Video: Understanding Scientific Theories

In this video, we will learn how to describe the process of forming and testing hypotheses to generate theories, and how competing theories are compared.

16:07

Video Transcript

In this video, we will be learning about the scientific method and the process that we undergo in order to make discoveries about how the universe works.

Now, to some, science feels like just a list of facts. And the more you know, the better you are as a scientist. But in reality, science is much more than that. Science is systematic curiosity. It is a process that allows us to model the behavior of the world we live in whilst doing our best to eliminate any biases we may have as human beings. Because sometimes what we perceive is not necessarily what is actually happening. And science, via the scientific method, allows us to get around that. And so, science is a very rigorous, very systematic, and yet often very creative process that allows us to build our understanding of our universe.

But anyway, that’s enough about what science actually is. Let’s take a look at the scientific method in a bit of detail. Now, it all starts with something, some event, happening in the universe, for example, a ball falling to the ground. And we also need a scientist to be present to notice this event happening. Now, the event itself, or the thing that’s happening in the universe, is known as a phenomenon. And the scientist is said to observe that phenomenon. And so, we can say that that’s the first step in the scientific method. A scientist observes a phenomenon.

And by the way, it doesn’t necessarily have to be a professional scientist. It could be anyone who notices something interesting happening in the universe and then wants to try and explain how it happens. But anyway, so after the first step has happened, after the scientist has observed the phenomenon, the scientist takes some time to think about what might be happening here. In other words, they try and come up with a reason as to why this ball would be falling on the ground in this case.

When they come up with a potential reason, this is known as a hypothesis. A hypothesis is basically an educated guess that the scientist makes as to why the phenomenon that they observed occurs. It is a potential explanation for the phenomenon. And so, we can say that the second stage in the scientific method is that the scientist presents a hypothesis. Now, as we said earlier, a hypothesis can even be an educated guess. This does not mean that the scientist is correct.

But in order to figure out whether the scientist is correct, the hypothesis needs to be tested. And before the hypothesis can be tested, the scientist has to develop what’s known as a scientific model, which is basically a framework of how the hypothesis relates to what’s actually happening in the universe, the ball falling to the ground in this case. And specifically, the scientific model can be thought of as the mathematical framework that shows how the scientist’s hypothesis would result in the event occurring that the scientist observed earlier if their hypothesis ends up being true.

And so, we can say that when the scientist presents the hypothesis, they also work on developing a scientific model. But then, this scientific model will produce predictions as to what else can happen in the universe. In other words, the mathematical framework, the scientific model, will suggest other phenomena that should be observed in the universe if it were true. And so, these predictions can be used to test the hypothesis.

Because if the scientist comes up with a hypothesis as to why something in the universe is happening, and then they develop a scientific model, and the model comes up with predictions as to other stuff that should happen. Then if this other stuff really does happen, then that’s evidence that the hypothesis that the scientist came up with might just be correct. And hence, we can say that the next step of our scientific method is that the predictions made by the scientific model that the scientist has developed can be used to test the hypothesis.

Now, when we say that the scientific model makes predictions, we don’t mean that it looks into a crystal ball and tells us what should happen in the future. What we mean is that the scientific model, often mathematical, can be followed through. The maths can be followed through. And that could lead us to some other interesting phenomena that also fit with the framework in the scientific model.

For example, in this case, our scientific model is that all objects with mass attract all other objects with mass, which is the wordy version, but there are also mathematical versions of this. Well, then, a prediction that our scientific model would make is that if we took a second ball and place it next to our first ball, then these two balls should also attract each other. Because both of these balls are objects with mass. And so, following our scientific model, they should attract each other.

Now, at first, it might seem like this is not the case. But actually, for objects this small, the force of gravity is very weak. So, we need some very sensitive equipment in order to see whether these objects would actually attract each other. But anyway, so the idea that these two balls should attract each other are a prediction made by our scientific model. And this can be tested. But ideally, we would take lots of different predictions from our model and test all of those. The more experiments we do, the better. And each experiment should strive to get the most accurate and precise numerical values possible.

In other words, for this experiment here, we should try and find as accurately as possible the force of attraction between these two objects. And so, in our experiments, we should be trying to make accurate and precise measurements. Where a measurement is the process of determining the value of a quantity in an observation. In other words, we’re trying to find a numerical value. So, in this experiment here, we’re trying to find the value of the force of attraction between the two objects. And hence, we’re making a measurement. We’re measuring the force between the two objects.

But anyway, so, coming back to our flow chart, we said already that the predictions made by the scientific model are going to be used to test the hypothesis. And as we’ve hinted at already, these tests are extremely rigorous. There are lots of different experimental techniques used in each and every experiment that allow us to get rid of human biases and ensure we test as fairly as possible what’s actually going on. And then, combine this with the fact that we try and do multiple experiments to test every single hypothesis. We come up with a pretty solid way of working at how the universe works.

Because if even one of the experiments that we conduct disagrees with our hypothesis, then the hypothesis is immediately deemed incorrect. It either has to be modified or completely scrapped, and we have to start from scratch again. And hence, we can say that the next step in our scientific method is to ask the question, do all the experiments that we’ve conducted agree with our scientific model? If the answer is yes, then we’ll come back to that in a second.

But if the answer is no, if even one of our experiments disagrees with our scientific model and with our hypothesis, then we need to go back to the drawing board. We need to either modify our hypothesis or completely scrap it and start from scratch again. Now, once we’ve modified the hypothesis or come up with a completely new one, we then go through all of these steps again. We have to do all the testing once more. Now, what happens if all of the scientific experiments we conduct do agree with our scientific model and our hypothesis? Well, then the hypothesis gets an upgrade. It is now known as a theory.

And notice the use of the word theory here. When we use the word theory in everyday life, we usually mean a guess, or a hunch, or an educated guess. But in the world of science, the word theory is very different. A theory is a hypothesis that’s been rigorously tested and every single piece of experimental evidence that we have agrees with that hypothesis.

And so, there are two main points that we really need to get. One is that theories aren’t just guesses; they’re very rigorously tested. And two is that experimental evidence is king. As a scientist, it does not matter how neat your hypothesis is or how clever it is. If even one single experiment disagrees with your hypothesis, then your hypothesis is wrong.

But that’s of course assuming that the experiment has been conducted thoroughly and fairly and accurately, which is the first thing that’s checked when an experiment provides an unexpected result. But of course, assuming that the experiment is done correctly, then the evidence gathered from that experiment has the power to dictate whether or not your hypothesis is a good description of our universe.

But anyway, so, coming back to our scientific method flow chart. What happens when a hypothesis becomes known as a theory? Is that the end of it? Well, no, there is another step to this method where our theory gets compared with other existing theories that describe fairly related phenomena. For example, our scientist here now has a theory that says all objects with mass attract all other objects with mass. But then, another scientist might have the theory that circular motion occurs when a centripetal force exists.

Now, that sounds a little bit complicated. But basically, if we take an object, and we see that that object is moving around in a circle. Then this scientist’s theory says that the reason that this object is moving in a circle is because there’s a force acting on the object towards the center of the circle. Which is known as a centripetal force. Now, the idea is to take our scientist’s theory and compare it with other existing theories.

And in this particular case, the way to do this is to think about our object in question as a planet. And at the center of that planet’s orbit is a star. Now, because our scientist’s theory says that all objects with mass attract all other objects with mass, then we could say that the star attracts our planet. And the way it does this is by exerting a force on our planet. And in this case, the force that’s exerted is in this direction towards the center of the star, which is therefore a centripetal force. And hence, the planet will go around in a circle around our star, which matches our observations.

And therefore, our scientist’s theory does agree with the other scientist’s theory. And the way that we found this out is by looking at situations where both theories must apply. Now, this process, the process of testing our scientist’s theory against other scientists’ theories, is known as scientific peer review. Where other scientists, the peers of our scientist, will review the scientist’s theory based on comparing it with existing theories. And as well as this, scientific peer review consists of making sure that our scientist, when they conducted all the experiments to test their hypothesis, did indeed conduct these experiments correctly.

Now, if everything works out and the scientist is known to have conducted the experiments correctly. And other scientists who tested our scientist’s hypothesis also conducted experiments correctly. And our scientist’s theory agrees with other existing theories. Then, all is well and good. And so, at this point, we can add another step to our scientific method flow chart. We ask the question, do the theories agree? In other words, the theory of our scientist with all the existing theories.

If the answer is yes, then yay! Everything is great. But if the answer is no, then the new theory that our scientist is working on and the existing theories are tested once more, specifically in the areas where our scientist’s theory doesn’t agree with the existing theories. And the theories that don’t agree with experimental results are thrown out. And so, this big flow chart is a brief overview of the scientific method. There’s, of course, a lot more to it than this. But what we’ve discussed so far is a pretty broad overview of what actually happens.

And as we can see, this is a very thorough, very rigorous process. All it takes is one experimental result where the experiment is done correctly that goes against our hypothesis or our theory, and our hypothesis, or theory, gets thrown out. Depending on how much our experiment disagreed with our theory or hypothesis, we have to either modify it or completely get rid of it and start from scratch.

And this is why, when something becomes a theory, we take it to be the best possible explanation that we have at that point in time of the phenomena that it is trying to describe. So, now that we’ve considered the scientific method and what it entails, let’s take a look at an example question.

Which of the following statements most correctly defines a scientific measurement?

Okay, so, in this question, we’ve been given four different options that are possible descriptions of a scientific measurement. So, let’s go through them one by one and see which one is correct, starting with option A. A measurement is a method of showing that a hypothesis is true. Now, this statement is very problematic. But let’s first realize that the word hypothesis means a possible explanation offered by a scientist for some event or some phenomenon happening in the universe. And when it’s a hypothesis, it’s basically just an educated guess.

Now, that hypothesis needs to be tested in order to see whether or not it’s a good description of what’s happening in the universe. And that’s what this statement is alluding to. This statement is saying that a measurement is a method of showing that our hypothesis is true. However, one can never show a hypothesis to be true. Any experiments that we conduct will either agree or disagree with the hypothesis.

And if an experiment disagrees with a hypothesis, then immediately we can say that the hypothesis is false. However, if all the experiments that we conduct agree with the hypothesis, then we can only say that the hypothesis is a good description of what’s happening in the universe. Because there might still be an experiment that we haven’t yet conducted that shows our hypothesis to be false. And for this reason, option A is not the answer to our question.

Moving on to option B then. A measurement is the act of noticing that some phenomenon seems to occur. Where the word phenomenon basically just means an interesting event, something that happens in the universe that a scientist will try and explain. And option B is saying that a measurement is the act of noticing this phenomenon. Well, the act of noticing that some phenomenon seems to occur is actually an observation, not a measurement. A measurement is a little bit more than that. And we’ll come back to that when we look at the next two options. But for now, we can say that option B is referring to an observation, not a measurement. And therefore, it’s not the answer to our question.

Moving on to option C then. A measurement is a prediction about the observation of some phenomenon. Now, when a scientist comes up with a hypothesis, a possible explanation as to why something that they observed occurs in the first place. Then, they develop that hypothesis, building a framework around it, a mathematical framework most commonly. And that mathematical framework is known as a scientific model. In other words, that scientific model is basically a more thorough description of what the hypothesis is trying to say. And that scientific model will have some predictions as to other phenomena that can occur, which the scientist can then test to see if they occur.

And if they do occur, then that’s good evidence that the hypothesis of the scientist is along the right lines. And if those predicted phenomena don’t occur, then it’s good evidence that the hypothesis of the scientist is incorrect. But the point is that a scientific model can make predictions about the observations of some phenomenon. But that in itself is known as a prediction, not as a measurement. And hence, option C is not the answer that we’re looking for.

So, moving swiftly on to option D. A measurement is the process of determining the value of a quantity in an observation. And this is exactly what a measurement is. A measurement is a little bit more than the description seen in option B, which was the description of an observation. Which is simply noticing that something is happening. Because a measurement is made when the value of some quantity is found.

So, for example, if we’re conducting an experiment where we take a ball and roll it along the ground, then we can make a measurement of the distance traveled by the ball. And the measurement itself will be made when we determine the value, let’s say 0.5 meters of the quantity, which is the distance traveled by the ball when we’re making an observation. And so, at this point we’ve found the answer to our question. A measurement is the process of determining the value of a quantity in an observation.

Okay, so, now that we’ve looked at an example question, let’s summarize what we’ve talked about in this lesson. In this video, we’ve seen that the scientific method is a highly rigorous process used to develop our understanding of the universe. We saw that the whole process begins when a phenomenon is observed by a scientist. Then, the scientist tries to explain the phenomenon by forming a hypothesis as well as a scientific model. At which point, the predictions made by the scientific model are tested.

If the predictions do not agree with scientific experiment, then the hypothesis either has to be modified or gotten rid of completely. But if all the experiments conducted do agree with the hypothesis, then the hypothesis is now known as a theory. Then, the theory undergoes scientific peer review, where it’s compared with other existing theories. And if the new theory agrees with existing theories, then all is well. But if it doesn’t, then both the new theory and the old theories are tested specifically where they disagree with each other. And the theories that don’t agree with the experimental results are discarded.

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