Tides Eclipses And Time Flashcards
What is the main cause of tides?
The gravitational pull of the moon on the Earth’s oceans
What does centrifugal forces do?
Cause bulge at point due to gravitational pull of moon. Another bulge appears on opposite point to balance the bulge at.
What are centrifugal forces?
Forces that act on a body that is moving in a circular path.
E.g: the earth, and is directed away from the center around which the body is moving.
How do you know when where it is high tides and where low?
Bulge - high
Water drawn away from oceans - low
Why does the moon have the greater force?
Sun much bigger mass than moon or Earth
Sun greater gravitational force.
Moon greater effect on Earth than sun, because closer to Earth.
When does spring tide occur?
High tide higher than normal
Lower tide lower than normal
Occurs during full or new moon phases
Sun, Moon, Earth in line
Sun moon forces work together, draw away more water and form larger bulge - lower tide than normal
When does neap tide occur?
High tide lower than normal
Low tide higher than normal
Moon in first, third or last quarter phases
Sun, Earth Moon right angles to each other
Forces of sun and moon work against each other, causing smaller bulge
Less water drawn away to form bulge - higher low tide
What is the def of a solar eclipse?
Sun hidden by shadow of moon
What is the def of lunar eclipse?
Moon hidden by shadow of earth
What does the conditions need to be for a lunar eclipse to occur?
Full moon
Sun, Earth, Moon
On its orbit around Earth, moon moves into shadow that is cast by earth
What is a total lunar eclipse?
Moon moves through dark shadow (umbra)
In its orbit, moon closest distance to Earth in order for dark shadow of Earth to reach moon
Can last up to 107 min
What is a partial lunar eclipse?
Earth between sun and moon. Three celestial bodies do not form straight line
Small part of moon’s surface covered by umbra
What does the conditions need to be for a solar eclipse to occur?
Very rare, spectacular event
Last total solar eclipse - 20 March 2015
New moon phase
Orbit of moon must cross orbit of sun
Moon must be in nearest position to Earth
What is a total solar eclipse?
Only seen in very narrow strip of Earth’s surface - 100 km wide
Where total shadow or umbra falls
Lasts only about 8 min
What is a partial eclipse?
When moon between sun and Earth
Only only partially covers sun’s disk
During partial eclipse, moon, sun and Earth not align in perfectly straight line .
Moon only casts outer part of shadow (penumbra) on Earth
