7.5 Matter and Energy
Where it all comes from.
Physics tells us that energy cannot be created or destroyed. So when you see a dog run or a firefly flash, that energy had to come from somewhere. Even the energy you are using to read this had the same common source as the others. That source is the Sun.
How it gets here.
The Sun converts Hydrogen to Helium in a process called nuclear Fusion. This process releases vast amounts of energy which radiates in all directions. A small portion of this energy reaches the Earth. Solar radiation mostly passes through the atmosphere and is absorbed by all objects, such as humans, trees, flowers, roads, etc. These objects will then warm up. Dark objects, such as asphalt roads, will absorb and warm faster than light colored objects, which reflect the radiation back to space.