One of the greatest challenges for science students transitioning from the K-12 education system to the college/university setting is realizing that everything your instructor tells you is not fact.
Why? We grow up believing everything our elders tell us and read textbooks believing everything that it states is fact. But there's a few problems. Textbooks summarize a huge body of work, and while most of is it generally accepted as scientific fact, the authors are not experts in everything, and can occasionally get things wrong. We first begin to learn about cutting-edge research in a college lecture because professors like to keep up to date with the material, but because it's cutting-edge, it hasn't had years of independent validation by other scientists, so occasionally, some of it may be wrong or out-dated.
In fact, many of you out there have probably wondered a question no one has figured out the answer to yet. So how do we ever figure out how the world works and further our scientific knowledge base so they become fact?
This varies amongst scientific disciplines, but I will discuss how we approach questions in the biological sciences. There are 3 basic types of experiments that help scientists become confident of their results:
1) Is it there at the right time and place? if it's not there, it can't be involved in the process
2) Is it necessary? If it's required for the process, eliminating it should block the process
3) Is it sufficient? If it's able to control the process, adding it to another tissue (where it normally isn't present) should allow the process to occur
Say you have a favorite gene (fave) that you hypothesize is important to form the spinal cord. If fave is expressed in the neural cells that give rise to the spinal cord, it passes test 1). If you remove fave from those cells and you don't form a spinal cord, it passes test 2). If you add fave into cells that normally make skin and they become neurons of the spinal cord, then it passes test 3). At this point, you can feel pretty confident that fave is involved in spinal cord formation.
In an ideal situation, biologists can demonstrate all these 3 types of experiments for their research project, but sometimes we can't because biology is complicated or there are other technical challenges we can't overcome. This can affect how confident we are in the result, but by having other researchers validate our results, we can increase our confidence and eventually accept it as general scientific fact.
Hope this brief lesson is helpful!