Download Chapter 18 review answers

Chapter 18 Science review answers
1. Astronomy is the study of all physical objects beyond Earth. P 482
2. Farmers looked to the sky to track the movements of the sun and stars and to determine when to plant. They
looked at the constellations. P 482
3. The calendar is made up of days (24 hours), months (28-31 days) and the unit of a year (12 months).
4. A day is the time it takes the earth to rotate on its axis. A month is approximately the time it takes for the
Moon to orbit the Earth. A year is approximately the time it takes for the Earth to orbit the sun once. P 482
5. The Ancient Hebrews based their calendar on the sun and the moon. Our modern day calendar is based on the
Roman calendar. P 483
6. Leap year is a year in which an extra day is added to the calendar. This was done by Julius Caesar in an effort
to put the seasons back into place, which had shifted significantly. P 483
7. The Romans created our modern day calendar. Julius Caesar corrected this original calendar and created the
Julian calendar by adding a Leap Year. P 483
8. Pope Gregory XIII created the Gregorian calendar to correct the problems with the Julian calendar. P 483
9. Nabta, in the Sahara Desert. 6,000 – 7,000 year old grouping of stones positioned such that they would have
lined up with the sun during the summer solstice 6,000 years ago. P 484
10. Stonehenge is a rock formation near Salisbury England. The stones are arranged to indicate the summer and
winter solstices. It was probably used for ceremonies and rituals. P 484
11. The astrolabe, algebra, our number system, many names for our stars and many developments in astronomy
were all given to us by the ancient Arabs. P 485
12. The Ptolemaic Theory stated that the sun and other planets revolved around the Earth. Ptolemy was not correct
in his prediction, he did predict the motions of the planets better than any other known methods. P 486
13. Copernicus was the 1st person to state a theory that the Sun was at the center of the universe & that the planets
orbited around the sun. p 486
14. Tycho Brahe was a Danish astronomer who used a mural quadrant to view the sky. He favored an Earthcentered theory that other planets revolved around the Sun, but that Sun and Moon revolved around the Earth.
P 487
15. Kepler was an assistant to Tycho Brahe. Kepler announced some new laws of planetary motion after analyzing
Kepler’s data. Kepler stated that all the planets revolved around the sun in elliptical orbits and not in the exact
center of the orbits.
16. Galileo was the first person to use a telescope to observe celestial bodies. He discovered 4 moons orbiting
Jupiter, craters & mountains on the moon, sunspots on the sun, and phases of Venus. P 487
17. Copernicus and Kepler both believed that the sun was at the center of the Universe. P 486-487
18. The invention of photography in the 1800’s allowed astronomers to make even better observations of the sky.
19. Aristotle first explained the phases of the moon and eclipses. He also correctly argued that the Earth is a
sphere. P 485
20. Copernicus, he theorized that if the starts were nearby there position would shift like the planets’ positions do
as the Earth travels around the sun. Since they did not, they must be very far away.
21. Sir Isaac Newton explained why the planets orbit the sun and why the moons orbit planets, force keeps all of
these objects in orbit. P 487
22. Hershel discovered the planet Uranus and the small fuzzy patches in the sky that were later determined to be
other galaxies. P 488
23. Sir Isaac Newton is most known for his Laws of Motion. P 487
24. Scientists divide the sky up into 88 sections called constellations. Pp 490
25. A constellation is a section of the sky that contains recognizable star patterns. P 489
26. No, most stars that appear together are actually very far apart. Even the constellations have stars that are at
different light years from us here on Earth.
27. The position of the constellations and the stars change from season to season because the earth is rotating
around the sun. 490
28. No, the stars you see in the sky are determined by where you are (latitude), the time of the year (season) and
what time it is at night. Not only are you at 2 different latitudes but because South Africa is in a different
hemisphere, you are experiencing different seasons. P 489 and 490
29. Astronomers use the collection of stars that form the constellations to create imaginary markers in the sky.
Through these constellations astronomers, sailors, and people alike can locate their position on Earth. P 492
30. With an astrolabe astronomers are able to measure the distance to objects in the sky. This measurement will
change based on your location and the time you look.
31. In astronomy, altitude is the angle between the object and the horizon.
32. A zenith is an imaginary point in the sky that is directly above an observer on Earth. P 491 (This question is a
tough one, make sure you understand this.) P 491
33. The horizon line is the line where the sky and the Earth appear to meet. P 491
34. An astrolabe is used to measure the altitude of a star by measuring the angle between your horizon & the star.
The altitude of any celestial object depends on where you are and when you look at it!!
35. The celestial equator is an imaginary circle created by extending Earth’s equator into space. P 492
36. Right ascension is the measure of how far east an object is from the point at which the sun appears on the first
day of Spring, it is known as the vernal equinox. Like latitude and longitude. P 492 (another tough concept)
37. Declination is the measure of how far north or south an object is from the celestial equator.
38. Ecliptic is the apparent path the sun takes across the celestial sphere each year, as seen from Earth.
39. Celestial equator, declination, right ascension, and ecliptic are all used to determine a stars universal position.
This is important because it enables you to describe the stars position regardless of where you are on the Earth.
Remember, when using an astrolabe, your position on Earth and the time determine the stars altitude.
40. An eclipse
41. Circumpolar stars are stars that can be seen at all times of year and all times of night.
42. A light year is a unit of length equal to the distance that light travels through space in 1 year.
43. Hubble was an astronomer who used photography to observe the sky. He determined that Herschel’s fuzzy
patches were other galaxies and explained that the universe is expanding.
44. A telescope is an instrument that collects electromagnetic radiation from the sky and concentrates it for better
observation. P496
45. An objective lens collects light and forms an image at the back of the telescope. The bigger the lens the more
light the telescope can gather.
46. Refracting. The curved lens bends the light that passes through it and focuses the light to be magnified by the
eyepiece. P 497
47. The reflecting telescope uses curved mirrors to gather and focus light.
48. The benefits of a reflecting telescope include the ability to use a mirror, which can be made much larger than
the lenses used in a refracting telescope. By using a larger mirror astronomers are able to gather more light. In
addition the mirrors are polished on the curved side, preventing light from entering the glass and preventing
any flaws from the glass affecting the light. Lastly, mirrors reflect all colors of light to the same place
allowing all colors to be seen at the same time. P 497
49. The electromagnetic spectrum is made up of all the wavelengths of electromagnetic radiation. Humans can
only see radiation from the blue light to the red light, the rest is invisible to us. These wavelengths include
radio waves, microwaves, infrared, ultraviolet, xrays, and Gamma rays.
50. Scientists use special telescopes on the ground but primarily up in space to extract electromagnetic waves.
They include ultraviolet telescopes, infrared telescopes, gamma-ray telescopes, and x-ray telescopes. They put
these in space because most of the electromagnetic waves are blocked by the Earth’s atmosphere.
51. No, gamma is different from radio which is different from x-ray and infrared. The universe would look very
different if viewed through these different wavelengths. See page 500
52. Radio waves have the longest and gamma rays have the shortest.
53. Radio telescopes are so large because wavelengths are about 1 million times longer than optical wavelengths.
Radio telescopes must be very sensitive to receive the small amount of waves that reach the Earth’s surface.
To make things easier, scientists actually link the radio telescopes together so that they can work as one.
54. Celestial sphere is a reference system astronomers use for describing a stars position in the sky. P 492
55. Telescopes have been put in space to avoid interference by the atmosphere and avoid pollution from light and
water vapor.