Chapter 21 Earth Science

The length of daylight on the Moon is about ________.

Two weeks

Alpha Centauri is a famous star because it is one of the closest stars to earth (other than the sun of course). Where would you look in the night sky for Alpha Centauri?

Look for the brightest star in the constellation Centaurus.

Axial precession is sometimes called the precession of equinoxes because it results in a gradual shift, relative to the celestial background, of the position where the sun crosses the celestial equator at the equinox. Astrology is a mythology based on things like your "sign" which refers to the position of the sun in the celestial zodiac (the 12 constellations along the ecliptic) on your birthday. This system was established almost two thousand years ago. If this mythology were true (and you believe your horoscope) can you use the dates for your "sign" based on this 2000 year old system?

No, because 2000 years is almost 1/12, or one full sign shift, in the zodiac, so the 2000 year old signs are off by almost one full sign.

What is the modern explanation for what the ancient Chinese called "guest stars"?

They are Nova or Supernova.

A statement you will sometimes hear people say is that a day is not 24 hours but is really 23 hr. 56 min. and 4 sec. What does this refer to?

This is sidereal time, not solar time; a solar day is 24 hours.

The ________ day is the time it takes for Earth to make one complete rotation with respect to a star other than our Sun.

sidereal

At the beginning of spring, the vernal equinox, what is the right ascension of the sun?

0

At first quarter it is approximately ________ week(s) until the new moon.

3

Kepler's third law states that the planet's orbital period squared is equal to its mean solar distance cubed. Consequently, the solar distances of the planets can be calculated when their periods of revolution are known. The orbital period of Jupiter is 12 years, what is its distance from the sun in astronomical units?

5.2

If you determine the number of days in a year with solar time and sidereal time how would they vary?

A year measured in sidereal time would be about one day longer than a year based on solar time

Why were planets called "wanderers" by early Astronomers?

They were more relative to the stars

This scientist was the first to use the telescope in astronomy.

Galileo

This scientist wrote a book entitled Dialogue of the Great World Systems that compared the Earth-centered system with the Sun-centered system.

Galileo

Tyco Brahe set out to disprove Copernicus, so why is he famous for developing modern astronomical theory?

He made very precise measurements that were key data used by Kepler.

Why did Galileo's observation that Venus showed phases like the moon indicate that the geocentric theory of the solar system was not possible?

It demonstrated that Venus could not be in orbit around earth between earth and the sun because it shows "full" and "new" phases that would never occur with geocentric geometry.

The true shape of the planetary orbits was discovered by ________.

Johannes Kepler

Three laws of planetary motion were discovered by ________.

Johannes Kepler

The first modern astronomer to propose a Sun-centered universe was ________.

Nicolaus Copernicus

Who wrote the book entitled Of the Revolutions of Celestial Spheres (De Revolutionibus)?

Nicolaus Copernicus

What is the right ascension and declination for Polaris, the North Star?

RA indeterminate, D 90 degrees

According to the Ptolemaic (Greek) model of the universe, how many "heavenly" bodies could be observed wandering along the background of stars?

Seven

Where will the North Star be, relative to the celestial coordinates, 12,000 years from now?

Several degrees from the North Pole position, with Vega as the North Star.

This scientist determined the nature of the forces that kept the planets in their orbits.

Sir Isaac Newton

Which of these men formulated the Law of Universal Gravitation?

Sir Isaac Newton

What is the modern explanation for "guest stars" that appear in the night sky and then disappear?

Stars that go nova or supernova and appear as bright objects during the event

Earth hits its perihelion position in January. Solar radiation is proportional to the distance squared between the sun and the earth, so why isn't it hot in "winter" at perihelion?

The ellipticity of the orbit is small, so the affect is small; seasons are caused by tilt of the earth's orbit.

Why are there only 4-7 eclipses per year?

The moon's orbit is inclined to the ecliptic and only crosses the ecliptic twice per year.

The planets are "wanderers" in the night sky because they move relative to the stars. However, there movement is limited to the plane of the solar system, which is disk shaped. So relative to the celestial coordinate system, how do the planets actually move across the sky?

The move along the zodiac.

Why do the planets "drift" east relative to the stars and then move west for periods of time?

They are moving in the same rotation sense as the earth around the sun, but as the earth moves faster (or slower, depending on the planet) the motion appears to be backwards.

How did the Greeks estimate the size of the earth?

They measured the angle of the sun above the horizon at midday in two places with different latitude and used the angle to estimate the circumference of the earth.

Astrology is the folklore that arose from watching alignments in the night sky and the belief that these "celestial events" controlled human events. A 1960's folk song, "The Age of Aquarius" has numerous astrology references that relate to the positions of objects in the sky. The song has a line: "When the moon is in the 7th house, and Jupiter aligns with Mars, then peace will guide the planet..." From your knowledge of the stellar constellations and the celestial coordinate system, what does this line mean?

When Jupiter and Mars align in the sky, and the moon is in the 7th constellation of the zodiac, then peace...

The Southern Cross is a Southern Hemisphere constellation that is as famous the big dipper in the Northern Hemisphere because of the brightness of the stars. It has a Southern Hemisphere declination slightly higher than the big dipper's Northern Hemisphere declination. Is it visible anywhere in the United States?

Yes, it is visible in Hawaii during the summer months.

The belt of constellations through which all the planets move is called the ________.

Zodiac

A total eclipse of the Sun is only possible at ________.

a new moon

A slow motion of Earth's axis that requires 26,000 years to complete is called ________.

axial precession

In the Ptolemaic (Greek) model of the universe, the stars are attached to the ________.

celestial sphere

The earliest astronomical records appear to have been made by the ancient Chinese, Egyptians, and Babylonians in order to ________.

determine when to plant crops or hunt animals based on seasonal changes

In the Ptolemaic (Greek) model of the universe, the ________.

earth was in the center of the universe

Planets appear to move ________ each night, but occasionally they appear to stop and reverse direction.

eatward

The apparent path of the Sun upon the celestial sphere is called the ________.

ecliptic

One of the discoveries which led to the modern view of the solar system was that the orbits of the planets are ________.

ellipses

When viewing the planets, Mars appears to move backwards, or retrograde, because ________.

it is rotating around the sun slower than the earth's rotation

When the moon appears as a thin crescent in the evening sky, just after sunset, the lunar phase is ________.

new moon

Think about the correlation of the celestial coordinate system, the tilt of the earth's axis, and the positions on Earth. If you are an observer in the Southern Hemisphere, 2 degrees north of the Tropic of Capricorn, What time of year will you be able to see the North Star?

on the Southern Hemisphere summer solstice, around Dec. 21

Any variance in the orbit of a planet from its predicted path is referred to as ________.

perturbation

The apparent westward "drift" of the planets compared to background stars is called _______.

retrograde motion

The period of time required for the Moon to complete a cycle of phases is called the ________ month.

synodic

During a total lunar eclipse, the moon remains visible because ________.

the atmosphere of the earth refracts light around its perimeter

A sidereal day is defined as ________.

the time for one complete revolution of the earth relative to the celestial reference

Galileo observed several features using the telescope. Which one of the following did he not discover?

the two moons of Mars

Relative to the celestial background, the moon moves ________.

west to east