Note Hawking s preposition It s to not by Also note that the on Earth seems to be your personal interpretation it s really quite hard to heat anything to 2 73 K on Earth because you won t find anything that needs heating Also note that your or Hawking s math is a bit off 271 3 C is only 1 88 K Since the CMB is roughly 2 73 K it would heat a pizza in otherwise empty space to 270 43 C unless my math is off which is a very real possibility at any time but especially when I lecture about other peoples shortcomings