ASTR123 Modules 5 & 6 Quiz

Spacetime effects like time dilation are only noticeable when a. objects move close to the speed of light b. we have proper telescopes c. events in spacetime are connected by light beams d. very massive objects are involved e. we are within a black hole's event horizon

a

The speed that gravitational waves travel is a. the speed of light b. one half the speed of light c. the speed of sound in empty space d. dependent on the black hole mass e. twice the speed of light

a

To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at? a. mass b. surface temperature c. color d. distance e. Diameter

a

Current measurements of the Hubble constant H0 a. all agree on a single value b. disagree depending on the method used c. all use Type Ia supernovae as standard candles d. indicate the universe will someday contract to a single point e. are meaningless

b

Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by: a. the presence of a planet inside the orbit of Mercury, whose gravity influenced Mercury b. a distortion in spacetime caused by the gravity of the Sun c. the pull of a small black hole that orbits our Sun so closely that we are not able to see it d. the presence of a strong magnetic field in the Sun, which causes huge outburst of materialsw2

b

Merging black holes can be observed a. only at night b. by their radio wave emissions c. only by their gravitational wave emission d. by radio and gravitational wave emissions e. by their x-ray and gravitational wave emissions

c

The object(s) created by the merger of two black holes is a. a neutron star b. a pair of black holes with slightly lower mass c. a single black hole with mass slightly lower than the sum of the merging ones d. a single black hole with mass equal to the sum of the merging ones e. a supernova

c

When scientists say that "black holes have no hair", what do they mean? a. that the event horizon of a black hole is very smooth and does not have parts that jut out b. that if you threw something toward a black hole (a furry animal, say) it would quickly be ripped apart into smaller pieces c. that time near a black hole slows down so much our hair would not grow at a normal rate d. that once a black hole forms, very little information can be extracted from it about the material that is now inside e. no one knows what this means; regular people are not meant to figure out some of the weird things physicists say about black holes

d

A student shines a flashlight out the window of a very fast rocket. If the normal speed of light is c, then a. if she shines it forward, the light travels a bit faster than c b. if she shines it backwards, the light travels a bit slower than c c. if she shines it forward, the light travels a bit slower than c d. if she shines it backwards, the light travels a bit faster than c e. the light always travels at speed c

e

The 170817 event demonstrated that neutron star mergers a. produce gamma ray bursts b. produce gravitational waves c. produce most of the heavy elements on earth d. produce kilonova afterglows e. all of the above

e

General Relativity predicts that light passing near a massive object like the sun will a. be spread into a spectrum of wavelengths b. appear bent when observed from Earth c. be the same as always d. make the sun's mass exceed 1.4 solar masses e. be reflected back

b

The main postulate of special relativity is that a. the speed of gravity is zero b. the speed of light is an absolute constant c. cosmic rays should be able to reach the earth d. space and time should be discarded e. the speed of thought is nonexistent in Wil 100

b

When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that? a. the ISS is so far from the Earth, the gravity there is essentially zero b. the ISS is falling around the Earth, and in free fall, things feel no weight c. spacetime is so different aboard the ISS, that time stops, and so nothing can fall d. the law of gravity only works on the Earth, it doesn't work in space

b

When laser beams in an interferometer combine a. the resulting light only gets brighter b. an interference pattern of bright and dark light is formed c. the resulting light travels at twice the speed of light d. the increased laser power melts the camera e. the photons are destroyed

b

Special relativity gives a "speed limit", meaning that a. time slows down in rockets b. elliptical galaxies have smaller redshifts c. objects cannot move faster than the speed of light d. vehicles in Bern, Switzerland move too fast e. Einstein did not watch Star Trek

c

According to the general theory of relativity, the presence of mass a. causes motion at the speed of light squared b. is equivalent to the presence of light c. causes curved paths to straighten out until they are exactly straight lines d. causes a curvature (or warping) of spacetime e. will cause a black hole to form, unless there is motion

d

In the 2015 gravitational wave discovery event, the two black holes a. were supermassive b. combined to form a neutron star c. were each about 1 solar mass d. were each about 30 solar masses e. never merged

d

The location of the 170817 neutron star merger was first determined using a. radio telescopes b. texts by ancient Chinese astronomers c. the iterative guess method d. three gravitational wave detectors e. the earth's rotation

d

The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called a. the singularity b. the neutron star radius c. the gravitational redshift zone d. the event horizon e. television

d

We now know that most heavy elements such as gold are produced in a. factories in China b. supernova explosions of massive stars c. black hole mergers d. neutron star mergers e. white dwarf mergers

d

What is a key reason that gravitational waves are so much harder to detect than electromagnetic waves? a. gravitational waves don't create any kind of disturbance the way electromagnetic waves do b. gravitational waves are so strong, they really shake our detectors, making measurements difficult c. gravitational waves get all mixed up with sound waves in the Earth's atmosphere, and are therefore hard to distinguish from all the sound d. gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect e. because the GW scientists are incompetent

d