TEST 11. 8A and 8B. Monday, April 20th

REVIEW

Appearances suggest that the sun moves around the Earth. The Earth appears to be motionless, and the Sun appears to move from one side of the Earth to the other. However the RETROGRADE MOTION OF MARS, AND THE SEASONAL CHANGES IN THE NIGHT SKY indicate that the Earth and other planet are revolving around the Sun.

Two models models are used to explain the motions of heavenly objects: HELIOCENTRIC AND GEOCENTRIC.

Heliocentric: The Sun is the center of the solar system and the planets revolve around the sun. Helio means Sun (Helium (an element), was first discovered in the Sun by astronomers before it was found on Earth). Held by Aristotle and Ptolemy.

Geocentric: The Earth is the center of the solar system and the Sun, the moon, and the planets revolve around the Earth. Geo means Earth. Held by Aristarchus and later Copernicus and Galileo.

The Sun rises at different locations on the horizon depending on the time of the year. It moves southward from June to December and northward from December to June.

The mean distance from the Earth to the Moon is 384,403 Km. The mean distance from Earth to the Sun is about 150 million kilometer.

How can you tell the Earth is spherical instead of flat?

We can't see all the way across it, even with a telescope. As ships disappear over the horizon, the top of the mast is the last to disappear. As you approach a point on the horizon, objects behind that point rise into view. Earth's Shadow on the Moon is curved. The Sun's angle above the horizon at noon is lower at more northern location. The Sun does not rise above the horizon at the North and South poles at certain times of year.

Day and night are caused by rotation of the Earth on its axis. Day when it is facing toward the Sun and night when it is facing ways from the sun.

Because of the Earth's tilt, sunlight strikes the Earth more directly in the Northern hemisphere during the summer than at any other time of the year. Also daylight hour are longer during the summer ,contributing to higher temperatures. When one hemisphere of the Earth is tilted toward the Sun, as the Earth rotates, that side of the Earth will be exposed to the Sun for longer period of time.

The tilt of Earth's axis causes the seasons to change. In Northern hemisphere, the Sun appears at its highest and lowest point during the summer and winter solstices, respectively.

Planet orbit the Sun in an Ellipse, NOT in a perfect circle.

Galileo Galilee, Italian astronomer. The first to effectively use the telescope. Consider himself a Copernican because he supported the idea that the planet revolve around the Sun. Was arrested for holding these ideas. (example of conflict between religion and science).

Copernicus: polish astronomer, who revived and expanded the ideas of Aristarchus. Speculated that Earth and all other planets revolve around the Sun.

The tropics include all areas on the Earth where the sun reaches a point directly overhear at lest once during the solar year. in the Temperates zones, north of the tropic of Cancer and South of the Tropic of Capricorn, the sun never reaches this zenith and is never directly overhead. The tropics of Cancer and Capricorn got their names from the fact that on the solstices, the Sun was in front of the constellations Cancer and Capricorns. But because the ellipse that describe the Earth's orbit rotates slowly with respect to the stars, the Sun is now in front of Gemini and Sagittarius at the solstices.

The Tropics, seated in the equatorial region of the world, are limited in latitude by the Tropic of Cancer in the northern hemisphere and the tropic of Capricorn in the southern hemisphere.

Solstice is an astronomical event that occurs twice each year, when the tilt of the Earth's axis is most inclined toward or ways from the Sun, causing the Sun's apparent position in the sky to reach its northernmost and southernmost extreme. (longest day and shortest day of the year (June and December) Summer and Winter solstices respectively).

Equinox: occurs twice a year, when the tilt of the Earht's axis is inclined neither ways from nor towards the Sun, The Sun being vertically above a point on the Equator. Night and day are approximately equally long. Vernal (spring) and autumnal equinoxes.

AU: Astronomical unit, is equal to 150 million kilometers.

Vocabulary: Astronomy, constellation, plane of the ecliptic, revolution, rotation. zodiac, and axis.

List: 12 constellation that make up the Zodiac, time the Earth, Mercury and Mars take to revolve once around the Sun (in days). Average distance from the Sun of Mercury, Earth and Mars on AU and kilometers