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

Please solve the following questions. This is not an assignment, 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 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!

These questions are not multiple-choice, to encourage you to think of the answers on your own, but the questions in the actual exam will be multiple-choice.

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

Question 1

Why is Newtonian mechanics incompatible with electromagnetism? How does special relativity fix that incompatibility?

Question 2

What are the two fundamental postulates of special relativity? What are their origins?

Question 3

What is a Lorentz transformation? How does it relate to the concept of spacetime?

Question 4

Challenge question: A vertical line on a spacetime diagram represents an object with zero speed, since it stays at the same position at all times. What would a horizontal line represent?

Question 5

What are three counterintuitive consequences of special relativity?

Question 6

Alice is moving at 10 m/s relative to Bob. Which one has the larger Lorentz factor? (Think carefully about your answer!)

Question 7

Explain how the twin paradox is resolved.

Question 8

What is the difference between special and general relativity?

Question 9

What is the weak equivalence principle?

Question 10

What is the Einstein equivalence principle?

Question 11

Challenge question: The equivalence principle predicts that light rays will curve in the presence of gravity. Can you figure out how?

Question 12

Right now, as you are reading this question, are you in an inertial frame?

Question 13

Is gravity a force? Why or why not?

Question 14

What are the differences between Newtonian gravity and general relativity in terms of where they can be applied?

Question 15

What is gravitational redshift?

Question 16

Challenge question: You can use a black hole (or another extremely dense and massive body) to "travel" to the future, by making time flow slower for you compared to Earth, due to gravitational time dilation. But can you use a black hole to travel to the past?

Question 17

Describe two of the tests that first confirmed general relativity.

Question 18

What is an Einstein ring?

Question 19

Describe the first indirect and the first direct evidence for gravitational waves.

Question 20

What is multi-messenger astronomy? Give an example.

Question 21

Could interstellar travel be feasible? List all arguments for and against.

Question 22

What is a closed timelike curve?

Question 23

What is dark matter, and why do we think it might exist?

Question 24

Galaxy A is located 1 billion light-years from the Milky Way and is moving away from us at 21,000 km/s. Galaxy B is located 2 billion light-years from the Milky Way. According to Hubble's law, at what speed is Galaxy B moving?

Question 25

Galaxy C is moving away from us at 200,000 km/s. Galaxy D is moving away from us at 50,000 km/s. What can you say about the distances to both galaxies, based on Hubble's law?

Question 26

According to Hubble's law, all galaxies are receding away from us at a velocity proportional to their distance. Does that mean that we are special? That we are the center of the universe?

Question 27

Challenge question: If the universe is expanding, does that mean that the Milky Way Galaxy is also expanding? What about the Earth? What about your body?

Question 28

Is the expansion of the universe decelerating, accelerating, or unchanging? Why?

Question 29

What is recombination?

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