When we think of paper, we think of newspapers and books. But there are many other uses. Only half of the world’s paper is used for books and newspapers.

Paper is very good for keeping you warm. You have perhaps seen homeless men sleep on a large number of newspapers. In Finland, it is sometimes -40℃ in winter. The farmers wear paper boots (靴子) in the snow. Nothing could be warmer.

Each year, more and more things are made of paper. We have had paper cups and plates for a long time. But now we hear that chairs, tables, and even beds can be made of paper. Besides paper boots and shoes, you can wear paper hats, paper dresses, and paper raincoats. When you have used them once, you may throw them away and buy new ones.

The latest use of paper seems to be paper houses. These are not small houses for children to play in, but real, big houses for people to live in. You can buy a house with three rooms for about 500 dollars. You can put it up by yourself in a few hours, and you can use it for about five years.

Physics can be amazing. The same force that makes airplanes fly can also cool down your bedroom on a hot summer night. This is called Bernoulli’s Principle (伯努利定律).

Recently, a science teacher’s video got a lot of attention. In the video, User Wolf-Science, from England, shows how to quickly fill a large bag with air using Bernoulli’s Principle.

Bernoulli’s Principle is named after Daniel Bernoulli, a Swiss physicist who introduced it in 1738. It says that when fluids (流体）liquids and gases move quickly, they create low-pressure zones（低压区域）. Faster movement means lower pressure. The higher-pressure fluids will rush to fill the low-pressure zone.

In the video, the teacher blows into a large bag 10 times with his mouth. But he can’t fill the bag with air like this. Then, he puts the bag a few centimeters away from his mouth and blows hard one time. The moving air creates a low-pressure zone inside the bag. Air rushes in, filling the bag in just one second!

How does this make an airplane fly? The secret is the shape of the wings. The shape causes air moving over the top of the wing to go faster than the air moving below. This creates a low-pressure zone above the wing. Higher-pressure air from below rushes upward, lifting the plane of the ground.

You can put Bernoulli’s Principle to work at home. If your bedroom is full of hot air, you can cool it quickly. Point an electric fan toward the window, but don’t put it too close. When the fan runs, it will create a low-pressure zone. The hot air will go out the window. Firefighters use this same trick to quickly clear smoke out of a house.

Your brain controls everything you do. It makes it possible for you to think, learn, create and feel; to blink(眨眼)and breathe and for your heart to beat--this fantastic control center is your brain. It is so amazing that a famous scientist once called it “the most complex (复杂) thing we have yet discovered in our universe.”

Can this small grey organ (器官) , which weighs less than one and a half kilos, really do so much? Amazingly, your brain contains about 100 billion neurons (神经元) --it would take you over 3,000 years to count them all. Believe it or not, the activity in your brain never stops. Your neurons create and send more messages than all the phones in the world. And although one neuron create only a little electricity, all your neurons together can produce enough electricity to power a light bulb (灯泡).

So exactly how fast does your brain work? Well, imagine this: a bee lands on your foot. Neurons in your skin send this information to your brain at a speed of more than 240 kilometers per hour, Your brain then uses other neurons to send the message back to your foot to shake the bee off quickly. These neurons can send this information at more than 320 kilometers per hour. No computer has your brain's unbelievable ability to deal with the amount of information coming from your eyes, ears and other sensory organs.

But how does your brain allow you to learn things that you will use in the future? The structure(结构)of your brain changes every time you have a new thought, remember or learn something. For example, riding a bike seems impossible at first, but soon you are able to do it. How? As you practice, your brain sends “bike riding” messages again and again. Soon, the actions are learnt and you are able to ride a bike easily from then on.