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midterm practice exam study
Terms in this set (46)
If we imagine the history of the universe compressed into one year, dinosaurs became extinct
Which statement about motion in the universe is not true?
the mysterious dark matter is the fastest-moving material in the universe.
Where is our solar system located within the Milky Way Galaxy?
Roughly halfway between the center and the edge of the visible disk of the galaxy.
How are galaxies important to our existence?
Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.
Why do the patterns of the stars in our sky look the same from year to year?
Because the stars in the constellations are so far away
During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
Earth is catching up with and passing by Mars in their respective orbits.
Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
Your friend will also see a crescent moon.
Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
The right of Polaris; that is, 90 degrees counterclockwise from its current position.
Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon.
Then you must be located at
latitude 40 degrees south
An angle of 1 arcsecond is _________.
less than the thickness of a human hair held at arm's length
If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then
the four seasons would each be twice as long as they are now
When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.
higher in the sky
According to Kepler's third law (p2 = a3), 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.
Only one of the statements below uses the term theory in its correct, scientific sense. Which one?
Einstein's theory of relativity has been tested and verified thousands of times.
Imagine for a moment that despite all the evidence, Earth actually is not rotating and orbiting the Sun. Which of these hypothetical observations (none of them are real) would be inconsistent with our Sun-centered view of the solar system?
We discover a small planet beyond Saturn that rises in the west and sets in the east each day.
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
Phases of Venus.
Which of the following is not part of a good scientific theory?
A scientific theory cannot be accepted until it has been proven true beyond all doubt.
All the following statements are true. Which one follows directly from Kepler's third law (p2 = a3)?
Venus orbits the Sun at a slower average speed than Mercury.
When Copernicus first created his Sun-centered 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.
How does a 12-month lunar calendar differ from our 12-month solar calendar?
It has about 11 fewer days.
Suppose the Sun were suddenly to shrink in size but that its mass remained the same. According to the law of conservation of angular momentum, what would happen?
The Sun would rotate faster than it does now.
Imagine another solar system, with a star more massive than the Sun. Suppose a planet with the same mass as Earth orbits at a distance of 1 AU from the star. How would the planet's year (orbital period) compare to Earth's year?
The planet's year would be shorter than Earth's.
Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit (well above Jupiter's atmosphere and far from all of Jupiter's moons.) Which of the following statements would be true?
The asteroid's orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on.
Suppose that the Sun shrank in size but that its mass remained the same. What would happen to the orbit of the Earth?
Earth's orbit would be unaffected.
Which of the following scenarios involves energy that we would typically calculate with Einstein's formula E=mc2?
A small amount of the hydrogen in of a nuclear bomb becomes energy as fusion converts the hydrogen to helium.
Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?
Charge = +2; number of remaining electrons = 6.
The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?
The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
Which of the following statements about thermal radiation is always true?
A hot object emits more radiation per unit surface area than a cool object.
All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?
the temperature of the corona's gas is some 1 to 2 million Kelvin
Which of the following best describes why we say that light is an electromagnetic wave?
The passage of a light wave can cause electrically charged particles to move up and down.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
star X is moving away from us faster than Star Y.
Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?
The total amount of light in the spectrum tells us the star's radius.
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
The photo will seem to show only one star rather than two.
The Chandra X-ray Observatory must operate in space because:
X rays do not penetrate Earth's atmosphere.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars
The stars in our sky twinkle in brightness and color because of ______.
turbulence in the Earth's atmosphere
Which of the following best describes the development of astronomical telescopes over the past 60 years?
The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
Which of the following best describes the principle advantage of CCDs over photographic film?
capture a much higher percentage of the incoming photons than film.
Which of the following studies is best suited to astronomical observations that fall into the category called timing?
Studying how a star's brightness varies over a period of 3 years.
Mars has two moons that are most similar in character to:
In what way is Pluto more like a comet than a planet?
It is made mostly of rock and ice.
Venus has a higher average surface temperature than Mercury. Why?
Because its surface is heated by an extreme greenhouse effect.
Why was it advantageous for the Voyager mission to consist of flybys rather than orbiters?
Each individual spacecraft was able to visit more than one planet.
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is ______.
Which planet listed below has the most extreme seasons?
Why has NASA sent recent orbiters to Mars (such as Mars Reconnaissance Orbiter) on trajectories that required them to skim through Mars's atmosphere before settling into their final orbits?
It saves money because the spacecraft uses atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines.
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