In this video, we're going to differentiate between predictions, hypotheses, and theories. A prediction is pretty straightforward for the most part, and a prediction can be defined as an expected outcome of an event that can either be correct or incorrect. Predictions will only address the answer to the question: what will happen? For example, I could make a prediction that tomorrow it will rain. Now tomorrow, it will either rain or it will not rain, and so my prediction will either be correct or incorrect. Predictions are pretty straightforward.

Now, a hypothesis, on the other hand, is often confused with a prediction. However, a hypothesis is different from a prediction as it is a proposed and testable explanation for an observation, and the term 'explanation' is incredibly key when it comes to a hypothesis. A hypothesis will address the answers to two questions: what will happen? And why will it happen? The 'why' here is what ties in the explanation term with this hypothesis. Since the hypothesis should answer the question: what will happen, just like a prediction, a good hypothesis or a well-structured hypothesis will often include a prediction. This is why hypotheses are often confused with predictions. However, a hypothesis is different because it is testable and will provide an explanation for the observation, meaning it will answer the question why something will happen. For example, if we go back to that rain analogy, I could make a hypothesis that tomorrow it will rain because I pointed to the sky. This might sound a little ridiculous, and it's not necessary for you to accept the hypothesis. However, the hypothesis must always be testable, meaning that you can design an experiment to determine if you want to accept or reject the hypothesis. The hypothesis must always provide an explanation and should answer the questions: what will happen and why it will happen.

Last but not least, we are going to discuss theories. A theory can be defined as a testable and broad hypothesis of many observations, supported by a large body of evidence. A theory is a broad hypothesis, and in many ways, it is similar to the hypothesis. But again, the theory is going to be much broader on a larger scale, and the key terms that differentiate the hypothesis from the theory are the terms 'broad,' 'many,' and 'large.' A theory is much broader with many observations and a large body of evidence. It's basically a hypothesis at a much larger scale.

If we take a look at our image down below, we can get a better understanding and look at another example to help us better differentiate predictions, hypotheses, and theories. Notice that we are starting with an observation, we have a motorcycle here, and this motorcycle won't start, which is our observation. After we make our observation that the motorcycle will not start, we ask ourselves a question: why doesn't the motorcycle start?

To differentiate predictions from hypotheses, from theories, let's examine these next three boxes. A prediction once again is going to be an expected outcome of an event that can either be correct or incorrect and will only answer the question: what will happen. The prediction here could be, if you add gas then the motorcycle will start. This is simply a prediction because it is an expected outcome of an event, but it will either be correct or incorrect. We could add gas to this motorcycle, and it will either start or it will not start, and so that is a prediction answering the question: what will happen if we add gas, but it doesn't answer any other questions.

Moving on, a hypothesis again is going to be a proposed and testable explanation for the observation. It will not only answer the question: what will happen but it will answer the question: why it will happen as well. For example, we could say that the motorcycle stopped working because it ran out of gas. So, if you add gas then it will work again. Notice that it includes the word 'because' here, and that 'because' automatically shows that this is an explanation explaining why something will happen. It’s saying that it ran out of gas, which is the explanation and it also answers the question, what will happen? So it says that if you add gas, it will work again. Notice here we have a gas meter that is on empty to show that this is explaining why this will happen.

Last, over here what we have is the theory. Again, the theory is very similar to the hypothesis but it's going to be at a much broader scale, supported by many observations, and also supported by a large body of evidence. Here with this theory, notice that we have multiple motorcycles here, so it's not just one motorcycle, it's multiple motorcycles, and we're looking at a much larger scale here. With this theory, what we're saying here is that all motorcycles stop working when they run out of gas so adding gas will allow them to work again. Notice that some of the keywords here are 'all motorcycles' so now it's at a much broader scale than just the one motorcycle we were looking at before. It’s also similar to a hypothesis in that it's answering the questions: what will happen and why it will happen. So it’s saying that they stop working when they run out of gas; that's an explanation, and if we add gas, they will work again; that's answering what will happen.

Now, another important note that I want to mention here is that technically, hypotheses and theories can never be proven to be correct, but they can be falsified, meaning that they can be proven incorrect. This is something that's important to keep in mind because, whereas a prediction can be determined to be correct or incorrect, hypotheses and theories can never be proven to be correct, and so this is why we can only accept a hypothesis and we can only accept a theory, but we can never say that they are true. As we move forward in our course, we will discuss some theories such as the cell theory and the theory of evolution, and again there are large bodies of evidence that support these theories and there are many observations that support these theories, but they can never be proven to be true. They can only be accepted, and they can also always be falsified. So there can always be some finding in the future that may falsify these hypotheses and theories. This is an interesting fact to keep in mind.

This concludes our brief lesson differentiating predictions, hypotheses, and theories, and I'll see you all in our next video.