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 Show/hide solution

If two people live in different cities, do they see the same zenith? What about the horizon? And the celestial sphere?

Solution: The zenith is the point directly above your head. So people in different places see a different zenith. The horizon is at 90 degrees below the zenith on every direction, so they will see a different horizon too. However, everyone sees the same celestial sphere - although they see different parts of it.

Question 2 Show/hide solution

What is the celestial sphere made of?

Solution: Nothing. It's an imaginary sphere that we use to describe the sky in familiar terms. Some ancient culture believed it was an actual material sphere, but today we know that's not true.

Question 3 Show/hide solution

Which points on the sky do the stars rotate around?

Solution: The north and south celestial poles.

Question 4 Show/hide solution

What causes the stars to appear to rotate? Do the stars actually move?

Solution: The stars stay in place - or more precisely, they move, but at a very slow rate that is only noticeable over many years or to very precise instruments. The reason that they appear to rotate is that the Earth itself rotates around its axis.

Question 5 Show/hide solution

Why does the Sun rise and set?

Solution: Because the Earth is rotating around its axis. The Sun doesn't actually move, it's us that are moving. During the day we are facing the Sun, and during the night we are facing away from it.

Question 6 Show/hide solution

Do all stars rise and set?

Solution: No. For example, at the North Pole, the stars would just circle around the north celestial pole, instead of rising and setting. Only at the equator do all stars rise and set (although we won't see all of them rise and set during the day).

Question 7 Show/hide solution

What phenomenon results from the rotation of the Earth around the Sun? What about the rotation of the earth around its axis?

Solution: The rotation of the Earth around the Sun is responsible for the seasons (in addition to the tilt of the Earth's axis, as we'll see in more detail later). The rotation of the earth around its axis is responsible for the day and night cycle.

Question 8 Show/hide solution

"The Sun follows the same path in the sky every day." True or false?

Solution: False. Since the Earth rotates around the Sun, the Sun will follow different paths in the sky on different days. For example, in June the Sun will cross the constellation Taurus, but in August it will cross the constellation Cancer.

Question 9 Show/hide solution

"The axis of rotation of the Earth around itself is in a different direction compared to the axis of rotation of the Earth around the Sun." True or false?

Solution: True. The axis of rotation of the Earth around itself is tilted by 23.5° compared to the axis of rotation of the Earth around the Sun.

Question 10 Show/hide solution

The zodiac is a narrow "belt" stretched across the sky. Which celestial bodies can always be found within it?

Solution: The Sun, Moon, and planets. This is because all bodies in the solar system are approximately on the same plane, The projection of the Earth's orbital plane in the sky is the ecliptic, and the zodiac is a narrow region around the ecliptic.

Question 11 Show/hide solution

In modern astronomical terminology, what is the difference between a constellation and an asterism?

Solution: A constellation is a region in the sky. An asterism is a pattern of stars.

Question 12 Show/hide solution

"All the constellations in the sky correspond to zodiac signs." True or false?

Solution: False. The zodiac signs correspond to the constellations along the ecliptic, but there are many other constellations that are not along the ecliptic (for a total of 88 constellations overall)

Question 13 Show/hide solution

Will aliens in a different galaxy see the same constellations that we see?

Solution: No. The constellations we see, or more precisely the patterns of stars (asterism) within each constellation, are composed of nearby stars in our galaxy. Aliens in another galaxy will see different stars and will divide the sky into different constellations. In fact, even aliens near a distant star in our own galaxy will see completely different patterns of stars in the sky, because they will be looking from a different perspective.

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