Chapter one

Question 1

Astronomy

Answer 1

defined as the study of the objects that lie beyond our planet Earth and the processes by which these objects interact with one another.

Question 2

scientific notation

Answer 2

(or sometimes powers-of-ten notation). This system is very appealing because it eliminates the many zeros that can seem overwhelming to the reader. In scientific notation, if you want to write a number such as 500,000,000, you express it as 5×108
. The

Question 3

a light-year,

Answer 3

distance light travels during one year. Because light always travels at the same speed, and because its speed turns out to be the fastest possible speed in the universe, it makes a good standard for keeping track of distances.

Question 4

how many kilometers are there in a light-year?

Answer 4

of 3×105
kilometers per second (km/s), which makes a light-year 9.46×1012
kilometers.

Question 5

nearest star is

Answer 5

4.3 light-years away—more than 40 trillion kilometers.

Question 6

Information about the universe comes to us

Answer 6

almost exclusively through various forms of light, and all such light travels at the speed of light—that is, 1 light-year every year. This sets a limit on how quickly we can learn about events in the universe. If a star is 100 light-years away, the light we see from it tonight left that star 100 years ago and is just now arriving in our neighborhood. The

Question 7

The farther out in space we look,

Answer 7

the longer the light has taken to get here, and the longer ago it left its place of origin.