Key Idea 1
"Earth and celestial phenomena can be described by principles or relative motion and perspective."
Introduction: "The universe is comprised of a wide array of objects, few of which can be seen by the unaided eye. Others can only be observed with scientific instruments. These celestial objects, distinct from Earth, are in motion relative to Earth and each other. Measurements of these motions vary with the perspective of the observer. Cyclical changes on earth are caused by interactions among objects in the universe.
Performance Indicator 1.1
"Explain daily, monthly and seasonal changes on Earth"
The sun is a star average in size. The sun is a hot glowing mass composed of gases. The core of the sun is made up Hydrogen and Helium gases. Which can reach temperatures of 15million degrees Celsius. The sun’s diameter is 1,392,000km, which is 109 times larger than the Earth. The suns mass is 333,000 times greater than that of the Earth. The average distance between the sun and the Earth is 150million kilometers. The light produced by the sun takes approximately 8 minutes to reach the Earth.
There are hundreds of billion of stars that constitute the Milky Way galaxy. Huge systems of stars that travel collectively are called Galaxies. The distances between the stars in the same galaxy are vast compared to distances within our own solar system. These stars appear as tiny points of light in the night sky.
Our solar system contains 8 planets which revolve around the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto, Eris and Ceres are considered dwarf planets (My Very Educated Mother Just Served Us Nacho's).
Birth of ourSolar System Video from National Geographic.
These planets are shaped nearly spherical, oblate spheroids. The planets and the sun are the major bodies within our solar system. There are also comets, asteroids and over 40 moons that make up the solar system of which the sun is the center. Gravity is what keeps the planets in an oval shaped orbit around the sun. Gravity also keeps our moon in orbit around Earth.
All planets turn on their axis. This turning is called rotation. Earth takes 24 hours to make one complete rotation. This is the reason for the length of our day. In addition to rotation all planets revolve around the sun, do to the sun’s pull of gravity. After 365.25 days (1 year) Earth has made one complete revolution around the sun. The planets closer to the sun take less time to revolve, while the planets farther away take more time to make their revolution. Earth revolves in a counterclockwise motion that causes the appearance of the sun rising in the east and setting in the west.
As Earth revolves around the sun it remains tilted. Earth has a tilt or inclination of 23.5 degrees in relation to a line perpendicular to it’s orbit. This tilt is what is responsible for the different seasons on Earth.
Season Video from Youtube.
During winter solstice the southern hemisphere is leaning toward the sun, while during summer solstice the northern hemisphere is leaning toward the sun. With direct rays from the sun hitting the region around the equator yearlong. Thus causing the opposition between the season of the northern and southern hemispheres. Also causing variation in the length of the day between the different seasons. Latitude will also play a role in the amount of daylight. The North Pole can have 24-hour periods of sunlight or complete darkness.
Lines of latitude are imaginary lines that run east to west and never intersect, also known as parallels. Lines of longitude or meridians run from the North Pole to The South Pole, intersecting at the poles, not parallel. These lines help find directions on Earth. The equator is 0degrees latitude running around the center most portion of Earth. One half of Earth is due north of the equator with lines of latitude reaching 90 degrees and the other half of Earth is due south of the equator with lines of latitude reaching 90 degrees. The prime meridian is a line of longitude running north to south over Greenwich, England. One half of Earth is west of the prime meridian with longitudes of up to 180 degrees. While the other half of Earth lies east of the prime meridian also with longitudes of up to 180 degrees. Time zones have been created similar to the lines of longitude. Time zones change approximately every 15 degrees longitude so sun rise can take place the same time (say 6am) all over the world.
The moon revolves around Earth while it rotates on its axis do to Earths’ gravitational pull. The moon also exerts a small pull of gravity on Earth causing the tides. The moon reflects light from the sun, as do the other planets and moons in the solar system. As the moon revolves around Earth the appearance of the moon changes. This change is called the phases of the moon. A new moon appears dark because the lighted side is facing away from Earth. As the moon revolves the lighted portion of the moon becomes visible. When the lighted side of the moon completely faces Earth we have what is known as a full moon. This pattern is completed in one month, when it starts all over again. The average length of one lunar cycle, full moon o full moon, in days is 29.
Sometimes Earth will pass between the moon and the sun causing a lunar eclipse. (lunar eclipse video 2/20/2008.) The rays from the sun are momentarily blocked from falling on the moon. The same can happen when the moon passes between the sun and Earth causing a solar eclipse. The outer portion of the sun called the corona is still visible around the moon. WARNING: Never look directly at the sun during an eclipse. You could be blinded.
The pull of gravity exerted by the sun and Earth will also cause meteor showers and comets to pass by and or fall on to Earths surface. Meteorites are pieces of an asteroid that leave orbit and can get caught in Earths gravitational pull. On impact with Earth, large meteors will leave a crater. Arizona is host to one of the largest craters, Meteor Crater.
Practice Quiz for this section.
