3.1. Exact value for the Pioneer acceleration
The anomalous negative acceleration of Pioneer spacecraft 10 and 11 being well-known (concrete investigations of that anomaly started in 1994 [
12]), it is not necessary to summarize this issue here. In light of the exact result presented below, it appears evident that this problem has not been correctly solved yet, despite copious investigations based on thermal simulations [
10–
16], which produced approximate results from several assumptions and different scenarios. In 2012 [
10] a value of 7.4 (± 2.5) × 10
−10 m·s
−2 was proposed. On the contrary, the exact solution (without models and assumptions) is directly offered by
(2), that is, via the interaction of the Pioneer probes with a shear-thickening vacuum. Let us put
(2) in Newton’s second law, using the known data of the Pioneer 10 and we directly obtain the exact negative acceleration of the Pioneer (
aP) detected by NASA
where
mP = 222 kg is the mass of the spacecraft (258 kg) minus that of the burned fuel (36 kg hydrazine) after the Jupiter flyby;
rP = 1.371 m is the radius of the antenna (diameter is 9 ft); and
vmax = 36 737 m·s
−1 is the maximum speed of the probe, as indicated by NASA’s Scientific and Technical Information Office [
18] after the swing-by caused by Jupiter. This exact and direct result cannot be ignored and the Pioneer issue has to be reopened. Moreover, NASA should now consider Doppler tracking other probes. Unfortunately this was not the case for the New Horizons spacecraft, for which data are missing. Testing other probes (maybe a dedicated probe) with
(2) would be useful to check this result.
3.2. Second test: stability of planetary orbits
The existence of a shear-thickening vacuum does immediately raise an objection as regards orbital stability. However, considering the second law of motion in the form
a =
F/
m and putting the large mass of a planet in the denominator and the modified Stokes’ equation in the numerator, we see that, despite the existence of a dilatant vacuum, planetary orbits are stable over trillions of years. For instance, the deceleration of the Earth (
a⊕) corresponds to the following negligible value:
using
(2) in the numerator, with mean radius and mean orbital velocity of the Earth and the mass of the Earth in the denominator. Subscript ⊕ refers to the Earth. Such a negative acceleration corresponds to a decrease in orbital speed < −3.13 × 10
−9 m·s
−1 per billion years, making orbits stable for thousands of billions of years. For Jupiter, orbital deceleration is −6.59 × 10
−28 m·s
−2. One therefore concludes that planetary orbits are stable despite the presence of a shear-thickening vacuum.
3.3. Deriving Einstein’s formula for the precession of perihelia
Net of classical gravitational contributions, perihelia precessions show an anomalous positive contribution, which is particularly evident for the planet Mercury. The correct calculation of this anomaly is one of the classical tests for general relativity (GR). Here Einstein’s formula for the precession of perihelia is differently derived via the modified Stokes’ equation presented above. In this way, it is suggested that the long-awaited quantum foundations of GR are situated in a shear-thickening quantum vacuum. In GR [
19], the anomalous perihelia precession is represented by a formula that can be observed in three equivalent forms
where
expresses the relativistic contribution to perihelia precessions in radians per revolution corresponding, using the data of Mercury, to the known value of 42.98″ per century (or 5.0186 × 10
−7 rad/rev),
a =
r is the semi-major axis,
T the orbital period, and
e = 0.205 the orbital eccentricity. The expression in the center of
(6) is obtained via the equivalence
T2 = 4
π2a2/
v2, resorting to mean orbital velocity, and in the expression on the right-hand side the stable second cosmic velocity,
, is used. As for the case of the Pioneer, the modified Stokes’ equation for a dilatant vacuum is used below. In this case, the treatment of the planet as a point mass is respected, as in GR, so the direct proportionality to planetary radius is not taken into account, and by using the dimensionless norm of
(2) we obtain
which can be expressed in radians. Invoking Taylor, let us proceed via the approximation
where, on the right-hand side, we see again the stable second cosmic velocity (here squared), as in the rightmost expression in
(6). Because we are considering an elliptic orbit, we have to use the elliptic parameter, correcting
a into
a(1 −
e2) and we obtain a formula that gives exactly 1/2 the result of GR found in
(6),
This 1/2 result can be considered as the precession
occurring in a semi-orbit and is due to the use of mean orbital velocity. Indeed, in the elliptic orbit, the orbital speed actually varies as in
Fig. 1 on the left-hand side. Because the mean orbital velocity is given as (
vmax/2) + (
vmin/2), let us adopt the reduced model on the right-hand side of
Fig. 1 (i.e., one semi-orbit at maximum orbital speed and one at minimum speed). The full precession
(6) is therefore given by
where
vmax and
vmin, each referring to a semi-orbit, recombine in the mean orbital velocity
v and the rightmost equivalence comes from
(6). Now, by merging the steps above into a single formula, we can look at the relationship between the modified Stokes’ equation, which expresses the viscous force in a dilatant vacuum, and the contribution to the precession of perihelia. The formula reads
where
D is the term of vacuum dilatancy
(3). By testing
(12) with the parameters of the planet Mercury, we see that it exactly gives the well-known value of GR
where, in
D,
is used, as in
(6). The positive contribution to the precession of perihelia treated in GR is in this way revealed as a phenomenon driven by a shear-thickening vacuum. We see that nothing, in the present study, contradicts GR: this investigation, by rederiving Einstein’s formula for perihelia precession, only highlights that the quantum foundations of relativity are in a dilatant quantum vacuum, as
(12) shows. After all, this is compatible with the stress–energy tensor of the field equation, in which
T00 is vacuum’s energy–mass density (
ρvac), also present in the cosmological constant Λ =
κρvac, and the remaining components of the tensor can be as well hydrodynamically interpreted, being pressure, shear stress, momentum flux, and momentum density. Interestingly, also an investigation by Marcucci and Conti [
20], following the present findings [
21], shows that the interaction at Planck-scale with a quantum fluid may be the cause of precession.