ASTR 1P01/02: Introduction to Astronomy I/II

Practice Exam #6

Please solve the following questions. This is not a real exam, it will not be graded, and you do not need to submit your solutions to anyone. The questions are simply intended to help you practice for the real exam.

These questions will not appear in the exam itself. Students who don't genuinely attempt to solve the questions on their own, and only memorize the solutions, will have a very hard time in the actual exam!

This sample exam is online, but the real exam will be given in person, at a time and place indicated on the course website.

THIS IS NOT THE ACTUAL EXAM!
THIS IS JUST A PRACTICE EXAM!
THE REAL EXAM IS IN PERSON!

If you need any clarifications for these questions, you can ask for them on the course Teams channel.

Question 1

The expansion of the universe is...

Accelerating.
Decelerating.
Unchanging.

Question 2

What is an Einstein ring?

The ring that Einstein gave his first wife.
A light source that is being gravitationally lensed into 4 distinct copies.
A light source that is being gravitationally lensed into a circular shape.

Question 3

Which of the following objects bends spacetime the least?

The Earth.
The Sun.
The Moon.

Question 4

How did LIGO provide evidence for gravitational waves in 2015?

Indirectly, by observing changes in the orbital period of a binary system.
Directly, by measuring the local influence of the gravitational wave itself on spacetime.
Directly, by detecting electromagnetic emission from the gravitational wave event.

Question 5

What is the difference between the weak equivalence principle and the Einstein equivalence principle?

The weak equivalence principle is formed in terms of mass, while the Einstein equivalence principle is formed in terms of energy.
The weak equivalence principle is formed in terms of acceleration, while the Einstein equivalence principle is formed in terms of mass.
The weak equivalence principle is formed in terms of mass, while the Einstein equivalence principle is formed in terms of acceleration.

Question 6

The relative velocity between Alice and Bob corresponds to a Lorentz factor of 5. Alice measures a proper time of 2 seconds between two events. How much time does Bob measure?

10 seconds.
2 seconds.
50 seconds.

Question 7

Which of the following was observed by the Event Horizon Telescope?

PSR B1919+21.
M87*.
Cygnus X-1.

Question 8

What is the Einstein cross?

A light source that is being gravitationally lensed into 4 distinct copies.
A light source that is being gravitationally lensed into a circular shape.
The cross that Einstein gave his first wife as a Christmas gift.

Question 9

The general-relativistic prediction for the perihelion precession of Mercury was...

Correct, because it took into account the curvature of spacetime.
Incorrect, because it did not take into account the curvature of spacetime.
Correct, because the curvature of spacetime is not relevant for this prediction.

Question 10

What will be the advantage of putting a gravitational wave detector in space compared to detectors on Earth?

The waves will not be blocked by interstellar dust.
It will be sensitive to waves with much longer wavelengths.
It will be sensitive to waves with much shorter wavelengths.

Question 11

In the Eddington experiment, why was it important to measure the position of the stars during an eclipse?

Because at that time their light is not bent due to the curvature of spacetime.
Because that was the only time those stars could be seen next to the Sun.
Because that was the only time during the year those stars could be seen.

Question 12

What was the significance of the gravitational wave event GW150914?

It was the first time a black hole was photographed.
It was the first time both gravitational waves and electromagnetic waves were detected from the same source.
It was the first time gravitational waves were detected directly.

Question 13

Why don't we notice special-relativistic effects like time dilation in our daily lives?

Because our clocks compensate for these effects.
Because we are moving at speeds much slower than the speed of light.
Because we are moving at speeds much faster than the speed of light.

Question 14

What was the source of the gravitational wave event GW150914?

Two neutron stars merging.
Two black holes merging.
A black hole and a neutron star merging.

Question 15

You are jumping from a tree down to the ground. According to Newtonian mechanics, while you are falling, you're...

Not in any kind of frame.
In a non-inertial frame.
In an inertial frame.

Question 16

The Schwarzschild radius of a black hole with 10 solar masses is around 30 km. What is the Schwarzschild radius of a black hole with 30 solar masses?

150 km.
90 km.
60 km.

Question 17

According to Kepler's second law, stars farther from the center of a galaxy should rotate...

Faster than stars closer to the center.
At the same speed as stars closer to the center.
Slower than stars closer to the center.

Question 18

Galaxy A is half as far from us compared to Galaxy B. According to Hubble's law, this means that Galaxy A...

Moves away from us half as fast compared to Galaxy B.
Moves away from us at the same speed as to Galaxy B.
Moves away from us twice as fast compared to Galaxy B.

Question 19

When the cosmic microwave background was released, the universe became...

Opaque.
Yellow.
Transparent.

Question 20

Geodesics outside the event horizon...

Can point in any direction.
Can only point toward the center of the black hole.
Can only point away from the center of the black hole.

Question 21

In Einstein's special theory of relativity, the speed of light in vacuum...

Depends on the observer, in contradiction with the predictions of electromagnetism.
Is constant and independent of the observer, consistent with the predictions of electromagnetism.
Is constant and independent of the observer, in contradiction with the predictions of electromagnetism.

Question 22

I live on the 23rd floor, and my friend lives on the 15th floor. If I send a radio wave to my friend, the wave will be...

Blueshifted (my friend will see a shorter wavelength).
Unaffected (my friend will see the same wavelength).
Redshifted (my friend will see a longer wavelength).

Question 23

How did the Hulse-Taylor pulsar provide evidence for gravitational waves in 1974?

Directly, by measuring the local influence of the gravitational wave itself on spacetime.
Directly, by detecting electromagnetic emission from the gravitational wave event.
Indirectly, by observing changes in the orbital period of a binary system.

Question 24

Which of the following is a stellar black hole?

M87*.
Cygnus X-1.
PSR B1919+21.

Question 25

I live on the 4th floor. Compared to my friend who lives on the 12th floor, I experience time...

At a slower rate.
At a faster rate.
At the same rate.