Mechanical energy swing because of the work done by the pendulum to oppose these non-conservative forces. That the loss of mechanical energy in a system always resulted in an increase of the system's temperature has been known for a long time, but it was the amateur physicist James Prescott Joule who first experimentally demonstrated how a certain amount of work done against friction resulted in a definite quantity of heat which should be conceived as the random motions of the particles that comprise matter. This equivalence between mechanical energy and heat is especially important when considering colliding objects. In an elastic collision,
Feathers: The Evolution of a Natural Miracle news magazine "Maclean's", Brian Bethune praised Hanson's storytelling, writing, "For all the intriguing science, what really livens up Hanson's passionate discussion of his 'natural miracle' are the stories he tells." Laurence A. Marschall, a physics professor at Gettysburg College, wrote in a review published in the magazine "Natural History", "In sum, "Feathers" is an impressive blend of beauty, form, and function." Frances C. James, in a review published in "The Condor", described the book as "scholarly and enjoyable", commenting that "Hanson has worked hard to summarize the science behind our current understanding of the form and function of feathers, their