Earth in Space

I. Celestial Sphere- Imaginary sphere on which we see all objects in the sky. (Like a Planetarium)A. Motion of Celestial Objects-(Sun, moon, planets, stars, and any other visible objects)1. Most objects appear to move in circular paths from east to west.2. Move at a rate of 15 0/hr.3. The speed is a result of the rotation of the Earth.

****See animations link on website.B. Star Paths- star trails1. stars in the east, south and the west appear to move from left to right and appear to rise and set like the sun.2. Stars in the north appear to follow a circular path around Polaris(North Star) a. Polaris does not appear to move because it is on the axis of rotation. b. Circumpolar stars-stars that do not appear to rise or set but follow a circular path around Polaris. ex. Ursa Major(Big Dipper) Ursa Minor(Little Dipper) Casiopia (W)

C. Constellations-figures that people have observed in the sky.1. Signs of the Zodiac-called your sun sign because they are on the ecliptic.2. Ecliptic-the path of the sun on the celestial sphere.

3. Seasonal Constellations-certain constellations are only visible at specific times of the year when they are not behind the sun. a. Spring-Leo b. Summer-Cygnus the Swan c. Fall-Andromeda (V) d. Winter-Orion the Hunter

II. Models of the Celestial SphereA. Geocentric-Earth centered1. Early observers believed that the Earth was the center of the universe.a. observed all celestial objects moving from east to west and they did not feel the Earth move.2. After detailed observations of the other planets orbits were made a new model could explain these motions better.

B. Heliocentric-Sun centered1. The Nine Planets (Pluto included) orbit the sun 2. This model includes the two motions of the sun.3. Two pieces of evidence a. Coriolis effect-winds curve to the right in the northern hemisphere b. Foucault Pendulum-a pendulum swinging in a north south orientation will change direction clockwise. -this was interpreted as the Earth rotating underneath the pendulum.III. Apparent Motions of the Sun - called apparent because the sun doesn't move it is a result of the motion of the Earth.A. Earth's Rotation-rotates on its axis once in 24 hours 1. results in day and nightB. Earth's Revolution-the Earth revolves around the sun in 365 days. 1. This motion results in the change in the angle and duration of insolation=seasons

IV. Angle and Duration of the Sun’s raysA. The duration and angle of the sun’s rays depends on an observer’s latitude and the season.B. The seasons are a result of the parallelism of the Earth's axis throughout the year. For the Northern Hemisphere 1. June 21st-the first day of summer -the longest period of day light - direct rays are at the tropic of Cancer-23 1/2 0N -highest angle of insolation for the year=shortest shadow at noon. -the sun appears to rise north of East and set north of west.

2.Sept 23rd and March 21st -Spring and Fall Equinox-12 hours of day light and 12 hours of darkness for all locations on the Earth-the direct rays of the sun are at the Equator.-the sun appears to rise due east and set due west.3.December 21st- the first day of winter-shortest day of the year

-the direct rays of the sun are at the tropic of Capricorn-23 1/2 0S-the lowest angle of insolation-the longest shadow of the year at noon-the sun appears to rise south of east and sets south of west

*****I. The Moon-closest celestial object to the EarthA. Theory of the formation of the Moon- -as the Earth was cooling a large meteor impact released the mass of debris that we know as our Moon.B. The Period of Rotation is the same as the period of Revolution=only one side of the Moon ever faces the Earth.C. Phases of the Moon-the Moon does not produce light it reflects the light from the sun. 1. The Moon orbits the Earth in 27 days but it takes 29 1/2 days for all the phases of the Moon because the Earth is also moving so it takes an extra 2 1/2 days 2. The different phases are a result of how much of the illuminated side we can see. 3.The Phases

II. Eclipses of the Sun and MoonA.2 Parts to a shadow -Umbra-inner darker part -Penumbra-outer part, not as darkB. Lunar Eclipse-occurs when the Earth is between the sun and the Moon=the Earth's shadow falls on the Moon 1. Occurs during the Full Moon, and not every full Moon because the orbital plane of the Earth and sun is not aligned with the orbital plane of the Earth and the Moon.C. Angular diameter-angle formed between the sides of an object and the observers eye. 1. Depends on the actual size and the distance from the observer -the closer it is the larger the angular diameter which explains how the small moon can block the giant sun.D. Tides-cyclical rise and fall of the oceans 1. 4 tides in a 24 hour period= 2 high and 2 low a. the average change is about 1 meter -maximum is the Bay of Fundy= 15 meter tidal change.2. caused by the gravitational pull of the sun and the moon, actually creates two tidal bulges and the Earth rotates through them in 24 hours.

Bay of Fundy High Tide Bay of Fundy Low Tide

3. The tides are not always the same a. Spring Tides: greatest tidal range as a result of the sun and moon working together. Full moon and New Moon

b. Neap Tides: smallest tidal range as a result of the sun and moon working at 90 O from each other. First and last quarter.

III. Geometry of OrbitsA. Ellipse-flattened circle1. Foci-2 fixed points that are on either side of the center.2. Major axis -line through the widest part of the ellipse -the sun is located at a focus for all the planetsB. Shape of an Ellipse 1. The closer the foci are located to the end of the major axis, the flatter the ellipse or the higher the eccentricity. 2. Formula for eccentricity=distance between the foci divided by the length of the major axis.

3. Eccentricity has to be a value between 0 and 1. 0 = a perfect circle and 1 = a straight line

C. Perihelion: when an object orbiting around an object is closest to that object.D. Aphelion: when an object is furthest from the fociE. Keplers law of equal area: states that a planet will cover equal area of space whether it is at perihelion or aphelion.

IV. Gravity-the force of attraction between two objectsA. Depends on the mass of the objects and the distance between them.

-increase mass = increase gravity-increase distance = decrease gravity

B. Gravity is what is responsible for keeping the planets in their orbits. 1. Attraction: between the planet and the sun 2. Satellite: an object that orbits another object 3. Inertia: reason that the planets are moving

V. Universe: everything that exists, more than 10 billion years old and possibly up to 17 billion.A. Began with the big bang-all matter started out concentrated in a small area.1. Large explosion: matter began to organize into subatomic particles.2. The universe is expanding -Doppler shift (Red shift): light that is going away will appear red because the wavelengths are stretched.

-if it were shrinking the rays would be compressed and would appear blue.

B. Galaxies-large clusters of billions of stars -Milky Way Galaxy-our galaxy, spiral galaxy that looks like a fried egg and the yoke is a bulge in the middle -we are located on one wing of the galaxy

C. Solar system-made up of the sun the planets and their moons.-planets are divided into two major groups

1. Terrestrial: rocky-Mercury, Venus, Earth and Mars -planets are small and very dense2. Gas Giants or Jovian-made mostly of compressed gasses and a liquid or rocky core.

-Jupiter, Saturn, Uranus and Neptune-much larger in size

3. Earth is the only planet with abundant liquid water and free oxygen; therefore it is the only planet that can support life.4. The sun is also orbited by other objects than the planets.

-Asteroids, Meteors and comets.a. Asteroids-large cluster located between Mars and Jupiter. -asteroids have hit the Earth-extinction of the dinosaurs about 65 mya.

b. Meteors-smaller objects in space that can be dragged down by the Earth's gravity: shooting star. -most would be burned up by friction from the atmosphere. -if it survives the fall through the atmosphere it is called a meteorite.c. Comets-masses of frozen gasses that have a highly eccentric orbit. -when they come close to the sun the frozen gasses vaporize forming a visible tail. -the tail is not behind the comet it is pointing opposite the sun.

D. Stars: self-luminous body that creates its own energy through the process of nuclear fusion. 1. The sun is the closest star but is only of average size and brightness. 2. Hertsprung Russel diagram in the reference table shows the life cycle of a star.

-on the chart in the ESRT the two axis are luminosity and temperature, which is determined by the color.-the chart is simplified because it is missing the diagonal axis which is the solar radii