# Big and Small Numbers

#### People are great at using and understanding numbers between one and ten but scientists often need to use much larger quantities.

• The speed of light is 300,000,000 metres per second.
• The distance to the moon is 384,467 kilometres.
• There are usually between 10,000,000 and 20,000,000 sperm per millilitre of human sperm.

Big numbers like these can get confusing.

• One thousand 1,000
• One million 1,000,000
• One billion 1,000,000,000
• One trillion 1,000,000,000,000

Some of these numbers are truly huge, think about them as measures of time:

• One thousand seconds is nearly 17 minutes
• One million seconds is 11½ days
• One billion seconds is nearly 32 years
• One trillion seconds is nearly 31,710 years

Things can get worse, there are around 8,360,000,000,000,000,000,000,000 molecules in a cup of tea!

#### Going to the other extreme very small numbers are used by scientists just as often.

• These marine diatoms (seen here through a microscope) range in size from ten to 150 millionths of a metre. That is from 0.00001m to 0.00015m.
• The wavelength of the blue light coming from this image is about 450 nanometres (nm) - 0.00000045m.

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