Astronomy

1. Astronomy

2. 1)In which months is the northern hemisphere most directly in the sun? 2)In which months is the southern hemisphere most directly in the sun? 3)Is there a time when the northern and southern hemispheres are equally exposed to the sun? 4)What do you call the day when the Northern hemisphere is most directly in the sun (the longest day of the year in the northern hemisphere)? 5)What do you call the day when the southern hemisphere is most directly in the sun (the longest day of the year in the southern hemisphere)? 6)On what two days are the northern and southern hemispheres equally exposed to the sun?

3. Day, Night, and the Seasons • Day and Night- The earth rotates around an axis, meaning that sometimes a particular point on earth faces the sun and other times it does not. • Seasons- The earth revolves around the sun, but its axis is always tilted, meaning that sometimes the northern hemisphere points towards the sun and sometimes it points away. • The day is longer when pointing towards the sun, meaning it has more time to warm.

4. Summer solstice- day when the northern hemisphere receives the most exposure to the sun; its longest day. Winter solstice- day when the southern hemisphere receives the most exposure to the sun; its longest day. Autumn equinox- day in September when both northern and southern hemispheres receive equal exposure to the sun. Vernal equinox- day in March when both northern and southern hemispheres receive equal exposure to the sun.

5. The lives of ancient and tribal peoples centered on the movement of the sun. Many holidays and feast days are scheduled to coincide with the solstices, equinoxes, and quarters of the year (half way between solstice and equinox). Think of a few holidays, do they line up with any of these periods of the year? June 21st Beginning of August September 22 Beginning of November December 21st Beginning of February March 20th End of April/Beginning of May

6. From what direction does the sun rise? Set? If you know the date and time of day, can you navigate by the sun?

7. What are the cardinal directions? Copy the compass below and fill in the missing directions. N NW NNE W E ESE SSE SW S

8. Planetary Motion What causes the revolution of the Earth around the sun? Planets move around the sun on predictable paths called orbits Johannes Kepler discovered that planets revolve around the Sun in elliptical orbits. Ellipse Circle

9. Kepler also established three laws of motion describing planetary motion • Kepler’s First Law- planets move around the sun in an elliptical orbit • Kepler’s Second Law- planets move faster during periods of their orbit closer to the Sun • Kepler’s Third Law- planets that are further from the sun take longer to revolve

10. Sir Isaac Newton clarified Kepler’s discoveries when he explained gravity Law of Universal Gravitation- the force of gravity between two objects depends on the masses of the two objects and the distance between them. The Sun orbits us while we are orbiting it

11. Gravity works with inertia to produce this elliptical motion

12. Did we always know the Earth revolved around the Sun? Geocentric Model Claudius Ptolemy (140 CE)- Theorized that the Sun and all of the other planets revolved around the Earth Heliocentric Model Nicolaus Copernicus (1543)-Theorized that the Earth and all other planets revolved around the Sun.

13. The movement of the Earth, Moon, and Sun have effects beyond the seasons and day and night. They also cause tides of the Earth’s oceans, eclipses, and the phases of the moon.

14. Tides are caused by the gravitational pull of the moon and sun on Earth’s fluid surface. -We experience two high tides and two low tides each day -All four tides occur simultaneously -High tide 1- Water is pulled by the moon’s gravity -High tide 2- Water opposite the moon is left behind as the Earth moves towards the moon -Low tide 1+2- Water from the two remaining sides of the Earth recede as the high tides draw away water.

15. The added pull of the sun’s gravity affects how extreme the tides develop. Spring Tides- the sun adds to the moon’s pull and makes high tides higher and low tides lower Neap Tides-the sun pulls opposite the moon, making the difference between high and low tides less extreme.

16. Eclipses take place when the sun, moon, and earth align causing either the moon or earth to cast a shadow on the other. Solar Eclipse- the moon comes between the earth and sun, causing its shadow to block some of the earth (from the earth, the sun is eclipsed from view). Lunar Eclipse- the earth comes between the moon and sun, causing its shadow to block the moon from the sun’s light (the moon is eclipsed by the earth)

17. During an eclipse part of the moon or earth is completely blocked from the sun’s light, while other parts are only partially blocked Umbra- darkest part of the shadow, completely blocked Penumbra- outer part of the shadow, partially blocked

18. Solar eclipses occur more frequently than lunar eclipses, but the shadow is smaller so fewer people can see them. You will see more lunar eclipses in your life than solar eclipses.

19. The phases of the moon are caused by relative positions of the moon, earth, and sun. In order for you to see the moon it must be facing the Earth (so you can see it) and the Sun (so there is light reflecting off of it). Half of the moon is always facing the Earth Half of the moon is always facing the Sun You see the part of the moon facing both the Earth and Sun

20. Why do you always see the same side of the moon? It rotates and revolves at the same speed, so the same side always faces the Earth. -Approximately one revolution/rotation a month -Our 12 month calendar is called the lunar calendar

21. Our Solar System • Our Solar System includes… • 1 star • 8 planets • Moons orbiting the planets • Dwarf planets • Asteroids and meteoroids • Keiper Belt bodies • The Oort Cloud

22. The eight planets ordered by their distance from the sun are… 1) Mercury 2) Venus 3) Earth 4) Mars 5) Jupiter 6) Saturn 7) Uranus 8) Neptune There are divided into two groups, terrestrial planets and gas giants Terrestrial Planets – Mercury, Venus, Earth, and Mars -made primarily of solid matter (rock), no rings, and few satellites (moons) Gas Giants- Jupiter, Saturn, Uranus, and Neptune -all have rings (Saturn has by far the most dramatic) and many moons

23. Mercury -closest planet to the sun -least mass and volume, second highest density -no atmosphere -drastic temperature changes between the day and night sides of the planet -most elliptical orbit

24. Venus -2nd planet from the sun -3rd least mass and volume, but 3rd highest density -thick sulfurous atmosphere, runaway greenhouse effect. -hottest planet in the solar system -Always appears in the sky near the sun (it is closer to the sun than us)

25. Earth -3rd planet from the sun -5th highest mass and volume, most dense -large electromagnetic field and biological functions support an atmosphere and global temperature suitable for life. -extensive liquid water on the surface

26. Mars -4th planet from the sun -2nd lowest mass and volume, 4th most dense -2nd least gravitational pull, only slightly stronger than mercury -Thin atmosphere and crater covered surface, lots of iron oxide (rust) -Olympus Mons- largest mountain in the solar system -Polar ice caps

27. Jupiter -5th planet from the sun -first planet outside the asteroid belt, first gas giant -most mass and volume, 6th most dense. -primarily gas (H and He), with a small solid or liquid core -known for its giant storms lasting hundreds of years (example: Great Red Spot) -60+ satellites (moons)

28. Saturn -6th planet from the sun -2nd most mass, 2nd most volume, lowest density -primarily gas, with a solid/liquid core -known for its extensive rings -60+ moons in addition to the rings orbit the planet

29. Uranus -7th planet from the sun -4th most mass, 3rd most volume, 2nd least dense - Made primarily of gas, but has more ice and organic gases in its atmosphere than Jupiter and Saturn. -Has an unusually large tilt. Earth’s tilt is approximately 23.5° from vertical, Uranus is approximately 90°.

30. Neptune -8th planet from the sun -3rd most mass, 4th most volume, 5th highest density -Similar composition to Uranus -Approximately 30 x as far from the sun as Earth. One Neptunian year is equal to almost 165 years on earth.

31. The solar system also has several dwarf planets, such as Pluto, Eris, and Ceres. -these have enough mass and gravity to be round, but not enough to significantly affect the objects around them like planets do. It is also filled with Asteroids, Meteoroids, Comets, and dust particles. All of these revolve around the sun like the planets do.

32. Asteroids are large rocks in space, not quite massive enough to have enough gravity to compact themselves into a round shape. -Meteoroids are small asteroids -Meteoroids that enter earth’s atmosphere and burn up are called meteors -Meteoroids that enter earth’s atmosphere and hit the ground are called meteorites. Comets are similar to asteroids except they usually are partially or entirely made of ice and usually have a long tail of dust and ice trailing behind them.

33. There are three important areas of the solar system to know about. -The Asteroid Belt – the area between Mars and Jupiter where most of the solar systems asteroids and meteoroids orbit the sun. The Kuiper Belt- area outside the planet Neptune, containing several dwarf planets as well as smaller objects, dust-like ice, and organic gases. The Scattered Disc- area outside the Kuiper Belt, made-up of similar material with the addition of some comets. It’s objects tend to have odd or scattered orbits, stretched ellipses, and sometimes a different orbital plane. The Oort Cloud- Area outside the Kuiper Belt and Scattered Disc to the end of our solar system (where the sun’s gravity is no longer strong enough to cause objects to orbit). Primarily composed of comets and loose dust and ice.