Ms. Scott

 Every object or body in the universe is in motion.  Earth itself is involved in a number of different motions. These motions are important for day and night and the seasons  Scientist have also discovered that the motions of the earth in space bring about changes in climate and physical processes on earth

 Just like humans, the earth is in constant motion.  Even though we are unaware of the motions of the earth- the biggest movements occur outside our experiences and/or senses  We are aware of smaller movements such as the rotation of the earth on its axis, and orbiting around the sun because that is what gives us day and night, and seasons.

 Most scientists believe that all the known galaxies in the universe are hurtling away at an incredible speed. From Earth it looks like the galaxies are moving away from us (same as if we were to be on a different planet) It is difficult to calculate the speed at which the galaxies are moving since there are no fixed points to use a reference

 In addition to general movement, the Milky Way is also spinning in space around a central axis like an enormous pinwheel  Our sun and solar system orbit the center of this galaxy along with over 100 billion other stars, taking about 175,000 years to complete one revolution. It is estimated that the speed of the rotation of the Milky way is about 250km/sec. and that the sun’s distance from the galactic center is 24, 000 to 26,000 light years away (one light year=distance of light travelled in one year (9.46 trillion kms)

 The term ‘revolution’ refers tot the Earth’s orbiting of the sun.  The earth revolves around the sun at a speed around 108, 000km/hr, travelling 929 million km to complete a single rotation.

Moving ObjectsSpeed of Movement (km/hr) Earth Rotation on Axis (Equator) 1,660 Earth Orbit Around Sun108,000 Sun Orbit Around Milky Way900,000 Movement of Milky Way Galaxy 2,000,000

 The orbit of the Earth is eliptical  The average distance from the sun is 150 million km.  Presently the Earth is at its greatest distance 152 million km form the sun on July 4 th and its closest at 147 million km on January 3 rd.

 The term aphelion refers to the point in the orbit of the earth where it is the furthest from the sun  The term perihelion refers to the point in the orbit of the earth where it is closest to the sun. The situation occurs approximately 21,000-22,000 In to years, the earth will be closest in July and furthest in January  The shift is called the PRECESSION OF THE EQUINOXES

 The Earth experiences a change in the eccentricity of its orbit around the sun over a period of approximately 100,000 years.  The orbit goes from more nearly circular to much more elliptical and back again during this cycle

 The Milky Way Galaxy and everything in its vicinity are moving towards the “Great Attractor”, a cluster of 75,000 galaxies about 150 million light years from Earth, at a speed of 2,000,000 km/hr. The journey will take about 100 billion years to complete.

 The Axis of the earth is defined as the line joining the North and South Poles, around which the Earth rotates.  The Earth is tilted at an average of 23.5 degrees from the plane of the elliptical This means the sun shines more fully on one side of the hemisphere than the other. There are two times a year when the sun shines equally on both hemispheres (March 21 and Sept 21)  The spring and autumn equinoxes  Sun rays perpendicular at the Equator

 The summer solstice occurs approximately June 21 st when the sun shines directly over the Tropic of Cancer in the Northern hemisphere  The reverse is true of the Southern hemisphere at this time- the winter solstice occur on or around December 21 st, at which the sun’s rays are perpendicular to the Tropic of Capricorn

 The tilt of the Earth’s rotational axis causes the different seasons experienced in the high latitudes of the southern and northern hemispheres.

 Another reason for higher summer temperatures in the northern hemisphere is the fact that the sun shines for much longer during the day in the summer season.  The sun is directly about the horizon for all 24 hours in the aria that lies north above the Arctic Circle In the southern hemisphere it is reversed

 The Earth’s angle of tilt form the plane of the elliptical varies form 21.5 degrees to 24.5 degrees over the course of about 40,000 years This ‘wobble’ in the axis changes th contrast between seasons.  When the earth’s tilt is the greatest the Earth’s winters are the coldest and the summers hottest. When the tilt is less, there is less difference between summer and winter.

 Looking through the Farmer Almanac try to determine what years the Earth’s tilts were the greatest and the least.  Using the Atlas label the following accordingly: Equator Earth’s tilt Tropic of Cancer Tropic of Capricorn North and South Pole