What Causes the Seasons? It Is Earth's Tilt, Not Its Distance From the Sun

Earth has seasons because its axis is tilted, not because its distance from the Sun changes. NASA says the popular idea that Earth is closer to the Sun in summer makes sense but is incorrect.

The distance idea is wrong

Earth's orbit is not a perfect circle, so the distance to the Sun does vary during the year. But NASA points out that in the Northern Hemisphere we have winter when Earth is closest to the Sun and summer when it is farthest away. Compared with how far away the Sun is, the change in distance does not make much difference to our weather.

How the tilt works

Earth spins around an imaginary axis running through its centre from "top" to "bottom". It makes one full turn each day, which is why we have day and night. But the axis does not stand up straight. It leans.

As Earth orbits the Sun, its tilted axis keeps pointing in the same direction. So through the year, different parts of Earth get the Sun's most direct rays:

• When the North Pole tilts toward the Sun (around June), the Northern Hemisphere gets more direct sunlight. That is summer in the north.
• When the South Pole tilts toward the Sun (around December), it is winter in the Northern Hemisphere and summer in the south.

NASA explains that the hemisphere tilted toward the Sun receives direct rays, while the hemisphere tilted away receives its rays at more of an angle. The two hemispheres have opposite seasons at the same time.

What caused Earth to tilt?

NASA says it is thought that, long ago, something big hit the young Earth and knocked it off-kilter. That object is called Theia. The impact sent a huge amount of dust and rubble into orbit, and most scientists think that rubble became our Moon. See also why the Moon changes shape.

Common questions

Why is it opposite in Australia? The Southern Hemisphere is tilted toward the Sun when the north is tilted away.

Does India have four seasons? The tilt causes seasonal change everywhere, but how obvious it is depends on location. This article covers only the cause, as explained by NASA.

Facts checked October 2, 2026.

Sources

• NASA Space Place, "What Causes the Seasons?": https://spaceplace.nasa.gov/seasons/en/