The Solar System Exam #1

Chapters 1-4

If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?

The altitude of the north celestial pole equals your latitute

During the time that a planet is in a period of apparent retrograde motion, _______.

over many days or weeks, the planets moves westward relative to the stars, rather than the usual eastward relative to the stars

The point in the sky directly above your head at any given time is called the

Zenith

What is really happening in space during the periods when we see a planet such as Mars going through apparent retrograde motion?

Earth is passing by Mars in its orbit around the Sun.

What celestial objects do rise in the east and set in the west, as viewed from the Earth?

galaxies, a planet during its apparent retrograde motion, the Moon, stars

What is the ecliptic?

the path the Sun appears to trace around the celestial sphere each year

The celestial sphere turns once around each day because

the planet on which we live is rotating

On the celestial sphere, halfway between the celestial poles lies the

celestial equator

In the Northern Hemisphere, the altitude (height in degrees above the horizon) of the North Star is always roughly equal to the

latitude of the observer

Where can you stand on Earth and see the stars always circling the zenith (and never rise and set)?

the south pole

Which one of the following constellations lies on the ecliptic?

Gemini

Scientific thinking is _______

based on everyday ideas of observation and trial-and-error experiments, which follow logical rules

Scientific models are used to _______.

make specific predictions that can be tested through observations or experiments.

What practical value did astronomy offer to ancient civilizations?

It helped them keep track of time and seasons, and it was used by some cultures for navigation.

Ptolemy was important in the history of astronomy because he _______.

developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries.

The ancient Greeks get a lot of attention for their contributions to science because _______.

they were the first people known to try to explain nature with models based on reason and mathematics, without resort to the supernatural.

What are some things that Galileo observed?

Four moons orbiting Jupiter, Phases of Venus, Mountains and valleys on the Moon, Sunspots

What discoveries helped to show that the heliocentric model was correct?

Kepler's discovery that the planets orbits are ellipses, Galileo observed a full set of phases for Venus and satellites orbiting Jupiter

Which of the following best describes how modern astronomers view astrology?

Astrology played an important part in the development of astronomy in ancient times, but is it not a science by modern standards.

When Copernicus first created his model of the Universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

Copernicus used perfect circles for the orbits of the planets.

Galileo challenged the idea that objects in the heavens were perfect by _______.

observing sunspots on the Sun and mountains on the Moon.

Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?

Phases of Venus

According to Kepler's third law, how does a planet's mass affect its orbit around the Sun?

A planet's mass has no effect on its orbit around the Sun.

Suppose a comet orbits the Sun on a highly eccentric orbit with an average (semi-major axis) distance of 1 AU. How long does it take to complete each orbit, and how do we know?

1 year, which we know from Kepler’s third law

What describes a characteristic of the solar system that is explained by Kepler's second law?

Pluto moves faster when it is closer to the Sun than when it is farther from the Sun.

If we have a new moon today, when will we have the next full moon?

In about 2 weeks

Suppose that instead of being inclined with respect to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. In such hypothetical situation, approximately how many solar eclipses would occur each year?

12

What conditions must exist for a lunar eclipse to occur?

The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

A total solar eclipse can occur

Anytime of year, anywhere on Earth, only on a new moon

We cannot see a new moon in our sky because

a new moon is quite near the Sun in the sky

The names of the seven days of the week are based on _______.

the seven naked-eye objects that appear to move among the constellations.

How does a 12-month lunar calendar differ from our 12-month solar calendar?

It has about 11 fewer days.

Given the map of Earth, the number of degrees that your location is north or south of the Earth's equator is called your:

latitude

The latitude of the Earth's equator is

0 degrees

Which of the following is an important part of the reason it is hotter in summer in North America than in winter?

the Sun's rays hit the Earth more directly in the Summer, and spread out less

Why is there a 4-minute difference between the solar day and the sidereal day?

because the Earth is going around the Sun in the course of a year

How did the world's countries solve the problem that mean solar time varies continuously as a traveler's longitude changes?

the world was divided into 24 time zones, with all communities within a time zone keeping the same mean standard time

Why was the problem of devising a workable yearly calendar so difficult on Earth?

The Earth's rotation period does not divide evenly into the Earth's period of revolution

A friend of yours who takes her astronomy class very seriously challenges you to a contest to find the thinnest crescent moon you can find just after new moon? What time of day is best for looking for this very thin crescent?

just as the Sun is setting, or just after

A serial killer from a strange cult only kills his victims when the Moon is full. He leaves a note on the body of his latest victim, explaining that the murder was committed when the Moon was rising. What time of day did the murder take place?

Roughly around sunset

What statement about the solar month and the sidereal month is correct?

The solar month is more than two days longer than the sidereal month

When the Sun and Moon are lined up and pull together, the tides they raise are called:

Spring Tides

How does the Sun influence the tides that we experience on Earth?

The Sun also raises tides on Earth, but its effect is smaller than that of the Moon

Recently, the media, always trying to make things sound sensational, have started to call totally eclipsed moon 'the blood moon.' Why does the Moon look reddish to us when there is a total lunar eclipse?

The Earth's atmosphere bends different colors of light to a different degree. During a total lunar eclipse, the red light of the Sun, filtering through the Earth's atmosphere colors the Moon red

What are the three possible types of solar eclipse?

Total, partial, annular

During a lunar eclipse, what is the name of the central, darker part of the
shadow?

Umbra

Where can we find evidence today about cosmic events that occurred billions of years ago?

By looking billions of light-years away out into space

Why is the ecliptic different from the celestial equator?

Earth’s tilt is 23.5 degrees

Where is the North Star located?

Tip of Ursa Major, count 5 lengths, located at the end of the handle for little dipper

Thales

• Prediction of a solar eclipse

• “What is the universe made of?”

• Proposed a flat Earth floating on infinite ocean

Anaximander

• Student of Thales

• Proposed a flat Earth floating in empty space surrounded by a sphere of stars

• Credited with the idea of Celestial Sphere

Pythagoras

• Obsessed with the idea of “Perfection”

• Envisioned Earth as a Sphere

Eudoxus

• Used concentric circles/spheres to (try) explain retrograde motion

Aristotle

• Gravity pulled “heavenly things” towards the center of the universe

• “Explained” why rocks fall down

• “Explained” why planets, moon, sun, stars revolve around Earth

Samos

• Determined the relative sizes of the moon

• Used Parallax to determine the size of the moon

• First to propose the sun at the center

Erastophenes

• Measured Earth’s radius and tlit

• Introduced leap day

Ptolemy

• Epicycles

• Used non-concentric circles/spheres to (try) to explain retrograde motions

What are three major innovations by the Greeks?

• The use of math

• The use of logic and reasoning

• The tradition of understanding without lying on supernatural explainations

The Heliocentric Model

• developed by Copernicus

• The model showed the sun at the center

What are some things Galileo discovered?

• Discovered craters, mountains, and plains on other planets, sunspots, and moons

• Moons of Jupiter obey Kelpler’s laws (4 moons)

What is Kelpler’s 1st law?

A planet orbits the sun in a ellipse

What is Kepler's 2nd law?

A planet's orbital speed is not constant: it moves fastest when closest to the Sun (perihelion) and slowest when farthest away (aphelion).

What is Kelpler’s 3rd law?

The planet’s sideral period squared is equal to major-axis cubed. Planets farther from the Sun have significantly longer orbital periods than planets closer to the Sun.

What is the difference between Synodic time and Sideral time?

One measures time based on the sun and the other based on stars; longer by 4 mins

Why do we always see only one face of the moon?

The moon’s orbit is in sync with Earth (Gravitational Pull)

What are the 3 types of Lunar Eclipse?

Penumbral, Total, Partial

Tides

Direct effects of Earth-Moon’s gravitational pull

How does gravity generate tides?

Moon pulls water towards it with gravitational force. Earth’s rotation creates a centripetal force