• Moiya McTier

Astronomy Fun Fact #87

It's common knowledge that there are different unit systems. That's why Americans use units like inches, pounds, and degrees Fahrenheit instead of meters, kilograms, and degrees Celcius.

The latter unit system -- the one that uses meters and kilograms -- is called the metric system of units. Most of the world uses it, and so most scientists use it, too.

But within the metric system, there are small variations that different scientific disciplines have adopted. Astronomers use the cgs system, which stands for centimeters-grams-seconds.

So even though astronomers study the biggest things that exist, we learn to measure values in terms of some of the smallest units. You might think it makes more sense to measure the distance between the Earth and the Sun in kilometers, or even gigameters (1 billion meters), but I learned it in centimeters instead because of the cgs system.

This has some interesting consequences for other measurements as well. For example, instead of using joules to measure energy, astronomers use ergs. And instead of using Newtons to measure force, astronomers use dynes.

It's pretty easy to convert between these different units, but it does get really frustrating to have to do those conversions in your head when you're talking to someone from a different scientific discipline!

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