Week 2 Lectures

Question 1

Roughly how much farther away are nearby galaxies (like the Andromeda Galaxy) than nearby stars (like Sirius)?

Answer 1

C. Millions of times farther.

Question 2

If I show you a picture of a galaxy and claim that it is 20 billion light-years away, why shouldn’t you believe me?

Answer 2

D. Because light has not had time to travel to us from that far away since the Universe began.

Question 3

WhydoestheSunappearinadifferentplaceinthe sky in the morning and at midday?

Answer 3

Because we are on a spinning Earth so we have to look different directions to look towards the Sun.

Question 4

One morning, the Sun rises on the eastern horizon near the star Regulus and the galaxy Fornax dSph. What direction would you need to look to see those objects 12 hours later at sunset?

Answer 4

West: Sun, Regulus, and Fornax dSph

Question 5

If you went outside right now, during the daytime, you would only see one star. Why wouldn’t you see any others?

Answer 5

Because the sky is too bright in daytime to see other stars, which are faint.

Question 6

• Fill in the blanks, thinking about how long it takes each of these things to fully happen once:
Earth spins around on its axis ________ (much / a little bit) _________ (faster / slower) than Earth orbits around the Sun.

Answer 6

A. much faster

Question 7

Duringwhichmonthis Earth closest to the Sun?

Answer 7

January

Question 8

Whatseasonisitwhen Earth is closest to the sun

Answer 8

No

Question 9

Seasons are caused by

Answer 9

the tilt of Earth’s axis

Question 10

Imagine if the Earth’s spin axis were tilted by 10° (instead of 231⁄2°) in its orbit around the Sun.

Answer 10

Summers would be less hot in the Northern Hemisphere and less hot in the Southern Hemisphere

Question 11

Given that Earth is a sphere, what shape is the shadow that it casts on an object?

Answer 11

Circle