How do scientists discover knowledge?

What part of central nervous system link brain and peripheral nervous system? What era featured the longest periods with no life forms on Earth.? If 100 grams of salt is removed from a container each day how long will it take to empty a 4kg container? What is the abbreviation for bushel? Is there any new planet discovered recently? What of the function of the epiglottis? What type of material is inside the holes in the outlet? How often do human skin cells divide them each day? The metric unit for measuring mass? Which island countries are India's southern neighbors? How shallow a pool can you jump into? Why is Cumberland falls special? How many moles of water are needed in order to produce 21.8 g of calcium hydroxide? What are 5 properties of sound? Is the third law of motion push and pull? What familly name is thorium in? Which vitamin is needed to synthesize nonessential amino acids from essential amino acids? Is physical geography no longer an issue in the modern world due to technological advancements? What can cause retinal damage? What is a call slip?