This is an odd question. I was talking with a social scientist the other day and he seemed to think that the amount of energy it takes to raise the temperature 1 degree Celsius or Kelvin was minutely different depending on the temperature (ie near absolute zero the energy it takes to increase T by 1 is different than the energy it takes to increase T by 1 at 300K). I tried explaining to him that kinetic energy is linearly proportional to temperature, but he insisted that he was right and that the scale was very slightly nonlinear (no proof or source I'm afraid, so it's been driving me nuts :/ ). I have done some searching to no avail, I turn to you for ideas. Are there any nonlinear effects that cause the energy separation between degrees K/C to be unequal?