# Why Do Scientists Need a Common System of Measurement?

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• 0:04 Making Measurements
• 0:33 Comparing Measurements
• 1:50 Shared Units of Measurement
• 2:23 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Part of the scientific process involves sharing your results with other scientists. To do this, we all need to use the same measurement system, which you'll learn about in this lesson.

## Making Measurements

Imagine you're trying to find out how much an elephant weighs. You're pretty sure it weighs a lot, but you don't know the exact number. So you ask your teacher, and she tells you an elephant weighs the same as three hippos.

Well that's nice to know, but how much does a hippopotamus weigh? Again, you ask your teacher, and she tells you a hippopotamus weighs the same as five alligators. That's a cool fact to know, but you still don't understand how much an elephant weighs because comparing elephants to alligators can be confusing.

## Comparing Measurements

To avoid confusion when measuring, scientists use a shared system of measurement, called the International System of Units (SI). 'Unit' is the word used to describe how something is measured. When researching a question in science, we collect data, interpret it, and share the results with other scientists. A common measurement system allows us to make direct comparisons instead of having to know things like how much a certain animal weighs.

For example, when we're measuring weight, a standard unit used by scientists is kilograms. Let's say the average elephant found in Africa weighs about 6,000 kilograms; if we use this unit of measurement, we can compare the weight of an elephant to other animals. If the average weight of a hippopotamus is 2,000 kilograms, it takes three hippopotamuses to weigh the same as one elephant. And if the average weight of an alligator is 400 kilograms, it takes five alligators to weigh the same as one hippopotamus, or 15 alligators to weigh the same as one elephant.

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