Unit 9: Earth Cycles
Vocabulary
Axis
Imaginary line about which an object rotates.
Rotate
To turn or cause to turn
about an axis or a center.
Revolve
To move in an orbit.
Counterclockwise
In a direction opposite to
that in which the hands of
a clock rotate.
Rotational Axis
The Earth is rotating
around an imaginary axis
at a 23.5° tilt. It points in
the same direction relative
to the stars, so that the
North Pole points towards
the star Polaris (North
Star).
Vernal Equinox
Earth reaches a point where the tilt is not toward or away
from the Sun, and the lengths of day and night are the
same all over Earth. March 21st.
Summer Solstice
Earth’s northern hemisphere is tilted toward the Sun and
days become longer and warmer. June 21st.
Autumnal
Equinox
Earth reaches a point
where the tilt is not toward
or away from the Sun, and
the lengths of day and
night are the same all over
Earth. September 22nd.
Winter Solstice
Earth reaches a point
when the northern
hemisphere is tilted away
from the sun and the
hours of daylight are the
shortest. December 21st.
Eclipse
The partial or complete hiding from view of an
astronomical object, such as the Sun or Moon,
when another astronomical object comes between
it and the observer.
Solar Eclipse
When the Moon blocks
the Sun or a part of it.
Lunar Eclipse
When the Earth casts a
shadow on the Moon.
New Moon
When the Moon is
between the Earth and the
Sun; the illuminated
portion is on the backside
we can’t see.
Waxing Crescent
During this phase, part of
the Moon is beginning to
show. We say that the
Moon is "waxing" because
each night a little bit more
is visible for a little bit
longer.
First Quarter Moon
Comes a week after new moon; rises at noon and is high
overhead at sunset, then sets around midnight.
Waxing Gibbous
When most of the Moon is visible we say it is a Gibbous
Moon. During this phase, the Moon remains in the sky
most of the night.
Full Moon
When we can observe the
entire face of the Moon,
we call it a Full Moon.
The Moon is opposite the
Earth and the Sun.
Waning Gibbous
Instead of seeing more of
the Moon each night, we
begin to see less and less
of the Moon each night.
This is what the word
"waning" means.
Third Quarter
Moon
Comes about three weeks
after new moon; rises
around midnight, appears
at its highest in the sky
around dawn, and sets at
noon.
Waning Crescent
Each night less of the Moon is visible for less time.
Gravitational Attraction
Force of attraction between all masses in the universe,
especially the attraction of the Earth’s mass for bodies
near its surface.
Neap Tides
Tides that are the least extreme; happen twice a
month, at first and last quarter moon phases.
Spring Tides
Tides that are most
extreme; occur twice a
month, at full and new
moon phases.
High Tide
The tide when the water is at its greatest height.
Low Tide
The tide at its lowest level at a particular time and place.