How Much is a

BILLION?

Astronomers estimate that there are more than 100 BILLION stars in our Milky Way Galaxy. That’s a lot of stars!

A “billion” is a very large number. Exactly how much is a billion? To help you visualize this number, you can use your power of estimation. It’s simple: start with a small amount and work your way out.

Let’s try it with oranges. Imagine…

10 oranges

would fill a large salad bowl

1 thousand oranges

would fill a pick up truck

1 million oranges

would fill a swimming pool

1 billion oranges

would fill a stadium to the brim!

Try it! It’s your turn to use your power of estimation.

For each of the five questions, first imagine what a small amount looks like and then imagine more and more. Do you think the total number is MORE or LESS than a billion?

How many hairs are on your head?

more than a billion

less than a billion

How to Write Big Numbers

Writing big numbers can take a lot of space.

If you write a 1 followed by three zeros,

you get 1,000 = one thousand

If you write a 1 followed by six zeros,

you get 1,000,000 = one million

If you write a 1 followed by nine zeros,

you get 1,000,000,000 = one billion!

That’s a lot of zeros! Astronomers often deal with even larger numbers such as a trillion (12 zeros) and a quadrillion (15 zeros). When astronomers write these really, really big numbers, they use a shorthand called scientific notation. For example, instead of writing out a billion using nine zeros (like this: 1,000,000,000), they write it like this: 10^{9}. The little number 9 means there are nine zeros.

Try it! It's your turn to use scientific notation.

How would you write a trillion (1,000,000,000,000)?

**10**^{10}

**10**^{12}

**10**^{16}

##### Image Credits:

All illustrations by Jim Steck