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2. The Earth in the Universe
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6.2.
Eclipses
In the system made up of the Sun, the Earth and the Moon, an eclipse occurs
when all three are aligned
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. Depending on the amount of the Sun or Moon that is
hidden from sight, an eclipse can be
total
or
partial
.
On average, there are a minimum of four eclipses a year: two solar eclipses and
two lunar eclipses.
6.3.
Tides
An
eclipse
occurs when one body comes between two others, so that one is
hidden
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from the other.
Types of eclipse
Tides
are the periodic rising and falling of sea levels due to the gravitational
pull of the Moon.
Key concepts
❚
The phases of the moon
are the different shapes of
the part of the Moon that is
illuminated by the Sun that
we see from Earth, as the
Moon revolves around the
Earth.
❚
An eclipse occurs when
one celestial body comes
between two others, so that
one is hidden from the other.
❚
Tides are the periodic rising
and falling of the sea levels
as a result of the gravitational
pull of the Moon.
In a
solar eclipse
, the Moon comes
between the Earth and the Sun. Although
the Moon is much smaller than the Sun,
it appears to be the same size as the Sun,
due to the distance between both of them
and the Earth.
In a
lunar eclipse
, the Earth comes
between the Moon and the Sun.
When the sea level rises,
high tides
are
created (1).
They occur on the side of the Earth
facing the moon and on the opposite
side. When the sea level falls,
low tides
(2) are created. They occur on the other
two opposing sides.
When the Moon, Earth and Sun are
aligned, high and low tides are stronger
(very high and very low). These are
spring tides
(3).
In contrast, when the Moon and the
Sun form a 90º angle with respect to
the Earth, the Sun counteracts
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the
Moon’s gravitational pull. The tides are
weaker. These are
neap tides
(4).
Analyse
31.
Why can’t there be a
solar or lunar eclipse in
the first quarter and the
last quarter of the
moon’s phases?
Understand
32.
Explain in your own
words the difference
between spring tides
and neap tides. Which
phases of the Moon do
they coincide with?
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10
hide
:
to cover so it can’t be seen
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align
:
placed in a line
12
counteract
:
act against and
neutralise the effect
