Astronomy Final Exam 2

1.

1 point

One of the central postulates of Special Relativity is

time can be measured with a universal absolute reference

gravity is an imaginary force

laws of physics are the same for uniformly moving frames

different observers measure identical times, masses, etc.

2.

1 point

The temperature in the center of the Sun us (blank) million degrees K.

15

1500

150

0.15

3.

1 point

If a star is moving toward us at nearly the speed of light, the light from the star

travels at a speed unchanged by the star's motion

has its wavelength red shifted

moves very slowly due to time dilation

travels toward us faster than usual

4.

1 point

The Michelson-Morley experiment showed that the measured speed of light depends on how fast the observer is traveling toward or away from the source of light.

False

True

5.

1 point

The shortest distance between two points on a sphere is

a hyperbola

a straight line

a parabola

a great circle

6.

1 point

Very close to a spinning black hole, which of the following statements is not true?

you can extract energy from the black hole

orbits rotating with/against the spin behave differently

there is no gravitational redshift

observers are forced to spin with the black hole

7.

1 point

The two most abundant elements in the Sun and stars are

hydrogen and helium

carbon and helium

calcium and hydrogen

oxygen and hydrogen

8.

1 point

If we were two-dimensional creatures living on the surface of a sphere, how could we tell the surface was curved?

Check to see if all the clocks ran at the same rate

Check if tennis balls were heavier than basketballs

Couldn't; must see sphere from outside to see curvature

Measure angles of triangles; see if they add to > 180 degrees

9.

1 point

The Sun is powered by fusing together four hydrogen atoms to make helium. Based on mass-energy conservation and Einstein's relation between mass and energy, E equals mc^2, the mass of the helium is (blank) the mass of the hydrogen atom?

greater than

less than

equal to

10.

1 point

If the rate of fusion in a star's core increases slightly, thereby increasing temperature, what happens next?

The core explodes

the core expands and cools back down

the core expands and heats up even more

the core collapses

11.

1 point

In his frame, Fred simultaneously sets off two flash bulbs separated by 10m. Ginger watches this from a moving frame and

also sees the flash bulbs go off simultaneously

sees the flash bulbs go off at two separate times

12.

1 point

According to our present thinking on the evolution of stars, the Sun will eventually become a supernova

False

True

13.

1 point

The strength of the tidal forces/accelerations on an observer will decrease as the size of the observer

does not depend on the size of the observer

becomes larger

become smaller

14.

1 point

Stars age and evolve because they

gradually use up their nuclear fuel

contract gravitationally

lose mass from their surfaces

form planetary nebulae

15.

1 point

Einstein concluded that an observer isolated in a small box but feeling his normal weight could not tell if he were

on Earth or being accelerated by a rocket in space

on Earth or the Moon

on a neutron star or a white dwarf

having his clock sped up by a nearby mass

16.

1 point

If the curvature of space is negative like a pringles chip, the circumference of a circle in terms of its radius is

larger than if space is flat

smaller than if space is flat

the same as in flat space

delicious

17.

1 point

A massive star dies when the core's gravity overcomes degenerate (blank) pressure. If the core collapse is stopped by degenerate (blank) pressure, a (blank) is formed.

electron; proton; black hole

electron; neutron; black hole

electron; neutron; neutron star

neutron; electron; electron star

18.

1 point

Suppose you fall into a black hole. An outside observer

sees you cross the event horizon

never sees you cross the event horizon

19.

1 point

For two chargeless black hole of the same mass, one is spinning and one is static. The event horizon of the static black hole is

the same as the spinning black holes

smaller than the spinning black hole

larger than the spinning black hole

20.

1 point

Fred and Ginger are flying in identical rockets. Ginger is flying away from Fred at a constant velocity. What does each see as the length of rocket parallel to the velocity?

Fred sees Ginger's rocket is longer

Both see the other's rocket is longer

Both see the other's rocket is shorter

Fred sees Ginger's rocket is shorter

21.

1 point

In Ginger's reference frame, Fred is moving at a constant velocity v directly away from her. She sees Fred's block running more (blank) and light from Fred (blank)

rapidly, redshifted to longer wavelengths

slowly, redshifted to longer wavelengths

slowly, shifted to shorter wavelengths

rapidly, blueshifted to shorter wavelengths

22.

1 point

During the late stages of evolution of a massive star, what energy loss mechanism becomes increasingly important as the core fuses heavier elements?

losses from neutrinos

losses from pressure expansion of the envelope

losses from convection of the envelope

losses from energy-to-mass conversion

23.

1 point

If there were no fusion reactions to the Sun, it would

shrink and become hotter and brighter

expand and become cooler and fainter

shrink and become cooler and fainter

expand and become hotter and brighter

24.

1 point

To see the first appearance of a white dwarf, we would most likely look

for a close binary system

in a young open cluster

at the center of a planetary nebula

for a star leaving the Main Sequence

25.

1 point

Consider three reference frames. 1) a space station, (2) a rocket accelerating out of the station, and (3) a rocket passing the space station moving at a constant velocity. Which of these are inertial reference frames?

1 and 2

all three

2 and 3

1 and 3

26.

1 point

Fred and Ginger are hovering in rockets above a Schwarzchild black hole. Ginger is closer to the event horizon so Fred (Ginger) sees Ginger's (Fred's) clock running blank, (blank)

slower, faster

slower, slower

faster, faster

faster, slower

27.

1 point

"Matter tells space-time how to curve; the curvature of space-time tells matter how to move". This is a summary of

Special relativity

Newton's laws of motion

Kepler's laws of planetary motion

General relativity

28.

1 point

In a pre-supernova star, nuclear fusion reactions in the core are halted when the core consists primarily of which element?

Uranium

Carbon

Iron

Hydrogen

29.

1 point

If you were to travel to a nearby star on a relativistic starship at near-light speed and then return to Earth, on your return you would find that

more time had passed on Earth than on your ship

you had arrived in the past before you left Earth

more time has passed on your ship than on Earth

no difference in the passage of time

30.

1 point

Suppose you fall into a black hole.

You would not notice crossing the event horizon

You would think you never arrived at the event horizon

31.

1 point

A photon emitted directly outward from an atom at the surface of a black hole would rise some distance above the black hole before gravity pulled it back.

False

True

32.

1 point

In general for high mass stars, after fusing all of element A to element B, what happens in the core of stars?

core cool down; fusion of element B stars

core heats up; fusion of element B starts

core unchanged; fusion of element B starts

core unchanged; nuclear reactions convert B back to A

33.

1 point

Tides are due to differences in the gravitational acceleration across an object according to Newtonian gravity. According to general relativity they are due to

the existence of black holes

the curvature of space time

differences in gravity across an object

34.

1 point

An observed, measurable result predicted only by the General Theory of Relativity

angular momentum is conserved

force equals mass times acceleration

complete confusion of the student body

path of light is deflected by gravitational fields.

35.

1 point

The Sun today is powered by

nuclear fusion of hydrogen into helium

droplets of liquid helium falling into its center

a black hole at its center

fires where hydrogen and oxygen chemically combine

36.

1 point

An object orbiting a black hole in an elliptical orbit must

Precess

eventually escape the black hole

no object can orbit a black hole in an ellipse

orbit in the same sense as the black hole is spinning

37.

1 point

The Main Sequence lifetime of a star depends on its

mass

electric charge

carbon abundance

angular momentum

38.

1 point

It is generally considered impossible to get a spacecraft up to the speed of light because

its mass would go to zero

it would require an infinite amount of energy

time would run backwards

its size would become infinite

39.

1 point

White dwarfs typically are about

cool as the coolest Main Sequence stars

massive as our moon

luminous as the sun

large as the Earth

40.

1 point

Changes in the composition of a star's core and changes in the way a star generates energy are the reasons

why the stars evolve

why some stars form planets and others don't

why stars move down the Main Sequence with time

why stars move up the Main Sequence with time

41.

1 point

It is possible to have circular obits around black holes.

True

False

42.

1 point

A spinning neutron star may be detected as a

black hole

shell star

supergiant

pulsar

43.

1 point

The properties of an isolated black hole will not depend on

mass

spin or angular momentum

magnetic fields

electric charge

44.

1 point

If you travel by the Earth in a rocket (with the engine turned off) at close to the speed of light, because of your speed you would

notice your clock running too slowly

notice your clock running too fast

notice your ruler was too long

feel nothing unusual

45.

1 point

If the sun suddenly collapsed into a black hole without losing any mass, the

Earth's mass would become considerably larger

Earth would have much higher tides

Earth's orbit would not be affected

Earth would escape from the solar system

46.

1 point

How do you make a gas with electrons in it degenerate?

You make the gas extremely dense

you pass a shock wave through it

you mix it in a lot of alcohol

you ionize it

47.

1 point

A neutron with a half life of ten minutes in its rest frame leaves a particle accelerator with a Lorenz factor of 5. What does a scientist at rest observe the half life to be?

1 minute

20 minutes

2 minutes

50 minutes

48.

1 point

Schwarzchild black holes have none of the following except

charge

mass

all of the answer choices

spin

49.

1 point

Can I make a photon orbit a black hole in a circular orbit?

Yes, but it is not stable.

No, photons can never have bound orbits

Yes, and it will stay there forever.

50.

1 point

A neutron star is typically the size of

a city

the orbit of Mercury

the sun

the orbit of the Earth