I sometimes read about scientific topics where the writer, often a student, says that something is obvious. Let’s think what “obvious” means. It means that we don’t even need to think about something to know whether it is true or false. I have two objections to using the word when writing about science.
My first objection is that if something really is obvious, we know it instinctively – so why bother telling us?
The second objection is more serious. Science is not a collection of facts, it is a way of thinking (see https://thinking-about-science.com/whats-this-blog-for/). If we say something is obvious, we don’t bother thinking about it – so, we’re not doing science.
Below I list some things that may seem obvious to some people.
Medicines should be proven to be safe before they are used on people. This is impossible, for the reasons described in post 16.1.
Scientists discover scientific laws that are always true. This isn’t true for the reasons described in post 16.2.
Scientists do experiments that prove something is true. Not true – see post 16.3.
An object that it moving in a straight line, at a constant speed, is behaving in a completely different way to an object that is standing still. As soon as we think about the motion of the person who observes the objects, we realise that this isn’t true – see post 16.4.
If the numbers of an animal that we consider to be a pest are increasing, we need to intervene to prevent the problem from becoming more serious. This may not be true because the population of animals may be limited by other factors, as described in post 16.8.
People who have high levels of high-density lipoprotein (“good cholesterol”) have a lower incidence of heart attacks than people with lower levels. It once seemed obvious that taking medicines to increase the level of high-density lipoprotein could help prevent heart attacks. But this recommendation confuses the ideas of association and cause (see post 16.10). It appears that taking these medicines doesn’t have the intended effect: for the reasons explained in http://www.huffingtonpost.com/dr-dean-ornish/cholesterol-the-good-the-_b_870655.html.
A movie shows the movement of an object exactly as it occurs in real life. This may not be true because what we see in movies depends on the number of frames recorded in a second – see post 16.14.
There is a clear boundary between living and non-living things. When we start to think about this, it is very hard to define a boundary – see post 16.18.
Science should be able to prove the existence, or non-existence, of a God. It can’t because science isn’t about this sort of question – see post 16.22.
At some point in space there either is a magnetic field that can be detected or there isn’t. This seems really obvious – either something exists or it doesn’t! But the existence, or otherwise, of the field depends on the motion of the instrument being used to detect it – as described in post 16.25.
When we measure a lot of things of type A, their average length is 10.8 cm. When we measure a lot of things of type B, their average length is 11.2 cm. So, it’s obvious that type B things are longer than type A things. Maybe they are but maybe they’re not. The difference may simply be a consequence of the examples of A and B we happen to have measured. This topic is explored in post 16.28.
We can know both the speed and position of an object. This is true for the things we observe every day. But it’s not true for very small things like electrons. If we know the speed of an electron, we know its kinetic energy – because we know its mass (post 16.21). According to Heisenberg’s uncertainty principle we cannot then know its exact position – the best that we can do is to calculate a region of space in which there is a high probability of finding it (see post 16.29).
Vitamin D is good for your health. It is – provided you don’t consume too much of it – see post 16.36.
If we add forces of2 kN and 3 kN, the answer is 5 kN. This is true if both forces act in the same direction. If they act in opposite directions, the answer is 1 kN. In general, the answer is in the range 1 to 5 kN, depending on the directions in which they act. This is covered in posts 16.49 and 16.50; it will be covered in more detail in posts 17.2 and 17.3.
In each of these examples, something may seem obvious. But when we think about it, or when we have some extra information, it’s not. Some people present these non-obvious results to make science look weird and difficult to understand. It isn’t! All we need to do is to collect the necessary evidence and think carefully about it.
Related posts
16.36 Good and bad
16.32 Faith in science
6.22 Science can’t explain everything
16.3 Scientific proof
16.2 Scientific laws
Follow-up posts
Thinking about Science with David Hukins 