The scientific method is a tool for investigating the physical world. The reason it is such a powerful tool is that it can return a result that counters human expectations.
The scientific method begins with a logical expectation, based on our knowledge of the system being tested. For example, our long experience with observing gravity would lead us to expect that a baseball, when thrown upwards, will come back down. In a scientific experiment, this becomes our hypothesis of how the baseball will behave if thrown upwards.
The next step is to design an experiment that tests our hypothesis convincingly. The best experiments control for known factors that are not the focus of our hypothesis. For example, if we wanted to test gravity's affect on a baseball thrown upwards, we would not throw the baseball over an upturned jet engine. Given what we know about wind resistance, it would be far better to conduct the experiment in the still air of a laboratory.
We then conduct the experiment and record its result. Did the baseball fall back down after it had been thrown upward? If not, what did the ball do? Whether the findings match our expectations or not, we repeat the experiment again and again, each time recording the result. After a large number of repetitions, a conclusion is made. The conclusion either supports or rejects our initial hypothesis.
The final step is to present our hypothesis and its reasoning, our experiment and its results, and our conclusions about the nature of a baseball when thrown upwards. The presentation, whether written or spoken, is then subjected to peer review. Peer review is a process in which other scientists knowledgeable about the subject matter will study carefully the methods and results of an experiment and see if they agree with the conclusion the scientist presented, particularly as to whether the quality of the evidence is sufficient to make the conclusion convincing.
If the experiment was compelling, and if the findings were of general interest, others might independently repeat the experiment to confirm its results. If these experiments are well designed, and the evidence is still compelling, scientists might then form a consensus about how a baseball will behave when it is thrown upwards in a still room.
The consensus will then become the scientific opinion about the matter until further evidence might refute that understanding. Scientific opinion is always open to revision.
