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What’s Wrong With These Drawings?

Phases of the Moon: 29.5-day cycle Waxing Moon visible in afternoon/evening Gets “fuller” and rises later each day Waning Moon visible in late night/morning Gets “less full” and sets later each day Change is gradual and continuous, night to night

Astronomy Myth #2 Lunar phases are caused by Earth’s shadows. Wrong! Instead, lunar phases are a consequence of the Moon’s 29.5 day orbit around Earth, with different illuminations of the side of the Moon facing us during the course of a month. It is impossible for the Moon to always be in the Earth’s shadow.

Phases of the Moon  Half of Moon is illuminated by Sun and half is dark at all times.  The phase of the Moon depends on what fraction of the lit half is visible from Earth.  There is no “dark side of the Moon” – this is a misnomer  There is a “back side of the Moon” which never faces Earth  Half of Moon is illuminated by Sun and half is dark at all times.  The phase of the Moon depends on what fraction of the lit half is visible from Earth.  There is no “dark side of the Moon” – this is a misnomer  There is a “back side of the Moon” which never faces Earth

Back Side of the Moon The unseen back side of the Moon (image taken with a spacecraft that flew around the Moon)

Phases of the Moon

Astronomy Myth #3 Wrong! The Moon orbits the Earth every 29.5 days. It must “lap” the Sun (in the sky) during that time, meaning it is up when the Sun is up half the time (and up when the Sun is down half the time). The Moon is just more noticeable when it is night time. You can’t see the Moon during the day.

Astronomy Myth #4 Wrong! The Moon MUST rotate in order for it to always keep the same face toward us. The Moon does not rotate.

We see only one side of Moon Synchronous rotation: the Moon rotates exactly once with each orbit (every 29.5 days). That is why only one side is visible from Earth (we never see the back side of the Moon).

Astronomy Myth #5 Wrong! As half the Moon is always lit by the Sun, the unseen side MUST be seeing sunlight when the side facing us is not illuminated (i.e., New Moon). The unseen far side of the Moon is always dark.

Back Side of the Moon Bathed in Sunlight The unseen back side of the Moon (image taken with a spacecraft that flew around the Moon)

Moon Myths The Moon does not rotate. - Wrong! The Moon rotates once every month (29.5 days). The unseen far side of the Moon is always dark. - Wrong! Far side of the Moon gets as much sunlight as the side facing us over the course of a month. You can’t see the Moon during the day. - Wrong! The Moon is often up during the day. The Moon phases are caused by the Earth’s shadow. - Wrong! No phase is caused by Earth’s shadow. The phases are caused by different illuminations of the side of the Moon facing Earth.

If you see the Sun just setting in the west, and the Moon is just rising in the east, what phase must it be in? A) Full B) Quarter C) Gibbous D) Crescent

If you see the Sun just setting in the west, and the Moon is just rising in the east, what phase must it be in? A) Full B) Quarter C) Gibbous D) Crescent Moon is opposite in the sky as the Sun  Moon must be full (side facing us is fully illuminated).

How long is a lunar “day”. That is, what is the length of time from sunrise to sunrise on the Moon? A) 24 hours B) 29.5 Earth days C) 365 Earth days D) 7 Earth days

How long is a lunar “day”. That is, what is the length of time from sunrise to sunrise on the Moon? A) 24 hours B) 29.5 Earth days C) 365 Earth days D) 7 Earth days A “day” is how long it takes a planet/moon to rotate once. The Moon rotates once for every orbit around the Earth (29.5 day period).

What causes eclipses?  The Earth and Moon cast shadows.  When either passes through the other’s shadow (a fairly rare event, few times a year), we have an eclipse.  The Earth and Moon cast shadows.  When either passes through the other’s shadow (a fairly rare event, few times a year), we have an eclipse.

When can lunar eclipses occur?  Lunar eclipses happen when the Moon moves into Earth’s shadow  Lunar eclipses can occur only at full moon.  Lunar eclipses last a few hours.  Lunar eclipses happen when the Moon moves into Earth’s shadow  Lunar eclipses can occur only at full moon.  Lunar eclipses last a few hours.

Total Lunar Eclipse of 2000 July 16 (Lahaina, Maui)

Why do lunar eclipses often appear blood red? Earth’s atmosphere refracts sunlight, bending a little bit of (preferably red) light into the Earth’s shadow. If Earth had no atmosphere  Moon would disappear completely in Earth’s shadow!

When can solar eclipses occur?  Solar eclipses can occur only at new moon.  Solar eclipses can be partial, total, or annular.  Total eclipses last no more than 7 ½ minutes at any location on Earth!  Solar eclipses can occur only at new moon.  Solar eclipses can be partial, total, or annular.  Total eclipses last no more than 7 ½ minutes at any location on Earth!

When can solar eclipses occur?  Solar eclipses can occur only at new moon.  Solar eclipses can be partial, total, or annular.  Total eclipses last no more than 7½ minutes at any location on Earth!  Solar eclipses can occur only at new moon.  Solar eclipses can be partial, total, or annular.  Total eclipses last no more than 7½ minutes at any location on Earth! Annular eclipse occurs when Moon is far and/or Sun is near Earth.

Solar Eclipse