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How big is a kilometer?
For those of us at UW-Madison, the distance from the edge of campus at Library mall to the steps of the Wisconsin state capitol building is 1 kilometer (km). But, there are plenty of other things around the world that are on the kilometer scale.
The world’s longest suspension bridge, Akashi Kaikyo Bridge, is just under 2 kilometers (km) long, measuring 1,991 m. It would take you approximately 23 minutes to walk across this bridge.
The Willis Tower in Chicago, the tallest building in North America, measures ~0.5 km (527 m) to the top of the antennae.
How big is a meter?
A meter is a little bit bigger than a yard. A lot of things in our everyday lives are around the same size as a meter. An elementary school student is approximately one meter (m) tall.
However, most professional basketball players are at least 2 meters (m) tall. Shaquille O’Neill, at 7’1″, is 2.1 m tall. He seems to tower over President Bush.
How big is a centimeter?
A centimeter (cm) is 1/100th of a meter. If you cut up a meter stick into 100 equal pieces, each piece would be one cm in size.
Your pinky finger is about 1 cm wide. Same goes for the width of the sugar cube.
Brown sugar cubes
How big is a millimeter?
A millimeter (mm) is 1/1000th of a meter. A dime is approximately 1 mm thick. Grains of sand range from 0.1 mm to 2 mm in size.
So far all the objects listed from kilometer to millimeter are all things that can be seen with your eyes. Some are easier to see than others, but you typically don’t need a special tool to see any of these objects. When things get smaller than a millimeter, it gets hard to see them with just your eyes.
How big is a micrometer?
A micrometer, also called a micron, is one thousand times smaller than millimeter. It is equal to 1/1,000,000th (or one millionth of meter). Things on this scale usually can’t be seen with your eyes.
The diameter of a hair, which is 40-50 microns wide, is challenging to discern without the use of a magnifying glass. A magnifying glass will help you see a dust mite. Dust mites are usually around 400 microns long.
Human hair magnified 200X
Dust mite magnified 40X
Things that are just a few microns in size can’t be seen with a magnifying glass. However, a light microscope, like the ones you may have used in biology class, can help you see things this small. Red Blood cells are 6-10 microns in diameter. Many types of bacteria typically measure 5-20 microns
Red blood cells magnified 1700X
How big is a nanometer?
A nanometer (nm) is 1,000 times smaller than a micrometer. It is equal to 1/1,000,000,000th or one-billionth of a meter. When things are this small, you can’t see them with your eyes, or a light microscope. Objects this small require a special tool called a scanning probe microscope.
Things on the nanometer scale include: Virus (30-150 nm), the width of DNA (2.5 nm), buckyballs (~1 nm in diameter), CNT (~1 nm in diameter). The SARS-Cov-2 coronavirus which causes COVID-19 and resulted in the 2020 global pandemic is a fairly large virus at 60-120 nm.
Electron micrograph of SARS-CoV-2 virions from
Virus magnified 20,000X
Model of DNA
Model of a buckyball
Model of a carbon nanotube
Atoms are smaller than a nanometer. One atom measures ~0.1-0.3 nm, depending on the element.
SEM image of atoms on a surface. Source: Image originally created by IBM Corporation.
Here are some other everyday objects measured in nanometers:
- One inch equals 25.4 million nanometers.
- A sheet of paper is about 100,000 nanometers thick.
- A human hair measures roughly 50,000 to 100,000 nanometers in diameter.
- Your fingernails grow one nanometer every second.