 Finally, in the case of heat transfer by thermal radiation, Newton's law of cooling holds only for very small temperature differences, and a more accurate description is given by Planck's Law.Sir Isaac Newton did not originally state his law in the above form in 1701, when it was originally formulated.Rather, using today's terms, Newton noted after some mathematical manipulation that "the rate of temperature change" of a body is proportional to the difference in temperatures between the body and its surroundings.