WHY does a log not sink in water?

The secret of this phenomenon is that the density of a tree is less than that of water.

Density is the ratio of the mass of a physical body to its volume. The density of water is one (1 g/cm3) and the density of most types of trees is less than 1.

 

WHY is yawning contagious?

Scientists have discovered that humans react unconsciously not only to yawning but even to the word “yawn” written on paper!

According to one theory, the contagiousness of yawning is related to the fact that humans used to live in packs, like chimpanzees, and they needed to go to sleep at the same time.

So yawning served as a signal that it was bedtime. Perceiving their neighbor’s yawn as a signal to yawn and then fall asleep themselves, herd animals got used to sleeping together, keeping each other warm and safe during sleep.

 

WHY should a tree frog not be picked up?

Under no circumstances should these frogs be handled

Their skin secretions are strong nerve poisons, providing them with protection from predators and explaining their bright cautionary coloration.

Yet exotic lovers raise tree frogs in terrariums. So what about their venomous nature? The fact is that in most cases it is caused by their nutrition: in nature, they eat small ants and termites and accumulate their venom. In terrariums, deprived of their “poisonous nourishment”, tree frogs become practically harmless after a while

 

WHY do bears hibernate?

Hibernating in a den helps bears survive the hungry winter season.

When a bear hibernates, it barely moves. At the same time, its body temperature drops to 30° C and the functioning of the heart and lungs slows down. Such a state of the body contributes to the economical use of the fat accumulated before hibernation.

The bear does not suck its paw because it wants to eat. It does this to moisten its dry feet and to chew off keratinized and coarsened skin.

 

WHY cannot we feel the air pressure?

An enormous ocean of air lies above our planet. Air presses on humans with a force of more than 15 tons

Imagine having three trucks on top of you. Yet these “trucks” never crush a human being. The reason is that the “air column” presses on us not only from above but from all sides evenly.

Besides, we also have air inside us. And that air comes under the same pressure. The pressure of the air from the inside balances the pressure on the body from the outside. That’s why we don’t notice the pressure on our bodies.

 

WHY does the fire come in various colors?

The color of fire is mainly determined by the temperature of the flame and what chemicals are burned in it.

The high temperature of the flame allows the atoms to jump to a higher energy state for a while.

When the atoms return to their original state, they emit light at a certain wavelength.