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

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

Revolution (orbit): Earth moves around the sun in a nearly circular orbit Earth orbits the sun in 365.25 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

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

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

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)

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

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)

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

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”

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

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

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)

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

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