Radiation
Radiation is energy that moves through space as waves, like heat from the sun.
A flat black tray sits on a table with nothing on it. A heat lamp hangs above, pointed straight down. After a few minutes, the tray grows warm even though no flame or hot air touched it. The warmth moved from the lamp to the tray as waves crossing the open gap. That is radiation — energy that travels through space on its own.
Explaining radiation by grade level
Stand in the sun and feel your skin get warm. No one is touching you. The warmth comes through the air from far away. The sun sends out heat that travels all the way to you, even through empty space.
Projects that explore radiation
A lamp sends energy through space as waves toward nearby objects. Dark surfaces absorb more of that energy than shiny ones. A shiny foil surface bounces the energy away, so the water beneath it stays cool.
Sunlight carries energy through space as waves. A dark surface soaks up more of that energy than a light one. Black boxes in direct sunlight heat up the most. White boxes stay coolest.
The sun sends energy as waves through space to surfaces below. On a hot day, a dashboard can reach over 75 degrees Celsius without any shade. You park three cars of the same make and model in the sun and measure the temperature inside over 10 hours.
Sunlight delivers energy as waves that heat a car's dashboard to extreme temperatures on a hot day. Different sunshade materials reflect different amounts of that incoming energy — which is why the choice of sunshade matters. You park three identical cars in the sun: one with no sunshade, one with a reflective foam sunshade, and one with a reflective bubble sunshade. Measuring each dashboard temperature every two hours from 8 AM to 6 PM shows that the reflective bubble sunshade keeps the dashboard coolest throughout the day.