High sun × long day is summer. Low sun × short day is winter. At 40° N the top-of-atmosphere sunlight runs about 483 W/m² in June and 156 W/m² in December — a factor of three, all from the tilt.

The distance, meanwhile, varies the total sunlight by only about 6.9% across the year (the orbit is very nearly a circle — its off-roundness is about 1 part in 60). And because Earth happens to be closest in January, that small effect actually makes northern winters a touch milder and southern summers a touch fiercer — a real, measurable, second-order nudge riding on top of the tilt, never competing with it.