A Feasible Experiment Contrary to the 2 nd Postulate of SR

Assuming the light as composed of longitudinal-extended elastic (and massive) particles emitted during an emission time T at speed c (=u) (with u the escape speed from all the masses, toward the infinity), it is shown that c is invariant (under the Newtonian mechanics laws), for an Observer fixed to the initial emission point Ep (the point where the emission starts), in spite of any motion of the source (of light) with respect to Ep. On the contrary, an Observer, in motion from Ep during the emission, will state (indirectly) a Galilean variation of c which can be proved and evaluated by an appropriate feasible experiment described here.


Introduction
This paper, in accordance with the Newtonian laws, is based on following assumptions: I. Gravity fields fixed to their related masses (intending that each field is co-moving with its generating mass).II.Finite mass of the universe, implying a finite value of U (total gravitational potential) and therefore of u escape speed toward the infinity due to all the masses in space.
III.Light composed of longitudinal-extended elastic particles (as defined in Section 3) moving at speed c = u.This equality is supported by a cosmological reason.
On above bases (including, needless to say, Newton's absolute time and space) we obtain: 1) The relation u = (−2U) 1/2 , where u is total escape speed, from all the masses, toward the infinity and U (total gravitational potential, due to all the masses in space), while the assumption c = u (which implies the massiveness of the light and also c ∞ → 0), gives to the speed of light a cosmological/anthropic reason to its value, as highlighted in Section 2.
2) The constancy of the speed of light, under the Newtonian laws, for an Observer fixed to the (initial) emission point, E p , (the point where the emission of light starts), in spite of any motion of the source with respect to E p .
3) A variation of c (in accordance with the Galileo's velocities composition law), if the Observer is in motion with respect to the said emission point (taken as reference frame): for instance, on Earth, an Observer in motion from the source (of light) fixed to the ground during the emission.This variation of c (contrary to the 2 nd postulate of Special Relativity) can be proved by a feasible experiment described here.

Total Escape Speed, from All the Masses in Space
Here we get the escape speed due to one, two and n masses; then we assume u = c (= −2U) 1/2 , with u the total escape speed (from all the masses), and U the total gravitational potential .
As known, considering in space one only mass M (regarded as a point-like), the gravitational potential U acting on a particle having mass m M  , assuming U ∞ = 0, with s the distance M-m, is U = −MG/s (this relation, according to our first assumption (I), is always valid in spite of any reciprocal motion between M and m).The related Conservation of Energy (CoE), E = U + K, where K (= 1/2u 2 ) represents the unitary (for unit of mass) kinetic energy of our particle arriving from the infinity (where u ∞ = 0), for E = 0, gives U = −K, leading to which is a scalar, (called escape speed), representing (in the considered point) the value of the velocity u, any massive particle, under a potential U, needs to reach the infinity; thus u (escape velocity) has to be referred to M; if M is a real mass, u has to be referred to the point of M where U has the max value, intending this point as the Centre of potential C p .Therefore we have to write meaning that the escape velocity of our particle m has to be referred to C p .Considering now two masses M 1 and M 2 , having, at a given time, distances s 1 and s 2 from a considered point, the potential U 1,2 in this point becomes ( ) ( ) Without the assumption I, the Equation (3) is still valid, but U 1,2 could have a different value, depending on the assigned values of s 1 and s 2 , at the considered time.Now, the escape speed from two masses can be written representing the value, in the considered point, of the (escape) velocity u 1,2 which has to be referred to the Centre of potential C p , (where 1,2 U has the max value).
Then, as ( ) therefore the escape speed due to all the n masses in space becomes with ∑ the total gravitational potential in the considered point, where u (function of U) can be called total escape speed (toward the infinity), while the escape velocity u is referred to C p (centre of potential of all the masses).Now, considering as origin of our Reference frame, the initial position of m, we may call it Emission point E p , (the point where m will be given the speed u), the following relation may be called as relative escape velocity of m from E p , with ( ) The particle m, at the time of its it turns out that m tends to the infinity: in particular, if the velocity p E m v is provided to a great number of particles all around E p , more than half of them will surely tend to the infinity.
We assume now the equality c = u, hereafter supported by the estimated mass of the universe and also by this cosmological/anthropic reason: in fact, if c < u, all the masses in space, (having speed lower than u), will tend to a gravitational collapse, whereas for c ≥ u, the mass of light, going toward the infinity in an unlimited time, tends to avoid the said collapse.
Here we also point out that the energy of light (mc 2 ) seems to be not in accordance with the relation E = U + K = 0, where K = 1/2mu 2 , but, as shown on [1], the energy of light is given by a kinetic energy K = 1/2mc 2 , complying the said relation (plus an internal energy of the same value).
This following part of Section 2, is only a support to our assumption c = u.
The mass of universe, by some authors, is estimated [2]- [4] to be ) of observable stars [5] [6], and since from Earth the distribution of the masses appears to be homogeneous and isotropic, under our assumption U ∞ = 0, we may assume their density as decreasing, from the Local Group (LG) toward the infinity, like a function ρ = ρ c e −as with c ρ ≅ 9.2 × 10 −27 kg/m 3 the critical density [7].So the mass of universe can be written ) From the LG, the variation of U, due to an increase of the distance ds, can be written as dU = −dmG/s where dm = ρ4πs 2 ds with ρ = ρ c e −as , hence the potential on Earth becomes ( ) Therefore, on Earth, u 0 = c 0 , so that and, in general we may argue The equality c = u means that, along any free path, the speed of light only depends on the value of the potential along that path.

Invariance of the Total Escape Speed u for a Particular Particle, Here Defined
Here it is shown that under the assumption III, should a source of photons, during their emission, move from its initial Emission point (E p ), their length will vary, and since their transit time, (time to cross an Observer), will also vary, their speed becomes constant for any Observer fixed to E p , in spite of any motion source-E p .
The Galileo's velocities composition law, which is related to point-particles, cannot be, apparently, applied to a particle defined as follows: "longitudinally-extended, elastic non divisible particle emitted at speed u by a source during an emission time T, and moving along rays, (continuous succession of photons)".
Of course, more photons emitted during an emission time T need an equal number of rays.
Calling front and tail the extremities of a photon, every tail, (along a ray free path), corresponds to the front of the next photon.Now, on Figure 1, let S be a Source (of light), starting to emit, at t = 0, a photon (with front A) and let the initial Emission point E p (the point where the emission starts), be the origin of our reference frame; then let S move, during the emission time T, from E p to S T .For instance, E p may be a generic point on the Earth's surface, with S coincident to E p at t = 0. Now, the relative escape velocity of the front A (being a point-particle), from Equation ( 7), can be written which gives, as hereafter shown, to the (whole) photon, for an Observer in E p , (or fixed to it), a constant speed (u), in spite of any motion of S from E p .At this purpose, still referring to Figure 1, let the source S have a velocity p E S v with respect to E p ; hence the velocity of the front A, with respect to S, that is, v SA , from Equation (13), becomes Therefore, at t = T, when S has reached the point S T , we get ( ) where λ' is the photon AB emitted with the source in motion from E p , while λ (≡ uT) should be the photon (AE p ) if S, during the emission, should be fixed to E p .Thus, after the emission time T, as for a source receding from the front A, as in Figure 1, the photon length λ', (for any Observer), from Equation (15), turns out to be ( ) v .Now, the speed of a point-particle is defined through two Observers, while the speed u' of a photon, (since its length could vary), does not correspond to the speed of any point of it, hence to define the speed of a photon we must consider its length referred to the time T' (transit time) the photon (front to tail) needs to cross one Observer, leading to which is the average speed of the photon along the path λ'.
As for this definition, let us consider a system composed of two balls connected through an elastic thread and let them fall in vertical line: during the fall, each part of the system has different speed, that is why we need the Equation (16) to define the speed of the whole photon.
Still returning to Figure 1, for an Observer fixed in E p , the transit time T' of the photon AB is given by the time the front A needs to cover the path λ, that is T (= λ/u), plus the time the tail B needs to cover the path S T -E P = ( ) which, (since the tail B is emitted by S, see Equation (13), at the same velocity u as the other parts of the photon), Thus, see Equation ( 17), the speed of the photon AB, referred to our Observer fixed to E p , becomes ( ) ( ) showing that, on our bases, an Observer, fixed to the Emission point E p (point where the light starts to be emitted), states that the speed of light is invariant (and equal to the total escape speed), in spite of any speed Source-E p .
Now, what about for an Observer in motion from E p ?Well, the length λ' of an emitted photon does not depend, see Equation ( 16) the Observer motion, while the photon transit time T', depends, for an Observer fixed to E p , see Equation ( 18 ( ) , where the sign ± is obviously given by the same/opposite direction Observer-source with respect to the one of the considered photon.For instance, if v SO = 0 (Observer co-moving with S, both moving from E p to S T during the emission), the photon length, see Equation ( 16), is still λ', while its transit time (for the Observer and for S too) is Hereafter, to detect this variation, we describe a feasible experiment where the Observer (measuring the times), has to be in motion from the Emission point (taken as reference frame): usually, the measurements of c (through the method d/t), to be accurate, requires the Observer(s) to be fixed with the photon emission point), but, on our proposed experiment, the distance d, (variable during the experiment), is not involved into the evaluation of Δc.

Description of a Feasible Experiment Showing the Variation of the Speed of Light
To evaluate our predicted variation of c stated by an Observer O in motion from the initial Emission point E p , we may assume, for simplicity, the source S fixed to E p .Thus, see Figure 2 same order of magnitude is given throughout the number ( 22 10 ≅

Figure 1 .
Figure 1.Emission of photon AB while the source S is in motion from the Emission point E p .
the path E p -S T covered by S during T, the length of an emitted photon, for a given source, only depends on p E S depends, for an Observer in motion from E p , on p E O v , leading, in short, to (a), at t = 0 (start of emission), let O be located in E p (our reference frame) and let p O E O v = v be the speed of O from E p .So, at t = 0, it is: O and A 1 (front of the first emitted photon) both in E p .At the end of the emission, lasting t e (= nT), where n is the number of consecutive photons (A 1 B 1 -A n B n ), the path covered by the front A 1 becomes L = nλ, the Observer has covered the path Δd = v O t e , while the tail B n is still in E p .Then, when the tail B n , at a certain time t O , reaches O, the path covered by O is ΔL = v O t O , where t O corresponds to the (transit) time the n photons need to cross the Observer (that is from t = 0 to the time the tail B n reaches O), hence we can write t O c = L + ΔL, so we get variation of time stated by the Observer O between the transit time t O and the emission time t e where t e is also the transit time for the Observer if this would be fixed to S. For instance, if v O = 10 m/s and t e = 3 s, one gets Δt = 10 −7 s, well measurable.Therefore the speed of light as stated by the Observer O (moving along the same direction as the light) becomes the speed stated by S (or by an Observer fixed to E p ) is: c L nT n nT c λ ′ = = = .Referring to Figure 2(b), where the source S and the Observer O are duly represented in a different position, as for the clock of the Observer we have: emission, has, in general, a velocity