Lecture Notes: Lunar Eclipses and Solar Eclipses

What is an Eclipse?

• An eclipse occurs when a planet or moon obstructs the Sun's light.
• On Earth, we experience two types of eclipses:
  • Solar Eclipses
  • Lunar Eclipses

Solar Eclipse

• Definition: Happens when the Moon blocks the Sun's light and casts its shadow on Earth.
• Occurrence:
  • Total eclipse occurs roughly every 1.5 years somewhere on Earth.
  • Partial eclipses happen at least twice a year.
• Visibility:
  • Not everyone can see every solar eclipse.
  • Rare to witness a total solar eclipse due to the small shadow cast by the Moon.
  • The same location on Earth sees a solar eclipse approximately every 375 years.
• Eye Safety:
  • Viewing requires specialized eye protection except during the total phase when the Sun is completely covered by the Moon.
  • For more info, visit the NASA Eclipse Safety Page.

Lunar Eclipse

• Definition: Occurs when Earth blocks the Sun's light from reaching the Moon.
• Appearance:
  • The Moon appears reddish during a total lunar eclipse due to Earth's atmosphere bending sunlight (Rayleigh scattering).
  • The phenomenon is similar to why sunsets are orange and red.
• Frequency:
  • Unlike solar eclipses, lunar eclipses can be seen by many people.
  • Occurs when the night side of Earth is facing the Moon during the eclipse.

Why No Monthly Lunar Eclipse?

• The Moon's orbit is tilted compared to Earth's orbit around the Sun.
• This tilt means the Moon often misses Earth's shadow.

Remembering the Difference

• Solar Eclipse: The Sun gets darker.
• Lunar Eclipse: The Moon gets darker.

Additional Resources for Educators

• Launchpad: Solar Eclipses

Note: Illustrations in the resource are not to scale. Credit for all diagrams: NASA/JPL-Caltech.