Mastering Astronomy: 03

Which of the following were key pieces of evidence that led to widespread acceptance of the Sun-centered model "extraordinary claim" during the period from about 1609 to 1630?

-Galileo's telescopic observations. -The fact that Kepler's laws allowed virtually perfect prediction of planetary positions.

Comet Tempel-Tuttle orbits the Sun every 33.0 years and has an orbital eccentricity of 0.91. Find the comet's perihelion and aphelion distances.

0.926, 19.7

Comet Tempel-Tuttle orbits the Sun every 33.0 years and has an orbital eccentricity of 0.91. Find the comet's average distance from the Sun (semimajor axis).

10.3

You are an astronomer on planet Nearth, which orbits a distant star. It has recently been accepted that Nearth is spherical in shape, though no one knows its size. One day, while studying in the library of Alectown, you learn that on the equinox your sun is directly overhead in the city of Nyene, located 1600 kilometers due north of you. On the equinox, you go outside and observe that the altitude of your sun is 74 ∘ What is the circumference of Nearth?

3.6x10^4 km

Which of the following is not true about a scientific theory?

A theory is essentially an educated guess.

Listed below are a series of statements about events that first happened in one of the four time periods identified in the sorting bins. Place each statement in the correct bin corresponding to when it first occurred in human history.

ANCIENT GREECE THROUGH PTOLEMY (about 150 A.D.) : - Suggestion that Earth might orbit the Sun - Recognition that Sun-centered model should lead to stellar parallax - Ability to predict planetary positions within a few degrees of arc EARLY COPERNICAN REVOLUTION (about 1543-1600) : - Copernicus proposes Sun-centered model - Planetary observations accurate within 1 minute of arc LATER COPERNICAN REVOLUTION (about 1609-1630) : - Ability to predict planetary positions within 1 minute of arc - Observation of phases of Venus - Sun-centered model with elliptical orbits NEWTON AND BEYOND (after about 1687) : - Mathematical descriptions of how gravity determines planetary orbits - Observations of stellar parallax

___ developed a model in which planets move around the Sun along perfectly circular orbits.

Copernicus

Consider again the set of observations from Part A. This time, classify each observation according to whether it is consistent with only the Earth-centered model, only the Sun-centered model, both models, or neither model. (Note that an observation is "consistent" with a model if that model offers a simple explanation for the observation.)

EARTH CENTERED ONLY: - A planet beyond Saturn rises in west, sets in east SUN-CENTERED ONLY: - Mercury goes through a full cycle of phases - Positions of nearby stars shift slightly back and fourth each year BOTH MODELS: - A distant galaxy rises in east, sets in west each day - Stars circle daily around north or south celestial pole - Moon rises in east, sets in west NEITHER MODEL: - We sometimes see a crescent Jupiter

Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law:

Earth travels faster in its orbit around the Sun in January than in July.

In Carl Sagan's statement "Extraordinary claims require extraordinary evidence," what does he mean by "extraordinary evidence"?

Evidence that is extremely strong.

___ answered the ancient objections to the heliocentric model, developed an enhanced telescope, and provided evidence in favor of the heliocentric model.5

Galileo

According to Kepler's third law

Jupiter orbits the Sun at a faster speed than Saturn.

___ described the laws of planetary motion for the heliocentric model, according to which planets move around the Sun along elliptical orbits.

Kepler

In which of the four time periods did the Sun-centered model gain widespread acceptance, meaning that nearly everyone who looked at the evidence concluded that it was correct?

Later Copernican Revolution (about 1609-1630)

Consider the following observations. Classify each observation based on whether it is a real observation (a true statement of something we can actually see from Earth) or one that is not real (a statement of something that does not really occur as seen from Earth).

REAL (true statements) : - Mercury goes through a full cycle of phases - A distant galaxy rises in east, sets in west each day - Stars circle daily around north or south celestial pole - Moon rises in east, sets in west - Positions of nearby stars shift slightly back and forth each year NOT REAL (false statements) : - We sometimes see a crescent Jupiter - A planet beyond Saturn rises in west, sets in east

Which of the following is not true about scientific progress?

Science advances only through the scientific method.

In the Greek geocentric model, the retrograde motion of a planet occurs when:

The planet actually goes backward in its orbit around Earth

___ provided a large amount of data from astronomical observations and suggested model in which the Sun orbits Earth while all other planets orbit the Sun.

Tycho

In Ptolemy's Earth-centered model for the solar system, Venus always stays close to the Sun in the sky and, because it always stays between Earth and the Sun, its phases range only between new and crescent. The following statements are all true and were all observed by Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?

We sometimes see gibbous (nearly but not quite full) Venus.

Let's start with an example from history. Listed below are a series of claims regarding United States President John F. Kennedy (1917-1963). Classify each statement according to whether or not it is falsifiable.

[Falsifiable: could be proven false] - Kennedy was the 35th president of the United States - Kennedy died from a bullet in his brain [Not falsifiable: could not be proven false] - Kennedy's death was the will of God - The murder of John F. Kennedy was an act of evil - If he'd lived, Kennedy would have ended the Vietnam War - Kennedy's murder was orchestrated by an undetectable shadow government of the United States

Let's now consider possible scientific claims. Recall that a scientific claim is falsifiable if it could in principle be shown to be false by observations or experiments, even if those observations or experiments have not yet been performed. Classify each claim according to whether or not it is falsifiable.

[Falsifiable: could be proven false] - The chemical content of the universe is mostly hydrogen and helium- Earth is at the center of the solar system- The Sun is at the center of the solar system - The observable universe contains approximately 100 billion galaxies [Not falsifiable: could not be proven false] - We are all playthings in a computer program created by advanced aliens - The laws of nature are magnificent and beautiful - The universe was created by God

Each of the four diagrams below represents the orbit of the same comet, but each one shows the comet passing through a different segment of its orbit around the Sun. During each segment, a line drawn from the Sun to the comet sweeps out a triangular-shaped, shaded area. Assume that all the shaded regions have exactly the same area. Rank the segments of the comet's orbit from left to right based on the length of time it takes the comet to move from Point 1 to Point 2, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.

all images go in middle spot

We'll now leave the comet behind, and instead consider the orbit of an asteroid in Parts D through F.Each of the four diagrams below represents the orbit of the same asteroid, but each one shows it in a different position along its orbit of the Sun. Imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. Rank the positions based on the area that would be swept out by a line drawn between the Sun and the asteroid during the one-week period, from largest to smallest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.

all images in middle spot

According to Kepler's second law, Jupiter will be traveling most slowly around the Sun's ______

aphelion

The following diagrams are the same as those from Part A. This time, rank the planets from left to right based on the amount of time it takes each to complete one orbit, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

arrange images from largest to smallest

The following diagrams are the same as those from Parts A and B. This time, rank the planets from left to right based on their average orbital speed, from fastest to slowest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

arrange images from smallest to largest

Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky?

at noon

When would a new Venus be highest in the sky?

at noon

Tycho Brahe's contribution to astronomy included:

collecting data that enabled Kepler to discover the laws of planetary motion.

The extent to which Mar's orbit differs from a perfect circle is ______.

eccentricity

Earth orbits in the shape of a/an ______ around the sun.

ellipse

Earth is located at one ___ of the Moon's orbit.

focus

In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is __________.

full whenever it is on the opposite side of the Sun from Earth

When we say that a planet has a highly eccentric orbit, we mean that:

in some parts of its orbit it is much closer to the Sun than in other parts.

When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been

incomplete.

We never see a crescent Jupiter from Earth because Jupiter __________.

is farther than Earth from the Sun

Consider again the diagrams from Part D, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions from left to right based on the distance the asteroid will travel during a one-week period when passing through each location, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.

longest to shortest - moon at the bottom, moon bottom right, moon top right, moon at the top

Consider again the diagrams from Parts D and E, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions (A-D) from left to right based on how fast the asteroid is moving at each position, from fastest to slowest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.

longest to shortest - moon at the bottom, moon bottom right, moon top right, moon at the top

Each of the following diagrams shows a planet orbiting a star. Each diagram is labeled with the planet's mass (in Earth masses) and its average orbital distance (in AU). Assume that all four stars are identical. Use Kepler's third law to rank the planets from left to right based on their orbital periods, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

longest: -one earth mass (2 au) -three earth mass (2 au) middle: -one earth mass (1 au) -two earth mass (1 au) shortest: -

When would you expect to see Venus high in the sky at midnight?

never

According to Kepler's second law, Pluto will be traveling fastest around the Sun when at ______.

perihelion

The mathematical form of Kepler's third law measures the period in years and the ______ in astronomical units (AU).

semimajor axis

Consider the hypothetical observation "a planet beyond Saturn rises in west, sets in east." This observation is not consistent with a Sun-centered model, because in this model __________.

the rise and set of all objects depends only on Earth's rotation