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 the byways of evolution and the wonderful world of birds." "Scientific American" published an online review of "Feathers" in their blog "Tetrapod Zoology" by Darren Naish. Naish commented that prior to Hanson's book, "it doesn’t seem that any one book has ever been devoted to feathers and feathers alone. ... "Feathers" is thus a rather significant book, and very nice it is too." Naish also stated that ""Feathers" is not the provincial view of someone only interested in ecology or conservation biology; on the contrary, this is a remarkably well-rounded review of the subject." In a review published in the