Earth science

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Video

Materials

• 1 newspaper
• 1 ruler (or a similar item made of wood) - This will break!

Short explanation

The reason the ruler breaks is that the newspaper is pushed down by the enormous weight of the atmosphere.

Long explanation

It's not the newspaper that is heavy enough to break the ruler. Because if you crumple a newspaper into a ball and put it on the ruler, it will fly away as expected. The reason why the ruler breaks has nothing to do with the weight of the newspaper, but with the atmosphere.

Above us is the tall atmosphere. The air that the atmosphere consists of weighs quite a lot, and all this weight presses on us. In fact, every square meter (11 square feet) of Earth's surface has an air column above it that weighs about 10 000 kg (22 000 pounds) and presses with incredible force (1 000 hPa)! The larger the surface of something, the more pressure it has upon it. The pressure on the newpaper is equivalent to two cars. No wonder the ruler breaks.

The strange thing about air pressure is that we don't feel it. The special thing about pressure is that it's "distributed" in all directions if you are inside the thing that is pushing. The air thus presses on us just as much from all directions - from below and from above, from within the body and from outside the body. It's only when one side gets very little air that the air pressure becomes noticeable, for example when we fly and the air in the cabin becomes much thinner than the air inside the body, which means that the air inside the body presses on the eardrums from the inside. In this demonstration, it's therefore important that there's very little air under the newspaper. Only then does the air pressure become noticeable, as it only comes from one direction.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you change the size of the newspaper?
• What is the biggest wooden item you can break with your newspaper?

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