ast 103 - test 1 Flashcards
Roughly how many stars are in the Milky Way Galaxy?
100 billion
Approximately how fast are you moving with the rotation of Earth?
1,300 km/hr
How long does it take our solar system to complete one orbit around the Milky Way Galaxy?
230 million years
Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
Copernicus, Kepler, and Galileo; about 400 years ago
Earth is made mostly of metals and rocks. Where did this material come from?
it was produced by nuclear fusion in the stars
What is the ecliptic?
the Sun’s apparent path along the celestial sphere
Momentum is defined as
mass times velocity
Kepler’s third law, p^2 = a^3, means that:
A) a planet’s period does not depend on the eccentricity of its orbit
B) all orbits with the same semimajor axis have the same period
C) the period of a planet does not depend on its mass
D) planets that are farther from the Sun move at slower average speeds than nearer planets
all of the above are correct.
Why do we have seasons on Earth?
as Earth goes around the Sun and Earth’s axis remains pointed toward Polaris, the Northern and Southern hemispheres alternately receive more and less direct sunlight
When are eclipse seasons?
when the nodes of the Moon’s orbit are nearly aligned with the Sun
According to the universal law of gravitation, the force due to gravity is
inversely proportional to the square of the distance between objects
According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
increase by a factor of 4
The names of the seven days of the week are based on the
most popular Norse gods
Which of the following statements about scientific models is true?
a model can be used to explain and predict real phenomena
Considering Einstein’s famous equation, E = mc^2, which of the following statements is true?
a small amount of mass can be turned into a large amount of energy
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
it held that the planets moved along small circles that moved on larger circles around Earth
Kepler’s second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun
What do scientists mean by verifiable observations?
statements that a person can, in principle, verify for themself
Suppose an object is moving in a straight line at 50 miles/hr. According to Newton’s first law of motion, the object will
continue to move in the same way until it is acted upon by a force
Newton’s second law of motion tells us that the net force applied to an object equals its
mass times acceleration
Changing the orbit of a spacecraft by firing thrusters is an example of
Newton’s third law of motion
Which of the following best describes the origin of ocean tides on Earth?
Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth
Which of the following statements about circumpolar stars is true at all latitudes?
they always remain above your horizon
What is stellar parallax?
it is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth’s orbit of the Sun
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
From Kepler’s third law, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to
4 astronomical units
In which of the following cases would you feel weightless?
while falling from a roof
What is meant by a hypothesis?
an explanation for a phenomenon that makes a prediction
The force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them
weakens by a factor of 4
The allowed shapes for orbits under the force of gravity are
ellipses, parabolas, and hyperbolas
Imagine we’ve discovered a planet orbiting another star at 1 AU every 6 months. The planet has a moon that orbits the planet at the same distance as our Moon, but it takes 2 months. What can we infer about this planet?
It is less massive than Earth
In addition to the conditions required for any solar eclipse, what must also be true in order for you to observe a total solar eclipse?
The Moon’s umbra must touch the area where you are located
Suppose you heat up an oven and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?
The water has a higher heat content than the oven
What makes the North Star, Polaris, special?
It appears very near the north celestial pole.
What is an astronomical unit?
the average distance from Earth to the Sun
The center of mass of a binary star system is
the point at which the two objects would balance if they were somehow connected
The fact that the Voyager spacecraft continue to speed out of the solar system, even though its rockets have no fuel, is an example of
Newton’s first law of motion
We can’t detect stellar parallax with naked- eye observations. Which of the following would make parallax easier to observe?
increasing the size of Earth’s orbit
Suppose that two objects collide. Which of the following things is not the same both before and after the collision?
the total temperature of the objects
Which of the following is smallest?
size of a typical planet
