winter 2017 final review
suppose Hubble's constant is 100 km/s/Mpc. what would the approximate age of the universe be in this case. you may assume a constant expansion rate.
10 billion years
a galaxy is discovered with a recessional velocity of 7000 km/s. assuming Hubble's constant is 70 km/s/Mpc, what is the distance to the galaxy?
100 Mpc
about how far does the moon travel on the celestial sphere each day?
12 degrees
pluto's average distance from the sun is 40 AU. what is the orbital period?
240 years
communications satellites are place in "synchronous" orbits about earth's equator, meaning that they orbit earth in exactly 24 hours and so stay above the same spot on earth at all times. roughly how distant from the center of earth and such satellites? (hint: use kepler's 3rd law, and the fact that the moon's distance is 240,00 miles.)
25,000 miles
suppose the universe is 14 billion years old. if we observe a galaxy 10 billion light years away, hold old was the universe at the same time the light we see left that galaxy?
4 billion years
the visible light spectrum of the full moon is
a continuous spectrum with absorption lines
when the moon is a thin crescent, what is the phase of earth as seen from the moon?
a gibbous (mostly full) earth
the Great Red Spot is
a large, long-lived storm system in Jupiter's atmosphere
a pulsar is
a rapidly rotating neuron star, emitting beams of radio and sometimes x-ray and visible energy.
hydrogen gas in a low-density, hot transparent cloud gives off what type of spectrum?
a series of emission lines spaced in a mathematical sequence
which is false? a. our intuition is not always a good guide to physics. b. logic has always worked in the study of physics. c. a theory is like a law of physics that is speculative. d. a theory is tested through its implicit predictions.
c. a theory is like a law of physics that is speculative.
which is NOT one of Newton's Laws, and is in fact false? a. any object remains stationary or moves at constant velocity unless a force acts on it. b. if a force acts, the velocity changes in the direction of the force, and in proportion to the force applied. c. any planet orbiting the sun does so at constant velocity. d. any force is accompanied by an equal and opposite reaction force.
c. any planet orbiting the sun does so at constant velocity.
suppose that at the same time on the same night we see one supernova (a star exploding) in the Andromeda galaxy, 2 million light-years away from us, and another in the galaxy M82, 6 million light-years away from us. which of the following statements is correct? a. both stars exploded at the same time, because we saw the explosions at the same time. b. we cannot tell which star actually exploded first, because they are so far away. c. the supernova in the Andromeda galaxy actually occurred after the one in M82. d. the supernova in the Andromeda galaxy actually occurred before the one in M82.
c. the supernova in the Andromeda galaxy actually occurred after the one in M82.
which is true? a. to see a total solar eclipse, you must travel to one particular small spot on earth. b. from the penumbral part of earth's shadow, the sun is totally obscured. c. at earth's poles, day and night are caused by earth's rotation. d. acceleration has units m/s^2, and technically, the direction must also be given. e. the planets follow elliptical orbits with the sun at the center.
d. acceleration has units m/s^2, and technically, the direction must also be given.
describe day and night at the north (or south) pole.
daylight and nighttime each last 6 months.
you are on the equator. where in the sky is Polaris?
due north on the horizon
we can't yet tell what's past the cosmic horizon of the universe, but hope to be able to with the successor to the Hubble Space Telescope.
false
a planet can occasionally act as a circumpolar star as seen from Santa Barbara.
false, circumpolar is near north
Venus's surface is very hot because it absorbs more sunlight than the earth does.
false, larger greenhouse effect because traps more sunlight rather than absorbs more sunlight
the sun appears to circle the celestial sphere in one year because the earth is circling the sun. the sun's apparent path is called the horizon.
false, the path is called the ecliptic
what is meant by the statement that space is curved near a black hole?
general relativity views the effect of gravity as a result of mass changing the geometry of space-time. ex. space around a massive object like a star as curved like a bowl, the planets orbiting star are just like marbles rolling around the sides of a bowl.
which is true about the Theories of Relativity?
if a light ray passes close to the sun, it will emerge out the other side in a different direction.
suppose you travel at constant speed to the Galactic Center, 25,000 light years away. which is false?
if the speed is high enough, you can make this trip and get back to earth before summer break - from the perspective of earth, it will still take 25,000 years one way even though it will seem like a shorter trip aboard the spaceship.
Olbers Paradox
if the universe were in fact isotropic, infinite, and static, we should be able to look in any direction and see a star (at some distance).
a supernova is produced by
the collapse of the core of a very massive star
retrograde motion of the outer (superior) planets occurs because
the earth is moving in its orbit faster than any superior planet, so when the planet is at opposition (opposite the sun in the sky), the planet seems to go backwards.
the intersection of the plane of the earth's orbit with the celestial sphere is known as
the ecliptic
the "block and feather" demonstration showed that in the absence of air friction:
the force of gravity must be proportional to the mass.
which planets can never be seen at midnight?
the inferior planets
In the chemical symbol "4 He", the "4" gives
the number of protons plus neutrons
what is the condition for applying the blackbody laws to get the approximate properties of the spectrum of a light source?
the source must be opaque.
suppose we observe an absorption line in a stellar spectrum, measuring a wavelength 5 nm below the laboratory value.
the star is approaching us but we don't have enough information to calculate the speed.
the autumnal equinox is about that time of year when
the sun crosses the equatorial plane, or celestial equator, moving south
it is warmer in the summer than it is in the winter because
the sun is higher in the sky and the days are longer.
what determines the temperature of a rocky planet without an atmosphere?
the sunlight absorbed and the infrared light emitted
which planets can be seen at midnight?
the superior planets
the fact that virtually all galaxies are receding from us implies that
the universe is expanding
according to the Doppler effect,
the wavelength of light is shifted to a shorter wavelength if the source of light is moving toward you.
how do red giants of 0.2 solar masses differ from those of 1.0 solar mass?
they do not exist, must be 0.4 and above
a main sequence star which is ten times more massive than the sun has luminosity which is
thousands of times that of the sun
a circumpolar star never sinks below the horizon over the course of a night.
true
a good example of a positive feedback effect in global warming is that melting sea icea causes a decrease in the earth's albedo, meaning we absorb more sunlight than ever.
true
a theory is a pattern in nature thought to have predictive power. the test of a theory is prediction. that's where pseudo-science fails.
true
all of the planets stay near the ecliptic as they move on the celestial sphere.
true
fluorescent light bulbs produce emission lines, so they don't obey the blackbody laws. they can be highly efficient emitters of visible light.
true
if a giant stopped the moon in its orbit, it would immediately fall to earth.
true
incandescent light bulbs are always operated at a relatively low temperature so that their output is mainly in the infrared part of the spectrum and is thus wasted.
true
incandescent light bulbs contain glowing wires which behave approximately according to the blackbody laws.
true
intuition has sometimes led us astray, but logic has never failed us.
true
it takes hours for light to get to us from Pluto, but years for light to get to us from the nearest stars.
true
old streambeds and other topographic features indicated that Mars once had liquid water on its surface.
true
ozone depletion may have stabilized becuase of an international agreement to reduce emission of certain industrial chemicals called CFCs.
true
red giant stars are powered by hydrogen burning in a shell surrounding a core, which has been depleted of hydrogen.
true
the Cosmic Microwave Background has a blackbody spectrum.
true
under exotic conditions, intuition sometimes fails, e.g. speed of light is the same for all observers.
true
when the Voyager mission flew past Uranus on its way to Neptune, it exerted just as much gravitational force on Neptune as Neptune did on Voyager.
true
while the heavy elements have been cooked up in stars, several of the light elements and isotopes were made in the first few minutes of the Big Bang.
true
opaque bodies approximately obey the blackbody laws: the Stefan-Boltzmann Law and Wien's Law.
true, opaque = blackbody & transparent → emission
the final stage in the evolution of a low-mass star
white dwarf
by which method have we found black holes left over from the collapse of massive star cores?
x-rays given off by hot matter as it approaches the event horizon
in the simplified version of Kepler's Third Law as applied to planets orbiting the sun, P^2 = a^3, the units of orbital period P and semi-major axis (the semi-major axis is 400,000 km) of the ellipse a must be respectively:
years and AU
the strength of gravity on the moon is about 40% of that on earth. if you were to visit the moon, what would happen to your mass and weight compared to when you were on earth?
your mass would be the same but your weight would be less.
in Newton's law of universal gravitation defining the force between earth with mass M and an orbiting satellite of mass m at a distance r from earth, G
is a constant, throughout all observable space and time
the escape velocity from the event horizon of a black hole
is the speed of light
on it's way to earth, the light from a distant quasar passes through a thin, cool cloud of intergalactic gas. what effect does that cloud have on the quasar spectrum we detect from earth?
it adds some absorption lines.
a pulsar rotates at 100 revolutions per second and its axis of rotation is aligned with its magnetic poles. the frequency of its pulses as seen from Earth is
it doesn't appear to pulsate at all.
which of the following is false regarding the Big Bang Theory?
it explains the production of the heavy elements, such as carbon, oxygen and iron.
which is true regarding the nature of light?
it has particle-like properties as well as wave-like properties.
what is the significance of the turn-off point in the H-R diagram of a star cluster?
it indicates the age of the star cluster.
how is the transparency of earth's atmosphere changing in optical light?
it's constant
how is the transparency of earth's atmosphere changing in infrared light?
it's decreasing
how does the UV transparency of earth's atmosphere today compare with its natural pre-industrial value?
it's greater, more transparent because we have lost some of ozone layer
the earth's shadow falling on the moon is the reason we see
lunar eclipses
we can find the distance to very remote galaxies by
measuring their redshifts
when the moon is waning half (the third-quarter position), at what time of day does it rise?
midnight
on the main sequence
more massive stars consume their fuel very quickly and have relatively short lives.
which is true regarding the transparency of earth's atmosphere?
more transparent than 100 years ago in UV region - anthropogenic destruction, carbon emission destroys ozone
the most common elements in the universe are
mostly hydrogen, smaller quantities of helium and very small quantities of heavier elements
a curious fact about the structure of the planet Jupiter, compared to that of earth, is that it has
much greater mass but much lower average density
the Southern Cross is a constellation near the South Celestial Pole. when will this object be visible in the Santa Barbara sky?
never
can a planet ever act as a circumpolar star as seen from Santa Barbara?
no
what is the closest the sun ever gets to the zenith (the point directly overhead) from Santa Barbara?
our latitude is about +34 degrees, 34 - 23 (tilt, closer during summer) = 11 degrees
the moon's orbital period and its rotation period are the same. therefore,
people on earth always see the same half of the moon
Captain Picard wishes to send a message to a Ferengi ship, which is located behind a large dust cloud. in order to ensure the best possible transmission he sends
radio waves
immediately after leaving the main sequence, a star becomes a
red giant, almost all stars will become red (super) giants, become planetary nebula near end of life.
the bright red clouds surrounding newly formed massive stars are
regions of ionized hydrogen
why are black holes often observed as x-ray sources?
stellar mass black holes, may reside in close proximity to a giant star. as that giant star pushes material outward, some of it can fall into the black hole, swirling around it in an accretion disk. high gravity = high speed = closer orbit faster than farther = energy conversion into heat (10^6 K) = high energy x-ray photons
the vernal equinox in the NH is that time of the year when the
sun crosses the equatorial plane, or celestial equator, moving northward
when the moon is full, at what time does it rise?
sunset
Venus shows changes in angular size, and also shows phases similar to those of the moon. when Galileo first saw these changes, he concluded that
Venus orbits the sun
the sun moves about 12 degrees on the celestial sphere each day.
false
these are all Great Circles: the celestial equator, the ecliptic, and lines of constant celestial latitude.
false
the gravitation acceleration on the earth's surface is ~10 m/s^2. what would it be on the surface of a planet with the same size, but one-half the mass?
5 m/s^2
earth's mass is 6.0 x 1024 kg while its radius is 6.4 x 106 m. approximate density?
5500 kg/m^3
the gravitational acceleration on the earth's surface is 32 ft/s/s. what would it be on the surface of a planet with the same size, but twice the mass?
64 ft/s/s
which of the planets fits the following description: "a hot, solid surface, cloud-shrouded, and with a dense CO2 (carbon dioxide) atmosphere?"
Venus
which is false? a. the moon must be full at the time of a solar eclipse. b. the moon must be full at the time of a lunar eclipse. c. the "inferior" planets Venus and Mercury always stay in the general direction of the Sun. d. retrograde motion of the superior planets is an illusion
a. the moon must be full at the time of a solar eclipse (it would be new).
which is true? a. the sun is a population 1 star. b. population 1 stars lack heavy elements in their atmosphere. c. the globular clusters are full of typical population 1 stars. d. the plane of the Milky Way has been almost completely cleared of dust. e. a star behind a dust cloud look redder but brighter than it would if seen directly.
a. the sun is a population 1 star.
the star Sirius produces 9.2 x 1027 J in one second. at what rate does it convert matter into energy?
about 1.0 x 10^11 kg/s
the star Sirius produces 9.2 x 10^27 J in one second. at what rate is H consumed in the solar core? (hint: take the efficiency of 0.007 into account.)
about 1.4 x 10^13 kg/s
how long does night last on the moon?
about 2 weeks
how strong is the gravitational force that acts on an astronaut in the space shuttle in a circular orbit 300 km above earth's surface?
almost (but not quite) as strong as when the astronaut is standing on the surface of earth
what do scientists mean by the word "theory" ?
an idea which allows you to try to predict future events
if you threw a rock into a black hole, how long would it appear to take for it to get to the event horizon?
as an object approaches the event horizon, it would appear to an outside observer that the object slows down and takes an infinitely long time to actually cross the event horizon.
atoms in a thin, hot gas (such as a neon advertising sign) emit light
at very specific wavelengths, the pattern depending on the type of atom
which is the false? a. ozone depletion has made the atmosphere more transparent to UV light. b. carbon dioxide production is making the atmosphere more transparent to infrared light. c. the surface of Mars is sterilized by UV light. d. the surface of Venus is extremely hot because its atmosphere traps infrared light. e. the earth's crust has about as much carbon dioxides as the atmosphere of Venus.
b. carbon dioxide production is making the atmosphere more transparent to infrared light.
which is false? a. incandescent light bulbs contain glowing wires which behave approximately according to the blackbody laws. b. incandescent light bulbs are operated at about the same temperature as the sun's surface, so that they produce visible light efficiently. c. incandescent light bulbs are always operated at a relatively low temperature so that their output is mainly in the infrared part of the spectrum and is thus wasted. d. fluorescent light bulbs produce emission lines, so they don't obey the blackbody laws. they can be highly efficient emitters of visible light.
b. incandescent light bulbs are operated at about the same temperature as the sun's surface, so that they produce visible light efficiently.
which is true of planetary orbits? a. they travel in elliptical orbits with the sun in the center. b. the speed is the greatest when the planets are closest to the sun in their orbits. c. the outer planets travel faster, but because of their huge orbits, they still take longer to go around the Sun than the inner planets. d. the outer planets travel around the celestial sphere in a single direction, without appearing to stop and back up. e. all the planets go through phases just like the moon does as seen from earth.
b. the speed is the greatest when the planets are closest to the sun in their orbits.
why does hydrogen "burning" by fusion reactions only occur in the deep interiors of the sun (and other stars)?
because the requisite conditions of high temperature and high density only occur there
an astronaut is floating freely in space. If (s)he were to push on a nearby spaceship, what would happen?
both the astronaut and the spaceship would move, but in opposite directions.
which of these statements is false? a. the temperature of an airless planet is determined by a balance between the sunlight absorbed and the infrared blackbody emission from the surface. b. the natural greenhouse effect causes a large warming of earth surface. c. the transparency of Earth's atmosphere in the infrared spectral region is rising, causing the surface to heat up. d. there is a huge natural greenhouse effect operating on Venus, causing the surface temperature to be around 900 degrees F. e. carbon dioxide is a powerful absorber of infrared light.
c. the transparency of Earth's atmosphere in the infrared spectral region is rising, causing the surface to heat up.
global warming is caused by
carbon dioxide and other gases making Earth's atmosphere less transparent to infrared radiation.
the motions of large portions of the earth's surface, the "plates", are caused by
convective flow of matter in the earth's interior
which is false? a. the terrestrial planets have low masses because the rocky elements have low abundances. b. earth has a substantial natural greenhouse effect. c. given earth's gravity and temperature, helium cannot be held in the atmosphere d. if a giant stopped the earth in its orbit, it would fall into the sun. e. all the terrestrial planets show plate tectonics
e. all the terrestrial planets show plate tectonics (ex. Mars has volcanoes but no plate tectonics).
which statement is true? a. Jupiter has at least one huge volcano (the Great Red Spot). b. Mars has chains of moderate-sized volcanoes like Earth does. c. although Jupiter has more mass than Mars, Mars is denser than Jupiter. d. Mercury is very dense. it is composed mostly of very heavy elements which resist vaporization, such as iron. e. c and d
e. c and d
which is false? a. light energy seems to come in discrete packets proportional to the frequency of the light. b. a blackbody absorbs all striking it. c. the hotter solid object blackbody emits more light at all frequencies than a cooler one. d. the same gas cloud can show an absorption line spectrum to one observer and an emission line spectrum to another. e. if the sun was twice as far from earth, it would appear only half as bright.
e. if the sun was twice as far from earth, it would appear only half as bright.
which is true? a. fusion of iron produces energy. b. fission (splitting) of iron produces energy. c. the sun will eventually develop an iron core. d. iron has the most mass per nuclear particle of all the elements. e. iron has the least mass per nuclear particle of all the elements.
e. iron has the least mass per nuclear particle of all the elements.
which physical phenomenon keeps a white dwarf star from collapsing inwards upon itself?
electron degeneracy or "quantum crowding"
what is the "observable universe" ?
everything within the "cosmic horizon"
Jovian planets have densities similar to that of water and we know in fact that they are mostly made of water.
false
a comet's orbit has a maximum distance from the sun (aphelion) twice as large as the minimum distance from the sun (perihelion.) at aphelion the speed is twice as large as at perihelion.
false
a particular star rises on the horizon when your watch says 8 pm. a month later that star will still rise at 8 pm.
false
all of the planets and moons are all roughly spherical.
false
all of the planets appear as crescents as seen from Earth at one time or another.
false
at the north pole the sun will pass directly overhead at zenith on the date of the summer solstice.
false
it's easy to determine your longitude when you're in earth's NH, just by measuring the altitude (angular distance about the horizon) of Polaris.
false
planetary orbits are circles with the sun in the center.
false