Driftgale: Thermal Expansion

Measurement, Noise & the Lab arc, page 137 of 193. Back to The Pixelated Physics Universe

Who they are

Driftgale has one line, and says it often: “One kelvin. 23 microns. no fringes.”

Driftgale is a character of the Measurement, Noise & the Lab arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.

The physics

Aluminium's thermal expansion coefficient is about 23 × 10⁻⁶ K⁻¹, so a 1 m aluminium path grows 23 µm per kelvin, about 36 HeNe wavelengths.

$$ \begin{gathered} \Delta L = \alpha L\, \Delta T \\ \alpha_{\text{Al}} \approx 23 \times 10^{-6}\ \text{K}^{-1}:\quad L = 1\ \text{m},\ \Delta T = 1\ \text{K} \Rightarrow \Delta L \approx 23\ \mu\text{m} \end{gathered} $$

Sources

• CRC Handbook of Chemistry and Physics, 'Thermal expansion of metals' (αAl ≈ 23.1 × 10⁻⁶ K⁻¹)

Crossovers

Driftgale meets Sir Aetheron (Luminiferous Aether and Michelson–Morley). Driftgale's thermal expansion shifts fringes by dozens of wavelengths. Sir Aetheron's interferometer floated on mercury and was read carefully because small drifts like hers could fake or hide a signal.

Driftgale meets Cryo Fault (Ductile-to-Brittle Transition). Driftgale stretches metal 23 µm per metre per kelvin for aluminium. Cryo Fault warns that over large cooldowns, the parts shrink at different rates, and stresses build up at the joints.

Wear the lore

• Driftgale, the Thermal-Drift Wind Spirit Mug

Concept keywords: Thermal Expansion, Driftgale, Measurement, Noise & the Lab, physics lore, Pixelated Physics