Corpuscle theory

The corpuscle theory (also emission theory or ballistic light theory ) is a physical theory attributed primarily to Isaac Newton , according to which light consists of the smallest particles or corpuscles (corpuscles). The corpuscular theory in the 19th century by the wave theory replaced the light, but the light have been used for the photon theory of Albert Einstein attributed (1905) partially again corpuscular properties.

Since the original emission theory is compatible with the relativity principle and thus with the Michelson-Morley experiment , such models were discussed again at the beginning of the 20th century and considered as an alternative to the relativity theory . However, in emission theory the speed of light would depend on the speed of the light source, which has been clearly refuted by a number of other experiments. Likewise, a fully worked out theory was never presented. As a result, the emission theory can no longer be taken into account.

Until the 19th century

There are many different theories of emissions in the history of science. Already Pythagoras and Empedocles had emission theories of sensory perception develops. Even Augustine described the process of seeing a "ray casting out of our eyes." Numerous emission theories have emerged and have been forgotten again. Emission theorists were, for example, Sir Isaac Newton (1643–1727), Pierre Simon de Laplace (1749–1827), Jean-Baptiste Biot (1774–1862), Sir David Brewster (1781–1868).

The corpuscle theory of light says that light consists of tiny particles or corpuscles, which are ejected or emitted in a straight line by the luminous bodies at high speed, the speed of light being dependent on the speed of the light source. This theory could explain both the linear propagation and the reflection of light. Different colors can also be explained by assuming different sizes of light particles. Diffraction , refraction at interfaces or partial reflection cause difficulties, however. The refraction was explained as follows: At a greater distance from the interfaces, the light particles are surrounded on all sides by (other) similar particles and therefore fly in a straight line. At the interface between two different “dense”, transparent materials, the “light particles” are attracted to different degrees and therefore suddenly change the direction of flight. Linked to this was the assumption that light flies faster in the “optically denser” medium. Only much later, after 1820, it was shown that the speed of light in the "optically dense" medium is less than, for example, in vacuo ( Snell's Law ). So although the rationale for “optically denser” is wrong, the term is still used today.

Some researchers drew further conclusions from the corpuscular nature of light: Newton indicated a possible deflection of light rays by gravity as early as 1704, but without calculating the deflection. John Michell (1783) and independently from him Pierre-Simon Laplace (1796) concluded that such massive stars could be imagined that even light could not escape them; that is, they designed an early form of a black hole . Finally (1801, published 1804) Johann Georg von Soldner calculated the light deflection indicated by Newton, whereby he received the value 0.84 ", which is only correct within the framework of Newton's theory of gravity. To determine the correct value, the curvature of space following from the general theory of relativity must be taken into account, which doubles Newton's value, as Albert Einstein calculated. This prediction has been repeatedly confirmed experimentally.

In the question of whether the ether- based wave theory of light founded by Christiaan Huygens (1690) or the corpuscle theory was correct, Newton was the first to win. In the 19th century, however, Newton's model was overcome primarily by the work of Thomas Young (1800), Augustin Jean Fresnel (1816) and James Clerk Maxwell (1864) and the wave theory seemed to be proven. On the one hand, this resulted from the fact that effects such as refraction and diffraction (especially in the form of the Poisson spot ) could be explained much more easily using wave theory, while auxiliary hypotheses had to be introduced again and again in the context of corpuscle theory. Likewise, the correspondence in the speed of light of different rays of light spoke for the wave model. However, the above-mentioned prediction of the corpuscle theory was decisive, according to which light must be faster in denser media than in less dense media. In 1850, Léon Foucault was able to determine the speed of light in media for the first time using the rotating mirror method and found that it was greater in air than in water, which corresponded to the predictions of the wave theory. This was taken as the final refutation of the corpuscle theory.

Since Einstein's photon theory (1905), corpuscular properties have been ascribed to light again, but according to the theory of relativity, photons have no mass , only energy and momentum. In the context of quantum mechanics , the wave-particle dualism is also used.

20th century

Emission theories are usually based on the assumption that light propagates constantly at the speed of light only in relation to the light source. In contrast to the (stationary) ether theory, according to which light spreads constantly in relation to the ether, and in contrast to the special theory of relativity (SRT), according to which light spreads constantly in all inertial systems . It follows from this, as in the original Newtonian corpuscle theory, that the speed of light depends on the speed of the light source. The change of the inertial system takes place through the Galileo transformation , whereby the classical relativity principle is fulfilled. That means, in contrast to the ether theory, in the emission theory only the relative movement of source and receiver is responsible for the Doppler effect as well as for the aberration . Similar considerations were occasionally applied to electromagnetic waves, not only to particles, although different ideas about the source dependence of the speed of light were incorporated. ${\ displaystyle f_ {E} = f_ {Q} \ left (1 \ pm {\ tfrac {v} {c}} \ right)}$

Since an emission theory, in contrast to the ether theory, does not violate the classical relativity principle and is therefore compatible with the unsuccessful ether drift experiments (such as the Michelson-Morley experiment ), it was considered again at the beginning of the 20th century as an alternative to Lorentz electrodynamics and the SRT . This was done primarily to avoid the radical change in the understanding of space and time that accompanies the constancy of the speed of light in all inertial systems. Albert Einstein himself considered an emission theory before 1905, but he rejected it before 1905 because he regarded it as incompatible with the knowledge gained in electrodynamics.

While in most emission models the light spreads constantly in relation to the original light source, there were different ideas as to what should be evaluated as a light source and whether mirrors should also be included. Different kinematic variants of emission theories developed from this:

Light only propagates constantly in relation to the original light source, regardless of whether it is later reflected off a mirror. That is, the center of the spherical wave always moves at the same speed as the original light source. This model was proposed by Walter Ritz in 1908 and was considered the most developed emission theory.
Every body is to be seen as a new source of light. This means that a mirror that is hit by a beam of light and reflects it acts as a new light source, relative to which the light now propagates constantly at the speed of light. Light propagates as a spherical wave, the center of which moves at the speed of the last body from which the light was last reflected. This model was proposed by Richard C. Tolman in 1910 (with Tolman himself favoring Einstein's theory of relativity).
Light, which is reflected by a mirror, propagates from now on with the speed of the mirror image of the original source. (This theory was proposed by Stewart in 1911).
A modification of the Ritz-Tolman theory was introduced by Fox (1965). He argued that the extinction (i.e. absorption, scattering and emission of the light within a traversed medium) must also be taken into account. In the air, the extinction length for visible light would be only 0.2 cm. After this distance the speed of light would no longer be constant to the source, but constant to the medium (Fox himself favoring Einstein's theory of relativity).

However, none of these models was fully worked out, which is why experts never considered them as a serious alternative to SRT. In particular, their basic prediction, namely the dependence of the speed of light on the speed of the source, has been repeatedly refuted experimentally (see following section).

Experiments

The basic kinematic statement or experimental prediction of most emission theories, namely the dependence of the speed of light on the speed of the source, was mentioned in some older articles up to the 1960s in connection with tests of the special theory of relativity or tests of light constancy.

Both emission theory and SRT agree that there is no ether wind or no influence of a preferred reference system. This means that if the source and receiver are in the same inertial system, both models predict a zero result and are compatible with the negative result of the Michelson-Morley experiment, for example.

Differences arise when the source and receiver are moved relative to one another. While also according to SRT remains constant the speed of light in all inertial systems, resulting in the emission theory at a source rate of ± v is a speed of light c ± v . The following scheme is usually used in experiments:

{\ displaystyle c '= c \ pm kv \,}

,

where c is the speed of light, v is the source speed, and c 'is the resulting speed; k indicates the extent of the source dependency. At k = 0 the speed of light is completely independent of the source speed (like in the SRT or the aether at rest), however at k = 1 it is completely dependent on it. Values between 0 and 1 are also possible and represent a limited source dependency. Since it was shown in the context of the current measurement accuracy that k∼0 , the emission theories are considered experimentally refuted, while the SRT is confirmed by this.

Michelson-Morley experiment

In the rest system of the interferometer or the light source, the light rays propagate in all directions at a constant speed. With an arm length of D (where D = ct ), the transit times in the longitudinal and transversal direction are t = D / c and thus for the outward and return journey from

{\ displaystyle T = {\ frac {2D} {c}}}

.

On the other hand, in an inertial system in which the arrangement moves with v , the speed of the light source is added to the light as in the case of a projectile according to the Galileo transformation. The speed of light in the longitudinal direction is c + v and the distance to be covered is D + vt . When returning, the light beam moves with cv and the path to be covered is D-vt . This results in a running time of:

{\ displaystyle T = {\ frac {D + vt} {c + v}} + {\ frac {D-vt} {cv}} = {\ frac {2D} {c}}}

.

In the transversal direction, the Pythagorean Theorem gives : a) if D is the path in y-direction and vt in x-direction, a path of , b) if c is the speed component in y-direction and v is in x-direction , a speed of light of . This results in a running time of ${\ displaystyle {\ sqrt {D ^ {2} + (vt) ^ {2}}}}$ ${\ displaystyle {\ sqrt {c ^ {2} + v ^ {2}}}}$

{\ displaystyle T = 2 {\ sqrt {\ frac {D ^ {2} + (vt) ^ {2}} {c ^ {2} + v ^ {2}}}} = {\ frac {2D} { c}}}

.

The running time T is therefore the same in all inertial systems, i.e. H. in all systems the light rays spread constantly relative to the light source . Emission theories are therefore compatible with the negative result of this experiment when using a stationary light source. On the other hand, as Tolman explained, the Ritz model produced a positive result when using sunlight or starlight.

Refutations

Astronomic

de Sitter's double star argument

The different speeds at which the light would be emitted depending on the position of double stars in the orbit would, according to emission theory, distort the image of the orbits received on earth. That is, the stars seem to behave as if they were no longer subject to Kepler's laws. However, this is not the case, as Daniel Frost Comstock (1910) and especially Willem de Sitter (1913) pointed out, where it was achieved. This objection does not apply to Fox's extinction model (i.e. absorption, scattering and emission of light by interstellar dust, which is practically at rest relative to the earth), whereby the light rays again assume the speed of light relative to the earth. However, Brecher (1977) examined the X-rays emitted by double stars , which hardly interacts with interstellar dust. As a result, the extinction is not large enough to significantly falsify the result. Here, too, no distortions and thus no dependence on the source speed could be determined, which corresponds. ${\ displaystyle k <2 \ times 10 ^ {- 3}}$ ${\ displaystyle k <2 \ times 10 ^ {- 9}}$

Hans Thirring pointed out in 1924 that » if an atom on the sun experiences a change in the speed component in the direction of vision during the act of emission due to a thermal collision, then the wave train emitted by it is about 3 m in total length on the way to earth The length of zero will shrink, then to a certain extent overturned and finally, with the rear end first, pulled apart to a total length of 500 km, arrive at the terrestrial observer, who receives the radiation as a radio wave with a wavelength of a few centimeters. The ballistic hypothesis is therefore refuted in its consistent version by the fact that solar radiation has a visible spectrum with sharp spectral lines . «

Terrestrial

Sadeh (1963) used a method of time-of-flight measurement to measure the speed differences of gamma rays propagating in the opposite direction, which were caused by positron annihilation. Another experiment was carried out by Alväger et al. (1963) who compared the time of flight of gamma rays emitted by stationary and moving sources. No source dependency could be found in either experiment.

Filippas and Fox (1964) were of the opinion, however, that Sadeh (1963) and Alväger (1963) did not take sufficient account of the extinction effects. Therefore, they conducted an experiment with gamma rays from the decay of π ⁰ - meson by, which was particularly aimed at avoiding Extinktionseffekten. Again, no source dependency could be determined.

Alväger et al. (1964) is now conducted further tests with π ⁰ - meson by which decompose at a rate of 99.9% the speed of light in gamma rays. The measurement of the flight time showed that the photons continued to move at the speed of light, at . Examination of the media through which the photons traversed in this experiment showed that the extinction is not sufficient to significantly falsify the result. ${\ displaystyle k = (- 3 \ pm 13) \ times 10 ^ {- 5}}$

In the meantime, measurements of the neutrino speed have also been made, using decaying mesons with almost the speed of light as a source. Since neutrinos only interact electro-weakly , extinction does not play a role. The maximum upper limits were found in the terrestrial experiment of . ${\ displaystyle k \ leq 10 ^ {- 6}}$

Interferometry

Emission theories contradict the Sagnac effect . This effect is based on the fact that, due to the rotation of an interferometer, the path becomes longer for one beam and shorter for the other. But this is only possible if the speed of light is independent of the speed of the source. Here, too, extinction does not play a role as the Sagnac effect also occurs in a vacuum.

Albert A. Michelson (1913) and Quirino Majorana (1918/9) carried out experiments with moving sources and mirrors and were able to show that there is no source dependency in the air. Beckmann and Mandics (1965) carried out similar experiments in a high vacuum, whereby a source dependency with k less than 0.09 could be excluded. Extinction could not be completely excluded, but it was very likely.

Babcock et al. (1964) placed rotating glass plates between the mirrors of a static interferometer. If the speed of the glass plates were to add to the speed of light, there should be a measurable shift in the interference fringes. However, the result was negative and since the experiment was carried out in a vacuum, absorbance is also irrelevant. Only Ritz's original theory, according to which the glass plates should not be regarded as new light sources, is compatible with the result. But there is no extinction in Ritz's theory, which contradicts all other experiments that can only be reconciled with the emission theory through extinction.

Other refutations

Maxwell's electrodynamics and the SRT are based on the independence of the speed of light from the source, and their predictions have all been experimentally confirmed with high precision. For example, emission theories are based on the Galileo transformation and thus on an absolute time that is independent of the reference system. However, by demonstrating time dilation, such as in the Ives-Stilwell experiments or the time dilation of moving particles , this concept could be ruled out and the Lorentz transformation confirmed. Likewise, the related Galilean velocity addition and also the Newtonian momentum relation are refuted by tests of the relativistic energy-momentum relation , according to which particles with mass cannot be accelerated to the speed of light and beyond.

So far, no emission theory has been developed that could explain all these experimental results at least as well, which is a prerequisite for them to be considered as a serious alternative at all. In addition, Maxwell's electrodynamics was further developed into quantum electrodynamics , which is considered to be the most precisely confirmed theory of all - here, too, the speed of light is independent of the source speed.

Web links

Critical Researches on General Electrodynamics, Walter Ritz, 1908

Individual evidence

^ ^A ^b ^c ^d Fox, JG: Evidence Against Emission Theories . In: American Journal of Physics . 33, No. 1, 1965, pp. 1-17. doi : 10.1119 / 1.1971219 .

^ ^A ^b Martínez, Alberto A .: Ritz, Einstein, and the Emission Hypothesis . In: Physics in Perspective . 6, No. 1, August, pp. 4-28. doi : 10.1007 / s00016-003-0195-6 .

^ ^A ^b Norton, John D .: Einstein's Investigations of Galilean Covariant Electrodynamics prior to 1905 . In: Archive for History of Exact Sciences . 59, 2004, pp. 45-105. doi : 10.1007 / s00407-004-0085-6 .

↑ Wolfram Schmitt: Ancient and medieval theories about the five senses. In: Specialized prose research - Crossing borders. Volume 10, 2014, pp. 7-18, in particular pp. 7 f. and 15.

↑ ^a ^b Wuellner, Adolph: Textbook of Experimental Physics. First volume, second section. Optics. . BG Teubner, Leipzig 1866, pp. 632-635, 699-708.

^ Newton, I .: New theory about light and colors . Fritsch, Munich 1672/1965.

^ Newton, I .: Opticks . William Innys, St. Pauls 1704/1730.

↑ Michell, John: On the means of discovering the distance, magnitude, etc. of the fixed stars . In: Philosophical Transactions of the Royal Society . 1784, pp. 35-57.

^ Laplace, Pierre-Simon: The system of the world (English translation 1809) , Volume 2. Richard Phillips, London 1796, pp. 366-368.

↑ Soldner, Johann Georg von: About the deflection of a ray of light from its rectilinear movement . In: Berlin Astronomical Yearbook . 1804, pp. 161-172.

↑ Foucault, Léon: General method for measuring the speed of light in air and other transparent means; relative speeds of light in air and water; Design of an experiment on the speed of propagation of radiant heat; . In: Annals of Physics . 157, 1850, p. 434.

↑ Foucault, Léon: Sur les vitesses relatives de la lumière dans l'air et dans l'eau . In: Annales de Chim. et de Phys. . 41, 1854, p. 129.

^ ^A ^b ^c Tolman, RC: Some Emission Theories of Light . In: Physical Review . 35, No. 2, 1912, pp. 136-143.

^ Kunz, Jakob: An Attempt at an Electromagnetic Emission Theory of Light . In: Physical Review . 3, No. 6, 1914, pp. 464-475. doi : 10.1103 / PhysRev.3.464 .

↑ Shankland, RS: Conversations with Albert Einstein . In: American Journal of Physics . 31, No. 1, 1963, pp. 47-57. doi : 10.1119 / 1.1969236 .

↑ Ritz, Walter: Recherches critiques sur l'Électrodynamique Générale Archived from the original on December 14, 2009. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Annales de Chimie et de Physique . 13, 1908, pp. 145-275. Retrieved June 2, 2010. @1@ 2 See also.

^ Tolman, RC: The Second Postulate of Relativity . In: Physical Review . 31, No. 1, 1910, pp. 26-40.

^ Stewart, Oscar M .: The Second Postulate of Relativity and the Electromagnetic Emission Theory of Light . In: Physical Review . 32, No. 4, 1911, pp. 418-428.

↑ ^a ^b De Sitter, W .: About the accuracy within which the independence of the speed of light from the movement of the source can be asserted . In: Physikalische Zeitschrift . 14, 1913, p. 1267.

↑ Cyrenika, AA: Principles of emissions Theory . In: Apeiron . 7. (This is a work directed against the recognized mainstream physics. It is listed here because it contains simple derivations for emission theory and MM experiment).

^ Comstock, DF: A Neglected Type of Relativity . In: Physical Review . 30, No. 2, 1910, p. 267.

↑ De Sitter, W .: An astronomical proof of the constancy of the speed of light . In: Physikalische Zeitschrift . 14, 1913, p. 429.

^ Brecher, K .: Is the speed of light independent of the velocity of the source . In: Physical Review Letters . 39, 1977, pp. 1051-1054. doi : 10.1103 / PhysRevLett.39.1051 .

↑ Thirring, Hans: About the empirical basis of the principle of the constancy of the speed of light . In: Journal of Physics . 31, No. 1, 1924, pp. 133-138.

↑ Sadeh, D .: Experimental Evidence for the Constancy of the Velocity of Gamma Rays, Using Annihilation in Flight . In: Physical Review Letters . 10, No. 7, 1963, pp. 271-273. doi : 10.1103 / PhysRevLett.10.271 .

↑ Alväger, T .; Nilsson, A .; Kjellman, J .: A Direct Terrestrial Test of the Second Postulate of Special Relativity . In: Nature . 197, No. 4873, 1963, p. 1191. doi : 10.1038 / 1971191a0 .

^ TA Filippas, Fox, JG: Velocity of Gamma Rays from a Moving Source . In: Physical Review . 135, No. 4B, 1964, pp. B1071-1075.

↑ Alväger, T .; Farley, FJM; Kjellman, J .; Wallin, L .: Test of the second postulate of special relativity in the GeV region . In: Physics Letters . 12, No. 3, 1964, pp. 260-262. doi : 10.1016 / 0031-9163 (64) 91095-9 .

↑ Sagnac, Georges: Sur la preuve de la réalité de l'éther lumineux par l'expérience de l'interférographe tournant . In: Comptes Rendus . 157, 1913, pp. 1410-1413.

^ Witte, Hans: Sagnac effect and emission theory . In: Reports of the German Physical Society . 16, 1914, pp. 755-756.

↑ Michelson, AA: Effect of Reflection from a Moving Mirror on the Velocity of Light . In: Astrophysical Journal . 37, 1913, pp. 190-193.

↑ Majorana, Q .: On the Second Postulate of the Theory of Relativity: Experimental Demonstration of the Constancy of Velocity of the Light reflected from a Moving Mirror . In: Philosophical Magazine . 35, No. 206, 1918, pp. 163-174.

↑ Majorana, Q .: Experimental Demonstration of the Constancy of Velocity of the Light emitted by a Moving Source . In: Philosophical Magazine . 37, No. 217, 1919, pp. 145-150.

↑ P. Beckmann, Mandics, P .: Test of the Constancy of the Velocity of Electromagnetic Radiation in High Vacuum . In: Radio Science Journal of Research NBS / USNC-URSI . 69D, No. 4, 1965, pp. 623-628.

↑ Babcock, GC; Bergman, TG: Determination of the Constancy of the Speed of Light . In: Journal of the Optical Society of America . 54, No. 2, 1964, pp. 147-150. doi : 10.1364 / JOSA.54.000147 .

[Fox1965-1] A ^b ^c ^d Fox, JG: Evidence Against Emission Theories . In: American Journal of Physics . 33, No. 1, 1965, pp. 1-17. doi : 10.1119 / 1.1971219 .

[Martinez2004-2] A ^b Martínez, Alberto A .: Ritz, Einstein, and the Emission Hypothesis . In: Physics in Perspective . 6, No. 1, August, pp. 4-28. doi : 10.1007 / s00016-003-0195-6 .

[Norton2004-3] A ^b Norton, John D .: Einstein's Investigations of Galilean Covariant Electrodynamics prior to 1905 . In: Archive for History of Exact Sciences . 59, 2004, pp. 45-105. doi : 10.1007 / s00407-004-0085-6 .

[4] Wolfram Schmitt: Ancient and medieval theories about the five senses. In: Specialized prose research - Crossing borders. Volume 10, 2014, pp. 7-18, in particular pp. 7 f. and 15.

[wuellner-5] Wuellner, Adolph: Textbook of Experimental Physics. First volume, second section. Optics. . BG Teubner, Leipzig 1866, pp. 632-635, 699-708.

[Newton1672-6] Newton, I .: New theory about light and colors . Fritsch, Munich 1672/1965.

[Newton1704-7] Newton, I .: Opticks . William Innys, St. Pauls 1704/1730.

[Michell1784-8] Michell, John: On the means of discovering the distance, magnitude, etc. of the fixed stars . In: Philosophical Transactions of the Royal Society . 1784, pp. 35-57.

[Laplace1796-9] Laplace, Pierre-Simon: The system of the world (English translation 1809) , Volume 2. Richard Phillips, London 1796, pp. 366-368.

[Soldner1804-10] Soldner, Johann Georg von: About the deflection of a ray of light from its rectilinear movement . In: Berlin Astronomical Yearbook . 1804, pp. 161-172.

[foucault-11] Foucault, Léon: General method for measuring the speed of light in air and other transparent means; relative speeds of light in air and water; Design of an experiment on the speed of propagation of radiant heat; . In: Annals of Physics . 157, 1850, p. 434.

[foucaultb-12] Foucault, Léon: Sur les vitesses relatives de la lumière dans l'air et dans l'eau . In: Annales de Chim. et de Phys. . 41, 1854, p. 129.

[Tolman1912-13] A ^b ^c Tolman, RC: Some Emission Theories of Light . In: Physical Review . 35, No. 2, 1912, pp. 136-143.

[kunz-14] Kunz, Jakob: An Attempt at an Electromagnetic Emission Theory of Light . In: Physical Review . 3, No. 6, 1914, pp. 464-475. doi : 10.1103 / PhysRev.3.464 .

[Shankland1963-15] Shankland, RS: Conversations with Albert Einstein . In: American Journal of Physics . 31, No. 1, 1963, pp. 47-57. doi : 10.1119 / 1.1969236 .