Nature of Science
- Caused by Earths rotation on its
- One Earth rotation takes 24 hours, therefore
we have 24 hour days: roughly 12 hours of darkness when we are facing
away from the sun and 12 hours of light when we are facing the sun directly.
- Earth spins counterclockwise, thus the
sun appears to rise in the East and set in the West.
Observing the Same Face of the Moon from
- We always see the same face of the Moon
when looking from Earth.
- On any given night/day, every place on
the Earth sees the same face of the Moon.
- This occurs because the Moon spins on
its axis once for every time it revolves around the Earth (28.5 days).
Phases of the Moon
- Every 28 days we see a complete cycle
of Moon phases:
New moon, waxing crescent, first quarter,
waxing gibbous, full, waning gibbous, third quarter, waning crescent
- Thus, the Moon changes in appearance gradually
- Phases are caused by the relative position
of the Moon with respect to the Earth and Sun.
- The Moons relative position changes
as it revolves around the Earth.
- Waxing means increasing in size. A waxing
phase appears to be lit on the right side.
- Waning means decreasing in size. A waning
phase appears to be lit on the left side.
- One half of the Moon is always facing
the sun and therefore one half is always lit.
- Because the Moons position relative
to the Earth is the same on any given day regardless of where one might
be on Earth, the same phase of the Moon is visible from everywhere on
Earth for any given night/day.
- Because the Moon revolves around the Earth
in a counterclockwise direction, the Moon rises later each day (approximately
- The Moon rises in the east and sets in
the west because the Earth rotates in a counterclockwise direction.
- The moon is in the sky for roughly 12
hours in a 24-hour period. Therefore, if the full moon rises at 6 PM,
it will set at 6 AM.
- The full moon rises at sunset and the
new moon rises at sunrise. Based on the position of the Moon in its
orbit around the Earth, it is possible to determine the approximate
rise time of each phase.
- The sun is blocked (eclipsed) by the Moon,
thus the Moon is between the Earth and Sun.
- In this position, the Moon is in a new
- Totality lasts only a few minutes.
- The shadow that is cast on Earth covers
a relatively small area, and so can be seen from only a few places on
- Can occur twice per (Earth) year
when the Moon, Earth, and Sun are aligned and in the same plane.
- The Earth is between the Sun and the Moon
and casts a shadow on the Moon, thus causing it to appear grey, black,
- In this position, the Moon is in a full
- Totality lasts a few hours.
- Lunar eclipses can be seen from any place
on the Earth that is experiencing night at the time of eclipse.
- Can occur twice per (Earth) year
when the Moon, Earth, and Sun are in the same plane.
- Seasons are caused by the tilt of the
Earth (23.5 °) and the Earths revolution around the Sun.
Even though the Earths orbit around the Sun is slightly elliptical,
the distance of the Earth from the Sun IS NOT the cause of the seasons.
(In fact, the Earth is closest to the Sun while the Northern Hemisphere
is experiencing winter.)
- In the Northern Hemisphere, the Sun appears
lower in the sky during the winter (is at its lowest noontime angular
height on December 21), and higher in the sky during the summer (is
at its highest noontime angular height on June 21).
- In winter, the Sun appears to rise in
the Southeast and set in the southwest, and the daylength is at its
shortest. In summer, the Sun appears to rise in the northeast and set
in the northwest, and the daylength is at its longest.
- In winter, the Suns rays are less
- In summer, the Suns rays are more
- Seasons are reversed in the Northern and
- The Sun is never directly overhead (at
a 90° angular height) at any latitude further north than the Tropic
of Cancer (23.5°N), or further South than the Tropic of Capricorn
(23.5°S). Within the tropics (23.5°S-23.5°N) the sun
is directly overhead two times each year.