In science, information about nature comes from our observations. Consider two types of observation-situations:
a) For several months you make observations about the moon's appearance, and the times and locations of its rising and setting.
b) You observe the growth of young plants in many contexts, by varying many factors: light, temperature, type of seed (lima bean,...), type of soil, amount and frequency of watering, amount and type of fertilizer, treatment of seed (by soaking, cooking,...) before planting, and more. You try different combinations of factors, and for each experiment you make observations both above and below the soil surface, before and after the plant grows through the surface.