Sir, – Further study for Dr Shane Bergin and Arlene O’Neill of the School of Physics Crann, TCD (December 21st), might be in the area of thermodynamics. At 30,000 times the speed of sound the temperature due to friction and compression at Rudolf’s nose would be about 300 times hotter than the surface of the sun: perhaps whiter than white hot would be the colour. – Yours, etc,