“Good” and “bad” are subjective words – what seems “good” to one person may seem “bad” to another. Science works because it attempts to eliminate subjective opinions and to be as objective as possible (see post 16.22). So we need to be careful to avoid thinking about something as being “good” or “bad” and define what we mean more precisely.
I have reviewed many scientific articles, intended for publication, and many PhD theses that have said that something has “good mechanical properties” But this phrase means nothing. Something that would be useful for making a beam to support part of a building would be useless for making a bungee rope!
Often people will wonder if some kind of food is “good” for us.
Is vitamin D good for us? We need about 10 µg of vitamin D a day to keep our bones healthy (to find out about the abbreviation µg see posts 16.12 and 16.13). Some of this vitamin D comes from our food (especially oily fish, red meat, liver and eggs) and we make some of it ourselves when sunshine falls on our skin. But if we eat more than about 250 µg of vitamin D a day, it can cause several different diseases. Fortunately, your body regulates how much vitamin D it can make when the sun shines on you – so you can’t make too much for yourself. But it is possible to eat too much food that contains vitamin D or too take too many vitamin supplements. (Sometimes doctors need to prescribe high doses of vitamin D, so the numbers I have quoted above are not always right for everybody.) Animals that live in very cold places may need to store vitamin D in their livers, for use in the winter when they can’t get much food or sunshine. So cod liver oil and halibut liver oil have been used for a long time as vitamin D supplements. But polar bears store so much vitamin D that their livers are poisonous!
So the question at the beginning of the previous paragraph is meaningless. We need to ask much more carefully defined questions in order to get useful answers. For example: do we need vitamin D to stay healthy? “Yes”. Can vitamin D be poisonous? “Yes”. We then need to ask two further questions:
- How much vitamin D do we need to stay healthy?
- How much vitamin D is poisonous?
Once we start to think that something is always “good” or “always” bad, there is a danger that we will stop thinking.
I have recently been reading reviews of a book called The Radium Girls by Kate Moore. It tells the story of how unscrupulous manufacturers of watches, clocks and military instruments in the USA allowed young women to poison themselves with radium. It appears to be a very interesting book – I want to read it.
However, one review of this book, in TLS (Times Literary Supplement) of 15 July 2016 shows how believing something is “bad” could easily mislead us. I quote the final paragraph of this review (in full) below.
“A final note: radium has a half-life of 1 600 years; it will continue its assault on what remains of the bones of the women it killed for many centuries to come.”
The statement about the half-life of radium (see post 16.6) is true. The rest of the paragraph appears to be false when I start to think about it. How can radium damage your bones? There are two main ways:
- It can act as a poison.
- The radioactivity it produces can cause healthy cells to become cancer cells.
Poisons have no effect on us when we are dead! We can’t get cancer after we’re dead!
So the author of the review appears to have written something without thinking. Why? I assume because he believed that radium is “bad” – everything about it is “bad” and it will go on being “bad” for a very long time! Interestingly, the subject of the book is the radium isotope 226Ra (see post 16.27); another isotope, 223Ra, is sometimes used to kill cancer cells.
Science is not a series of “facts” that we should remember or quote. It’s a way of thinking that helps us to understand aspects of the world around us (see What’s this blog for?). Information like half-lives of radioactive nuclei should not be used as a substitute for thinking.