Astronomy Ch.1 Charting the Heavens: The Foundations of Astronomy, Astronomy Ch. 2 The Copernican Revolution: The Birth of Modern Science, Astronomy Ch. 6 The Solar System: Comparative Planetology and Formation Models, Astronomy Ch. 7 Earth: Our Home...
Which of the statements below is part of both the Ptolemaic and Copernican models? A) The Earth orbits the Sun once a year. B) The Sun lies in the center of the Cosmos. C) The Moon orbits the Earth once a month. D) Epicycles are needed to explain retrograde motion of the planets. E) Venus' epicycle must always lie between us and the Sun.
Answer: C
If you are in the Moon's umbral shadow, then you will witness: A) nighttime. B) a total solar eclipse. C) a total lunar eclipse. D) a partial solar eclipse. E) some kind of lunar eclipse.
Answer: B
If your astrological sign is Aries, the Sun should be in the constellation Aries on your birthday. The dates, according to astrological tradition, during which the Sun is in the constellation Aries are March 21 to April 20th. In which constellation is the Sun actually in, during this time period? A) Aquarius B) Pisces C) Aries D) Taurus E) Gemini
Answer: B
On which of these assumptions do Ptolemy and Copernicus agree? A) The Earth must be the center of all motion in the Cosmos. B) All orbits must be perfect circles. C) The Sun was bigger than the Earth. D) Venus must always stay between us and the Sun. E) The Sun must orbit us, but the planets do orbit the Sun.
Answer: B
Where on Earth can you observe all the stars in the sky over an entire year? A) North Pole B) Arctic Circle C) Tropic of Cancer D) Equator E) Everyone on Earth can see the whole sky.
B) Arctic Circle
That Polaris will not always be the pole star is due to: A) the sidereal day being shorter than the solar day. B) precession shifting the celestial pole. C) the Moon following the ecliptic, instead of the equator. D) the Earth's revolution being slightly less than exactly 365.25 days. E) the Solar winds blowing the Earth farther away from the Sun.
Answer: B
Where would you be if the Sun passes through your zenith on December 21st? A) Equator B) Tropic of Cancer C) Tropic of Capricorn D) Antarctic Circle E) South Pole
Answer: C
While watching a star, you see it moves 15 degrees across the sky. How long have you been watching it? A) 1 hour B) 3 hours C) 15 minutes D) 15 seconds E) 1 minute
A) 1 Hour
Where on Earth would you be if Polaris was at your zenith? A) North Pole B) Arctic Circle C) Tropic of Cancer D) Equator E) It lies overhead everywhere on Earth.
A) North Pole
Escape velocity is the speed required to: A) orbit an object. B) overcome the gravitational pull of an object. C) overtake an object in orbit and pass it. D) keep from falling out of orbit around an object. E) maintain a constant distance from an object.
Answer: B
If the Moon rose tonight at 6 PM, then tomorrow it will rise about: A) the same time. B) 7 PM. C) 5 PM. D) dawn. E) midnight.
Answer: B
A circular orbit would have an eccentricity of: A) 0. B) between 0 and 0.5. C) between 0.5 and 1. D) exactly 1.0. E) infinity.
Answer: A
A solar eclipse can only happen during a: A) new moon. B) solstice. C) first quarter moon. D) full moon. E) perihelion passage of the Sun.
Answer: A
According to Copernicus, retrograde motion for Venus must occur around: A) inferior conjunction, when it passes between us and the Sun. B) quadrature, when the planet is 90 degrees away from the Sun. C) greatest elongation, when the planet is farthest from the Sun. D) superior conjunction, when the planet is on the far side of the Sun. E) opposition, when the planet lies opposite the Sun in the sky.
Answer: A
Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh: A) the same as you do here. B) twice as much as you do here. C) half as much as you do here. D) 20X more that you do here. E) 400X more than you do here.
Answer: A
Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as: A) elliptical, not circular. B) much larger than Copernicus had envisioned. C) around the Sun, not the Earth. D) being on equants instead of epicycles. E) complex, with epicycles to account for retrograde motions.
Answer: A
The Ptolemaic model of the universe: A) explained and predicted the motions of the planets with deferents and epicycles. B) is the basis of our modern cosmology. C) could not account for the stellar parallax observed by Hipparchus. D) describes the orbits of the planets as being ellipses, not circles. E) always kept Mars and Mercury between the Earth and Sun.
Answer: A
The constellations of the zodiac fall along: A) the ecliptic. B) the celestial equator. C) lines of longitude. D) lines of latitude.
Answer: A
Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was: A) his detailed and accurate observations of the planet's position. B) his observations of Jupiter's moons. C) a mathematical explanation of epicycles. D) a precise lunar calendar. E) the correct explanation of lunar phases.
Answer: A
What celestial line is a product of the Earth's orbit around the Sun? A) Ecliptic B) Prime Meridian C) Equator D) Galactic Plane E) Analemma
Answer: A
What conditions are necessary for a partial solar eclipse? A) new moon on ecliptic, with us in the penumbral shadow B) full moon on equator, with us in the umbral shadow C) new moon at perigee D) full moon at apogee E) first or third quarter moon at a node
Answer: A
What conditions are necessary for a total solar eclipse? A) new moon on ecliptic near perigee B) full moon on ecliptic near aphelion C) new moon on equator at perigee D) full moon on equator at perigee E) new moon on ecliptic near aphelion
Answer: A
Where would you be if the Sun sets for six continuous months, beginning on September 23rd? A) North Pole B) Arctic Circle C) Equator D) Antarctic Circle E) South Pole
Answer: A
Which of these observations of Galileo refuted Ptolemy's epicycles? A) the complete cycle of Venus' phases B) the rotation of sunspots across the Sun's surface C) the revolution of Jupiter's moons around it D) the craters on the Moon E) the visibility of many more stars with the telescope
Answer: A
Which of these was NOT a telescopic discovery of Galileo? A) the moons of Saturn B) the craters and mare of the Moon C) sunspots and the rotation of the Sun D) the four largest moons of Jupiter E) the phases of Venus
Answer: A
Which planet by itself contains the majority of mass of all the planets? A) Jupiter B) Saturn C) Earth D) Venus E) Uranus
Answer: A
A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years? A) 3 B) C) D) 9 E) 81
Answer: B
During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare: A) total solar eclipses. B) transits of the inferior planets across the Sun. C) passages of comets close to the Earth. D) maximum elongations of Venus. E) oppositions of Mars.
Answer: B
The force of gravity between two objects: A) increases with the masses of the bodies, but decreases with their separations. B) increases with the masses of the bodies, but decreases with the square of the distances between them. C) increases with the square of their masses, but decreases with the cube of their periods of orbit about the Sun. D) depends on the density, not the mass of the bodies. E) depends on the temperature, density, and size of the bodies.
Answer: B
The most famous prehistoric astronomical observatory is: A) the Sphinx. B) Stonehenge. C) Big Horn stone circle. D) Carcacol. E) Mount Rushmore.
Answer: B
Today we rely largely on what technique to precisely measure distances in the solar system? A) transits of Venus across the Sun B) radar echo timings C) measurement of stellar parallaxes. D) timings of the eclipses of its moons by Jupiter's shadow E) precise measurements of length of the year with atomic clocks
Answer: B
Which of the following describes parallax? A) It is best measured over exactly one year intervals. B) It is inversely proportional to the distance to the star. C) It was first observed by Galileo with his new telescope. D) It is only applicable to objects within the solar system. E) It is more accurate as the distances to objects become greater.
Answer: B
Which statement about the first quarter moon is FALSE? A) It rises about noon. B) From the Earth, it appears 25% sunlit. C) It is the half moon of the evening sky. D) It is highest in the sky at sunset. E) It occurs about a week after new moon.
Answer: B
Seasons on Earth are primarily caused by: A) the distance from the Earth to the Sun. B) the tilt of the Earth's rotational axis. C) the tilt of the Earth's magnetic axis. D) the precession of the Earth's rotational axis. E) the dates of the solstices and equinoxes.
Answer: B) the tilt of the earth's rotational axis
A fatal flaw with Ptolemy's model is its inability to predict the observed phases of: A) the Sun during an eclipse. B) the Moon in its monthly cycle. C) Mercury and Venus. D) Mars and Jupiter. E) Jupiter and Saturn.
Answer: C
A lunar eclipse can only happen during a: A) new moon. B) equinox. C) full moon. D) perigee. E) aphelion.
Answer: C
A star with a large parallax: A) is at a great distance from Earth. B) is moving at a great speed with respect to Earth. C) is at a short distance from Earth. D) is moving at a slow speed with respect to Earth. E) is not moving with respect to Earth.
Answer: C
Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know: A) its density as found by spectroscopy. B) its temperature as found by Wien's Law. C) the size of the A.U. and exact length of the year. D) the Earth's mass and circumference. E) the exact timings of the transits of Venus and its diameter.
Answer: C
Compared to orbital velocity, escape velocity is about: A) the same. B) 70% less. C) 40% more. D) twice as large. E) four times greater.
Answer: C
Galileo found the rotation period of the Sun was approximately: A) a day. B) a week. C) a month. D) three months. E) a year.
Answer: C
If Taurus is now rising at sunset, which constellation will rise at sunset next month? A) Scorpius B) Aquarius C) Gemini D) Aries E) Pisces
Answer: C
If new moon fell on March 2nd, what is the Moon's phase on March 14th? A) waxing crescent B) first quarter C) waxing gibbous D) full E) waning crescent
Answer: C
If the distance between two asteroids is doubled, the gravitational force they exert on each other will: A) also be doubled. B) be half as great. C) be one fourth as great. D) be 1/16 as great. E) be four times greater.
Answer: C
It took two centuries for the Copernican model to replace the Ptolemaic model because: A) in Copernicus' time, there were no telescopes. B) the Church wouldn't let anyone talk about Copernicus' model for 200 years. C) there was no scientific evidence to support either model until Galileo made his observations. D) the Ptolemaic model was simpler and more aesthetically pleasing. E) the Copernican model required complicated new terms to explain it correctly.
Answer: C
The Law of Universal Gravitation was developed by: A) Kepler. B) Galileo. C) Newton. D) Copernicus. E) Einstein.
Answer: C
The angular size of an object depends on which two quantities? A) the object's actual size and its mass B) the object's distance from us and its brightness C) the object's actual size and its distance from us D) the objects brightness and its mass
Answer: C
The heliocentric model was actually first proposed by: A) Aristotle. B) Archimedes. C) Aristarchus. D) Alexander the Great. E) Hipparchus.
Answer: C
The last quarter phase of the Moon: A) rises at sunrise. B) sets at sunrise. C) crosses the meridian at sunrise. D) rises at sunset. E) sets at sunset.
Answer: C
The place in a planet's orbit that is closest to the Sun is called: A) vernal equinox. B) aphelion. C) perihelion. D) crossing the ecliptic. E) None of these; a planet's distance from the Sun never changes.
Answer: C
What contribution to astronomy was made by Tycho Brahe? A) The planets' orbits around the Sun are ellipses, not circles. B) The Earth is not the center of the Universe. C) His observations of planetary motion with great accuracy proved circular orbits could not work. D) His telescope revealed the moons of Jupiter before Galileo noted them. E) Retrograde motion must be explained by epicycles larger than those of Ptolemy.
Answer: C
What does Kepler's third law imply about planetary motion? A) All planets orbit the Sun at the same speed. B) Planets closer to the Sun orbit at a slower speed than planets further from the Sun. C) Planets further from the Sun orbit at a slower speed than planets closer to the Sun. D) Planets further from the Sun orbit at a faster speed than planets closer to the Sun. E) This law implies nothing about a planet's motion.
Answer: C
When the Sun rises, it is located in the constellation Gemini. When the Sun sets later that same day, it will be: A) in the constellation Aries. B) in the constellation Taurus. C) in the constellation Gemini. D) in the constellation Cancer. E) in the constellation Leo.
Answer: C
Which was a contribution to astronomy made by Copernicus? A) The planets move around the Sun in elliptical orbits. B) His theory of gravity accounted for the variable speeds of the planets. C) He laid out the order and relative motion of the known solar system. D) He discovered the Sun was not at the center of the Milky Way. E) His telescope revealed the four moons of Jupiter, a model solar system.
Answer: C
You note that a particular star is directly overhead. It will be directly overhead again in: A) 1 hour. B) 12 hours. C) 23 hours 56 minutes. D) 24 hours. E) 24 hours 4 minutes.
Answer: C
From a location in the United States of America, a star is observed to be rising due East. Where will this star be located 6 hours later? A) directly overhead B) high in the Northern sky C) high in the southern sky D) setting due West E) The location of the star cannot be determined from the information given.
Answer: C) high in the southern sky
According to Kepler's third law, the square of the planet's period in years is: A) equal to its perihelion distance from the Sun in A.U. B) inversely proportional to its mass in kilograms. C) equal to the fourth power of its average temperature in degrees Kelvin. D) proportional to the cube of its semimajor axis in A.U. E) equal to the square of its aphelion distance in A.U.
Answer: D
According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would: A) increase by a factor of 3. B) decrease by a factor of 3. C) increase by a factor of 9. D) decrease by a factor of 9. E) stay the same.
Answer: D
Driving eastward just before sunrise, if you observe the Moon in the eastern sky, its phase must be: A) full moon. B) first quarter. C) waxing Gibbous. D) waning Crescent. E) new moon.
Answer: D
How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? A) 5X B) 10X C) 25X D) 100X E) 250X
Answer: D
If the angular size of a spherical object is known, along with its distance from Earth, what third quantity can be determined? A) the object's brightness B) the object's mass C) the baseline D) the object's diameter
Answer: D
Jupiter lies about 5 A.U. from the Sun, so at its distance: A) the Sun's gravity is just as strong as it is here at Earth. B) the Sun's gravity must be five times stronger to hold massive Jupiter in orbit. C) the Sun's gravity is five times weaker there than at one A.U. distance. D) the Sun's gravity is 25 times weaker than its pull on the Earth. E) the Sun's gravity is so weak that ultimately Jupiter will escape the solar system.
Answer: D
Kepler's second law implies what about planetary motion? A) A planet moves at a constant speed during its orbit of the Sun. B) A planet moves faster when it is farther from the Sun. C) A planet moves slower when it is closer to the Sun. D) A planet moves faster when it is closer to the Sun. E) This law implies nothing about a planet's motion.
Answer: D
Some type of solar eclipse will happen about: A) every month at new moon. B) every week at full moon. C) every month at full moon. D) about every six months at new moon. E) every year at new moon.
Answer: D
The Earth's circumference was first determined by: A) Aristotle using lunar eclipses. B) Pythagoras with geometry. C) Hipparchus with stellar parallaxes. D) Erastothenes with solstice shadows. E) Aristarchus with first and third quarter Moon timings.
Answer: D
The Ptolemaic model probably persisted for all these reasons EXCEPT: A) it had the authority of Aristotle behind it. B) it was consistent with the doctrines of the Catholic Church. C) it used perfect circles, which appealed to geometry. D) it accounted well for Galileo's observations of the phase cycle of Venus. E) it explain why stellar parallax was not observed by the Greeks.
Answer: D
The greatest contribution of the Greeks to modern thought was: A) the idea that all the planets orbited the Sun. B) that their mythology was the basis for the naming of the constellations. C) that their observation of stellar parallax proved the Earth orbited the Sun. D) the development of scientific inquiry and model building. E) the invention of the telescope.
Answer: D
The largest asteroid, and probably the only one to be a spherical "world," is: A) Eros. B) Ida. C) Vesta. D) Ceres. E) Gaspra.
Answer: D
The principal culture that transferred Greek astronomical knowledge to Renaissance Europe was: A) Byzantine. B) Chinese. C) Mongol. D) Islamic. E) Mayan.
Answer: D
Upon which point do Copernicus and Kepler disagree? A) The Moon orbits the Earth. B) The Earth orbits the Sun. C) Retrograde motion occurs when one planet overtakes another. D) The orbits of the planets are ellipses, with one focus at the Sun. E) Venus will appear as a crescent when she retrogrades between us and the Sun.
Answer: D
Which concept was NOT a part of Kepler's Laws of Planetary Motion? A) All planetary orbits are ellipses. B) The square of the planet's period is equal to the cube of its average distance. C) A planet must move fastest in its orbit at perihelion. D) Epicycles are needed to explain the varying brightness of the planets.
Answer: D
Which of the following was NOT a contribution of Galileo to astronomy? A) Sunspots showed the Sun was rotating on its axis, like the Earth does. B) The four moons of Jupiter are a model for the solar system motions in general. C) The phases of Venus prove it orbits completely around the Sun. D) The changing appearance of Saturn's rings corresponds to our seasons. E) The craters and mare of the Moon prove it a world in its own right.
Answer: D
Which of these was NOT seen telescopically by Galileo? A) Sunspots B) Venus' phase cycle C) Four moons around Jupiter D) Stellar parallax E) Craters and mare on the Moon
Answer: D
Which statement about the ecliptic is FALSE? A) The Sun appears to move about a degree per day eastward long it. B) It is tilted 23.5 degrees with respect to the equator. C) The year is marked by the Sun's return to the same place along it. D) The Moon can never leave it, but moves twelve times faster than the Sun. E) The major planets stay close to it, but not always on it.
Answer: D
Why is there a two day difference in the sidereal and synodic months? A) The Moon speeds up at perigee, and slows down at apogee. B) The sidereal day is four minutes shorter than the solar day, and it adds up. C) The Earth is closer to the Sun during the sidereal month. D) The Earth is also revolving around the Sun, so the Moon must "catch up". E) The Moslem lunar year is only 354 days long, on average.
Answer: D
The places where the Sun crosses the equator are called the: A) annalemmas. B) prime meridians. C) zeniths. D) equinoxes. E) solstices.
Answer: D) equinoxes
A year is defined as: A) the time it takes for Earth to complete a rotation on its axis. B) the time it takes for the Moon to complete an orbit of Earth. C) the time it takes for the Moon to complete a phase cycle. D) the time it takes for Earth to complete an orbit around the Sun. E) the time it takes for the Sun to complete an orbit around Earth.
Answer: D) the time it takes for earth to complete an orbit around the Sun.
According to Copernicus, the retrograde motion for Mars must occur: A) at inferior conjunction, when Mars laps the Earth and passes between us and the Sun. B) at superior conjunction, when Mars lies on the far side of the Sun. C) at quadrature, when Mars lies exactly 90 degrees east or west of the Sun. D) at greatest elongation, when Mars can get up to 47 degrees from the Sun. E) at opposition, when the Earth overtakes Mars and passes between Mars and the Sun.
Answer: E
Geosynchronous satellites orbit at about four Earth radii, where the Earth's gravitational pull is: A) 2 g. B) 1 g. C) 1/2 g. D) 1/4 g. E) 1/16 g.
Answer: E
How does Newton's Universal Law of Gravitation explain Kepler's laws? A) Universal gravitation implies that the orbits of the planets must be elliptical (Kepler's first law). B) Universal gravitation implies that the planets will sweep out equal areas in equal times (Kepler's second law). C) Universal gravitation implies that the planets further from the Sun will move more slowly than the planets closer to the Sun (Kepler's third law). D) Universal gravitation implies that when a planet is closer to the Sun in its orbit, it will move faster than when it is farther from the Sun (Kepler's second law). E) Both C and D are correct.
Answer: E
Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by: A) the mass of the planet only. B) the mass of the Sun only. C) both the mass of the planet and the mass of the Sun. D) the mass of the planet and its distance from the Sun. E) the mass of both the planet and the Sun and the distance between the two.
Answer: E
Scientists today do not accept the Ptolemaic model because: A) it is ancient history. B) it was too complicated, compared to Copernicus' heliocentric model. C) it has been shown that Ptolemy faked his data. D) it had no explanation for retrograde motion. E) the work of Tycho and Kepler showed the heliocentric model was more accurate.
Answer: E
The force of gravity varies with the: A) product of the two masses. B) inverse of the distance separating the two bodies. C) inverse square of the distance separating the two bodies. D) Both A and B are correct. E) Both A and C are correct.
Answer: E
The star Wolf 1061 has a parallax of 2.34 arcseconds, while the star Ross 652 has a parallax of 1.70 arcseconds. What can you correctly conclude? A) Both stars are outside the Milky Way galaxy. B) Wolf 1061 must have a larger proper motion than Ross 652. C) Ross 652 must have a larger proper motion than Wolf 1061. D) Ross 652 is closer to Earth than Wolf 1061. E) Wolf 1061 is closer to Earth than Ross 652.
Answer: E
What conditions are necessary for an annular solar eclipse? A) new moon on equator at perigee B) full moon on ecliptic at perihelion C) new moon on ecliptic at perigee D) new moon on equator at apogee E) new moon on ecliptic at apogee
Answer: E
When the Moon is directly opposite the Sun in the sky, its phase is: A) new. B) waxing or waning crescent. C) first or third quarter. D) waxing or waning gibbous. E) full.
Answer: E
Which of the following is a contribution to astronomy made by Galileo? A) The astronomical telescope can show us far more detail than the eye can. B) Jupiter has four moons orbiting it. C) The Moon has craters, mountain, valleys, and dark flat areas on its surface. D) Venus appears almost fully lit when it lies on the far side of the Sun. E) All of the above.
Answer: E
Which of these was NOT a part of the original Copernican model? A) The Sun lies at the center of the solar system. B) Mercury must move faster in its orbit than any other planet. C) The Earth rotates on its axis once a day. D) Venus can go all the way around the Sun. E) Mercury speeds up at perihelion, and slows down at aphelion.
Answer: E
Which of these was a contribution of Newton to astronomy? A) Artificial satellites could be put into orbit about the Earth. B) The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up. C) The Moon pulls as strongly on us as we do on it. D) His differential calculus lets us calculate planetary motions more accurately. E) All of these were due to Newton's work.
Answer: E
Which statement about the length of a day is FALSE? A) At the North Pole, the day lasts six months, then six months of night. B) At the equator, every day is twelve hours long, then twelve hours of night. C) For the United States, June 21st will be the longest day. D) The solar day is four minutes longer than the sidereal one. E) The sidereal day includes both the Earth's rotation and revolution around the Sun.
Answer: E
Why did early civilizations observe constellations? A) only for religious reasons B) for practical reasons, such as navigation and helping to determine seasons C) only for recreational reasons D) only to predict a person's destiny
B) for practical reasons, such as navigation and helping to determine seasons
What are constellations? A) groups of galaxies gravitationally bound and close together in the sky B) groups of stars making an apparent pattern in the celestial sphere C) groups of stars gravitationally bound and appearing close together in the sky D) ancient story boards, useless to modern astronomers E) apparent groupings of stars and planets visible on a given evening
B) groups of stars making an apparent pattern in the celestial sphere
Aristotle's hypothesis was that: A) lunar eclipses were created by our shadow. B) only a spherical Earth would always cast a circular shadow on the Moon. C) lunar eclipses would have to happen every full moon. D) the Sun lay at the center of the planet orbits. E) the Moon orbited the Earth.
B) only a spherical Earth would always cast a circular shadow on the Moon.
An effective theory must: A) have been proven. B) must have been around for centuries or longer. C) be continuously tested. D) include mathematical formulae.
C) Be continuously tested
The place the Sun stops its northward motion along the ecliptic is the: A) equator. B) prime meridian. C) summer solstice. D) vernal equinox. E) node of the ecliptic.
C) Summer Solstace
About how many stars are visible on a clear, dark night with the naked eye alone? A) a few dozen B) a few hundred C) a few thousand D) tens of thousands E) millions and millions
C) a few thousand
Into how many constellations is the celestial sphere divided? A) 12 B) 44 C) 57 D) 88 E) 110
D) 88
1) Which of the choices below correctly lists things in order from largest to smallest? A) Local Group, Solar System, Milky Way, Universe B) Universe, Milky Way, Local Group, Solar System C) Solar System, Local Group, Universe, Milky Way D) Universe, Local Group, Milky Way, Solar System E) Milky Way, Universe, Solar System, Local Group
D) Universe, Local Group, Milky Way, Solar System
Modern scientific theories are NOT: A) testable. B) continuously tested. C) simple. D) perfect. E) elegant.
D) perfect
How long is the precession cycle? A) 1 day B) 29.5 days C) 365.24 days D) 18 years, 11.3 days E) 26,000 years
E) 26,000 years