The GOAL of SCIENCE is to produce a STRUCTURED BODY of KNOWLEDGE CONSISTING of Concepts, THEORIES and GENERALIZATIONS that have PREDICTIVE POWER.
Science is a process used to obtain knowledge based upon observable evidence. Observation is the foundation upon which science is built. As our powers of observation increase, through the use of instruments like telescopes, microscopes, MRI imaging, satellites, etc..., our ability to obtain knowledge increases and our body of scientific knowledge changes.
So what does this have to do with FACTS, HYPOTHESES, THEORIES, and LAWS? These are the words we use to describe the body of scientific knowledge and it is important that we learn to use them accurately. A fact is something that is directly observable and that has been documented to reoccur on a predictable basis. Under a standard set of conditions a fact will be observable by multiple individuals and can be validated consistently with instruments. For example: The sun rises in the east. The temperature outside is 25 degrees Celsius. Sandstone is more dense than water.
Based on Knowledge and Experience, INFERENCES ARE SUGGESTED EXTENSIONS OF FACTS! For example: I could infer from the fact that John's temperature is 2 degrees above normal that he has an infection. I did not actually observe the infection. I infer that he has an infection based on the fact that his temperature is elevated. Perhaps his temperature is elevated because he just finished an intense game of soccer played outside under an afternoon sun. Perhaps his temperature is elevated because he is suffering from heat exhaustion. However, based on the fact that earlier in the week he did homework with a friend who has since been diagnosed with strep throat, I infer that his temperature is caused by infection. If we were to take a culture of John's throat and discover a strep-causing organism, then we would no longer have to infer that his elevated temperature was caused by an infection; it would be a fact.
HYPOTHESES ARE TESTABLE INFERENCES. They are predictions that we make based on our current understanding. Knowing what I know about infectious diseases, I could hypothesize that John's infection is caused by the same microbe as the friend with whom he did homework. We could test my hypothesis by taking a culture of both students' throats.
A SCIENTIFIC LAW IS A STATEMENT OF FACTThat Has Been Validated By Hundreds Of Thousands, If Not Millions, Of Pieces Of Observable Evidence. For example, the law of gravity has been verified millions of times in millions of situations. A law can also be a statement of a relationship, for example the speed of light, the period of a pendulum, or the independent assortment of genes. Laws state facts and/or relationships. They do NOT give explanations.
THEORIES EXPLAIN SCIENTIFIC LAWS For example the Theory of Plate Tectonics explains the facts that mountains exist, that earthquakes happen, and that the sea floor spreads, to name a few. Theories give explanations about HOW and WHY things happen in our world. Theories are very big; they explain a lot of things. Theories tie together a lot of facts and observations that may seem unrelated. Referring again to our example, until scientists developed the Theory of Plate Tectonics earthquakes and sea floor spreading seemed to be two totally unrelated phenomenon. Now we understand that they are different manifestations of the same process. Theories also have predictive powers. Using what we know about plate tectonics, we can predict the general areas where earthquakes and volcanoes are likely to occur. SCIENCE IS A WAY OF KNOWING BASED ON OBSERVABLE EVIDENCE. It is not the only way of knowing. We can know things about love, values, and faith however; knowledge based on love, faith, and values is not science because it is not based on observable evidence. That is not to say that it is wrong, it simply is not science.