The misleading use of language

One of the banes of science is that the way we use the English language often gives rise to misconceptions about scientific facts, giving people the wrong idea about how things work. I have found that it is often the case, when studying science at school, that these ideas have to be “unlearned” and replaced with the actual science. Here are eight particularly popular examples, many of which are favourites among my own science teachers.

1.       “Close that door – you’ll let all the cold in!”

A consequence of the second law of thermodynamics is that heat naturally flows from higher temperatures to lower temperatures. So in fact, by having the door wide open when it’s below room temperature outside, you’re not letting “cold” into the house, you’re letting heat out. “Cold” isn’t a tangible thing, it’s just a lack of heat; if you were to touch a dirty surface, you wouldn’t say that you were transferring cleanliness from your hand to the surface.

2.       “You’ve got a cold? Here, have some antibiotics!”

This one is a favourite of my Biology teacher’s (is favourite the word?). The same goes for a cough. The common cold and cough are viral infections – no amount of antibiotics will cure them, because antibiotics only target bacteria.

3.       “There are an almost infinite number of stars in the universe!”

This idea of “almost infinite” being a synonym of “an extremely large number” is one that I’ve even read in Biology textbooks. In the case of the stars, no-one’s denying that there are an enormous number of stars in the universe – more than we can imagine. Well, now think about how many atoms there are in the universe. If you think too long, it’ll make your head hurt – I mean, just think of how many atoms are in a single star. Stars are made of hydrogen and helium; a single gram of hydrogen contains over 600 billion trillion atoms, whilst a gram of helium contains more than 150 billion trillion. That’s not even to mention all the atoms present in planets like our own, as well as comets and meteors. Clearly, the number of atoms in the universe is many, many orders of magnitude greater than the number of stars – but it’s no closer to being infinite! Conversely, if you believe that the universe is infinitely large, then there may well be infinitely many stars (and atoms). But there is a clear distinction: a number is either infinite, or it is not. There is no crossing bridge between the finite and the infinite; you can never reach infinity by continually adding one. Thus there can be no concept of “almost infinity”.

4.       “I’ve got a respiratory condition.”

Breathing and respiration are completely different processes and it does little to help the situation that breathing disorders are called “respiratory conditions”. Breathing is the physical process of ventilating the lungs, taking in oxygenated air and expelling deoxygenated air. Respiration, in contrast, is a biochemical pathway in which glucose is metabolised in the presence of oxygen to carbon dioxide and water, releasing energy. (There’s more to come on breathing and energy!)

5.       “Maximum luggage weight: 20kg”

This is one we are bombarded with all the time, and again it simply boils down to how we use the English language. Kilograms, stones and ounces are not units of weight – they are units of mass. Weight is the gravitational force that is pulling you towards the centre of the Earth, and is measured in Newtons. As long as you stay on Earth, your weight will remain directly proportional to your mass (one kilogram corresponds to around 9.8 Newtons). However, if you went to the moon – or even further afield – where the size of the gravitational field was different, your mass would not change, but your weight would.

6.       “Black surfaces absorb heat.”

This isn’t scientifically inaccurate, but it can lead to some confusion about cause and effect. It is not the case that, because a surface is black, it therefore absorbs heat – in fact it is more like the opposite. A surface which absorbs all wavelengths of visible light, as well as infrared (heat), will not reflect any visible light (or at least very little) and will consequently be black.

7.       “We breathe oxygen in and carbon dioxide out.”

This makes it sound like our breathing system has some sort of filter, which only lets oxygen in one way and only lets carbon dioxide out the other. When we breathe in, we create a pressure gradient that forces air – containing nitrogen, oxygen, carbon dioxide and small amounts of other gases – to enter the lungs. Oxygen then diffuses from the lungs into the blood, so that it can be used for respiration; whilst carbon dioxide, produced in respiration, passes from the blood back into the lungs. The air is then expelled from the lungs thus has a lower concentration of oxygen and a higher concentration of carbon dioxide than the air that was inhaled, but it is still a mixture of the original gases. Breathing is necessary in order to maintain a concentration gradient between the lungs and the blood.

8.       “We respire to make energy.”

This is an old one, and we’re back again to the good old laws of thermodynamics. Energy can’t be created or destroyed – it can only be transferred from one form to another!