stars and galaxies

Astronomers infer that the universe is expanding because distant galaxies all appear to _________

• be moving away from us, with more distant ones moving faster.

• be growing in size.

Why do the patterns of the stars in our sky look the same from year to year?

• Although these stars move quite fast by human standards, they are so far away that it would take thousands of years for their motion to be noticeable to the eye.

• Because these stars are not moving.

Our solar system consists of _________

• the Sun and all the objects that orbit it.

• the Sun and the nine planets, and nothing else.

What do astronomers mean by the Big Bang?

• The event that marked the beginning of the expansion of the universe.

• A gigantic explosion that blew all the galaxies in the universe to smithereens.

Which of the following best describes what we mean by the universe?

• The sum total of all matter and energy.

• A vast collection of stars that number as many as the grains of sand on all the beaches on Earth.

How long does it take the Earth to complete one orbit around the Sun?

• one year

• one day

The term observable universe refers to ______

• the portion of the universe that is not hidden from view by, for example, being below the horizon.

• that portion of the universe that we can see in principle, given the finite age of the universe.

An astronomical unit (AU) is ________

• the average distance between the Sun and Earth.

• the average distance between the Sun and Pluto.

Using the ideas discussed in the text, in what sense are we "star stuff"?

• Nearly every atom from which we are made was once inside of a star.

• Movie stars and other people are all made of the same stuff, so we all have the potential to be famous.

A television advertisement claiming that a product is light-years ahead of its time does not make sense because __________

• it uses "light-years" to talk about time, but a light-year is a unit of distance.

• it doesn't specify the number of light-years.