Why is it hot in summer and cold in winter?

Everyone says summer is when Earth gets closest to the sun. That sounds right… but it's wrong. Let's send Earth around the sun and catch the real reason in the act.

1Two things to feel first

The same light can be strong or weak

Before we blame the sun for being far away, you need two simple ideas. Watch each one move:

Spread-thin light

One beam, two ways to land. Straight down = a tight, bright bullseye. Slanted = it smears over more ground, so every spot gets weaker.

The lean that never moves

Earth leans a little — and keeps pointing the same way all year. So sometimes our half leans toward the sun, and half a year later it leans away.

2The two ways sun hits your half

The bullseye and the smear

Leaning toward the sun

The "bullseye" — summer

When your half tips toward the sun, the light comes down steep and lands in a tight, hot patch. Same sun, packed into a smaller spot — so the ground really cooks. Bonus: the days are long, so it heats up for hours.

Leaning away from the sun

The "smear" — winter

When your half tips away, the light arrives slanted and smears across a wide patch. The same sun spread thin — so each spot stays cool. The days are short too, so there's less time to warm up.

3Your turn — grab the tilt

Tip the Earth and watch the light land

Here's Earth with the sun off to the left. Drag the tilt and watch the sunbeam hitting our northern half. The light meter shows how packed-together that light is.

Tilt our half: leaning toward the sun
LEANING AWAYLEANING TOWARD
Light on our halfstrong

4The big test

So is it the distance, or the tilt?

Right now it's summer up north. Before we send Earth around the sun, lock in why you think it's hot.

Guess before you find out

It's summer in the north. Why is it hot? Tap your guess — then we'll fly Earth all the way around the sun and watch what really changes.

5The honest catch

Distance isn't zero — it's just the wrong story

The tilt is the real boss

The lean decides which half gets the steep bullseye light and the long days. That's why summer and winter are opposite on the two halves at the very same moment.

The catch: even in peak summer the sun isn't perfectly overhead, so the light is always a tiny bit slanted unless you live near the equator.
Distance does change a little

Earth's path isn't a perfect circle, so we really are a bit closer some months. But it's a small change.

The twist: we're actually closest in January — northern winter! If distance ran the show, that's when it'd be hottest. It isn't. Tilt wins.

Summer isn't about being closer to the sun — it's about your half leaning toward it, so the same sunlight lands in a tight, hot bullseye instead of a weak, slanted smear.

Psst, grown-ups: Earth's rotation axis is tilted about 23.4° and stays pointed the same way in space (toward Polaris) as Earth orbits, so each hemisphere alternately tips toward and away from the sun. A higher sun angle packs the same energy onto less ground (the cosine-of-incidence effect) and shortens the path through the atmosphere, while longer daylight adds heating time — together that's the season. Earth's orbit is slightly elliptical, so distance does vary, but perihelion (closest approach) falls in early January, during northern winter — making distance a small, out-of-phase factor, not the cause.