Sun and Moon have the same angular size in the sky, meaning their visible angular diameters (around 0.5°) are the same
Solar eclipse
1. Moon passes between Earth and Sun
2. Moon casts its shadow on Earth
Solar eclipse
Occurs when the moon "eclipses" the sun, blocking the sun and preventing sunlight from reaching us
Alignment of Earth, Moon, and Sun
Determines the type of eclipse
Affected by several factors
Results in different shadows cast by Moon
Umbra
Shadow where no sunlight is present, the darker part of the shadow where light is totally blocked
Penumbra
Larger shadow surrounding the umbra where sunlight is only partially blocked, the lighter part of a shadow where light is partially blocked
Partial solar eclipse
Moon only manages to block part of Sun, visible to regions of Earth under Moon's penumbra
Annular eclipse
Moon passes directly in front of Sun but does not manage to cover all of it, leaving Sun's visible outer edges to form a "ring of fire" around the Moon
Total or annular-total eclipse
Moon completely covers Sun's disk, an extremely rare astronomical phenomenon
Node
The exact point where a solar eclipse can occur in the sky
Sun is dangerous to look directly into at all times, as it emits large amounts of radiation which damages human eyes
Acceptable filters for eclipse observation
Aluminized Mylar
Shade 14 arc-welder's glass
Historical solar eclipses
4 ka in ancient China, where locals believed the darkening of Sun was caused by a dragon
May 17, 603 B.C.E., an eclipse that frightened two warring armies into forming a truce, known as the Battle of the Eclipse
