In previous activities, you have built sensors to measure only one environmental variable like temperature, light or distance. But scientists often measure more than one variable at a time because sometimes they can be related. For example, in the morning you might measure an increase in light intensity as the sun rises, and also an increase in temperature as the sun warms up the air around you. Measuring more than one variable can tell us about how these conditions affect one another and can help us explain environmental processes in the world around us.