The Scientific Method
It can be anything from astronomy to medicine to biology to agriculture.
The basis of the scientific method is asking questions and then following an organized process to come up with answers or theories.
You could ask, "Why do dogs and cats have hair?"
One answer might be that it keeps them warm.
That is how it starts. It's the scientific method in action. You could proceed from there to test you supposition (that the hair is to keep them warm).
QUESTIONS AND ANSWERS
Just about everything starts with a question.
Usually, scientists come up with questions by looking at the world around them.
"Hey look! What's that?" See that squiggly thing at the end of the sentence, a question has been born.
So you've got a scientist. They see something they don't understand. Because they are a scientist, they probably have some huge urge to answer questions and discover new things. The trick is that you have to be able to prove every answer you give. If you can't test your answer, other scientists can't prove it to see if you were right or not.
As more questions were asked, scientists worked really hard and came up with a bunch of answers. Then it was time to organize. One of the cool things about science is that other scientists can learn things from what has already been proven. They don't have to go out and prove everything again and again. That's what makes science special, it builds on what has been learned before. This process allows the world to advance, evolve, and grow. All of today's advancements are based on the achievements of scientists who already did great work.
Experimental proof is the thing that makes all of the observations and answers in science VALID (proven). The proof shows that the statements are right. It sounds like a really simple idea, but it is the basis of all science. Statements must be proven. Enough said.
Scientists start with observations and then make a HYPOTHESIS (a guess), then the fun begins. They must prove their hypothesis with trials and tests which show the why their data and results are correct. They must use CONTROLS which are QUANTITATIVE (based on values and figures, not emotions). Science needs both ideas (the hypothesis) and facts (the qualitative results). They examine their data and develop newer ideas. Then they have more observation and refinement of their hypotheses.
Back to the fur idea. The question: Why do bears have fur? The hypothesis: Bears need fur to keep warm. Trials and tests: Can bears stay warm when you shave them? If you double the amount of hair, do bears overheat? The results: Bears have hair to stay warm, they shiver when shaved and overheat when they have too much hair. A new idea/question: do bears use their hair for protection?
THE WHOLE PROCESS
There is an evolution for every idea...
(1) Hypothesis (something that uses a few observations)
(2) Theory (something that uses many observations, it can also use additional, unrelated facts and new relationships)
(3) Principle or Law (stands the test of time, is proven over and over, can create true predictions for different situations, has uniformity and is universal)