6.
What are two characteristics of each of Earth’s four major systems?

Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air. These four subsystems are called "spheres." Specifically, they are the "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air)

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.