Oh, it's so nice with the sun shining. I could stay here all day. OK, but remember that it's dangerous to stay too long in the sun, when it's at its highest. Because I get too warm? No, it's a bit worse than that.
The rays from the sun are full of energy. And that energy comes in the form of electromagnetic radiation. Some types of radiation goes straight through the atmosphere. Visible light for example, and most of the heat radiation. Other types of radiation that could be harmful for us, are filtered out by the air, like gamma rays and X-rays.
And that's lucky. But there is one type of radiation which does travel straight through normal air, and is definitely not good for us... And that is... ... ultraviolet light! If too much of this kind of radiation -- UV radiation -- reaches us, it's not only dangerous to those with lighter skin, it can also damage our DNA and pre-dispose us to skin cancer.
But what is that? Is it a bird? Is it a plane? No, it's an ozone molecule! Ozone is a form of the element oxygen.
It can stop most of the ultraviolet radiation. The ozone molecule is composed of three oxygen atoms. When they are hit by ultraviolet radiation they are split up into two parts: an oxygen molecule and a lone oxygen atom. The single oxygen atom is not at all happy being alone, so after a short while it attaches itself to an oxygen molecule again and forms new ozone. So the amount of ozone is more or less unchanged.
But where did the UV-radiation go? Well, the energy carried by the radiation was used up in breaking apart the ozone molecule. The radiation was stopped by the ozone. Ozone has protected the Earth from ultraviolet radiation for more than five hundred million years. But about fifty years ago, things almost went horribly wrong.
This top of the line refrigerator uses a really good substance: Freon. The best part about this is that it's not at all harmful for the environment! It doesn't react with anything! The problem was that when these freons leaked out into the atmosphere they could break down the ozone. But it took several years before we discovered that.
As the ozone started disappearing, more and more ultraviolet radiation reached the Earth. And that's not good. Apart from damaging our skin and increasing the risk of getting cancer, it can affect plants as well as plankton in the sea. But if the ozone goes away because of chemicals that we've emitted, can't we just make more ozone, to replace that which the freon has destroyed? A lot of ozone is actually emitted from car exhaust fumes and from industries.
But that is not good at all, because it is toxic to inhale. So we want there to be a large amount of ozone up high to protect us from the UV rays, but we don't want it to be down near the ground, making it difficult for us to breathe. Today, freons are almost completely banned, but they will stay in the atmosphere and destroy ozone molecules for many more years. So unfortunately, we'll have to live with getting hit by a lot of ultraviolet radiation. Just like Michael and Jenny on the beach.
Lucky we brought this sunscreen lotion. Now we can stay here a bit longer.