Poincare-Henri · Source catalogue

A lecture-style essay for a general audience, with no equations in the running text and one line diagram (p.2). Poincare opens by saying scientific theories are like empires and Newtonian mechanics is shaken, naming Max Abraham (Gottingen) and H. A. Lorentz as its attackers, but he calls it premature to say it has fallen [read: p.1]. He sets old mechanics (equal impulses give equal velocity increments, so velocity is unbounded) against a new mechanics in which a body cannot be pushed past the speed of light. The resistance (inertia, mass) therefore grows with velocity [read: p.1-2]. He says that experiments on radium projectiles at about 100,000 km/s, deflected by electric and magnetic fields, show that mass depends on velocity [read: p.3]. The principle of relativity (no experiment can show absolute motion) is given 'an absolute value'. Poincare notes that optical experiments looking for motion through the ether gave null results [read: p.3-4]. He explains Lorentz's 'apparent time' (a 'local hour') with two observers, A in Paris and B in Berlin, who try to synchronise chronometers by wireless signals while carried along with the Earth through the ether [read: p.4-6]. The third hypothesis is that a body moving through the ether is deformed in the direction of motion (Earth about 1/200,000,000), which 'Michelson's experiments' are said to have verified [read: p.6-7]. The electromagnetic picture of matter follows. Atoms are miniature solar systems of electrons: a positive central mass with many negative electrons circulating, a 'universe' of planets around 'tiny suns' (a nucleus-like model stated before Rutherford's 1911 paper [memory: high]) [read: p.7]. An electron's field energy is localised in the ether. Kaufmann's experiments are said to show the electron's constant 'real' mass is negligible, so only the ether is inert [read: p.7-8]. Lorentz's electron gas is used to explain incandescence ('a swarm of gnats in a jar'), and cathode rays striking the anticathode give an electromagnetic agitation which 'many physicists identify with the Rontgen rays' [read: p.8-9]. Accelerated electrons radiate (Hertzian waves, incandescence, Crookes tube), and accelerated planets would radiate and spiral into the sun over millions of milliards of centuries [read: p.8-9]. Before the relativistic correction he recalls Leverrier's ad hoc fix for Mercury, an undiscovered planet, and an amateur astronomer's sighting of it crossing the Sun: 'it is unhappily certain that this planet perceived was only a bird' [read: p.10]. Lorentz's velocity-dependent attraction law is applied to Mercury, whose perihelion motion is 38 arcseconds too fast. The new mechanics 'explains perfectly the sense of the error' but leaves a margin of 32 arcseconds, and other planets are not sensibly changed [read: p.9-10]. He concludes that classical mechanics is not finally condemned and stays the mechanics of small velocities and of practical technology, and he warns of a 'pedagogic danger' that students will be taught to despise it [read: p.10-11].

Key claims

• A body cannot be accelerated from rest past the velocity of light, so its inertia (mass) increases with velocity and equal impulses give ever smaller velocity gains (assumed as a postulate in the essay) [read: p.2].
• Experiments deflecting radium projectiles (about one-third of light speed) in electric and magnetic fields show that inertia increases with velocity (no experimenter is named at this passage) [read: p.3].
• The principle of relativity holds without restriction: no experiment can detect absolute motion, and the null results of delicate optical experiments confirm this [read: p.4].
• Observers moving with the Earth through the ether cannot synchronise clocks truly and can know only an 'apparent' (local) time, so that nothing reveals to an observer whether he is moving or at absolute rest [read: p.5-6].
• A body moving through the ether is deformed in the direction of motion (a sphere becomes a flattened ellipsoid; the Earth in its orbit about 1/200,000,000), and Michelson's experiments 'perfectly verify' this [read: p.6-7].
• The constant mass of matter vanishes: the electron's inertia is electromagnetic, a property of the ether; Kaufmann's experiments show its real constant mass is negligible, or null [read: p.8].
• Accelerated electrons lose energy as electromagnetic radiation, and accelerated celestial bodies would also radiate, so planets would eventually fall into the sun after millions of milliards of centuries [read: p.9].
• Lorentz's velocity-dependent attraction law corrects Mercury's perihelion motion in the right direction: observed motion exceeds the classical calculation by 38 arcseconds, and 32 arcseconds remain unexplained (no time period is stated in the text) [read: p.10].
• Newtonian mechanics is not finally condemned and remains the mechanics of velocities small against that of light, and the new mechanics cannot be understood without it [read: p.10-11].

Relevance: This is the only document in the project folder, so it is the entire primary-source basis for the project. It is a popular statement by a leading mathematician-physicist of the new (Lorentz-Poincare) mechanics, a lecture of 1909, between Einstein's 1905 paper and Minkowski's 1908 spacetime. It shows what Poincare held then: the ether retained, the principle of relativity as absolute, local time, contraction as a hypothesis, electromagnetic mass, and a velocity-dependent gravity giving a partial Mercury correction. Einstein, Minkowski and Fitzgerald are not named in it [read: p.1-11].

Mainstream conflict: It is a historical statement of a position that later standard relativity replaced, not a current fringe claim. It differs from the later standard theory in these ways: (1) the ether is retained as the carrier of light, the seat of inertia and of field energy; (2) time is presented as 'apparent'/'local' with the difficulty framed as one of knowing the true time; (3) all mass is electromagnetic and direction-dependent; (4) gravity is a Lorentz-type velocity-dependent law that leaves 32 of 38 arcseconds for Mercury unexplained, whereas general relativity later accounted for the Mercury excess; (5) planets are claimed to radiate and spiral into the sun [read: p.4-10]. Whether any of this survives is for the reviewers to judge.