17.9 Scientists believe that…

Have you ever read the phrase, “Scientists believe that…”, or has anyone ever said it to you? What does it mean? I think it means that something is supposed to be too difficult for you to understand but somebody in authority believes it – so you ought to believe it too!

Fortunately, science doesn’t work like that. It is a way of thinking that we can do for ourselves (see https://thinking-about-science.com/whats-this-blog-for/ and post 17.1). It’s not a series of beliefs that we must share because we have been told to.

The phrase “scientists believe” implies that all scientists believe the same things. Why should they? Not all Marxists agree with each other about everything. And the same applies to philosophers, artists, musicians, Buddhists, Christians etc. So why should scientists all be in perfect agreement?

I know a very good scientist who doesn’t believe in Darwin’s theory of evolution. According to some American politicians and journalists, this makes him “anti-science”. But he isn’t!

Similarly, questioning any aspect of the science behind the idea that global warming is caused by human activity is often considered to be “anti-science” too. But questioning what we are told is an essential feature of science that leads to a deeper understanding and, sometimes, to the generation of new ideas (see post 16.2).

I once heard an “expert” on global warming saying, on the television, that his computer models proved that global warming existed. I’m sure his models are very useful for understanding the effects of carbon dioxide levels in the atmosphere on climate. But they can’t prove that global warming is true. Firstly, any scientific investigation can prove that an idea is false but not that it is true (post 16.3). Secondly, any computer model tells us about the consequences of the assumptions we have made – if these assumptions are inaccurate, the predictions of the model will be inaccurate too (post 16.8). Thirdly, global weather systems are very complicated and so a model may miss some important factors that nobody has yet thought about (post 16.42). Ideally, the predictions of computer models should be tested by experiment (post 16.43) but this isn’t possible for global warming. Am I “anti-science” because I question the statements made by this “expert”? No! And I’m not saying that the idea of global warming is not true. All I’m saying is that if we believe something without thinking about it, we are not doing science.

potatoes-411975_640

In 2010, Reiner Rummel and his colleagues at the Technische Universität München made accurate (post 16.24) measurements of the earth’s gravitational field (post 16.16); they also thought of a new graphical way of presenting their results (https://earth.esa.int/documents/973910/1002056/RR1.pdf/5522a69b-fed3-44d5-9ace-e0408429a518). A reporter for a British newspaper, the Daily Mail, thought that the result looked like a potato. So the newspaper published an article headed “Potato Earth” (http://www.dailymail.co.uk/sciencetech/article-1372012/Potato-Earth-Gravity-satellite-reveals-planet-REALLY-looks-like.html). Unfortunately, this has led to some people saying, “Scientists believe the world is potato-shaped”. But potatoes don’t all have the same shape. Describing something as “potato-shaped” would be meaningless. Why should we believe something that is meaningless? This is another example of the need to think before we believe.

I believe that our planet is roughly spherical but that its radius is less at the poles than at the equator. More importantly, I can tell you why I believe this. The motion of neighbouring planets, as well as ideas like night and day, can all be explained by one idea – that we live on the surface of a spinning lump of stuff in orbit around the sun (post 16.9). When we look at the other planets, through a telescope, they always appear circular – the simplest explanation of this observation is that they are all, at least roughly, spherical. Why should planet earth be an exception – let’s suppose that it’s spherical too. It certainly looks as if it is in pictures taken from space. It seems that the heights of mountains and the depths of canyons would be negligibly small compared to the radius of this sphere.

Now let’s think about the gravitational field (acceleration due to gravity) on the surface of planet earth (post 16.16). If the earth is a sphere of mass M and radius R, its magnitude would be

g = GM/R2

where G is the gravitational constant (post 16.16). So, a perfectly spherical planet would have a constant value of g because it would have a constant value of R. (This statement is complicated a bit by the centripetal force generated by the rotation of the earth about its axis – a subject for a future blog!) The value of g is always 9.8 m.s-2, to two significant figures (see post 16.7). But it is less at the equator (9.78 m.s-2) than at the poles (9.83 m.s-2). So, R is a bit less at the poles than at the equator. It is as if the earth bulges a bit around the equator. (If the earth was once a rotating blob of cooling liquid, this shape could be explained by centripetal force.)

I believe we should try to understand the reasons for things and not hide behind a belief in authority. If we simply believe what others tell us we risk being victims of their lies, propaganda, mistakes and misunderstandings.

 

Related posts

17.1 It’s obvious…
16.36 Good and bad
16.32 Faith in science
16.22 Science can’t explain everything
16.15 Science education

 

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