Energy All Around Us

The Power to Make Things Happen

What do a running cheetah, a glowing lamp, a loud drum, a warm fire and a growing plant all have in common? The answer is one of the biggest and most important ideas in all of science: energy.

Energy is the power to make things happen. Anything that moves, heats up, lights up, makes a sound or grows is using energy. You cannot hold energy in your hand or put it in a box, but it is everywhere, all the time, hiding inside everything around you. This book will help you spot energy in all its surprising disguises and understand the secret rules it follows.

What Energy Does

The simplest way to think about energy is this: energy makes things happen. Without energy, nothing in the universe could move, change or do anything at all. Everything would be frozen and still.

You use energy every second of every day. When you run, jump or even just sit and read, your body is using energy to keep going. You get that energy from your food. Food is like fuel for your body — it gives you the energy to play, to grow, to think, and even to keep your heart beating while you sleep. This is why you feel tired and hungry when you have used a lot of energy. Your body is telling you to refuel.

The Many Forms of Energy

Here is one of the coolest things about energy: it comes in many different forms, like a shape-shifter wearing lots of different costumes. Once you know what to look for, you will start to spot energy everywhere.

• Light energy comes from the Sun, from flames and from lamps. It lets us see.
• Heat energy makes things warm. It comes from the Sun, from fires, and even from your own body.
• Sound energy is what we hear. Every drumbeat, shout and song is sound energy travelling through the air.
• Movement energy belongs to anything that moves, from a rolling ball to a galloping horse. Scientists call this kinetic energy.
• Electrical energy flows through wires to power our lights, screens and machines.
• Stored energy is energy waiting to be used. A stretched rubber band, a battery, and the food in your lunchbox all hold stored energy, ready to be released.

Every time you notice something happening — a light shining, a car moving, music playing — you are really watching energy at work in one of its many forms.

Energy on the Move

Energy loves to change from one form into another. In fact, this happens constantly, all around you, every single day. Let's follow a few examples.

When you switch on a torch, the stored chemical energy in its battery changes into light energy so you can see in the dark. When you bang a drum, the movement energy of your hand changes into sound energy that you hear. When you slide down a slide, the stored energy of being up high changes into the movement energy of whooshing down.

Even your own body is an energy-changing machine. The stored energy in your food changes into the movement energy of your muscles when you run, and into heat energy that keeps you warm. Once you start looking, you will see energy changing form everywhere you go.

The Great Rule of Energy

Now for one of the most amazing secrets in all of science. Energy can change its form as much as it likes, but it can never be created out of nothing, and it can never be destroyed. The total amount of energy always stays the same.

This rule is so important that scientists give it a grand name: the conservation of energy. "Conservation" means saving or keeping. It means energy is always saved — it just moves around and changes its costume.

So when a torch battery seems to "run out," the energy has not really vanished. It has simply changed into light and heat that have spread out into the room. When a bouncing ball finally stops, its movement energy has turned into a tiny bit of heat and sound each time it hit the ground. The energy is never lost. It only ever changes hands.

Where Does It All Come From?

If energy is everywhere, you might wonder where it all came from in the first place. The answer might surprise you. Almost all the energy on Earth can be traced back to one place: the Sun.

The Sun pours out an enormous amount of light and heat energy, and that energy powers our whole world. Plants capture sunlight and use it to grow and make food. When animals eat those plants, they take in that energy. When you eat your meals, you are taking in energy that started its journey at the Sun. So the energy in your muscles today is really sunshine in disguise!

The Sun's energy also stirs up the wind and the weather, lifts water into the sky to make rain, and warms the seas. Even coal and oil, which we burn for power, are made from plants and creatures that lived long ago and captured the Sun's energy. In a way, almost everything that happens on Earth is powered by sunlight.

Using Energy Wisely

Because we use so much energy to light our homes, power our machines and travel from place to place, it is important to use it wisely. Some of the energy we use comes from burning fuels like coal, oil and gas, which can pollute the air and which will not last forever.

The good news is that we can also collect energy from sources that never run out. Solar panels catch energy straight from the Sun. Wind turbines turn the energy of the wind into electricity. Water rushing through dams can be used too. These are called renewable sources because nature keeps refilling them. You can help as well, simply by switching off lights and screens when you are not using them, so that no energy is wasted.

What We Learned

Energy is the power to make things happen, and it is hidden inside everything around us. It comes in many forms — light, heat, sound, movement, electricity and stored energy — and it is always changing from one form into another. The great rule of energy is that it can never be created or destroyed; it only changes its costume. And almost all the energy on Earth began as sunlight pouring down from the Sun. Energy really is all around us, every moment of every day.

To see one special form of energy up close, read The Story of Electricity. Or discover how light energy from the Sun travels to us in The Story of Light.