Picture the scene if you will. Night has fallen, I’m reading my Kindle in front of a gently crackling log burner - all very pleasant.
Maybe I’ll have a glass of something later, but for some reason I check the digital thermometer. This little gadget tells me it is chilly outside, but a comfortable 22°C inside. Most satisfactory.
The digital thermometer has one of those radio-controlled clocks, supposedly accurate to the second. It claims the time is 10:05pm which is later than I thought. Rather odd too, because the grandfather clock ticking away in the corner of the room says the time is about 9.30. It doesn’t do am or pm, being about 250 years old.
So I sigh, get up from my chair and open the grandfather clock case to check the pendulum is swinging. Although I already know it must be swinging because I can hear that lovely peaceful tick – and it is – nothing wrong there.
Now in spite of the formidable accuracy of radio-controlled clocks, if an ancient grandfather clock goes wrong it tends to stop and that’s that - all pretty obvious. If the thing is ticking away like a good 'un, it is most unlikely to be wrong by as much as 35 minutes. Clockwork regulated by a pendulum just doesn’t tend to do that.
So I compare the digital thermometer clock to other clocks in the house and sure enough the grandfather clock is right and the digital thermometer wrong. Yet by the following morning it had corrected itself.
I’ll never know why of course. A modern gadget goes wrong – nobody knows why – chuck it away and buy another.