I just read this headline in an Australian newspaper: “The mercury could plummet by as much as half this weekend.” In the same story was the caption: “Temperatures could halve in some places.”
This is stroppy-making balderdash!
Having read the article it was clear that its author was referring to a drop from 20°C to 10°C. If the Fahrenheit scale were used, the drop would be 36%, not 50%. But the only sensible scale to use in this way is the Kelvin scale, in which zero corresponds to absolute zero – colder than which it is impossible to go. On that scale the drop would be a mere 3.4%. That wouldn’t make much of a headline, would it?
This isn’t an isolated instance. Journalists seem to lack basic scientific understanding, and their sub-editors are more interested in concocting clever puns (“Lion Park Roaring Success”) than ensuring accuracy.
Here’s another example. Elon Musk is going to build the world’s biggest lithium battery in South Australia, my home state. It has been variously described in the press as a 100MW battery and a 100MWh battery. The former makes no sense. A watt is a rate of flow of energy. A watt-hour is a unit of energy analogous to a volume of fuel. In fact 1 litre of diesel oil contains about 10,000 watt-hours (or 10kWh) of energy.
When I use the rowing machine at the gym I can maintain an energy flow of about 140W (or 0.14kW). So if I rowed for a living, selling the energy I generate for 23 cents per kWh (which is roughly what I pay for electricity in my home) I would earn 0.14 x 0.23 x 40 = $1.29 for a 40-hour week.