Synthesized answer
According to the passages, light pressure is the force exerted on a body placed in a beam of light, tending to move it in the direction of the light [1]. This force was derived by Maxwell and Boltzmann and verified experimentally by Nichols and Hull [1]. The experimental verification of light pressure, combined with the law of conservation of momentum, "inevitably leads" to the conclusion that a beam of radiation carries momentum because a body acquiring momentum from the pressure must be balanced by an equivalent momentum lost by the beam [1]. This is shown mathematically: the force on the body equals the rate of momentum gain, and the ratio of energy to momentum for the beam equals the velocity of light [2].
This insight is crucial for Lewis's revision of fundamental laws because it leads him to propose that a beam of radiation also possesses mass, traveling with the velocity of light [4]. He adopts the view that a beam of radiation carries not only momentum and energy but also mass, and that a body absorbing radiation acquires this mass along with the momentum and energy [4]. This allows him to construct a simple system of mechanics consistent with all known experimental…
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From the book
beam of light it is subject to a pressure or force which tends to move it in the direction in which the light is moving. If d E d t {\displaystyle {\frac {d\mathrm {E} }{dt}}} denotes the time-rate at which the body receives energy, f the force, and V the velocity of light, we have in rational units the formula f = 1 V d E d t {\displaystyle f={\frac {1}{\mathrm {V} }}{\frac {d\mathrm {E} }{dt}}} . (1) This important equation, which was obtained by Maxwell as a consequence of his electromagnetic theory, and by Boltzmann through the direct application of the laws of thermodynamics, has…
inevitably, as Poynting has shown, to the idea that the beam of radiation carries not only energy but momentum as well. The body subject to the constant force of radiation f , will obviously acquire momentum at the rate d M d t = f {\displaystyle {\frac {d\mathrm {M} }{dt}}=f} . (2) Combining equations (1) and (2) gives d E d M = V {\displaystyle {\frac {d\mathrm {E} }{d\mathrm {M} }}=\mathrm {V} } . (3) The ratio of the acquired energy to the acquired momentum is equal to the velocity of light. The beam of radiation must, therefore, possess energy and momentum in the same ratio. Hence for…
ose fundamental principles of the mechanics of ponderable matter which have remained unaltered since the time of Newton. The recent experiments which indicate a change in the mass of an electron with the speed, together with the phenomenon of radioactivity, have in some minds created a doubt as to the exact validity of some of the most general laws of nature. In the following pages I shall attempt to show that we may construct a simple system of mechanics which is consistent with all known experimental facts, and which rests upon the assumption of the truth of the three great conservation…
e that in such a beam something possessing mass moves with the velocity of light and therefore has momentum and energy . Notwithstanding its apparent divergence from the commonly accepted light theories, I propose to adopt this view and see whither it leads. Postulating the validity of the fundamental conservation laws mentioned above, we shall need in the following development only this one cardinal assumption, that a beam of radiation possesses not only momentum and energy, but also mass, travelling with the velocity of light, and that a body absorbing radiation is acquiring this mass as it…
h (5) and (9) which we obtained for the momentum and the energy of a beam of light. Further Consequences of the Theory . The view here proposed, which appears at first sight a reversion to the old corpuscular theory of light, must seem to many incompatible with the electromagnetic theory. If it were really so I should not have ventured to advance it, for the ideas announced by Maxwell constitute what may no longer be regarded as a theory, but rather a body of experimental fact. The new theory is offered, not in any sense to replace, but to supplement the accepted theories of light. I hope in…
More questions about this book
- Lewis states his intention to "modify those fundamental principles of the mechanics of ponderable matter which have remained unaltered since the time of Newton." Explain in your own words what makes such a drastic revision necessary at this time, citing specific experimental and theoretical advancements mentioned in the text.
- The text suggests that phenomena like "a change in the mass of an electron with the speed" and "radioactivity" created doubt about "the exact validity of some of the most general laws of nature." How might these specific observations *appear* to challenge one or more of the "three great conservation laws" Lewis ultimately seeks to uphold?
- Lewis proposes to build a "simple system of mechanics" consistent with known facts and resting on the conservation laws. Articulate, as if explaining to a peer, the historical significance of *reaffirming* the conservation of mass and energy in 1908, given the scientific landscape described in the excerpt.
- Considering Lewis's 1908 publication date and his reference to Einstein, how does this "revision of the Fundamental Laws of Matter and Energy" reflect the broader conceptual revolution in physics occurring at the beginning of the 20th century? What previously held assumptions about the nature of matter and energy are being challenged and potentially integrated?