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Test 1 review from SMartwork questions Astro 131
Terms in this set (75)
We normally write our address as a street number in a city or town, which is in a state or province, followed by a country. How would you state our cosmic address (small to large)?
Earth-> Solar System -> Milky Way Galaxy-> Local Group-> Supercluster -> Universe
a light-year is a measure of
if we represent the Sun as a volleyball (diameter= 65 cm), how far away would we find the earth model? (actual 1.4x10^9 meters) Earth is 1.5x10^11 meters from the Sun
6.96 X 10^1
What is the diameter of Earth in this model? Earth's actual diameter is 1.3 x 10^7 meters.
As shown in the pictures, the time it would take light to travel between the Earth and Moon is 1.25 seconds, so we call the distance 1.25 light-seconds. Knowing that the distance between the Sun and Earth is 8.3 light-minutes, how many Earth-Moon distances could fit between the Sun and Earth?
398.4 Earth-Moon distances
light from Earth to moon is
light from Earth to Sun is
Light from Pluto to nearest star
Light from Across the length of the Milky Way galaxy:
The average distance from Earth to the Moon is 384,000 km. How many days would it take, traveling at 800 km/h (the typical speed of a jet), to reach the Moon?
Suppose we find Earth- like planet around our nearest stellar neighbor, Alpha Centauri (located only 4.4 light-years away). If we launched a "generation ship" at a constant speed of 1750.00 km/s from Earth with a group of people whose descendants will explore and colonize this planet, how many years before the generation ship reached Alpha Centauri? (Note there are 9.46 ××1012 km in a light-year and 31.6 million seconds in a year.)
choose one of the following conclusions that best explains the cause of the shift from day to night.
The shift from day to night is caused by the rotation of the Earth around its axis
The stars we see at night depend on
Earth's location in its orbit, the time of the observation, and our location on earth
No matter where you are on Earth, stars appear to rotate about a point called the
The horizon is defined
by the direction perpendicular to a line to the zenith
The reference points in your sky above head is
the reference points in your sky near waist is
Highest altitude to the lowest altitude:
zenith-> North celestial pole -> Highest point of celestial equator-> Horizon
Based on this info, determine where you would expect to find Polaris in your local sky when you are standing at the equator
Which way do most objects travel when viewed from far above the North Pole of Earth?
Examine the following figure, which demonstrates star trails that would be visible in a photo centered on the North Star (Polaris) when the camera's shutter is left open to reveal the path the stars are taking as they move during part of one night.
The stars closest to polaris move in smaller circles, all of the stars move in a counterclockwise path around Polaris
The celestial equator
is directly above Earth's equator
Which of the following terms are specific to the observer (that is, they are unique for the observer)?
horizon, meridian, zenith, and nadir
Which of the following terms define locations that are the same for everyone?
ecliptic, celestial equator, and north celestial pole
During the day, the sun is too bright for us to see where it is located with respect to the constellations, but we can use our observations of stars at night to figure this out. Based on the way stars shift position over the course of a year, your knowledge of how the time of day is defined, and the fact that the same constellations are seen at the same place in the sky at the same time of night on a given day of the year, which of the following is most likely correct?
The sun appears to move across the constellations over the course of a year, ending where it started with respect to the background stars by the end of that period.
If the star Polaris has an altitude of 35 degree, then we know that
our latitude is 35 degrees north
The southernmost star in the famous Southern Cross constellation lies approximately 65° south of the celestial equator. What is the northernmost latitude in the US from which the entire Southern Cross is visible?
25 degrees N
How does the changing position of the Sun on the ecliptic affect our view of the sun in our local sky at different locations on Earth?
In the northern Hemisphere, the length of day is shorter in December than it is in June, also at latitudes closer to the poles, the difference in the Sun's illumination throughout the year is more extreme. also in the northern Hemisphere, the sun is lower in the sky in December than it is in June
What causes the angle of the sun to change over the year?
Earth's North pole always points in the same direction in space. Sometimes this is toward the sun, and sometimes it's away from the sun.
What does the angle of the sun's rays matter in regard to Earth's seasons?
They are more spread out if they strike at an angle
Hypothesis= seasons are caused by a variable distance between the Earth and the Sun...For hypothesis:
closer light source has stronger intensity. - Earth's orbit is elliptical
Hypothesis= Seasons are caused by a variable distance between the Earth and the sun... Against Hypothesis:
Earth's closest approach to sun is in january - S and N hemispheres have opposite seasons.
The Earth's orbit is elliptical (not a perfect circle).
- The Southern Hemisphere experiences opposite seasons from the Northern Hemisphere.
- The intensity of light from a source is stronger closer to the source.
- The Earth's closest approach to the Sun is in January.
Is the hypothesis that the seasons are caused by a variable distance between the Earth and the Sun verified or falsified by the evidence?
they hypothesis is falsified because some of the evidence is against it
What causes the seasons?
The tilt of the Earth's rotation axis to its orbit around the Sun causes parts of the Earth to experience more direct illumination from the Sun and longer days during the summer than the winter
Suppose the tilt of Earth's equator relative to its orbit were 30 degrees instead of 23.5 degrees. At what latitudes would the arctic and antarctic circles be located?
60 degrees latitude.
Why is there an angle between the ecliptic and the celestial equator?
Earth's axis is tilted with respect to its orbit.
If Earth's axis were tilted by 45 degrees instead of its actual tilt, how would the seasons be different than they are currently?
Winters would be colder.
Looking down on Earth from above the North Pole, the Moon orbits Earth
What phase is the Moon in when you initially open the simulation?
What time of day is it for the person shown on the Earth when you initially open this simulation?
At which of these times would the person shown on Earth be able to observe this waxing crescent moon?
At this instant, when is the first quarter moon in the person's sky?
The moon is high in the south
Arrange the observer and the moon so that it is approximately 6:00PM (sunset) for the observer and the Moon is just rising on the eastern horizon. What is the phase of the Moon?
You see the moon rising, just as the sun is setting. What phase is the moon in?
You see the moon on the meridian at sunrise. The phase of the moon is
When the moon is closer to the sun than Earth is, which phases are visible?
Waxing crescent, Waning crescent
3 observations about the phases of the moon are connected: the location of the Moon in the sky, the time for the observer, and the phase of the Moon. If you know two of these, you can figure out the third. An observer sees the moon in______ phase, overhead, at midnight.
You see the first quarter Moon on the meridian. Where is the Sun?
on the western Horizon
Arrange the observer and the moon so that the Moon is the 3rd quarter, and the time for the observer is approximately noon (the sun is on the meridian). Where is the Moon in the observer's sky?
on the western horizon
A lunar eclipse occurs when ____ shadow falls on the ____.
If the moon were in its same orbital plane but twice as far from Earth, which of the following would happen?
Total eclipses of the sun would not be possible
How did the ancients know the planets were different from the stars?
They saw that the planets move with respect to the stars over the course of many nights
What can you conclude from this, assuming that the geocentric model holds that the Sun, Moon, and planets like Mars all orbit around Earth in simple circles?
The geocentric model is wrong because it falsely predicts that Mars should always move in the same direction with respect to the stars
Which of the following most closely explains what we would see from Earth according to the geocentric model that includes epicycles?
The Planets would usually move west to east through the stars, but they appear to reverse direction when they are on the part of the epicycle that has motion opposite to that of the larger circle.
Choose the answer that most closely matches what we would observe in our sky, according to this figure, if the Earth orbits around the Sun.
Over the course of a year, stars should appear to move back and forth, with stars closer to us moving a larger distance
However, they did not measure stellar parallax—the stars did not appear to move back and forth at all over the course of a year. What is the most likely reason for this apparent lack of motion?
The stars must be so distant that their parallaxes are too small for the ancient greeks to have been able to measure with their technology
Which of Galileo's astronomical observations were best explained by a heliocentric model?
phases of Venus, moons of Jupiter
This is known as Kepler's first law of planetary motion, which of these statements are true:
Halley's Comet has a highly eccentric orbit and, Elliptical orbits cause a planet to sometimes be closer to and sometimes farther away from the sun
Kepler's second law says that
planets move fastest when they are closest to the sun
Choose the statement below that directly follows from kepler's second law of planetary motion
Venus is traveling faster when it is at perihelion ( the closest distance to the Sun) than when it is at aphelion ( the farthest distance from the sun)
What happens to the period when you make the semimajor axis larger?
the period increases
What happens to the period when you make the semimajor axis smaller?
The period decreases
Largest semimajor to smallest semimajor..
1. A planet with a period of 2 Earth years 2. a planet with a period of 1 Earth year 3. A planet with a period of 0.5 Earth years 4. A planet with a period of 84 Earth Days
You have discovered the planet Zoltron. It is 12.0 times farther from the sun than Earth (12.0 AU). How long does it take this planet to go once around the Sun?
41.6 years (12 cube root then squared)
Halley's Comet has an orbital period of 76 years. What is the semimajor axis of its orbit?
17.9 AU (76 years cube root then sqared)
Imagine that Earth were in a stable orbit at its current distance from the Sun, but around a different star that had twice the mass of the Sun. Which of the following would have to be true?
Earth's year would be shorter
When the professor tosses the ball in the air, what forces are acting on it once it leaves her hand?
gravity pulling downward
If you push with a different force on 2 cars of the same mass, which car will have the bigger acceleration?
the car you pushed with the larger force
imagine a planet moving in a perfectly circular orbit around the sun. Is this planet experiencing acceleration?
Yes. it is changing its direction of motion all the time.
Lowest acceleration to Highest acceleration
(2m, F=0) (2m, F) (m,f) (m, 2F)
Isaac Newton developed a theory of gravity by first considering Galileo's experiment of dropping objects of different masses from the Leaning Tower of Pisa. Galileo found that, when air resistance is negligible, all objects took the same amount of time to hit the ground when dropped from the top of the tower.
The acceleration of all objects dropped from the tower is the same
F is the force that is causing the object to accelerate. In the case of dropping objects from a height, the force that causes them to accelerate toward the Earth is gravity. If the acceleration of objects dropped from a height does not depend on the object's mass (as shown by Galileo's experiment), what does this imply about the force of gravity?
The force of gravity increases with increased mass
Compared to your mass on Earth, on the Moon your mass would be
the same; mass doesn't change
If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would
increase by a factor of 4
Rank the following pairs of masses by the strength of their gravitational force. Smallest Force to Greatest Force= Note: The captions under the images give the relative masses of each object and their distance from one another (M1, M2, d)
(m,m,1.5r) (m,m,r) (m,2m,r)
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