Rocket arrives at the Sky Deck waving a page. "An eclipse is coming to a city far from here. Can we go?"
Raven reads over his shoulder. "Scientists predicted it years ago. The Moon's path is that regular."
"What do you notice about the safety line?" she adds. Rocket reads it. "Never look at the Sun. Even a little exposure can hurt your eyes."
Nova hovers between them. "The Moon covering part of the Sun does not make the uncovered part safe," she says.
"So in this course we model eclipses, not watch them," Rocket says. "Lamp and balls."
"And a lunar eclipse?" Raven says. "The Moon is safe to look at, with a grown-up, on a clear night."
Nova hums. "Shadows you can predict. Eyes you cannot replace."
OpenStax Astronomy says it is extremely dangerous to look directly at the Sun. Even a brief exposure can damage your eyes.
During a partial solar eclipse the temptation to look is strong. The uncovered part of the Sun is just as dangerous as always.
In this course we never look at the Sun. Not with sunglasses, not through a camera or a phone, not during an eclipse.
A lunar eclipse is different. The Moon is never dangerous to look at, so a family can watch one together on a clear night.
Because the Moon orbits Earth in a regular pattern, eclipses can be predicted centuries in advance.
Long ago people stood frightened when the Sun or Moon darkened. Today we know exactly when the shadows will line up.
During a total solar eclipse the sky darkens as if it were dawn or dusk. NASA says the Sun's outer atmosphere, the corona, comes into view.
A total solar eclipse is seen from somewhere on Earth about every year and a half. Any one spot waits about 375 years.
Next week the same tilted-axis idea explains something you feel every year: the seasons.
| Situation | Safe to look? | Why |
|---|---|---|
| Ordinary sunny day | never look at the Sun | even a brief exposure can damage your eyes |
| Partial solar eclipse | never look at the Sun | the uncovered part is just as bright |
| Total lunar eclipse | yes, with a grown-up at night | the Moon is never dangerous to look at |
| Sky Deck lamp model | look at the shadows, not into the lamp | the flashlight never shines in anyone's eyes |
| Week review | True or false? |
|---|---|
| A solar eclipse happens when the Moon's shadow falls on Earth. | ? |
| A lunar eclipse happens at new Moon. | ? |
| The Moon's orbit is tilted about 5 degrees, so most months have no eclipse. | ? |
| Totality in a lunar eclipse can last as long as 1 hour 40 minutes. | ? |
| It is safe to look at the Sun during a partial eclipse. | ? |
Strong week, shadow scientist. Tomorrow is Sky Night: the family predicts the Moon and plays the eclipse game.