Science Common Sense

1406 - What units are used to express different scales, such as length units, and how do scientists use scientific notation to express sizes?

Imagine you have different rulers for measuring things. Here are some units used for measuring different scales:

• Length units:
• Millimeters (mm) or centimeters (cm) for small things like toys and pencils.
• Meters (m) for bigger things like your room or a house.

• Kilometers (km) for really big things like a city or a country.

• Weight units:

• Grams (g) for light things like a pen or a piece of candy.

• Kilograms (kg) for heavier things like a big bag or you.

• Scientific units:

• When measuring very small or very big things, we use units like:
  • Micrometers (μm) for tiny things like cells (one-hundredth of a millimeter).
  • Nanometers (nm) for super tiny things like the building blocks of everything (one-thousandth of a micrometer).
  • Light-years (ly) for enormous distances like the distance between stars or galaxies (the distance light travels in one year).

Scientists use something called scientific notation to easily express very big or very small numbers.

It looks like this: 4.23 x 10^5.

• The '4.23' is the number you're talking about.
• The 'x 10^5' is like a shortcut to say 4.23 multiplied by 100,000.

For example, the distance from the Earth to the Sun is 149,600,000 kilometers. Using scientific notation, it's written as 1.496 x 10^8 kilometers.