How do we know?
↻ One of the pages with a moving picture
Earth is closer to the Sun in January, and yet January is winter in the north.
- Earth doesn’t stand up straight. It leans to one side.
- As Earth goes around the Sun, the lean always points the same way.
- When your half leans toward the Sun, sunlight hits it more directly and warms it up: summer.
- When your half leans away, sunlight hits at a slant and spreads out, so it warms less: winter.
It’s not about distance! Earth is about 3 million miles closer to the Sun in January than in July. Yet January is winter in the north. So being near the Sun cannot be what makes summer.
People noticed the seasons’ rhythm long ago. At Stonehenge in England, the midsummer Sun rises close to the Heel Stone. At Newgrange in Ireland, sunlight shines through a “roof box” into a stone chamber at dawn on the winter solstice.
Both places point at the same thing: the Sun climbs high in summer and stays low in winter.
Wow number
23.5° is how much Earth leans. That tilt gives us summer, fall, winter and spring.
Myth or fact?
Summer happens everywhere in July. Myth. July is winter in the south half of the world.
In the north, the shortest day is around 21 December. Fact. That is the winter solstice.
Think about it
If Earth didn’t lean at all, do you think we would still have seasons?
Where in the world?
Stonehenge, England where on midsummer morning the Sun rises close to the Heel Stone. At Newgrange in Ireland, dawn sunlight shines into a stone chamber on the winter solstice — 51.1789° N, 1.8262° W.
Where these facts come from
Every number on page 11, and who measured it
This page explains how Earth's lean makes the seasons.
What Causes the Seasons? — NASA Space Place, NASA's science site for kids
spaceplace.nasa.gov/seasons/en
We checked it on 31 October 2026
This page tells us how much Earth leans, and that Earth is closest to the Sun in January.
What Is Earth? (Grades 5-8) — NASA, the U.S. space agency
nasa.gov/learning-resources/for-kids-and-students/what-is-earth-grades-5-8
We checked it on 31 October 2026
This page tells us the midsummer Sun rises near Stonehenge's Heel Stone.
Description of Stonehenge — English Heritage, the group that looks after Stonehenge
english-heritage.org.uk/visit/places/stonehenge/history-and-stories/history/description
We checked it on 31 October 2026
This page tells us winter sunrise shines into Newgrange's stone chamber.
Winter Solstice — World Heritage Ireland, which looks after Newgrange
worldheritageireland.ie/world-heritage-properties/bru-na-boinne/historical-background
We checked it on 31 October 2026
Has this changed?
Earth’s lean has not changed in any way you could notice, so this answer is not going to change.
The dates do shift a little from year to year, so the exact minute of each solstice is published ahead of time.
Words from this page
- solstice
- The day when the Sun is at its highest or lowest in the sky: the longest or the shortest day of the year.
Try it!
See why slanted sunlight is weaker.
1. Shine a flashlight straight down on graph paper. Trace the spot of light. 2. Now tilt the flashlight and trace again. 3. Count the squares inside each spot.
What happens: the slanted light spreads over more squares, so each square gets less light. That’s winter sunshine!
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