The same child stands in the same backyard under the same golden sun, split down the middle: on the left it is green summer and the child wears a t-shirt, on the right it is snowy winter and the child wears a coat and hat.

Why is it hot in summer and cold in winter?

Same yard, same you, the same sun up there — yet summer bakes and winter freezes. Everyone says summer is when Earth is closest to the sun. Is that really it?

One clue first. The same beam of sunlight can be strong or weak. Straight down, it packs into a tight, bright bullseye. Slanted, it smears across a wide patch — so every spot gets a thinner, weaker share.

Two panels compare the same gold sunbeam: on the left it comes straight down and lands as a small tight bright bullseye of light, on the right it comes in slanted and smears across a much wider, dimmer patch of grass.

Your turn. Here's Earth with the sun off to the left. Drag the lean and watch the sunbeam hit our north half — steep and strong, or slanted and weak.

light on our north half: strong
leaning awayleaning toward

Same sun — the lean just changes how the light lands.

Here's the trick. Earth leans a little — and its lean always points the same way, at one far-off star. It never swings around to follow the sun. Keep that in mind.

A tilted globe of Earth with a violet axis line running through it, and a dotted violet line from the top of the axis pointing out to a single far-off star, showing the lean always aims at that one star.

Look down on the orbit. The arrow shows the sideways part of the northward lean. Slide from June to March: that arrow never turns.

Earth has moved to: June
JuneMarch

Most of the northward axis points out of this map toward you.

So there are two ways the sun can hit your half.

Two panels of a tilted Earth lit by the sun: on the left the coral northern half leans toward the sun and the beam lands as a steep tight bullseye, on the right the same half leans away and the beam grazes it as a wide dim smear.

Leaning toward the sun: steep light, a hot bullseye. Leaning away: slanted light, a weak smear. Now use those clues at the new March stop. 🤔

You followed the same fixed lean from June toward the March stop.

At March, which half of Earth gets stronger sunlight?