Why do flies rub their legs together?

When you see a fly rubbing its legs together, it is just cleaning itself, and scraping off some of the material that has gathered there. But how dangerous that material may be! It may be the bacteria of such diseases as tuberculosis, typhoid fever or dysentery. Flies get such germs from garbage and sewage. If they happen to our food, the germs spread to the food, and if we eat it, we may become infected. You may wonder how the fly carry these germs around. If you notice a fly under a magnifying glass, you would notice that the fly's body, it's claws and its padded feet, are covered with bristling hairs. The fly's tongue is also coated with sticky glue. This means that any place the fly stops for even a moment, it's going to pick up things, that stick to its body, its feet, or its tongue. In fact, each foot on its three pairs of legs has claws and two hairy pads-so that it can pick up plenty of things. 

Why do we blink our eyes?

The lids of our eyes, which move up and down when we blink acts as built in wind screen wipers. The lids are made up of folds of skin, and they can be raised and lowered by certain muscles. But they move so rapidly that they don't disturb our vision in any way. A curious thing about our lids is that they work automatically. Blinking is important to us. It protects our eyes. The lashes attached with the lid, catch dust which might go into our eyes. When you walk through rain or sandstorm, the lids automatically drop down and the eyelashes keep out foreign matter. The eyebrows, by the way, carry off rain or perspiration to a side, so that the drops won't run into the eyes. But the chief benefit of blinking is that this provides automatic lubrication of the eyes. Along the edge of each lid there are twenty or thirty tiny sebaceous glands. These glands have their opening between the lashes. Every time our lids close, these glands go to work and a secretion comes out. This secretion lubricates the edge of the eye lid and the lashes, so that they don't become dry. In each eye we have a tear gland, where the liquid that makes tears is stored. Every time we blink, the eyelid applies suction to the opening of the tear gland and takes out some of the fluid. This prevents the eye from drying out. We might say that we "cry" every time we blink our eyes!

Why does the moon follow us when we drive?

The great distance of the moon from the earth explains why the moon seems to follow us when we drive in a vehicle and look up at it. When we speed along a road, we notice that everything moves past us. Trees, houses, the road, fences - all fly past us in the opposite direction. We naturally expect the moon also to be flying past us. When this does not happen, we have the sensation that it is "following" us. It happens because the distance of the moon from the earth is quite great. Compared to the distance our vehicle travels in a few minutes, that distance is enormous. So as we move along, the angle at which we see the moon hardly changes. In fact, we could go along a straight path for miles and the angle at which we could see the moon would still be basically the same. And as we notice everything else flying past, we get that feeling of the moon following us.

What makes us feel hungry?

The feeling of hunger is a message sent to your brain by your body. The message being that the blood is missing the nutritive materials. The bodies of all living beings must maintain a state of metabolic equilibrium. This means there has to be a certain balance and control over our intake of fuel and its use. To regulate our body weight we have thirst, hunger and appetite. In the brain, we have a hunger center. It acts like a brake on the activities of the stomach and intestines. When the blood has sufficient nutritive materials, the hunger center stops the activities of the stomach and intestines. But when there is a lack of nutrition, the intestines and stomach become active. That is precisely why you hear your stomach rumbling when you are hungry. When you feel hungry, your body is crying out for fuel. A really hungry person will eat any kind of food. It is your appetite that sees to it that you choose the mixed diet that your body requires. 

Why do we laugh?

Laughter is the biological reaction of human beings to moments of humor. Depending upon the extent and pitch, laughter can be subcategorized as giggles, chuckles, guffaws etc. Human laughter has its biological origins as a kind of shared expression of relief at the passing of danger. Laughter is a part of human behavior regulated by the brain. It provides an emotional context to our conversations. We also tend to laugh on being tickled. The reason being that when anyone is tickled, there is an element of surprise followed by feelings of panic, laughter and sensation, which eventually breaks into peals of laughter. 

Why are pebbles on the beach round?

Owing to the constant battering by the sea waters, pebbles become smooth and round. Originally, they are part of much larger rocks, but various natural phenomena such as earthquakes and volcanoes have gradually broken them down. Caught in the movement of the sea and rubbed against other hard materials, the pebbles lose their irregular edges and acquire a roundish shape. 

Why do doctors take your temperature?

The body temperature of a human being is an indication of his physical condition. An abnormally high or low temperature is generally a sign that something is wrong. In case of human beings, the normal temperature is usually given as 36.9 degree centigrade (98.4 degree Fahrenheit), but it varies throughout the day. A raised temperature is often the sign of bacterial or viral infection. It may be owing to a heatstroke or a brain injury or disease or even sudden shock.

Why is grass green?

The green color in grass and in most other plants, comes from chloroplast in the cells which contains four different colors. Of these, chlorophyll-a, which is blue-green in color, is the strongest. The colors are yellow-green (chlorophyll-b), yellow (xanthophyll) and orange (carotene). The color of the grass changes from light green in early spring to dark green and brown in summer and autumn because the amount of pigment changes, like paint on a palette.