Presentation on theme: "Eclipses Eclipses are named after the object that “disappears” Lunar eclipse: Solar eclipse: Moon “disappears” Sun “disappears” Geometry: Sun – Earth –"— Presentation transcript:
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 side b)Anyone on Earth’s night side c)Anyone near the Earth’s equator d)Anyone at all
Anatomy of a Lunar Eclipse
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 side b)Anyone on Earth’s day side c)Anyone near the Earth’s equator d)Only people along a certain path
Anatomy of a Solar Eclipse
Solar Eclipse Moon is between Earth and Sun
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
Solar Eclipse Movie
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.
The Line of Nodes
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 Frequency Eclipses 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
Tides Gravity: The Moon pulls more on the near side of the Earth than the far side.
Tides As 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
The Sun has less effect, but it does modify the lunar tides: Spring and Neap Tides
Synchronous Rotation The Moon’s near side is always towards the Earth.