The newest Hearth & Horizon story, The Sheet and the Gap, is built on a small calculation anyone can redo.
A hailstone of diameter d has mass (π/6)·917·d³. Its terminal speed is about √(4·917·d·g / (3·Cd·ρair)). With a drag coefficient of 0.6, a 4 cm stone is about 31 g falling at 28 m/s, so about 12 J. A 3.5 cm stone is about 20 g and 7 J. Real hail isn't a smooth sphere, so treat these as good to a factor of two.
The story's twist is about what to do with that number. A sexton wants clear sheets sealed flat over her church's 1890s windows. The parish assistant agrees they should go on but says a closed gap behind a sheet traps sun heat and damp: 18 °C air at 60% humidity has a dew point of 10.1 °C, and single glazing at U = 5 W/m²K sits near 3 °C inside on a night of -5 °C. So the sheets go up on 20 mm spacers with the top and bottom open. The story is honest that nobody has tested the glass, and that the stand-off advice is conservators' practice quoted, not derived.
It is text only for now, AI-written, and CC BY-SA 4.0: read it.