The Earth in Space Ch 26

Astronomy The scientific study of the universe Scientist who study the universe are called what? Astronomers What are some important things astronomers do? Discover new stars, galaxies, planets, & black holes Protect Earth against objects that may hit us

The Universe Galaxy – a collection of stars, dust, and gas bound together by gravity. Our solar system is part of what galaxy? Milky-Way Galaxy What are some things found in our solar system? Earth Sun Other planets Small asteroids and comets

Measuring Distances in Space astronomical unit the average distance between the Earth and the sun; approximately 150 million kilometers (symbol, AU) Astronomers also use the speed of light to measure distance Light travels at 300,000,000 m/s. In one year, light travels 9.4607 x 1012 km. This distance is known as a light-year.

Earth’s Rotation Rotation – The spin of a body on its axis Does the Earth rotate from west to east or east to west? West to east At any given time, Earth’s hemisphere facing the sun is experiencing daylight and the Earth’s hemisphere away from the sun is experiencing night time.

Earth’s Rotation perihelion the point in the orbit of a planet at which the planet is closet to the sun aphelion the point in the orbit of a planet at which the planet is farthest from the sun Earth’s orbit around the sun is an ellipse An ellipse is a closed curve whose shape is determined by two points, or foci, within the ellipse Earth is not always the same distance away from the sun

Earth’s Orbit

The Revolving Earth Revolution – the motion of a body that travels around another body in space; one complete trip along an orbit Earth’s revolution around the sun causes seasons to occur. At what speed does the Earth travel around the sun? 29.8 km/s How long does it take Earth to orbit the sun? Be specific! 365 ¼ days ~ 1 year

The Foucault Pendulum How did we figure out the Earth was spinning? A brilliant man used a pendulum! Jean-Bernard-Leon Foucault – scientist who provided evidence of Earth’s rotation by using a pendulum http://www.youtube.com/watch?v=S2id35aQH0s

The Coriollis Effect The rotation of Earth causes ocean currents and wind belts to curve to the left or right. This curving is caused by Earth’s rotation and is called the Coriolis effect.

Earth’s Rotation Question: What’s one way we can prove the Earth is rotating? As the night passes, the constellations move in the sky. (Earth’s rotation) Earth’s revolution around the sun is evidenced by the apparent motion of constellations. Thus different constellations will appear in the night sky as the seasons change. (Earth’s revolution)

Constallation constellation - a group of stars that are organized in a recognizable pattern. As the night goes on, constellations appear to change positions in the sky – this is caused by the rotation of the Earth.

Measuring Time Earth’s rotation = one day (about 24 hours) Earth’s revolution = one year (about 365 ¼ days) Moon’s revolution = 29.5 days calendar - a system created for measuring long intervals of time by dividing time into periods of days, weeks, months, and years. Question: Why do we have a leap year? Since a year has an extra ¼ day, every 4 years we add a day to the month of February Who revised the calendar to account for the extra day every four years? – Julius Ceaser

Measuring Time con’t. The modern calendar was created by Pope Gregory XIII – much like the acient ROMANS Time Zone – 24 different time zones. The zone to the east is an hour later than the zone on the west. Each time zone is about 15 degrees apart International Date Line International Date Line was established to prevent confusion about the point on Earth’s surface where the date changes. The line runs from north to south through the Pacific Ocean. The line is drawn so that it does not cut through islands or continents.

Measuring Time con’t. Daylight Savings Time - Because of the tilt of Earth’s axis, daylight time is shorter in the winter months than in the summer months

Season’s Earth’s axis is tilted at 23.5˚. Question?? Earth’s axis always points towards what?? – North Star Changes in the angle at which the sun’s rays strike Earth’s surface cause the seasons.

Equinoxes equinox the moment when the sun appears to cross the celestial equator - at an equinox, the sun’s rays hit the Earth’s equator at a 90 degree angle. Night and day light are appx. Equal everywhere on Earth. The autumnal equinox occurs September of each year and marks the beginning of fall in the Northern Hemisphere. The vernal equinox occurs on March 21 or 22 of each year and marks the beginning of spring in the Northern Hemisphere.

The Season’s con’t solstice the point at which the sun is as far north or as far south of the equator as possible The summer solstice occurs on June 21 or 22 of each year and marks the beginning of summer in the Northern Hemisphere. Most daylight in the summer solstice!!!! The winter solstice occurs on December 21 or 22 of each year and marks the beginning of winter in the Northern Hemisphere.