eclipses eclipses are named after the object that “disappears” lunar eclipse: solar eclipse:...
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Eclipses
Eclipses are named after the object that “disappears”
Lunar eclipse:
Solar eclipse:
Moon “disappears”
Sun “disappears”
Geometry: Sun – Earth – Moon
Geometry: Sun – Moon– Earth
Lunar Eclipses
Lunar eclipses occur when the Moon enters the shadow of the Earth
The Earth’s shadow has 2 parts:• Umbra – all sunlight blocked• Penumbra – only some sunlight blocked
3 types of lunar eclipses:• Total – all of Moon in umbra
• Partial – only part of Moon in umbra
• Penumbral – Moon only in penumbra
TPS Question
Who can see Lunar Eclipses?
a) Anyone on Earth’s day sideb) Anyone on Earth’s night sidec) Anyone near the Earth’s equatord) Anyone at all
Solar Eclipses
Solar eclipses occur when the Earth enters the shadow of the Moon (the Moon blocks the Sun).
Moon and the Sun have approximately the same (apparent) angular size (1/2 degree).
Sometimes the Moon doesn’t cover the whole Sun and we get an annular eclipse.
The Moon’s shadow also has 2 parts:
•Umbra – all sunlight blocked
•Penumbra – only some sunlight blocked
3 types of lunar eclipses:
• Total – Sun completely covered by Moon
• Partial – Only part of the Sun covered by Moon
• Annular – Some sunlight gets around edge of Moon
TPS Question
Who can see total Solar Eclipses?
a) Anyone on Earth’s night sideb) Anyone on Earth’s day sidec) Anyone near the Earth’s equatord) Only people along a certain path
Solar Eclipses
Solar eclipse is partial when only part of Sun is blocked, total when it all is, and annular when Moon is too far from Earth for total
Eclipse Frequency
Why isn’t there a lunar eclipse during every full moon?
Why isn’t there a solar eclipse during every new moon?
Because the Moon’s orbit around the Earth is tilted.
New Moon – Solar Eclipse
Full Moon – Lunar Eclipse
When the Moon is in the plane of the ecliptic, eclipses can occur.
When the Moon is off the plane of the ecliptic, no eclipses can occur.
New Moon, but no Solar Eclipse
Full Moon, but no Lunar Eclipse
Eclipse FrequencyEclipses don’t occur every month because Earth’s and Moon’s orbits are not in the same plane
Number of eclipses per year:• Solar – at least 2, no more than 5
• Lunar – maximum is 3
• Combined -- maximum is 7
Maximum duration of eclipses:• Solar – 7 ½ minutes
• Lunar – 1 hour, 47 minutes
TidesAs a result, water in the oceans is at “high tide” twice a day. Once on the near side to the Moon and again on the far side from the Moon.
At what lunar phase would the variation between high & low tides be greatest?
TPS Question
a) new moon
b) full moon
c) third quarter moon
d) both new and full moon
At what lunar phase would the tidal variation be greatest?
TPS Question
At new & full moon phases, the Sun and Moon combine to stretch the Earth and its oceans even more.
We see higher high tides and lower low tides.
a) new moon
b) full moon
c) third quarter moon
d) both new and full moon
The Sun can also cause tides, but only half as strong as the Moon.
Spring tide – when the tides from the Sun and the Moon combine
Neap tide – when the tides from the Sun and the Moon counter-act each other.
Spring and Neap Tides