Starting from birth, babies are immediately attracted to faces. Scientists were able to show this by having babies look at two simple images, one that looks more like a face than the other. By measuring where the babies looked, scientists found that the babies looked at the face ㅡ like image more than they looked at the non-face image. Even though babies have poor eyesight, they prefer to look at faces. But why?. One reason babies might like faces is because of something called evolution. Evolution involves changes to the structures of an organism(such as the brain) that occur over many generations. These changes help the organisms to survive, making them alert to enemies. By being able to recognize faces from afar or in the dark, humans were able to know someone was coming and protect themselves from possible danger.

If you had to write a math equation, you probably wouldn′t write, Twenty-eight plus fourteen equals forty-two. It would take too long to write and it would be hard to read quickly. You would write, 28 + 14 = 42. Chemistry is the same way. Chemists have to write chemical equations all the time, and it would take too long to write and read if they had to spell everything out. So chemists use symbols, just like we do in math. A chemical formula lists all the elements that form each molecule and uses a small number to the bottom right of an element′s symbol to stand for the number of atoms of that element. For example, the chemical formula for water is H2O. That tells us that a water molecule is made up of two hydrogen (H and 2) atoms and one oxygen (O) atom.

Imagine yourself at a party. It is dark and a group of friends ask you to take a picture of them. You grab your camera, point, and shoot your friends. The camera automatically turns on the flash as there is not enough light available to produce a correct exposure. The result is half of your friends appear in the picture with two bright red circles instead of their eyes. This is a common problem called the red-eye effect. It is caused because the light from the flash penetrates the eyes through the pupils, and then gets reflected to the camera from the back of the eyes where a large amount of blood is present. This blood is the reason why the eyes look red in the photograph. This effect is more noticeable when there is not much light in the environment. This is because pupils dilate when it is dark, allowing more light to get inside the eye and producing a larger red-eye effect.

Mirrors and other smooth, shiny surfaces reflect light. We see reflections from such surfaces because the rays of light form an image on the retina of our eyes. Such images are always reversed. Look at yourself in a mirror, wink your right eye and your left eye seems to wink back at you. You can use a mirror to send a coded message to a friend. Stand a mirror upright on the table, so that a piece of paper on the table can be clearly seen in the mirror. Now write a message that looks right when you look in the mirror. Keep your eyes on the reflected image while you are writing and not on your paper. After a little practice, it will be easier to write backwards. When your friend receives such a message he will be able to read it by holding the paper up to a mirror.

Students work to get good grades even when they have no interest in their studies. People seek job advancement even when they are happy with the jobs they already have. It′s like being in a crowded football stadium, watching the crucial play. A spectator several rows in front stands up to get a better view, and a chain reaction follows. Soon everyone is standing, just to be able to see as well as before. Everyone is on their feet rather than sitting, but no one′s position has improved. And if someone refuses to stand, he might just as well not be at the game at all. When people pursue goods that are positional, they can′t help being in the rat race. To choose not to run is to lose.

When we compare human and animal desire we find many extraordinary differences. Animals tend to eat with their stomachs, and humans with their brains. When animals′ stomachs are full, they stop eating, but humans are never sure when to stop. When they have eaten as much as their bellies can take, they still feel empty, they still feel an urge for further gratification. This is largely due to anxiety, to the knowledge that a constant supply of food is uncertain. Therefore, they eat as much as possible while they can. It is due, also, to the knowledge that, in an insecure world, pleasure is uncertain. Therefore, the immediate pleasure of eating must be exploited to the full, even though it does violence to the digestion.