Question 1

If the Moon in its orbit around Earth moves between Earth and the Sun and then 2 weeks later it moves to the other side of Earth as seen from the Sun, why then do we not see both a solar and a lunar eclipse every month?
A)The Moon's orbital plane is at right angles to the ecliptic.
B)Earth's orbital plane is slightly inclined to the ecliptic.
C)The Moon's orbital plane is slightly inclined to the ecliptic.
D)The Moon's orbital plane is inclined slightly to the celestial equator.

Accepted Answer

The reason we do not see both a solar and a lunar eclipse every month is because the Moon's orbital plane is slightly inclined to the ecliptic (the path of the Sun in the sky). As a result, most of the time the Moon appears to pass above or below the Sun from our perspective on Earth, and most full or new moons do not result in an eclipse. Only when the Moon's orbit intersects with the ecliptic at the right angle can we see a solar or lunar eclipse.

Question 2

You travel to an exotic place to observe a total solar eclipse in December and someone on this trip tells you that the next eclipse to occur on Earth will be a lunar eclipse in March. Is this likely to be true?
A)It could be true, since such an eclipse can occur when the Sun's position with respect to the celestial equator is changing rapidly.
B)Yes, but only once about every 1000 years.
C)No, it is not likely to be true.
D)Yes, it is likely to be true.

Accepted Answer

The statement is not likely to be true. While lunar eclipses are more common than total solar eclipses, they do not occur immediately after each other. Typically, there will be at least one partial solar eclipse and/or one or more partial lunar eclipses between a total solar eclipse and a lunar eclipse. Additionally, lunar eclipses occur when the full moon passes through Earth's shadow, which can only happen when the moon is opposite the sun in the sky. Therefore, a lunar eclipse cannot occur in March if a total solar eclipse occurred in December of the previous year, since the two events are separated by less than six months.

Question 3

What is the declination of the Moon?
A)0°
B)+5°
C)-5°
D)a number that changes significantly over 1 month

Accepted Answer

The declination of the Moon changes significantly over 1 month as it moves through its orbit around the Earth. Therefore, there is no fixed declination for the Moon.

Question 4

What is the right ascension of the Moon?
A)0 hours
B)20 minutes
C)23 hours 40 minutes
D)a number that changes significantly over 1 month

Accepted Answer

The right ascension of the Moon changes significantly over the course of one month due to the Moon's orbit around the Earth. This means it does not have a fixed right ascension value.

Question 5

When in total lunar eclipse, the Moon shows a reddish color because:
A)light from the northern and southern lights (the aurora) on Earth, which is predominantly red, illuminates the Moon.
B)this is the color of the residual thermal glow from a still-warm Moon, after the abrupt removal of the heat of the Sun.
C)the Moon is illuminated only by the residual glow from the dark side of Earth, which is predominantly red.
D)the red part of the solar spectrum, predominantly, is deflected onto the Moon by Earth's atmosphere.

Accepted Answer

During a total lunar eclipse, the Earth's atmosphere bends the sunlight passing through it and filters out the shorter-wavelength blue and green light, leaving only the reddish hues to fall on the Moon's surface, hence giving the Moon a reddish color.

Question 6

One eclipse year is the time needed for:
A)three saros intervals.
B)the line of nodes of the Moon's orbit to go from alignment with respect to the Sun-Earth line to the next identical alignment.
C)365 successive eclipses.
D)two consecutive identical alignments of the Sun, the Moon, and the line of nodes.

Accepted Answer

One eclipse year is the time taken for the line of nodes of the Moon's orbit to return to alignment with respect to the Sun-Earth line. This is because during this time, the Earth completes one revolution around the Sun, and the Moon completes approximately 12.37 orbits around the Earth, causing the line of nodes to move approximately 19.4 degrees due to the precession of the lunar orbit. This is also equivalent to approximately 223 synodic months.

Question 7

The saros is the period of time between:
A)successive solar eclipses in a series of similar eclipses at about the same latitude on Earth.
B)two successive total lunar eclipses, seen from the same point of Earth.
C)two successive passages of the Sun through the vernal equinox.
D)two successive eclipse seasons, about 6 months.

Accepted Answer

The saros is a period of approximately 18 years and 11 days, which is the time between successive solar eclipses in a series of similar eclipses at about the same latitude on Earth. This means that after a saros, the Sun, Earth, and Moon return to nearly the same relative positions, resulting in a similar eclipse.

Question 8

Total solar eclipses seen at approximately the same latitude occur in a sequence with a time interval, the saros, of 223 lunar sidereal months. How many eclipse years is this?
A)19
B)16.7
C)18
D)17.6

Accepted Answer

1 lunar sidereal month = 27.321661 days223 lunar sidereal months = 223 x 27.321661 days = 6082.93 days1 eclipse year = 346.62 days6082.93 days / 346.62 days = 17.55 eclipse yearsThe closest answer choice is A) 19 eclipse years.

Question 9

The time interval between one total solar eclipse and the next total solar eclipse, visible from the same location on Earth, must be all of the following EXCEPT ONE. Which is the EXCEPTION?
A)a whole number of lunar months
B)a whole number of sidereal months
C)a whole number of eclipse years
D)a whole number of saros intervals

Accepted Answer

The time interval between two total solar eclipses visible from the same location on Earth is not a whole number of sidereal months. This is because the synodic month (the time between two consecutive new moons) is slightly longer than the sidereal month (the time it takes the Moon to return to the same position relative to the stars). As a result, the Moon must travel a little bit farther in its orbit to return to the same position relative to the stars, and this means that it takes slightly longer than a whole number of sidereal months for the Earth-Moon-Sun geometry to repeat itself for a total solar eclipse.

Question 10

How does the duration of a total solar eclipse compare with the duration of a total lunar eclipse?
A)The solar eclipse is always longer.
B)The lunar eclipse is always longer.
C)They are the same length.
D)Depending on where the Moon and Earth are in their orbits, either eclipse might be longer.

Accepted Answer

Total lunar eclipses last longer than total solar eclipses because the Earth's umbra (the shadow within which the eclipse is total) is much larger than the Moon's, allowing the Moon to spend more time in the Earth's shadow than the Earth does in the Moon's during a solar eclipse.

Question 11

Which significant observation led the Greeks to accept the idea that Earth was a sphere?
A)The shape of the darkening across the Sun's disk during a solar eclipse always appeared circular.
B)The shape of Earth's shadow on the Moon during a lunar eclipse was always circular.
C)The Sun disappears below one horizon each day and reappears above the opposite horizon.
D)The shape of the eclipse shadow on Earth during a solar eclipse was always circular.

Accepted Answer

The observation that the shape of Earth's shadow on the Moon during a lunar eclipse was always circular led the Greeks to accept the idea that Earth was a sphere. This is because only a spherical object can cast a circular shadow from any angle.

Question 12

The Greek astronomer who first measured the radius of Earth reasonably accurately was:
A)Archimedes.
B)Eratosthenes.
C)Aristotle.
D)Ptolemy.

Accepted Answer

Eratosthenes is credited with first measuring the radius of Earth with an error of less than 2%. Archimedes was a mathematician and physicist, Aristotle was a philosopher, and Ptolemy was an astronomer and mathematician, but they are not known for accurately measuring Earth's radius.

Question 13

Eratosthenes, an ancient Greek astronomer, is famous for:
A)measuring the diameter of Earth by comparing the direction to the Sun at noon at two different points on Earth.
B)measuring the diameter of Earth by timing how long it took the Moon to traverse Earth's shadow during a lunar eclipse.
C)measuring the relative distances to the Sun and the Moon by timing the exact moments when the Moon was at first and third quarter.
D)measuring the distance to each of the known planets by timing how long it took the planet to orbit the Sun.

Accepted Answer

Eratosthenes is famous for measuring the diameter of Earth by comparing the direction to the Sun at noon at two different points on Earth. This was done by measuring the angle of the Sun's rays at noon on the summer solstice in two different cities and using trigonometry to calculate the distance between the two cities and the circumference of the Earth.

Question 14

Eratosthenes measured the radius of Earth by:
A)timing the disappearance of the Sun at sunset for two different positions on Earth on the same day of the year.
B)estimating the size of the shadow of Earth on the Moon during a lunar eclipse.
C)measuring the angular position of the pole star from several positions on Earth.
D)noting the different angles of the Sun at midday on the same day of the year at different positions on Earth.

Accepted Answer

Eratosthenes noticed that on a certain day of the year, the Sun was directly overhead in the Egyptian city of Syene, but was at an angle in Alexandria. By measuring the angle of the Sun's rays in Alexandria, he was able to calculate the angle between Syene and Alexandria. Using this angle and the distance between the two cities, he was able to calculate the circumference of the Earth, and from that, its radius.

Question 15

Eratosthenes, an astronomer in ancient Greece, measured the radius of Earth by making observations of:
A)the Sun's direction at midday at two positions on Earth, on the same day of the year.
B)the tidal ebb and flow of ocean waters.
C)the deviation of magnetic north, as seen from a compass, from true north.
D)relative times of arrival of the Sun due south of an observer at two positions on Earth.

Accepted Answer

Eratosthenes measured the Earth's radius by observing the angle of the Sun's rays at midday in two different locations (Alexandria and Syene) on the same day of the year. He used the difference in the angles to calculate the circumference and thus the radius of the Earth.

Question 16

The ancient Greek astronomer Aristarchus is famous for devising a method for measuring the:
A)length of an eclipse cycle.
B)diameter of Earth.
C)relative distances of the Sun and the Moon.
D)precise distance between Alexandria and Syene in ancient Egypt.

Accepted Answer

Aristarchus is known for being the first to propose a heliocentric model of the solar system and for estimating the relative sizes and distances of the Sun and Moon from Earth.

Question 17

In about 280 B.C., Aristarchus devised a method of estimating the relative distance of the Sun and the Moon from Earth by:
A)measuring the angle between the Sun and Moon when the Moon is at first or third quarter.
B)calculating their orbital radii from their orbital periods around Earth, using Kepler's law.
C)noting the size of Earth's shadow on the Moon during a lunar eclipse.
D)estimating the positions of the Moon and Sun in the sky from different positions on Earth as they passed through the due south direction on the same day.

Accepted Answer

Aristarchus used the method of measuring the angle between the Sun and Moon when the Moon is at first or third quarter to estimate the relative distance of the Sun and the Moon from Earth. This method is known as the "lunar distance method."

Question 18

Which of the following investigations did the Ancient Greeks NOT carry out?
A)determination that Earth's orbit around the Sun is an ellipse
B)determination that Earth is approximately spherical
C)measurement of the relative distances of the Moon and the Sun from Earth
D)measurement of Earth's radius

Accepted Answer

The determination that Earth's orbit around the Sun is an ellipse was not carried out by the Ancient Greeks, but by Johannes Kepler in the 16th century. The Greeks did, however, make significant contributions to astronomy and mathematics, including the other investigations listed.

Question 19

How did the ancient Greek astronomer Aristarchus of Samos determine that the Moon's diameter was about 1/3 that of Earth?
A)by measuring the time it takes the Moon to cross the face of the Sun during a solar eclipse
B)by measuring the relative durations of lunar and solar eclipses
C)by measuring the time it takes the Moon to pass in front of a background star
D)by measuring the time it takes the Moon to move through Earth's shadow during a lunar eclipse

Accepted Answer

Aristarchus of Samos determined the Moon's diameter was about 1/3 that of Earth by measuring the time it takes the Moon to move through Earth's shadow during a lunar eclipse. This method allowed him to estimate the relative sizes of the Earth and Moon based on the geometry of the Earth's shadow and the time the Moon took to pass through it.

Question 20

What is the diameter of the Moon compared to that of Earth, as measured by the ancient Greek astronomer Aristarchus of Samos?
A)1/3 the diameter of Earth
B)1/20 the diameter of Earth
C)20 times the diameter of Earth
D)3 times the diameter of Earth

Accepted Answer

Aristarchus of Samos estimated the Moon's diameter to be about 1/3 that of Earth, which, while not accurate by modern standards, was a remarkable attempt for ancient astronomy.

Quiz 3: Eclipses and the Motion of the Moon

If the Moon in its orbit around Earth moves between Earth and the Sun and then 2 weeks later it moves to the other side of Earth as seen from the Sun, why then do we not see both a solar and a lunar eclipse every month?

You travel to an exotic place to observe a total solar eclipse in December and someone on this trip tells you that the next eclipse to occur on Earth will be a lunar eclipse in March. Is this likely to be true?

What is the declination of the Moon?

What is the right ascension of the Moon?

When in total lunar eclipse, the Moon shows a reddish color because:

One eclipse year is the time needed for:

The saros is the period of time between:

Total solar eclipses seen at approximately the same latitude occur in a sequence with a time interval, the saros, of 223 lunar sidereal months. How many eclipse years is this?

The time interval between one total solar eclipse and the next total solar eclipse, visible from the same location on Earth, must be all of the following EXCEPT ONE. Which is the EXCEPTION?

How does the duration of a total solar eclipse compare with the duration of a total lunar eclipse?

Which significant observation led the Greeks to accept the idea that Earth was a sphere?

The Greek astronomer who first measured the radius of Earth reasonably accurately was:

Eratosthenes, an ancient Greek astronomer, is famous for:

Eratosthenes measured the radius of Earth by:

Eratosthenes, an astronomer in ancient Greece, measured the radius of Earth by making observations of:

The ancient Greek astronomer Aristarchus is famous for devising a method for measuring the:

In about 280 B.C., Aristarchus devised a method of estimating the relative distance of the Sun and the Moon from Earth by:

Which of the following investigations did the Ancient Greeks NOT carry out?

How did the ancient Greek astronomer Aristarchus of Samos determine that the Moon's diameter was about 1/3 that of Earth?

What is the diameter of the Moon compared to that of Earth, as measured by the ancient Greek astronomer Aristarchus of Samos?