The south of England doesn’t get particularly cold in winter, but temperatures do sometimes lurk below freezing for a few days. At those times, an intermittent roaring and rumbling sounds through my house: our gas boiler and central heating pump labouring to keep the rooms warm, and enough hot water in the tank.
If I look through the small window in the boiler’s front panel while it’s roaring, I see flames dance: blue peaks fading to white. That’s as close as daily life brings me to t...