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! 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?

1

more than a billion

less than a billion

Nope. Try again!
You got it!

Question 1 of 5
NEXT QUESTION
2

How many people are in the world?

more than a billion

less than a billion

Nope. Try again!
You got it!

Question 2 of 5
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3

How many cells are in your body?

more than a billion

less than a billion

Nope. Try again!
You got it!

Question 3 of 5
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4

How many gallons of water do Americans flush down the toilet every day?

more than a billion

less than a billion

Nope. Try again!
You got it!

Question 4 of 5
NEXT QUESTION
5

If you are 10 years old, how many seconds has it been since you were born?

more than a billion

less than a billion

Nope. Try again!
You got it!

Now try writing big numbers!

Question 5 of 5
You got out of 5 right on the first guess.

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: 109. The little number 9 means there are nine zeros.

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

1

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

1010

1012

1016

Nope. Try again!
You got it!

Question 1 of 2
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2

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

1013

1015

1018

Nope. Try again!
You got it!