Scientific method
From Wikipedia, a free encyclopedia written in simple English for easy reading.
The scientific method is the way scientists test out ideas about how the world works. The difference between science and things that are not science (such as pseudoscience) is often defined by whether they use the scientific method.
There is no one scientific method, but in general it is usually written as a number of steps:
- Come up with a question about the world. All scientific work begins with having a question to ask. Sometimes just coming up with the right question is the hardest part for a scientist. The question should be answerable by means of an experiment.
- Create a hypothesis — one possible answer to the question. A hypothesis is a word meaning "An educated statement about how something works", and it should be able to be proven right or wrong. For example, a statement like "Blue is a better color than green" is not a scientific hypothesis. It cannot be proven right or wrong. "More people like the color blue than green" could be a scientific hypothesis, though, because one could ask many people whether they like blue more than green and come up with an answer one way or the other.
- Design an experiment. If the hypothesis is truly scientific, it should not be hard to design an experiment to test it. An experiment should be able to tell the scientist if the hypothesis is wrong; it may not tell him or her if the hypothesis is right. In the example above, an experiment might involve asking many people what their favorite colors are. Making an experiment can be very difficult though. What if the key question to ask people is not what colors they like, but what colors they hate? How many people need to be asked? Are there ways of asking the question that could change the result in ways that were not expected? These are all the types of questions that scientists have to ask, before they make an experiment and do it. Usually scientists want to test only one thing at a time. To do this, they try to make every part of an experiment the same for everything, except for the thing they want to test.
- Experiment and collect the data. Here the scientist tries to run the experiment they have designed before. Sometimes the scientist gets new ideas as the experiment is going on. Sometimes it is difficult to know when an experiment is finally over. Sometimes experimenting will be very difficult. Some scientists spend most of their lives learning how to do good experiments.
- Draw conclusions from the experiment. Sometimes results are not easy to understand. Sometimes the experiments themselves open up new questions. Sometimes results from an experiment can mean many different things. All of these need to be thought about carefully.
- Communicate them to others. A key element of science is sharing the results of experiments, so that other scientists can then use the knowledge themselves and all of science can benefit. Usually scientists do not trust a new claim unless other scientists have looked it over first to make sure it sounds like real science. This is called peer review ("peer" here means "other scientists").
Not all scientists use the above "scientific method" in their day to day work. Sometimes the actual work of science looks nothing like the above. But on the whole it is thought to be a good method for finding out things about the world which are reliable, and is the model for thinking about scientific knowledge usually used by scientists.
[edit] Example: Dissolving sugar in water
Let's say we are going to do an experiment to find out what things might change how sugar dissolves in a glass of water. Below is one way to do this, following the scientific method step by step.
[edit] Coming up with the question
We know that sugar does dissolve in water, because we see this happen whenever people put sugar into hot beverages like coffee or tea. But does it dissolve faster in hot water or cold water? Does the temperature affect how fast the sugar dissolves? This is a question we might want to ask.
[edit] Creating a hypothesis
Now that we have the question, we need to come up with a hypothesis which can be tested. One hypothesis might be: "Sugar will dissolve faster in hot water than cold water." (It could be the opposite just as well.) This can be tested: either sugar will dissolve faster in hot water than cold water, and prove our hypothesis correct, or it may dissolve faster in cold water, or it may dissolve at the same speed in both, proving our hypothesis wrong. In any case we will know part of the answer to our first questions.
[edit] Planning the experiment
One simple way to create an experiment would be to dissolve sugar in water of different temperatures and to keep track of how much time it takes for the sugar to dissolve.
We will want to make sure that we use the exact same amount of water in each trial, and the exact same amount of sugar. If we did not have the same number of either, we might influence the experiment in a way that would make it impossible to tell if the change in temperature was what was changing the speed of dissolving. To be extra careful, we would also run the experiment in a way that the water temperature does not change during the experiment.
This is called "isolating one variable" — which means making sure that only one thing is being changed each time.
[edit] Running the experiment
We will do the experiment in three trials, which are exactly the same, except for the temperature of the water.
- We put exactly 25 grams of table sugar into exactly 1 litre of water almost as cold as ice (1 °C). We do not stir. We notice that it takes 30 minutes before all the sugar is dissolved.
- We put exactly 25 grams of table sugar into exactly 1 litre of room temperature water (20 °C). We do not stir. We notice that it takes 15 minutes before all the sugar is dissolved.
- We put exactly 25 grams of table sugar into exactly 1 litre of warm water (50 °C). We do not stir. We notice that it takes 4 minutes before all the sugar is dissolved.
[edit] Drawing conclusions
One way that makes it easy to see results is to make a table of them, listing all of the things that changed each time we ran the experiment. Ours might look like this:
| Temperature | Dissolving time |
|---|---|
| 1 °C | 30 min |
| 20 °C | 15 min |
| 50 °C | 4 min |
If every other part of the experiment was the same (we did not use more sugar one time than the other, we did not stir one time or the other, etc.), then this would be very good evidence that heat affects how fast sugar is dissolved.
We cannot know for sure, though, that there is not something else affecting it. An example of a hidden cause might be that sugar dissolves faster each time more sugar is dissolved into the same pot. This is probably not true, but if it were, it could make the results exactly the same: three trials, and the last one would be fastest. We have no reason to think that this is true at this time, but we might want to note it as another possible answer.
If we wanted to, we might create a new experiment, where we would try to dissolve sugar in the same pot three different times at the same temperature. By not changing the temperature, we would know if it was the pot which was causing the change in dissolving, if there was any change at all. But this would be a different experiment. This example is just meant to show how the results of one scientific experiment can lead to another brand-new experiment.
[edit] Writing up the results
When writing up the results we would describe exactly what we did, from the first step, including: why we asked the question; what we assumed when asking it; what our hypothesis was; what our experiments were; how we ran the experiments; what the results were (our data table would make them easy for others to read); and what our conclusions were. In the end, our hypothesis seems to be correct. After writing up our conclusions, we would, if we were professional scientists, send them to other scientists to look at, to see if it sounded right to them. Maybe they would have suggestions, or get ideas for new experiments. If we were professional scientists, we would probably have the results published in a research journal, where other scientists would have a chance to agree or disagree. It does not matter if other scientists find us out to be wrong later, because this is how knowledge grows in science.
