Lunar and Solar Eclipses Overview
Overview
The lecture explains the types of lunar and solar eclipses, focusing on Earth's shadow (umbra and penumbra), and describes how each type of eclipse appears.
Types of Lunar Eclipses
- Earth's shadow consists of two parts: the darker umbra and the lighter penumbra.
- The umbra is the darkest part of the shadow where the Sun is completely blocked.
- The penumbra is a lighter shadow where only part of the Sun is blocked.
- A penumbral lunar eclipse occurs when the Moon passes only through the penumbra, causing a slightly dimmer full moon.
- A partial lunar eclipse happens when part of the Moon passes through the umbra, making part of the Moon appear dark, like a "bite" taken out of it.
- A total lunar eclipse occurs when the entire Moon passes through the umbra, causing it to appear red.
- The Moon appears red during a total lunar eclipse because Earth's atmosphere refracts and filters sunlight, allowing only red light to reach the Moon in the shadow.
- During a partial eclipse, the red color is not visible due to the brightness of the illuminated part of the Moon overwhelming the eyes.
- The shape of Earth's shadow projected is circular, with the umbra as a dark circle and the penumbra as a larger, lighter ring.
Key Terms & Definitions
- Umbra — the darkest, central part of a shadow where the light source is fully blocked.
- Penumbra — the lighter, outer part of a shadow where only part of the light source is blocked.
- Penumbral Lunar Eclipse — an eclipse where the Moon passes only through Earth's penumbral shadow.
- Partial Lunar Eclipse — an eclipse where only part of the Moon enters Earth's umbra.
- Total Lunar Eclipse — an eclipse where the entire Moon passes through Earth's umbra and appears red.
- Refraction — bending of light as it passes through Earth's atmosphere, which causes the reddish appearance during a total lunar eclipse.
Action Items / Next Steps
- Review diagrams of Earth's shadow (umbra and penumbra) and types of lunar eclipses.
- Read textbook sections on solar eclipses for the next class.