Book VIII (which occupies almost a fourth of the entire Physics , and probably constituted originally an independent course of lessons) discusses two main topics, though with a wide deployment of arguments: the time limits of the universe , and the existence of a Prime Mover — eternal, indivisible, without parts and without magnitude. Isn't the universe eternal, has it had a beginning, will it ever end? Aristotle's response, as a Greek, could hardly be affirmative, never having been told of a creatio ex nihilo, but he also has philosophical reasons for denying that motion had not always existed, on the grounds of the theory presented in the earlier books of the Physics . Eternity of motion is also confirmed by the existence of a substance which is different from all the others in lacking matter; being pure form, it is also in an eternal actuality, not being imperfect in any respect; hence needing not to move. This is demonstrated by describing the celestial bodies thus: the first things to be moved must undergo an infinite, single and continuous movement, that is, circular. This is not caused by any contact but (integrating the view contained in the Metaphysics, bk. XII ) by love and aspiration.
Minds On Physics - Legacy Version is the browser-based, Shockwave-dependent version of Minds On Physics the App. Relying on the Shockwave plug-in and a collection of carefully crafted questions, the Legacy Version of MOPs seeks to improve students' conceptions of physics. Formerly named the Minds On Physics Internet Modules, this Shockwave-delivered program combines interactive questioning modules with web-based instructional resources to engage students in an exercise in thinking, reflecting and learning. Students will enjoy using these for practice and teachers can use them as homework assignments.
During the life of Arrhenius' "Greenhouse Effect", the scientific community understood that radiation was electromagnetic (Maxwell, 1864; Heaviside, 1881; Hertz, 1888), and by the time Arrhenius first published on the subject of the "Greenhouse Effect", Thompson (1896) had extended his idea of electrons to photoelectric effects on gases due to ionizing radiation, known then as röntgen rays. The photoelectric effect, by which a current or charge could be generated in certain materials by their exposure to electromagnetic radiation, was a matter of inquiry at the time. The emission of radiation in discrete quanta, though first suggested by Boltzmann in 1877, was mathematically formalised by Planck (1901). Einstein (1905) experimentally confirmed Planck's Equation after adapting it to the photoelectric effect, which was the subject of his study. However, ideas concerning the internal structure of the atom and it's relationship to ionisation, magnetism, photoelectric interactions, and discrete quanta of electromagnetic radiation were under intense development at the time (Thomson, 1902; Thomson, 1903; Thomson, 1904). By the time Bohr (1913) corrected the problems in Thomson's atomic model, the relationship between changes in electron shell (. orbit) potential and photoelectric emission of radiation were a foregone conclusion. The relevance of these discoveries to the question of heat transfer is that unlike the notion of aethereal heat transfer, emission of electromagnetic energy quanta by atoms and molecules in materials confirmed that the radiative mode of heat transfer was as much a part of thermal conduction as any other mode of heat transfer.