You are making observations about the world all of the time. You may notice that it’s cold outside, that it’s raining, that your friend has a pink shirt on, that a drink has spilled on the ground, or that someone has food caught in their teeth. Most of the time, these observations happen and they cause some sort of reaction: You put on a hoodie in order to warm up, grab an umbrella, compliment your friend, clean up the drink, or tell the person that they have food in their teeth.
However, sometimes you observe something and then you wonder why it happened the way it did. This is the birth of science! Scientists are no different than anyone else – in fact, anyone can be a scientist. When you are doing science, you are asking questions and then going through a process to answer them. We’ve already seen some parts of the scientific method: Making hypotheses, collecting data and drawing conclusions are all part of the scientific process. But how do you go about actually answering the questions?
Typically, scientists do not work alone when answering scientific questions. There is way too much scientific knowledge for any one person to remember all of it. In fact, for any one branch of science (biology, physics, chemistry, geology, etc.), there are hundreds more branches, and finding an “expert” who knows all that there is to know for any one of those smaller branches is nearly impossible. For example, the bacterium E. coli is such a well-studied bacterium that thousands of scientists research and study it, write papers and books about it, and go to conferences to talk about it. Yet, no one person has all of the information about E. coli – these scientists still must work in groups in order to put all of the information together.
This works for your life, too: think about your favorite musician or group. Do you know everything there is to know about them? What if you got in a group of people who knew a lot about this musician or group? How many people do you think it would take to form a group who knew everything there was to know? And do you think it might be useful to include people who had a different favorite musician or group?
Many people think that the internet has the answers to all of the questions, but this is definitely not true. For example, if you tried typing, “Who is the best football player in the world?” into Google, you would not only get websites that talk about soccer, but you get over 33 million results! If you get a group of people together who have studied football for a long time, they would more accurately be able to come to a conclusion than the internet currently can.
So far, we’ve only talked about simple questions: the questions that books and the internet are very good at answering. Scientists are much more interested in open-ended questions. To answer these types of questions, scientists design experiments. Experiments are actually very basic, so let’s take a simple one: does a plant need light in order to grow?
First of all, the question needs to be more specific. What kind of plant? What kind of light? What is meant by “grow”? So, let’s use a black-eyed pea plant, a normal incandescent light bulb (like the kind you use in your house), and let’s say that “grow” means to make a leaf that’s longer than one centimeter. Now, our question is: can a black-eyed pea plant grow at least a one-centimeter leaf with only incandescent light?
After we make our hypothesis (go ahead, make your own right now), then we can design our experiment. Clearly, we’re going to need some black-eyed peas, some soil, some water, an incandescent light and a metric ruler. Those are our materials. Now, we need to identify the independent and dependent variables.
Independent and dependent variables are related to one another. The independent part is what you, the experimenter, change in order to do your experiment. The dependent variable is what changes when the independent variable changes – the dependent variable depends on the outcome of the independent variable. What are you going to change in order to do this experiment? Think about it … it’s the light!
So, the incandescent light is the independent variable, which means that we’re going to need two plants: a plant that grows with the light bulb and a plant that grows without the light bulb. In fact, the experiment will go even better if we use more than one plant, so let’s try growing three plants with the light bulb and three plants without the light bulb. The plants in the light are called the experimental group and the plants without the light are called the control group.
|Experimental Group||¼ cup water||8 hours incandescent light||75 F|
|Control Group||¼ cup water||8 hours sunlight||75 F|
Black-eyed pea Experiment
The experimental group always contains what we are testing for, while the control group usually contains what we know normally works. So, in the control group, we’ll give the black-eyed peas ¼ cup of water every day and we’ll let them sit in the sun for eight hours every day at 75 degrees F (did you notice how the experiment got even more specific?). This means that in the experimental group, we also need to give them ¼ cup of water every day and let them sit underneath the light bulb for exactly eight hours at 75 degrees F. A good scientific experiment has one and only one change between the control group and the experimental group (or, in some cases, groups).
If we design our experiment in this way, we’ll be able to say if eight hours underneath an incandescent light bulb works to grow one centimeter leaves better or worse than eight hours in the sunlight, at 75 degrees F. However, we cannot draw any conclusions past that: we can’t say that it will work at 30 degrees F, that it will work with any amount of light, or that you can use any amount of water. In other words, your conclusions need to be as specific as your experiment!