Cosmic Relativity: The connection between relativity and cosmic gravity
It is a curious fact that all our fundamental theories of physics were more or less completed before we gained any significant knowledge about the universe beyond our galaxy. This can have the startling implication that these fundamental theories are either incomplete or incorrect if the vast amount of matter in the universe and its gravity have significant effects on local microscopic physics. Therefore, a re-examination of our fundamental theories in the context of modern cosmological observations becomes necessary. Then it turns out that our fundamental theory of motion, the theory of special theory of relativity, was a wrong direction taken in 1905, deviating from the previous theories of relativity in an absolute frame. A new theory of relativity consistent with cosmology is formulated, and we will briefly review its essence here. Cosmic Relativity is a theory of relativity that is meant to replace the special theory of relativity. It is the only theory of relativity at present that is consistent with all known experimental results and with the gravitational presence of the matter filled universe. It essential point is that we have forgotten the large gravity of the universe while making our physical theories, perhaps because we did not know that there was so much matter in the universe, but this gravity is in fact very important in determining even the laws of physics and many of its effects, from time dilation to the different behaviour of bosons and fermions (particle with integer and half-integer spins).
The fundamental assertion of Cosmic Relativity (CR) is that all kinematical physical effects known today, including Newtonian effects like the centrifugal and Coriolis force, relativistic effects like time dilation and length contraction, and quantum effects like the Thomas precession, are all really physical effects originating in the gravitational influence of the matter in the universe. The all pervading Cosmic Microwave Background Radiation (CMBR) provides a practical way of determining both the absolute velocity and the universal absolute time. Therefore, the correct theory of relativity cannot be the one based merely on relative velocities. Thus, special relativity has to be discarded as inconsistent with cosmology that we know today. Replace the ‘aether’ of pre-1905 physics with ‘Universe and its gravity’, and then one gets the correct theory of relativity.
There are two important predictions of the theory of Cosmic Relativity; one pertains to the time registered by clocks that are transported, and the other to the one-way speed of light, which has never been measured directly. Since the physical effects on clocks depend on the speed through the preferred frame of the universe (absolute speed) rather than on the speed relative to an observer, the motion of the frame through the preferred frame becomes relevant, and the time dilation has to be calculated using the ‘absolute speed’ (relative to the CMBR, practically) rather than using the speed relative to a reference observer. It is the universe that is important and not some observer. This implies that there are situations in which a transported clock can run faster than a stationary reference clock in the same frame, unlike in the Einstein prediction that transported clocks always run slower. More importantly, the value of the speed of light is determined uniquely in the preferred frame, and depends on the gravitational properties of the universe. This implies that while the speed is independent of the velocity of the source, just as it is for other familiar waves of classical physics, the speed of light is not independent of the velocity of the observer who measures it; it is not an invariant constant.
The special theory of relativity was constructed in an attempt to arrive at a theory of motion consistent with the invariance properties of the Maxwell electrodynamics and in particular with the ‘failure to detect the motion of the earth through the hypothetical medium of aether’. The Lorentz-Poincare theory of relativity of motion with length contraction and time dilation did achieve these goals retaining the aether. But it was Einstein’s formulation based on the Lorentz transformations of coordinates and the assumption of the invariance of the speed of light, the special theory of relativity, which was accepted as the correct theory even though both the theories are consistent with all experimental results. While the Lorentz theory was based on motion and velocities relative to the preferred frame of the hypothetical aether, Einstein’s theory was meant for inertial motion in empty space, and hence all inertial frames were to be considered equivalent. This naturally made the physical effects in the theory dependent only on the relative velocity between different frames of references. The essential aspect of Einstein’s SR is that an observer in inertial motion is equivalent to an observer at rest, and therefore it is always the clocks and rods in the ‘other frame’ that suffer time dilation and length contraction. In the words of Planck, “The gist of the principle of relativity is the following. It is in no wise possible to detect the motion of a body relative to empty space; in fact, there is absolutely no physical sense in speaking about such motion. If, therefore, two observers move with uniform but different velocities, then each of the two with the same right may assert that with respect to empty space he is at rest, and there are no physical methods of measurement enabling us to decide in favour of one or the other”.
But we now know that there is good physical sense in talking about the motion of a body relative to space because universe is not empty. Matter and CMBR in the universe provide reference markers to determine our absolute velocity. Since the average temperature of the CMBR is constantly decreasing with cosmic time, and since this temperature is the same at all points in the universe due to its homogeneity, it serves as the absolute time. Thus, new cosmology restores the concept of absolute space and absolute time in physics, even stronger than it was postulated in Newtonian physics.
The physical argument goes deeper than this, and becomes stronger as well when we realize that the universe is very large and that the actual matter content is extremely large even with a small average density. The gravitational potential of such a mass distribution can be calculated, by integrating over all mass shells from our position, all the way to the Hubble radius or the notional size of the universe, and this turns out to be a billion times larger than the gravitational potential at the surface of the earth! Also, curiously the numerical value of this potential is almost equal to the square of the speed of light. This observation is at the core of cosmic relativity. If we move through such a vast matter distribution, a large amount of matter is in motion relative to us. Matter is the charge of gravity, and just as the motion of the electric charge generates magnetic potentials and fields, this current of matter generates new gravitational potential called the gravitomagnetic potential. Just as the current in a solenoid generated a magnetic field, the circular movements of matter in the universe will generate a ‘gravito-magnetic field’ if we are in a frame that is rotating in this universe. Needless to say, a piece of matter (‘test charge of gravity’) moving in that field will deflect from its straight trajectory (the ‘v-cross-B’ force in gravity), and this turns out to be the Coriolis force. It is known from direct experiments that clocks kept in different heights, and hence in different gravitational potentials, run at different rates. Since the gravitational potentials are different in a frame that is stationary in the universe and in another that is moving through it, clocks in these two different frames will have different gravitational time dilations, and this is what is seen in the time dilation of muons, wrongly interpreted as a proof of the Einstein time dilation of special relativity because nobody had realized the importance of the gravity of the universe.
Speed of light is a major theme in the development of the theories of relativity. In the aether theory, aether is the medium for the propagation of light, and light is like any other wave in a medium of support. The speed if light is of course determined by the properties of the medium, and therefore it is independent of the velocity of the source that generates the waves. This is true for waves of sound or for water waves on the surface of a pond. However, the speed of the waves relative to an observer moving with respect to the medium depends on the velocity of the observer . That is our usual experience.
To explain the ‘failure to detect the motion through the aether’, Einstein postulated in 1905 that the speed of light is a universal constant, c, and remains the same constant for all observers in inertial motion. This of course implies that the inertially moving observer is equivalent to one who is stationary. But very few people realize that Einstein’s hypothesis of the constancy and universality of the speed of light is not based on direct empirical evidence regarding the one-way speed. It is based on the invariance of the two-way speed of light, as in the Michelson-Morley experiment where light reflects and comes back to observer. But in two-way experiments a major asymmetry proportional to the velocity gets cancelled out. But this postulate was accepted because it was considered impossible to measure the true one-way speed of light. This task requires two clocks, at start and finish points, and to synchronize these two clocks to read the same starting time one needs to send light or other signals between them. But then signals that are used to synchronize are the same signals about which a postulate is being made, and the logic and the argument become circular! So, as long as nobody manages to measure the one-way speed, one can assume that the postulate could be true.
It turns out that there is just one way of measuring the one-way speed of light without using two spatially separated clocks. The main requirement is not to allow the signal to retrace its path, and yet bring the signal back to the starting point so that the same clock can be used to measure the duration between the emission and reception of the signal. There is an amazingly simple way of doing this by sending the light along a race-track shaped path, just as we often measure the ‘one-way speed’ of sprinters along a 400 m race-track in a stadium, by making the start point the same as the finish point. To make the measurement relative to a moving observer, make the platform on which the laser source and the detector are set up move smoothly, and then one has a way of measuring the one-way speed of light relative a moving reference point. If two light pulses or wave fronts are used in opposite directions a direct comparison of relative speeds in two directions can be made.
If the relative speeds of light in the two directions are identical, then the two pulses should reach the observer simultaneously after a round trip. This is an unambiguous prediction from the special relativity because in this theory the observer in linear inertial motion is equivalent in all respects to an observer at rest.
Figure 1: Comparison of the one-way speed of light in two directions relative to a moving observer ‘O’. The light pulses move in opposite directions. The hollow optical fiber is the one-dimensional path and the entire configuration is in motion as in a conveyor belt.
The experiment can obtain the best possible accuracy using the interferometry technique, just as Michelson discovered. Thus the race-track interferometer (which is a variant of the ‘Sagnac interferometer’) compares the one-way speed of light in two different directions relative to a moving observer, whereas the Michelson interferometer used in the M-M experiment compared the two-way speed of light in two different directions relative to the moving observer.
The result of the experiment is a direct blow to the fundamental hypothesis of special relativity. The light pulses reach back the inertial reference frame (source/detector combination) exactly as sound waves or water waves do, with a time delay proportional to the linear velocity of the reference frame! Therefore, it can be concluded unambiguously that the one-way speed of light does depend on the velocity of the reference frame in which it is measured.
In his 1905 paper Einstein predicted, "If one of two synchronous clocks at A is moved in a closed curve with constant velocity until it returns to A, the journey lasting t seconds, then by the clock that has remained at rest the travelled clock on its arrival at A will be (1/2)tv²/c² second slow". If one has examples where the transported clock has aged more compared to a clock that remained stationary in the same frame, then special relativity would be contradicted by empirical evidence. In special relativity there is no way one can get a travelled to clock to age more than a stationary clock. But it is an experimental fact that a clock that is made to travel westwards relative to a stationary clock in the laboratory and then brought back after the trip around the earth ages more than the stationary clock. A clock that is transported eastwards ages much less than the Einstein prediction. The explanation is simple in cosmic relativity because what we thought as the clock at rest in the laboratory is actually moving along with the surface of the earth relative to the cosmos. The westward clock has less absolute velocity than the clock, and therefore clock transported westwards runs faster than a clock that is stationary in the laboratory.
The conflicts between special relativity and the experimental results we discussed so far are good reasons to expect that relativity based on the gravitational influence of the matter in the universe on moving bodies – the theory of Cosmic Relativity – will emerge as the correct theory.
