Not to scale. The Sun is drawn about 30× too big and Earth about 1,700× too big, or you couldn't see them. The shape of the orbit is real, though: almost a perfect circle.Not to scale: the Sun and Earth are drawn much bigger so you can see them. The orbit's round shape is real.
Drag to look around · scroll to zoom
Warming up the Sun…
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Step 1 of 5 · The big question
Why is summer hotter than winter?
Before we look, make a guess. What do you think causes the seasons?
Surprise! Earth is closest to the Sun in early January, right in the middle of Canada's winter. It's farthest in early July, when it's summer.
Closest (Jan 3)
147.1 million km
Farthest (Jul 6)
152.1 million km
So being closer can't be what makes summer. The difference is only about 3%, and we're closest when it's cold!
Look at the orbit
The dashed gold line is a perfect circle. Earth's real path (the white line) sits almost exactly on top of it. Lots of drawings show a long, stretched oval. That's wrong, and it's one reason so many people believe the "closer = summer" idea.
Fun fact: if Earth's orbit were a 30 cm pizza, the Sun would sit only about 2.5 mm off-centre.
Step 2 of 5 · The tilt
Earth is tipped over
Earth spins around an imaginary line called its axis. The axis runs through the North and South Poles, and it's tipped 23.4° (degrees) away from straight up.
Here's the key: the axis always points the same direction in space, toward the North Star, all year long. It doesn't swing around to face the Sun.
So for half the year the top half of Earth (the Northern Hemisphere, where Canada is) leans toward the Sun. For the other half it leans away.
Right now:
We're looking from the side, so the round orbit looks squashed. It's the same trick that makes a round plate look like an oval when you tilt it.
Step 3 of 5 · Why tilt matters, part 1
High sun vs. low sun
Think of the Sun as a giant flashlight. Point a flashlight straight down and you get a small, bright spot. Tilt it, and the same light spreads out over a bigger area, so each patch of ground gets less.
Sun height69°
Ground lit up
1.1×
compared with straight down
Energy per square
94%
In southern Ontario the noon Sun climbs to about 69° in late June but only 23° in late December. The summer Sun gives each square of ground about 2½ times as much energy.
Why the difference? When our half of Earth leans toward the Sun, the Sun climbs higher in our sky. When we lean away, it stays low.
Step 4 of 5 · Why tilt matters, part 2
Longer days, more heating
Earth spins once a day. The glowing ring is everywhere at 44° north, like southern Ontario. Its gold part is in daylight and its purple part is in night.
Daylight in southern Ontario
15 h 30 min
Night: 8 h 30 min
When we lean toward the Sun, more of our ring is in daylight: about 15½ hours in late June vs. about 9 hours in late December. More hours of sunshine means more time to warm up, and shorter nights mean less time to cool off.
Watch the red pin (that's us). In June it spends much more of each spin in the sunlight.
Step 5 of 5 · The other half of the world
Meanwhile, in Australia…
Canada and Australia are on the same planet, so they're always the same distance from the Sun. Earth is so tiny compared with its orbit that the difference is less than 0.01%.
Southern Ontario
Noon sun: Daylight:
Sydney, Australia
Noon sun: Daylight:
In June, Canada has summer while Australia has winter. In December they swap, and Australians have Christmas at the beach. If distance caused seasons, the whole planet would get summer at once. It doesn't, so it's the tilt!
Free play
Run the year yourself
JanMarMayJulSepNov
Noon sun · Ontario
Daylight · Ontario
Canada
Australia
Distance from the Sun: million km. It barely changes, and it's smallest in January!
The short version
Seasons come from Earth's tilt, not its distance from the Sun. The tilt changes how high the Sun climbs (concentrated vs. spread-out light) and how long the days last.