ASTR 1020: Midterm 1
67 Cards in this Set
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Ranked the historical events of the universe
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1. Big bang/universe begins to expand
2. Elements (carbons/oxygen) begin to exist
3. nulear fusion begins in the sun
4. earliest life on earth
5. dinosaurs go extinct
6. earliest humans
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On a cosmic calendar, when did earth form?
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Early September
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On a cosmic calendar, when did life arise on earth?
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september
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On a cosmic calendar when did humans first walk?
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few hours before 12/31 midnight
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Rank distance for Alpha Centauri, Andromeda galaxy, Orion Nebula, milky way
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Farthest: Andromeda, Milky way, orion nebula, alpha centauri
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Total number of stars in the observable uni is roughly equal to ...
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number of grains of sand on all the beaches in earth
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what is a general difference between a planet and a star?
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stars glow in infrared and visible light, planets only glow in infrared
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how long would it take to drive around the earth's equator?
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8.8 days
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As elevator starts upward, its speed increases. During this time, your weight will be...
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greater than normal
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Elevator is moving upward, as it nears floor it slows down, your weight will...
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be less
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What other motion would weight be greater than normal?
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elevator moves downward while slowing in speed
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What does the scale measure
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the force you exert on the scale
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As a cloud collapses, the force of gravity drawing the cloud inward ____ because ____
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become stronger, the strengh of gravity follows an inverse square law with distance
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as a cloud shrinks in size, its rate of rotation ____ because ____
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speeds up, its total angular momentum is conserved
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a cloud shrinks in size, its central temp ____ as a result of ____
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increases, gravitational potential energy being converted into thermal energy
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if the sun collapsed from its radius of 700,000 km to 6,000 km, what would happen
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a lot of gravitational potential energy would be converted into other forms of energy and the sun would spin much more rapidly
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suppose that two asteroids are orbiting the sun on nearly identical orbits, and they happen to pass close enough to each other to have their orbits altered by this, if one of the asteroids ends up moving to an orbit thats closer to the sun, what happens with the other
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it goes on orbit farther from the sun
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when a spinning ice skater pulls in his arms, he spins faster because...
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his angular momentum is conserved, reducing his radius must increase his speed
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what does temperature measure?
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average kinetic energy of particles in a substance
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average kinetic energy of particles in a substance
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fire an engine that shoots out gas to the right
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as an interstellar gas cloud shrinks in size, its gravitational potential energy...
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gradually transforms into other forms of energy
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according to the universal law of gravitation, if you triple the distance two objects, then the gravitational force btwn them...
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decreases by a factor of 9
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why is newtons version of keplers 3rd law so useful to astronomers
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it can be used to determine the masses of many distant objects
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according to the law of universal gravitation, what would happen to earth if the sun were somehow replaced by a black hole of the same mass
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earths orbit wouldnt change
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if earth were twice as far from the sun, the force of gravity attracting earth to the sun would be
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one quarter as strong
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What type of light: visble meets clear glass
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transmission
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What type of light: cell phone signals pass through walls
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transmission
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What type of light: visible light doesnt pass through a black wall
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absorption
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What type of light: blue light hits a red sweatshirt
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absorption
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What type of light: white light hits a white piece of paper
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reflection/scattering
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What type of light: red light hits a red sweatshirt
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reflection or scattering
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What type of light: light comes from a light bulb
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emission
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What type of light: light comes from your computer screen
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emission
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The higher temperature object peaks on a graph at
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a shorter wavelength
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Neon sign appears reddish-orange because
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neon atoms emit many more yellow and red photons than blue and violet photons
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what type of visible light spectrum does the sun produce
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absorption
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nuclear fusion of hydrogen into helium occurs in the ___
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core
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energy moves through the suns ___ by means of the rising of hot gas and falling of cooler gas
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convection zone
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nearly all the visible light we see from the sun is emitted from the ___
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photosphere
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most the suns uv light is emitted from the narrow layer called the ... where temp increases w/ altitude
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chromosphere
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we can see the suns ... most easily during total solar eclipses
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corona
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the ... is the layer of the sun between its core and convection zone
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radiation zone
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In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea?
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It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth.
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What do we mean when we say that the Sun is in gravitational equilibrium?
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There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
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The phase of matter in the Sun is
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plasma
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Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen?
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Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal.
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Which of the following changes would cause the fusion rate in the Sun’s core to increase?
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an increase in core temp, a decrease in the core radius
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Which of the following must occur for a star’s core to reach equilibrium after an initial change in fusion rate?
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Which of the following must occur for a star’s core to reach equilibrium after an initial change in fusion rate?
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What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?
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The Sun’s core would start to heat up and the rate of fusion would increase even more.
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"The corona is hotter than the photosphere." Which of the following statements provides observational evidence for this claim?
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The corona primarily emits X rays while the photosphere primarily emits visible light.
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How do we know the Sun’s mass?
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We can calculate it by applying Newton's version of Kepler's third law with Earth's orbital period (1 year) and Earth’s average distance from the Sun (1 AU).
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Which of the following observations can be used to check that we really do know the Sun’s internal fusion rate?
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Measurements of the Sun’s total energy output into space
Observations of neutrinos coming from the Sun
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Which of the following must be true of a person who shares the same reference frame as you?
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The person must not be moving relative to you.
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A man is moving by you at a speed close to the speed of light. Which of the following correctly summarizes the effects you would notice on his mass, size, and time?
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His mass would be increased from its value at rest, his length would be decreased from its rest value but only in the direction in which he is moving, and his time would be running slower than yours.
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Kim is in a spaceship moving past you at half the speed of light. Which of the following correctly describes how you will perceive each other's time?
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You will say that Kim's time is running slow, and she will say that your time is running slow.
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How will you and the passenger on the other spaceship observe each other’s heart rates as you pass by in your spaceships?
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You would observe that the passenger in the other spaceship has a slower heart rate than you do, and she would observe that you have a slower heart rate than hers.
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f we made a scale model of the solar system with the sun
as a grapefruit, the planets would be various small objects (pea, grape)
scattered at distances from feet to tens of yards. On the same scale, where
would the next star (next grapefruit) be?
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across the US
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Inverse square law
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3x farther away-> 9x fainter
10x farther away-> 100x fainter
10^6 farther away-> 10^12 fainter
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Greeks believed the earth was...
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spherical, size unknown
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How long does light take to go from the sun to the earth
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8 light minutes
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How long does it take to go from the sun to pluto
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about 5 hours
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how does light take to go from the sun to alpha centauri
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about 5 years
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If a planet travels in a circular orbit w/o speeding up or slowing down is it accelerating
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yes
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when i drive at 30 mph, does it have more kinetic energy than at 10 mph
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yes, 9 times more
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Can newtons law of gravity be used to find the force between the earth and you? what is D
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yes, D is distance from you to the center of the earth
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the total kinetic energy something contains is called its
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heat, heat content, or thermal energy
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What's the most common element in the universe
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hydrogen, 74% by mass
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ASTR 1020: Midterm 1