Astronomy: Apparent Motions Making sense of celestial observations.

How does the Earth move? animation animation Earth rotates- spins on its axis Earth revolves- travels around the sun

How fast does the Earth Rotate?

How many degrees in a circle? 360 o

How many hours in a day? (mean solar day) 24 hours Or one rotation on the axis.

How many degrees does the earth rotate in a day? Which direction? 360° Counter Clockwise

How many degrees does the earth rotate in one hour? 360° divided by 24 hours All celestial objects move at this rate across the sky!!!!!

How long does it take for the Earth to revolve around the sun?

How many days in a year? days Leap Year web site The length of time for one orbit around the sun.

How many degrees does the earth travel in its orbit around the sun in one day? Approximately 1 degree 360° orbit divided by days

Apparent Daily Motion Animation Animation Celestial objects appear to move due to the Earth’s rotation Apparent motion = Earth’s rotation 15 degrees/hr Counter Clockwise rotation

How can you prove that the Earth Rotates?

Foucault Pendulum Foucault Pendulum

Proof of Earth’s Rotation Foucault Pendulum: It changes its position 15 degrees/hour due to Earth’s rotation.

Proof of Earth’s Rotation Coriolis effect video Coriolis effect video Coriolis effect video Coriolis effect: Causes objects to deflect (bend) to the right in the N. Hemisphere and to the left in the S. Hemisphere.

Proof of Earth’s Rotation Star Paths: Paths stars appear to make in the sky.

Shape of the Sky Dome shaped Celestial objects make an arc across the sky ( You are at intersection of N-S, E-W line) Zenith-directly above at 90°

Apparent Solar (Sun) Motion Arcs across the sky ( like all celestial objects) Sun’s apparent path in the sky varies by latitude and season.

Solar Noon- when the sun is the highest in the sky. The noon sun is never directly overhead anywhere in the U.S. The Sun appears to rise towards the east and set towards the west.

Apparent Motion of the Stars Polaris Why do they have this pattern? Earth is rotating. Star Trails in the Northern Horizon

Star trails in the Southern Horizon Notice that the pattern is different.

Star trails in the western horizon

Star Trails in the Eastern Horizon

Apparent Motion of the Stars Constellations, groups of stars that form a pattern, appear to move east to west.

Are stars the same color? No, look at the different color star trails. Stars also vary in brightness.

Models of the Solar System Based upon observations of the apparent motion of celestial objects. Geocentric Model – Earth is the center of the solar system, and all objects revolve around it. Geocentric Model – Earth is the center of the solar system, and all objects revolve around it. Earth Sun Planet

Retrograde Motion: Explained by Geocentric Model (Epicycles) Explained by Heliocentric Model etrograd.html etrograd.html

Geocentric Model: Used epicycles (small sub-orbits) to explain retrograde (backward) motion of planets

Galileo Sun-Centered System.flv Galileo Sun-Centered System.flv

Teachers' Domain:Galileo's Thought Experiment Teachers' Domain:Galileo's Thought Experiment

Models of the Solar System Heliocentric Model – The Sun is at the center, and the planets revolve around it Proof: Movement of constellations and changing of the seasons

What causes seasons? Seasons Song Seasons Song Seasons Song

Comparing the seasons. Summer Solstice Winter Solstice One year on earth

What causes the Seasons? Revolution of the Earth around the Sun. Earth’s axis of rotation is tilted 23.5° and always points at Polaris (North Star).

Is distance important to seasonal change? NO! Farthest away on July 4, Closest on Jan. 3. Distance does not cause seasons

Name the four seasons and their starting date. Summer Solstice– June 21 Autumnal Equinox (Fall)– September 23 Winter Solstice– December 21 Vernal Equinox (Spring) – March 21

Label Diagram: Date and Season

What changes do we observe during seasons? Sun’s altitude changes with the season. Highest – June 21, Lowest – Dec. 21, NEVER overhead at our latitude.

What changes do we observe during seasons? Sun rise / set positions change with the seasons. South of E/W in fall and winter. North of E/W in spring and summer. Due E/W on the equinoxes

What changes do we observe during seasons? Duration of Insolation: (amount of daylight) 3. Longest on Summer Solstice, June 21 1.Shortest on Winter Solstice, Dec hours on Equinox for all.

Apparent Path of the sun Animation Animation

What changes do we observe during summer in NY? What to know about the Summer Solstice. 1.June 21, longest day of the year. 2.Sun at highest altitude at noon, 71.5° hrs of daylight at North Pole. 4.Direct sun ray at 23.5° north latitude. 5.Sun rise – NE, Sun set - NW

What changes do we observe during winter in NY? What to know about the Winter Solstice. 1.Dec. 21, shortest day of the year. 2.Sun at lowest altitude at noon, 24.5° hrs. of darkness at North Pole. 4.Direct sun ray at 23.5° south latitude. 5.Sun rise – SE, Sun set – SW

What changes do we observe during Equinox in NY? What to know about the Equinox. 1.Sept. 23 and March Sun altitude at noon, 48° hrs of daylight, 12 hrs of night. 4.Direct sun ray at Equator. 5.Sun rise – E, Sun set – W.

What effect does the moon have on the earth? What effect does the moon have on the earth? Revolution around Earth causes the phases of the moon. Causes the ocean tides. Reason for solar eclipse and lunar eclipse

Moon’s MotionMoon’s Motion (video start at 22 seconds Moon’s Motion Revolution – Counter clockwise, 1 revolution takes 27 1 / 3 days. Rotation - Counter clockwise, 1 rotation takes 27 1 / 3 days. Always see the same side of the moon. Phases of Moon- 29½ days long

Phases of the Moon Caused by the positions of earth, moon and sun. Repeat because moon orbits earth. Current Phase of Moon

Phases Moon Phases are apparent changes in shape due to the position of the Moon in its orbit. Phase names: –New –Crescent –Quarter –Gibbous –Full Waxing – becoming more visible Waning – becoming less visible

Light vs. Dark Only half is lit up at any time. What does this look like from earth?

Why are Phases longer? Moon’s orbit Earth moving around Sun. Earth Moon Moon has to revolve for 2 more days to get back to the new moon phase. This occurs because the Earth is revolving around the Sun. Moon phases demo

Moon’s Orbit Elliptical shape Earth closer farther Moon appears larger when close and smaller when farther away.

Tides Earth High Low Caused by Moon’s gravity pulling Earth’s water. Two of each because the Earth rotates. Tides always High in line with Moon.

Spring and Neap Tides Earth Sun Neap Tide Spring Tide Quarter Phase – not a large change from high to low tide. New and Full Phase – big change from high to low tide. Water being pulled in two directions. Moon and Sun’s gravity pulling in one direction.

Lunar Eclipse Lunar Eclipse

Lunar Eclipse Umbra Penumbra Sun’s Rays Can only occur during the full moon phase.Can only occur during the full moon phase. Earth blocks light to the moon.Earth blocks light to the moon. Moon must be in Umbra for a Total Lunar Eclipse.Moon must be in Umbra for a Total Lunar Eclipse. Does not occur that often, moon orbit is tilted.Does not occur that often, moon orbit is tilted. Every one on the night side sees the eclipse.

Solar eclipse Solar eclipse

Solar Eclipse Sun’s Rays Penumbra Umbra Only occurs during the new moon phase.Only occurs during the new moon phase. Only total eclipse if in the umbra. Only a few people see it.Only total eclipse if in the umbra. Only a few people see it. Moon blocks light to the Earth. Occur less often than lunar.Moon blocks light to the Earth. Occur less often than lunar. Solar Eclipse Photo

Phases of the moon rap Phases of the moon rap