Astronomy It’s out of this world!

Rotation Earth rotates or spins west to east or counterclockwise (ccw) on its axis. Axis is tilted 23 ½ ⁰

Effects of Rotation Apparent motion of Sun, Moon and stars Appear to rise in the east and set in the west

Day and Night Side facing Sun = day Side facing away from Sun = night Areas near the poles may have several weeks in darkness or light

Length of day About 24 hours to rotate = about 24 hours in a day 360⁰ in 24 hours = 15⁰ per hour The farther east you are, the earlier the sunrise

Solar System Milky Way Galaxy The Universe

Our Place in the Universe Our Solar System consists of our star, the Sun, and its orbiting planets (including Earth), along with numerous moons, asteroids, comet material, rocks, and dust

The Milky Way galaxy, a spiral galaxy, consists of the Sun and 200+ billion other stars.

The Universe is incredibly huge The Universe is incredibly huge. It would take a modern jet fighter more than a million years to reach the nearest star to the Sun. Travelling at the speed of light (300,000 km per second), it would take 100,000 years to cross our Milky Way galaxy alone. No one knows the exact size of the Universe, because we cannot see the edge – if there is one. All we do know is that the visible Universe is at least 93 billion light years across. (A light year is the distance light travels in one year – about 9 trillion km.) The Universe has not always been the same size. Scientists believe it began in a Big Bang, which took place nearly 14 billion years ago. Since then, the Universe has been expanding outward at very high speed. So the area of space we now see is billions of times bigger than it was when the Universe was very young. The galaxies are also moving further apart as the space between them expands.

Revolution The Earth’s motion around the Sun The orbit is elliptical (oval) Objects that revolve around the Sun are held in place by gravity

Effects of Revolution The length of a year = 365 ¼ days (every 4 years we add the four ¼ days to make 1 whole day = leap year)

Seasons (along with the tilt) Tilted towards the Sun = summer Tilted away from the Sun = winter A tilted towards C tilted away D and B not tilted so equal day and night

It is not the CLOSENESS to the Sun that causes the seasons…remember, we are CLOSER to the Sun in the winter and FARTHER from the Sun in the summer! 152,500,000 - 147,500,000 5,000,000 km

Position of the Sun in the sky changes due to season highest in the sky at noon in the continental US the Sun is never directly overhead, it’s in the southern sky, so shadows at noon point north

Position of the Sun in the sky changes Summer = high in the sky = more direct rays = longer time to get to highest point = longer day = more heat So…..it’s not the closeness to the Sun!

4. Constellations Different constellations appear at different times of the year, so the earth MUST be changing it’s position in relation to the Sun.

Earth, Sun and Moon Positions The positions of the Earth, Sun and Moon change in a regular, repeating pattern that produces predictable events: Phases of the moon Eclipses Tides

Phases of the Moon Caused by the Moon’s orbit Moon appears to change shape as it revolves around the Earth (more or less of the Moon’s surface can be seen) The Moon takes 29 ½ days to complete one cycle of its phases (approx. one month)

Phases of the Moon Waxing = growing, moving towards full Waning = shrinking, moving towards new

Eclipses Solar eclipse= new moon casts shadow on Earth (only seen in a small area and lasts a few minutes) Lunar eclipse= moon passes through Earth’s shadow (seen over large area and lasts a few hours) Solar Eclipse Lunar Eclipse

Tides Due to the gravitational pull of the Sun and Moon, because the Moon is closer to Earth, its gravitational pull affects the tides more.

Spring and Neap Tides

Tidal Activity Every 6 hours the tides change from high to low and back again… At approximately what time would the next high tide occur?