Coming from the sun and other stars,
Radio masts, WiFi, and driverless cars.
To and from ‘phones and orbiting satellites,
Roaring fires and household lights.
Radiation is all around.
If we can hear it, we call it sound.
What our eyes see as something bright,
We call that radiation ‘Light’.
This page introduces the idea of (electro-magnetic) radiation. To discuss this well, you are likely to want to talk about the spectrum of colors in radiation – we deal with that on the next page.
The topic may be too abstract and beyond the comprehension of younger kids. If this is the case, just move on as the arguments are not critical to the rest of the book. It deals with colors of organisms, patterns, and perceived advantages of certain colors. BUT, if you can get the concept across, it will help you to dig deeper and explain better.
There are several issues that should be addressed if you want to try this:
- Radiation comes from a source
- The most important source for us is our Sun
- Only some radiation can be seen. There are forms of radiation that are invisible to our eyes (but may be sensed by our ears or by our skin), and yet more that we cannot detect at all – we need to use special machines for this.
- Energy. The source needs to be energized in some way before it can radiate. The radiation carries some energy with it.
Warmth too is a form of radiation,
We know what’s hot from its sensation.
Science tells us there is so much more
For which, we need machines to explore;
Such as medical scanners for X-rays
Or telescopes for night-time surveys.
Warmth as an example
- The second page deals with warmth. Our eyes can see that the wood is hot because it glows red to white. Energy is released when the wood burns, and that energy heats up the wood and keeps it burning. Some is released as visible light. Consider mentioning ‘white-hot’.
- You can feel warmth with your hand or face, even though you are not touching the source. Here is where you can introduce the concept that heat is being ‘radiated’ from the source to you. Use warmth to strengthen the ideas that radiation
- comes from a source and
- that we can detect it.
- You can use a candle to make these points. If you put something opaque between the flame and yourself, you can show how it blocks the radiation in two ways. First, the sense of warmth goes away when there is no direct line from the source to your skin; and secondly, because the light is blocked, it doesn’t land on walls on other surfaces – shadows are formed.
- Use electric lamps and shadows also to show that the lamp is the source of the light. Again, block the radiation with something opaque. If you want to get adventurous, consider blocking only some colors with colored paper or plastic. Then of course, expect questions about how come some light is colored.
This picture draws attention back to the sun. It is the source of most visible light. Moonlight is just sunlight reflected from the surface of the moon. And the stars visible in the night sky are just other suns, but very very far away that they just look like pinpricks. Not only is the sun the source of visible light, it is the source of most of the energy that is captured by our vegetation, and converted into stuff that we and other animals eat. Light can come from other sources, under Luminescence you will find examples of light made by living organisms.
The page makes the point that radiation comes in many forms. Telephones and GPS systems rely on radiation – they carry information and messages to and from the device, connecting via towers and satellites so that it can travel around the globe. We do not see this radiation. A little reminder that we are able to sense some radiation (sound and light), but not all.
You may be asked why, in this picture, the sun seems to be orange. This can get interesting. To deal with this, you’ll need to point to the fact that light is made of many colors. The colors form a spectrum. We can see this spectrum as a rainbow when the different colors in light are deflected differently as they pass through water droplets. How light hits objects, or moves through air, may affect some of the colors of the spectrum differently to others. Then light changes from colorless to colorful. This is familiar – remember the old saying
Red sky at night is a sailor’s delight, red sky in the morning, sailors take warning.
As sunlight passes through the sky, its color may change for one of two reasons. The first is if there is something in the air. We can start with the example of the picture of the sea in the pages called ‘Why‘ In this picture the sky is a pinky color. That is because dust from the red soil is blown into the air, and tiny red dust particles are changing the color of the air.
Smoke can do the same thing, often it looks blue. This is caused by the very tiny particles in the smoke that change the light to favor the blue end of the spectrum. You can see the same if you look at distant hills … and if you don’t have any hills nearby, this picture from England makes the point. The land near the camera is green/brown. But, the distant hills look blue – as does the distant air. This is caused by tiny particles in the air. The air is not empty, but filled with all kinds of things, such as dust, droplets of water, pollen from the plants. And just like smoke, these small things interact with the light to favor the color blue. The daylight sky looks blue because of the small particles in the air.
When light is passes through tiny drops of water, it is deflected. Each color is deflected a different amount. The result is a rainbow with a spectrum that ranges from the red to the violet end of the spectrum. Something similar happens when the light from the setting (or rising) sun passes through the atmosphere. Then we just get some of the spectrum – the red end (or orange as is the case in this picture).
If you have more ideas, please let us know below.