Astronomy basics
What causes a solar eclipse?
A solar eclipse happens when the Moon passes between Earth and the Sun, blocking some or all sunlight from reaching observers on Earth.
Formula
Angular diameter calculation
Angular diameterθ = 2 × arctan(radius ÷ distance)
The calculator compares the apparent size of the Sun and Moon in the sky. Similar angular sizes allow total eclipse conditions.
Science explanation
Total and annular eclipses
When the Moon appears larger than the Sun, it can completely cover the solar disk. When it appears smaller, a bright ring of sunlight remains visible.
Questions and answers
Calculator FAQ
How does a solar eclipse happen?
A solar eclipse occurs when the Moon passes between Earth and the Sun and blocks some or all sunlight from reaching Earth.
What does a solar eclipse calculator measure?
It compares the apparent angular sizes of the Sun and Moon to explain eclipse geometry.
Why can the Moon cover the Sun during an eclipse?
The Sun is much larger than the Moon, but the Moon is much closer to Earth, making their apparent sizes similar in the sky.
Does this calculator predict eclipse dates?
No. This calculator explains eclipse geometry using astronomical measurements rather than predicting future eclipse events.