1. angular resolution ability to distinguish between two adjacent objects in the sky.

2. Cassegrain telescope - reflector telescope where light is reflected back through a hole in the center of the curved mirror

3. charge-coupled device (CCD) - electronic device that detects amount of light hitting different pixels

4. chromatic aberration dispersion of light into its colors by the prism-like edges of lenses

5. coma - formation of tails on stars at the edges of the field of view, caused by improper focus

6. focal length - distance from edge of mirror or center of lens to the point of the focus of light rays.

7. image - picture of object after focusing by lens or mirror

8. Newtonian telescope - reflector where light is reflected to the side near the top of the telescope

9. prime focus - reflector telescope where the image is viewed at the point of focus of the main reflector

10. radio telescope - reflector telescope which only detects radio waves

11. reflector - telescope where light rays are focused by reflecting light at angles

12. refractor - telescope that focuses light rays by bending them with lenses

13. seeing disk the circle over which a star’s light is spread due to atmospheric blurring

1. How does a refracting telescope focus light? A refracting telescope uses a lens to bend light and focus it at a point.

How does a reflecting telescope focus light? A reflecting telescope uses a curved mirror to focus light at a point.

2. Why do all the world’s largest optical telescopes use the reflector design?

Reflectors are used for four basic reasons: (1) Lenses suffer from chromatic aberration. (2) Lenses are opaque to IR and UV radiation. (3) Large lenses are heavy, mirrors can be supported across the back surface. (4) A lens has two surfaces that need to be polished.

3. What advantages does the Hubble Space Telescope have over ground based telescopes? No atmospheric blurring.

What disadvantages? Must be serviced in space.

4. Why do radio telescopes have to be extremely large? The radio waves to be reflected are extremely long.

5. How does a radio telescope work? The radio waves are reflected to a central focal point.

1. atmosphere - gaseous layer on the surface of the Earth.

2. aurora - Light caused by atmospheric particles being excited by solar energy.

3. aurora australis Aurora at the south pole.

4. aurora borealis Aurora at the north pole.

5. basalt - Material that makes up the crust under the oceans.

6. convection Circulation of fluids caused by differences in density due to differences in temperature.

7. core - Hot center of the Earth; made of iron and nickel.

8. crust - Thin surface of the Earth; mostly made of granite on the continents, basalt under the oceans.

9. density - Mass divided by volume.

10. differentiation Separation of materials of the Earth by density; most dense in core, least dense on surface.

11. dynamo theory - Convection currents in the outer core combined with the rotation of the Earth produces the Earth’s magnetic field.

12. exosphere - The outermost layer of the Earth’s atmosphere (about 250 km).

13. granite - Material that makes up most of the crust material at the continents.

14. greenhouse effect The atmosphere of the Earth traps much of the heat re-emitted by the surface.

15. hydrosphere - The water on the surface of the Earth.

16. inner core - Central part of the core. Extremely hot (5000 K), but compressed into a solid.

17. ionosphere - Atmospheric layer that is very ionized. Conducts electricity. About 100 km.

18. lithosphere - Crustal plates and upper mantle. Area that undergoes tectonic activity.

19. magnetosphere - Area of charged particles trapped by Earth’s magnetic field.

20. mantle - Layer of Earth beneath the crust.

21. mesosphere Layer of atmosphere from km.

22. neap tide - Lower than normal tides caused by the Sun’s gravity pulling at right angles to the Moon.

23. outer core - Outer part of the core. Very hot and liquid.

24. ozone layer - Atmospheric layer where UV radiation is absorbed by oxygen, ozone, and nitrogen. ( km)

25. plate tectonics Movement of crustal plates. Continental drift.

26. solar wind - Outward flow of charged particles from the Sun.

27. spring tides - Higher than normal tides caused when the Sun’s gravitational pull is added to the Moon’s because all three are in line.

28. stratosphere - Atmospheric layer above troposphere km.

29. thermosphere Layer of Earth’s atmosphere above 90 km.

30. tidal bulge - Elongation of the Earth caused by gravitational pull of the Sun.

31. tides - Rising and falling motion that bodies of water follow.

32. troposphere Atmospheric layer closest to Earth. Up to 15 km. Weather.

33. Van Allen belts - Two donut-shaped regions of magnetically trapped charged particles high above atmosphere.

1. By comparison with Earth’s average density, what do the densities of water and rocks in Earth’s crust tell us about Earth’s interior?

Earth’s average density is 6 g/cm 3. Water and crust are 1 g/cm 3 and 3 g/cm 3. Therefore, inner Earth must be greater than 6 g/cm 3.

2. Give a brief description of the magnetosphere, and tell how it was discovered. Area that is affected by the magnetic field of the Earth, trapping charged particles produced by the solar winds. Discovered by satellites launched in the late 1950’s.

3. What process has created the surface mountains, oceanic trenches, and other large-scale features on Earth’s surface? Plate tectonics.

4. How do we know that Earth’s magnetic field has undergone reversals in the the past? Study of the slight magnetization of the areas around the Mid-Atlantic Ridge.