Indeed, many people assume Earth is closer to the sun in summer than in winter. As it happens, this is true during summer in the southern hemisphere, but it can't also be true for summer in the northern hemisphere.

In the southern hemisphere, Earth is 5 million kilometers closer to the sun in summer than in winter, but it's the reverse in the northern hemisphere. The average Earth-sun distance is 150 million kilometers, and the main reason for the seasons is Earth is tilted, so each pole is sometimes pointing more toward the sun and sometimes more away from it.

So, Earth's orbit only has a relatively tiny deviation from perfect circularity. But why is it so often shown as practically an egg shape? And how can we visualize the real situation?

Consider the bike wheel

In order to try to understand myself how circular the orbit of the Earth was and other planets, I decided to compare the shape of Earth's orbit to an ordinary 26-inch bike wheel by scaling down the real dimensions to fit—and consulting my local bike shop about what the deviations would mean for a real wheel. I was very surprised at the result.