system
Given the following post, respond as if you're commenting on Reddit:
human
Does the earth expand and contract?

OK this may sound dumb but here's my reasoning. I work in construction and one of the common misunderstandings most people have is that everything in their house expands and contracts as the weather changes. This causes a lot of cracks and why there is usually a tolerance with materials.

But I was wondering does the earth expand and contract as it revolves the sun since it's not a perfect circle around the sun and gets closer and farther?
gpt
Not in any appreciable sense, no. Earth’s radius remains quite unchanged over the course of a year, although it’s shape is slightly altered as a consequence of the gravitational force exerted on the Earth from the moon, as well as Earth’s rotation. This results in Earth being very slightly “Pear-shaped,” with a minor bulge extending outward toward the Moon. Although, the bulge is obscenely small, you could never recognize the difference with your eyes.

That being said, the dominant geometric shape the Earth most accurately fits is what’s known as an oblate spheroid (Imagine squishing a flexible ball between two surfaces, flattening it a little bit). Bear in mind that this deviation from a sphere is minimal, only about one part in three hundred. It comes from the equatorial regions experiencing a greater centripetal acceleration than locations at other latitudes. 

But as you mentioned, Earth’s orbit is not perfectly circular. It is indeed an ellipse, but not in an extreme sense. The orbital eccentricity of the Earth (How far the Earth’s orbital path deviates from a perfect circle) is minimal, measured to only about 0.017. So the amount of solar radiation that Earth absorbs barely changes at all throughout the year. On top of that, solar radiation doesn’t really penetrate the surface and wouldn’t contribute to any significant internal heating, anyway. So we don’t see any “Breathing” of expansion and contraction.