1. Unit 2: Earth in Space Terminology
Frame of Reference: a fixed background which we can measure motions against
P.O.V.
Polaris: the North Star directly above Earth’s North Pole/axis of rotation
Celestial Object: an object outside of Earth’s atmosphere
Stars, our Sun, Valenti in a space suit orbiting earth, other planets

2. Earth’s Motions in Space
a) Angular Diameter: how large a celestial object appears to be to an observer
It depends on
The objects actual size
How far it is from the observer
Earth’s Motions in Space
Rotation: Earth spins on its axis once every 24 hours
Earth turns 15o/hour from west to east-
-how do we know?
Day and night- either the sun actually “rises” and “sets” or Earth rotates

3. Revolution (orbit): Earth moves around the sun in a nearly circular orbit
Earth orbits the sun in days-
-how do we know?
Star Shift- constellations appear to change position each night (slightly)
This is why we see different constellations during different seasons; we see different views or snapshots at different times
Sun

4. Seasons and Earth-Sun Relationships
The Seasons are a result of 3 factors:
Tilted axis of rotation- 23.5o
Revolution around the sun
Parallelism- earth’s axis always point to the same place in space
It points at the North Star (Polaris)
Polaris

5. Season Characteristics
September 21- Autumnal/Fall Equinox
Direct rays of the sun hit the Equator (0o)
Because of where we are in space, tilt is neither towards or away from sun
Everywhere on Earth has 12 hours of daylight/night
EQUAL on an EQUInox 0o

6. December 21- Winter Solsitice
Direct rays of the sun hit the Tropic of Capricorn (23.5o S latitude)
Because of where we are in space, Northern Hemisphere is tilted AWAY from the sun
In NYS, we have 8 hours of daylight/16 hours of night
Shortest day of the year
Travel north towards the North Pole you approach locations of 24 hours of night (Artic Circle to the North Pole)

7. March 21- Vernal/Spring Equinox
With the exception of the date and name, it’s the same as it’s twin the Autumnal Equinox! 0o

8. June 21- Summer Solstice
Direct rays of the sun hit the Tropic of Cancer (23.5o N latitude)
Because of where we are in space, Northern Hemisphere is tilted TOWARD the sun
In NYS, we have 16 hours of daylight/8 hours of night
Longest day of the year
Travel north towards the North Pole you approach locations of 24 hours of daylight (Artic Circle to the North Pole)

9. Observing our Moon
It takes the moon about one month (29.5 days) to go through a complete cycle of phases
The moon’s period of rotation and revolution are the same
We always see the same side of the moon facing the Earth
Moon Phases- the amount of lit surface as seen from Earth
Phases are caused by the moon’s revolution
The angle and set up of SUN, EARTH and MOON determines what phase we see

10. Phases repeat every month in a cyclic manner
Waxing/1st/New Phases- to see more of the moon each night
“when the light is on the right, the moon is getting bright”
New Moon to Full Moon
Waning /3rd/Old Phases- to see less of the moon each night
Waning= Fading away
Getting dark on the right, the moon is getting “erased”

15. Moon’s Affect on Earth The moon’s gravity affects our hydrosphere
Tides are created by the “pull” of the moon on the oceans
There are 4 changes in tides in 24 hours
2 high tides
2 low tides
This means every 6 hours the level of the oceans change (from high to low OR from low to high)
Special Tides
Spring Tides (Severe high and low tides)
Happens when the moon is Full or New
Moon and Sun work together to “pull” on the oceans making height of tides more extreme
Neap Tides (Weak high and low tides)
Happens when the moon is a Quarter
Moon and Sun work against one another and the “pull” on the oceans making height of tides less significant

16. The Moon’s Gravity Causes a change in our tidal levels throughout the day:

18. Eclipses
Lunar Eclipse- Earth’s shadow is cast on the surface of a Full Moon
Sun, Earth and moon align exactly in this order
Happens during a FULL MOON ONLY
Relatively common (about every 18 months)
Safe to view
Visible to everyone on the nighttime side of Earth
Solar Eclipse- Moon’s shadow is cast on the surface of the Earth
Sun, Moon and Earth align exactly in this order
Happens during a NEW MOON ONLY
Rare (about 1 every 7 to 10 years)
Dangerous to view (burns your retinal nerve in your eyes (you’d go blind)
Visible to only certain locations/latitudes on Earth (you must be located at the right spot on the daytime side of Earth to experience a solar eclipse)

19. Lunar Eclipse: How do the Sun, Earth and moon align to create this common celestial phenomenon?

20. Solar Eclipse: How do the Sun, Earth and Moon align to create this more rare phenomenon?