Eclipse Shadow Lab: Solar and Lunar Eclipses
See that a solar eclipse is the Moon’s shadow landing on Earth at new moon, a lunar eclipse is the Moon entering Earth’s shadow at full moon, and that the 5° tilt of the Moon’s orbit is why this does not happen every month.
Before you try
What if the Moon’s orbit were not tilted at all? How often would we get eclipses?
Try it out
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What happened?
Move a control to see what changes and why.
Sizes and distances are far from scale and the orbit tilt is drawn four times larger than it is; the eclipse decisions use real distances and angular sizes.
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Try these ideas
- Set the tilt to 0° and run a month. Count the eclipses.
- Make a total solar eclipse, then push the Moon to its farthest distance and see it turn annular.
- Go to full moon and move the node slider until the Moon slips into Earth’s shadow.
Why it works
The Sun is 400 times wider than the Moon and, by coincidence, about 400 times farther away, so the two look almost the same size in our sky. At new moon the Moon is between Earth and the Sun; if it lines up exactly, its shadow falls on Earth and people inside the dark umbra see a total solar eclipse. If the Moon is at the far end of its slightly oval orbit it looks a little smaller than the Sun and a bright ring stays: an annular eclipse.
The Moon’s orbit is tilted 5.1° to Earth’s path round the Sun, so most months the new Moon passes above or below the Sun and nothing happens. Eclipses come in seasons about six months apart, when the line where the two orbits cross points at the Sun. This lab lets you move the Moon, change the tilt, the distance and the crossing points, and shows which eclipse, if any, results.
Check your understanding
Question 1 of 4
Why is there not a solar eclipse every new moon?
An annular eclipse leaves a bright ring because
A lunar eclipse can only happen at
Why does a total lunar eclipse turn the Moon red?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Find the date of the next solar eclipse visible from India and check whether it is total, annular or partial.
- Ask: why can far more people see a lunar eclipse than a total solar eclipse?
- Use a torch, a ball and a smaller ball to make both kinds of shadow at home.