Lecture Notes: Why Solar Eclipses Move from West to East

Introduction

Standard celestial movement:
- Sun, Moon, and stars rise in the east.
Eclipse anomalies:
- Some solar eclipses (e.g., April 2024, August 2027) move from west to east.
- Rare instances near poles have complex paths.

Rotational Speed vs. Linear Speed:
- Sun & Moon paths are influenced by rotational speed.
- Eclipse paths depend on the moon's straight-line speed.

From the North Pole perspective:
- Earth and Moon rotate counterclockwise (towards the east).
Moon's Path:
- Determined by Earth's rotation & sight line.
- Appears to rise in the east and set in the west due to Earth rotation.
Eclipse Path:
- Determined by the Moon's shadow location on Earth.
- Moon travels east at ~2000 mph.
- Earth's surface moves east slower (~1000 mph at the equator).
- Moon's shadow outpaces Earth's motion, making eclipses appear west-to-east.

Distance and Time:
- Earth’s diameter: ~8000 miles.
- Moon crosses Earth in ~3.5 hours.
- Earth’s surface takes 12 hours to rotate halfway.
Relative Speeds:
- Moon’s orbital journey: ~1.5 million miles per month (~2000 mph).
- Equator point journey: ~25,000 miles/day (~1000 mph).

Relative Sizes:
- If Earth were bigger or Moon closer, eclipse directions might change.
- Adjusting Earth and Moon sizes could lead to a mix of directions for eclipse paths.

Tilted Axis and Night-Time Effects:
- Earth's tilt causes Moon’s shadow to hit night-time areas.
- This can create west-moving eclipses at poles.
Visualizing with Google Earth:
- Drawing arrows for eclipse paths shows complex trajectories.
- Tilted Earth during spring and fall helps understand curvy eclipse paths.

Main takeaway: Moon orbits east slower than Earth rotates day-wise (a month vs. a day), but travels east faster speed-wise.
This faster eastward speed of the Moon determines the west-to-east movement of eclipses.