Why don't birds fall off branches? Birds don't fall because they are locked into place when they land on branches.
Long tendons run all the way down the inside of a bird's legs to its toes.
A bird bends its legs when it settles on a branch. Bending pulls the tendons. The tendons pull on the toes, making them curl around the branch.
As long as the bird is perched on the branch, its legs are bent, and as long as its legs are bent, its toes are locked in place, so it will not fall, even if it's asleep.
What causes tides? Tide refers to the daily rise and fall of sea level in oceans and other large bodies of water. These changes are caused mainly by the gravitational attraction of the moon.
If the moon attracted every point on the Earth with equal force, there would be no tides. But according to Newton's law of gravitation, the gravitational force decreases as the distance increases.
Therefore the force exerted by the moon is greater on the side of the Earth facing the moon than on the opposite side, and the difference in the moon's force at various points on the Earth's surface produces tides.
At any given time, there are two high tides on the Earth, a direct tide on the side facing the moon and an indirect tide on the opposite side.
What is evolution ? Ever since people began to study nature, they have been aware living things are designed for the way they live.
Birds' beaks, for example, are different shapes to deal with their different diets, while cats' claws are perfect weapons for catching prey. But why is it so? Some people believe it is because each species has been specially created. Others, including most scientists, believe it is because living species gradually change, or adapt, to particular ways of life. This process of change is called evolution.
Evidence of evolution can be seen in plants and animals that lived in the past - and in everything that is alive today.
Why is soap so slippery? Because it's all the better to clean you with. Like all things, soap is made up of millions of molecules.
When soap gets wet, water molecules free the soap molecules so they can slip and slide around.
They slip easily on to our skin, mix with the dirt, and slide the dirt right off our body, leaving us clean as a whistle.
What does SOS stand for? SOS is the international distress signal in Morse code.
It consists of ... --- ... which are the Morse letters SOS. While many people think it stands for save our souls or save our ship, it actually has no meaning.
The letters SOS are simply the easiest and most distinctive signal to send. This combination was adopted as the international distress signal by the International Radiotelegraphic Convention in London in 1912. By radio, the signal is Mayday, which comes from 'm'aidez', French for 'help me'.