Energy

Energy is the ability to make things happen, cause changes and carry out work. Any change anywhere in the Universe, from a tiny meteorite hitting a planet to an exploding star...

Energy A-Z

Heat

Heat is a type of energy—the vibrations of atoms and molecules. The more an atom moves or vibrates, the more heat or thermal energy it has. In a solid, the atoms have fixed...

Heat A-Z

Electromagnetic radiation

Radio waves, microwaves, light and X-rays have different characteristics, but they are all forms of electromagnetic radiation. Together with other forms, they make up a family...

Electromagnetic radiation A-Z

Light

Light is the form of energy that our eyes can detect, enabling us to see. It is produced by very hot things—stars like the Sun, fire and the tiny wires inside electric light...

Light waves and particles

Scientists have attempted to answer the question "what is light?" for hundreds of years. The English scientist Isaac Newton (1642–1727) believed light was made up of microscopic...

Shadows

When light falls on a substance that it can pass straight through, for example, clear glass or water, that substance is said to be transparent. Materials that do not allow light to...

Colour

Sunlight is not colourless, but is made up of all the colours of the rainbow: the spectrum of light. We see these colours when a rainbow forms. In fact, only three, red, green and...

Light A-Z

Nuclear energy

Nuclear energy is the energy contained by an atom, due to the strong force that holds together the protons and neutrons in its nucleus. Nuclear energy is released naturally inside...

Sound

Sound is a form of energy made when objects vibrate (move to and fro rapidly). As an object vibrates it sets the air around it vibrating, too: molecules of the gases in the air...

Musical sounds

Musical sounds have wave patterns that are evenly spaced and regular, while noises—unpleasant sounds—usually have irregular patterns. Each musical note has a specific pitch...

Ultrasound

Some sounds are so high-pitched (those with frequencies above 20,000 Hz) that our ears cannot detect them. They are known as ultrasounds. Many animals, like dogs and bats, can hear...

Sound A-Z