Encyclopedia For Kids

More than half of the human body is made of water. The rest of the body is built from a huge number of complicated chemicals. These chemicals, together with water, are assembled into tiny building blocks called cells.

History is the study of things that happened in the past. History can be very recent, or it can extend back to the earliest times from which any sort of records can be obtained. History cannot be understood properly by the study of a single event. 

No one knows exactly how life on the Earth began. Most scientists think that it started as a result of reactions taking place in the soup of chemicals dissolved in the ancient seas. The atmosphere contained poisonous gases, and fierce electrical storms raged.

Most plants and animals have popular names that vary from place to place. Scientific names are given so that the same name is recognized everywhere.

^ Carl Linnaeus (1707-1778)  established the modern scientific method for naming plants and animals.

Latin is used for scientific names. Centuries ago, it was the language of learned people. Scientific names are in two parts. The first is the generic name, which describes a group of related living things, and the second name is the specific name, which applies only to that living thing.

Nature is the term we use to describe all living things and the ways in which they relate to the earth we live on.

Atoms are the smallest pieces of matter. They are the tiniest particles into which a substance can be divided without changing into something else. Atoms actually consist almost entirely of open space, in which tiny particles orbit the central particle, or nucleus.The particles travel so fast that they seem to be solid.

> Electrons and protons are tiny charged particles that hurdle around the nucleus of an atom at enormous speed. The nucleus consists of protons and neutrons.

The Big Bang is the most popular theory about the creation of the Universe. According to it, the whole Universe was created in a split second in one huge explosion. All matter was squeezed together into a tiny, super-hot, dense ball that was smaller than an atom. The ball gradually expanded as it cooled, then exploded, releasing energy and matter in all directions.

> All of the matter in the Universe is flying out at enormous speed from the central point where the Big Bang took place.