Why do the Sun and Moon appear nearly the same size in Earth’s sky?

The Sun and the Moon appear to be nearly the same size in Earth’s sky due to a remarkable coincidence regarding their physical dimensions and their respective distances from Earth. Both celestial bodies have an apparent angular size of approximately 0.5° when viewed from our planet.1

While the Sun is vastly larger than the Moon in actual physical diameter, it is also significantly farther away. This geometric relationship allows the two objects to occupy a similar portion of the observer's field of view.1

It is important to note that this apparent size is not constant. Because both the Earth’s orbit around the Sun and the Moon’s orbit around the Earth are elliptical, the distances between these bodies fluctuate throughout the year and month. These variations mean that the apparent size of the Moon’s disk can change, which is why the Moon sometimes appears smaller than the Sun, resulting in an annular eclipse rather than a total one.1