##### Title : Observation and Relativity: The speed of light is not truly invariant!

#### Abstract:

In 1905, inspired by the Michelson-Morley experiment, Einstein proposed the hypothesis of the invariance of light speed (ILS), from which he theoretically deduced the Lorentz transformation, established the theory of special relativity (SR), and revealed the relativistic phenomena of spacetime and matter motion. However, to this day we still do not know exactly what role light plays in Einstein’s theory of relativity, do not fully understand why the speed of light is invariant in the Michelson-Morley experiment, and do not truly comprehend why spacetime and matter motion exhibit relativistic phenomena. Based on the axiom system consisting of the definition of time, the conditions of wave-particle duality, and the principle of physical observability, we deduce the general Lorentz transformation (GLT) with the same form as that of the Lorentz transformation, prove the theorem of the invariance of information-wave speed (IIWS), and at last establish the whole theoretical system of observational relativity (OR). In the GLT, the position originally belonging to the light speed c is now occupied by the information-wave speed ?. In particular, the GLT has generalized and unified the Galilean transformation and the Lorentz transformation: as ??c, the GLT exactly converges to the Lorentz transformation; while as ???, the GLT exactly converges to the Galilean transformation. So, the GLT is logically consistent not only with the Lorentz transformation but also with the Galilean transformation. The theorem of IIWS suggests that the Michelson-Morley experiment does not truly support the ILS but demonstrates a significant phenomenon in physical observation: the speeds at which observation media transmit the information of observed objects exhibit observational invariance relative to inertial observers. The ILS is only a special case of the IIWS, and is only valid if light acts as the observation medium. In the Michelson-Morley experiment, the observation medium is light, so the speed of light relative to Michelson and Morley appears invariant. In fact, the speed of light is not truly invariant. The theory of OR discovers that: all relativistic effects, including the invariance of light speed and the so-called spacetime bending, are observational effects and apparent phenomena, rather than the objective and real natural phenomena. According to the theory of OR, Einstein’s relativity and Newton’s classical mechanics are just two partial theories of OR: Einstein’s relativity is the theory of the optical observation in which light acts as the observation medium, and the information-wave speed is naturally the speed of light; while Newton’s classical mechanics is the theory of the idealized observation in which the speed of information-wave is idealized as infinite, so it takes no time for observed information to cross space. Now, the theory of OR has generalized and unified Einstein’s SR and the Galilean-Newtonian inertial theory: as ??c, the relations of OR exactly converges to that of Einstein’s SR; while as ???, the relations of OR exactly converges to the Galilean-Newtonian laws. So, the theory of OR is logically consistent not only with Einstein’s SR but also with the Galilean-Newtonian inertial theory. Obviously, this corroborates the logical self-consistency and the theoretical validity of theory of OR. The theory of OR has significant implication. As Hawking remarked: “If we discover a complete theory, it would be the ultimate triumph of human reason – for then we should know the mind of God.”

**Audience Take Away:**

- The attendees of ELOS-2022 will be mostly physicists in the field of optics or photonics. However, they do not truly understand why the speed of light is invariant and why photons have no rest mass. The theory of OR will help them understand that the speed of light is not really invariant and the rest mass of a photon is not really zero.
- According to the theory of OR, the invariance of light speed is just a sort of observational effects or apparent phenomenon, and holds only if light acts as the observation medium. So, the speed of light is not really invariant. Or in other words, the speed of light is not really insurmountable. The theory of OR will inspire physicists to explore the superluminal forms of matter motion.
- According to the mass-velocity relation in Einstein’s special relativity, any object moving at the speed of light has no rest mass. So, Einstein thought that photons have no rest mass. Now, the theory of OR tells us that any object has the rest mass of its own, and moreover, only the rest mass is the real mass. The mass-velocity relation of OR theory suggests that the rest mass of a photon can be observed or detected by means of superluminal observation media. The theory of OR will inspire physicists to explore the rest mass of a photon or a particle travelling at the speed of light.
- The theory of OR discovers that all relativistic phenomena, including the invariance of light speed, time dilation and length contraction, the relativity of simultaneity, the rest-mass problem of photons, and spacetime bending, are observational effects, rather than the objective and really natural phenomena. The theory of OR reveals the root and essence of relativistic phenomena: the essence is a sort of observational effects or apparent phenomena; the root is the observational locality, that is, the speeds of information waves or observational media are limited. The theory of OR signifies that physicist have to reexamine the Galilean-Newtonian theory of classical mechanics, to reexamine Einstein’s theory of relativity, and to reshape human view of nature.
- Physicists, especially young ones, might make new discoveries if they introduce the theory of OR into the research work of their own.