Though my childhood dream was always to become a scientist of some sort, I have not quite gotten there. I do have my BA in biology, however, which I think gives me some right to comment on what science means (or doesn’t).
So first, what is science? Probably the most common definition is “anything that follows the scientific method.” This certainly seems a bit circular.
The scientific method is where someone will observe something happening in the world and realize that, for some reason, this thing is interesting. The individual will then try to find and define a pattern for what s/he observes, and come up with a testable hypothesis that explains those observations. A “hypothesis” is simply an educated guess (but it can be very educated indeed). “Testable” pretty much means “can be proven wrong.”
Once a hypothesis is generated, an experiment must be thought up to check the validity of the hypothesis. If your hypothesis is true, it must be able to correctly predict an end result based on new data. An experiment is simply a process where you say, “If my hypothesis is right, then when I do this [the experiment] to these [the data source] I should get that [another data set, related to the first by the hypothesis].” Let’s do an example from my own life.
One of my and my gf’s two cats, Kati, is a bit of a fatty. It’s not really her fault, she was simply born different. She was found by my mother in a ditch in Grinnell “the Jewel of the Prairie” Iowa and I took her back with me to Chicago. This was after we already had our first cat (Yoshi) for six months or so.
Kati, looking glamorous as ever in her cardboard box.
Kati was extremely funny shaped, with a tiny head and paws and a gigantic rib cage and belly. Over the year that we’ve had her she has grown up and stretched out a bit, so she looks less strange. But still a bit goofy.
She loves her food. We found out early that we couldn’t just make sure there was always food in the bowl, as we can with Yoshi, but instead we have to feed her daily defined amounts. Otherwise she won’t stop eating. Ever. So we taught Yoshi to only eat his food on the counter, since Kati is too funny shaped to get up there. It works marvelously.
Now we feed the cats every night at 10pm. Here’s the observation:
Kati is very quiet throughout the entire day, until around 9-9:30pm, at which points she starts whining so much that I want to throw her out into the wintry night. Why is this? It would seem rather obvious to most people that this is because her food time has nearly arrived, and she has become impatient/hungry and wants to make sure we know about it.
That was a simple hypothesis. How would you test it?
I would spend a week recording exact feeding and whining start times, and then abruptly change the feeding time. Food will still be given in the same quantity, and still every 24 hours. This is an important point; an experiment tries to keep as many things constant as possible so that only the variable thing of interest is tested. I would then allow a week of readjustment.
Now, since the hypothesis was that Kati whines when hungry and I have shifted the feeding time to (let’s say) 8pm, we would predict that she will now begin to whine around and a little before 8pm.
I haven’t actually tried this, since I see no reason to, but the possible results in whining time are: (1) no change, (2) later start, (3) earlier start. If it turns out that either of the first two possibilities are true, then we know that our hypothesis fails. Only a subset of possibility (3), roughly 2 hours earlier will indicate a successful hypothesis
So let’s say she starts meowing at 7:30pm, which is what we predicted. Does that mean that she is meowing because she is hungry/impatient? The answer is a gigantic “NO!” This is really important.
If the results of an experiment line up with the hypothesis, usually you have shown correlation, but not causation. Just because she meows an hour before food time doesn’t mean she does so because she is hungry. Perhaps it is the realization that she is a slave to food and will soon eat an entire bowl in under five minutes that makes Kati whiny and depressed. Or maybe the the whining expresses her joy at the knowledge that the two bipedal giants roaming the land will be soon passing out that sweet, delicious nectar.
In any event, science never “proves” anything in the sense of the word where “to prove” is to show that something is the Truth. And I use the capital “T” to mean absolute, unarguable fact. For instance, physics has some of the best laws of nature that appear to be the Truth. Take gravity. Every single measurement ever done has, within error, shown that the laws of gravity hold in the way they are expected to (incorporating relativity, of course). Does this mean that the universe always follows those laws? No. It means that every time we have measured the universe we got the same result. No one ever says “I wonder if gravity exists today.” We just assume it will be there. In fact, we predict that it will be there, based on all of our previous experience. In science you really just have predictions, not knowledge (if knowledge is define as pieces of the Truth). Usually, though, we still say that we know.