Large Numbers

Large Numbers

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Note: Many facts have been simplified to make them easier to understand.
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The scientific way to talk about large numbers is to write them like this: 1.23*10^45. This means that you must move the decimal point 45 places to the right to find the true number.

Scientists have given names to some large numbers. These can be used as prefixes to units. So kilogram means 1000 grams. Here is a list of all the prefixes for large numbers. See the page Small Numbers for information on numbers less than 1.

prefix	symbol	multiply by
yotta	Y	10^24
zetta	Z	10^21
exa	E	10^18
peta	P	10^15
tera	T	10^12
giga (same as a billion)	G	10^9
mega (same as million)	M	10^6
kilo (same as thousand)	k	10^3
hecto or hect	h	10^2
deca or dec	da	10

The words thousand, million and billion are used in History of the Universe. Let's try to get some idea of what these numbers mean.

Here is a little box, a cubic millimeter (about the size of a grain of rice).

Million
A million is a thousand times bigger (written as 1,000,000 or 10^6). It will take you about 12 days to count a million seconds. There are about a million people in a large city.

There are a million little boxes in the pink box.

Billion
A billion is a thousand times bigger than a million. It is written as 1,000,000,000 or 10^9.

It will take you about 31 years to count a billion seconds.

There are about a billion people in a very large country.

There are a billion little boxes in the big green box.