Barometer: Measuring Air Pressure

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Audio:

As you learned in the previous Weather Instruments lesson, found in Related Lessons in the right-hand sidebar, a thermometer is a very useful tool that is used to measure the temperature of air, water, and even your body.

Even though a thermometer can tell you what the temperature is outside, it cannot tell you if it is going to rain or what the air pressure is outside. But a barometer can!

Take a look outside.

• Is it a rainy day?
• Is it hot and sticky?
• Does it look like snow is on the way?

If not, it may be sunny and clear. Whatever it may be, a barometer can help predict if it is going to rain, if it is going to be sunny, or if it is going to snow. This is because a barometer measures air pressure, and air pressure can vary from a rainy day to a sunny day to a snowy day.

• Now, you may be wondering, “It is neat that barometers can measure air pressure, but why is it so important to know exactly what the pressure in the air is right now?”

Well, that’s a great question! Maybe Flo would know!

• Say, what if you were to MAKE your own barometer? Are you ready to give this a try?

A barometer can tell you a lot about air pressure. Air pressure is important to know because it helps meteorologists know what the weather is going to be like: cloudy, rainy, sunny, or even snowy.

• Have you ever played a board game or a math game that used dice?

The amount of air space — one cubic centimeter — that you heard Flo say contained about 10 quintillion molecules, is the size of one of those dice (or "die," which is the singular form of "dice"). That definitely is a lot of molecules!

All these molecules help add to the pressure in the air.

For instance, if there are a lot air and water molecules in the air, there is a high chance that it is going to rain. However, if there are not a lot of water molecules in the air, then the air pressure will be a lot lower and it will be sunny outside.

Air pressure can affect a LOT of things in the world, such as the weather, and even your body! That’s right, a big change in air pressure can cause discomfort to your body in your ears and sinuses, and even give some people headaches. Talk about feeling under pressure!

• Do you want to know the answer to the joke about the old barometer?

Continue to the Got It? section to find out!