Everything in the is made from energy. It can take many forms: , , , and many others. One key fact about energy is that it can change from one form to another.
For example when you walk, the muscles in your legs change the in your food into a physical force on your bones. These push your feet against the ground and so produce movement. But movement is also a form of energy. So your muscles have changed chemical energy into movement energy.
Another key fact about energy is that it can never be created or destroyed. The total amount of energy in the Universe today is the same as yesterday and last week and a million years ago.
In most of this story we will be watching how energy changes from one form into another. If these changes did not happen there would be no story, no life, no Universe at all.
Reflections on Energy
Throughout this story I will be reflecting on why the ideas we meet, such as energy, are important to humans. In the case of energy it is very obvious. We are in the middle of an energy crisis. Modern industrial societies rely to a huge extent on the supply of fossil fuels and as they run out we are constantly seeking new sources of energy.
Looking at the big picture, the food humans eat depends ultimately on plants capturing energy from the in the process called . Even fossil fuels (such as petroleum) are the remains of ancient plants.
Another thing I try to do in this story is to learn lessons from the past to make predictions about the future. Our thoughts about the future tend to come towards the end of the website, but I will add links so, if you want to, you can jump forward to read my thoughts and then use the ‘Back’ button to come back and continue reading. For example you can click for some thoughts about future sources of energy.
Conservation of Energy
There’s a fundamental law of physics which says that energy cannot be created or destroyed in this Universe, it can only be changed from one form into another. This is the law of conservation of energy and it has never been found to fail.
The logical conclusion is that all the energy we see in the Universe today must have always been here since the time it was created. And the expansion of the Universe which we saw in tells us that it was smaller in the past.
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