Wesson’s space-time-matter 5D gravity
In Einstein’s theory of general relativity space and time is combined to form curved spacetime, where the curvature is determined by mass and the Einstein equation relates spacetime curvature on the left side to the properties of matter on the right side:
Spacetime Curvature (4D) = Matter Properties
Matter-free spacetimes – vacuum – thus require the right hand side to be zero, and spacetime curvature is entirely due to gravitational energy in the system (which may also form black holes).
Paul Wesson extended that theory by introducing a 5th dimension to describe the properties of matter in their interaction with curved spacetime. In this extended space-time-matter continuum, the equation of gravity becomes
Space-Time-Matter Curvature (5D) = 0
With the equation of gravity becoming a “vacuum” equation, yet in 5D, it is somehow simpler, somehow more complex, but in any case a unification of spacetime and matter. This is similar to the unification of electric and magnetic forces as the electro-magnetic force. The commonly known four Maxwell equations, written in 3D, become one single unified equation when written in 4D: d*dA = J . Going to higher dimensions definitely allows to reduce mathematical complexity.
Whether such higher dimensions are real or mere mathematical constructs, is a matter of belief though – what is real anyway? Is there even anything that is real? Platonists believe so, Positivists believe that we can only come up with numerical descriptions of nature that improve over time, but attempting to explain anything is futile per se.
Time Travel without Causality Violation
Russian physicist Igor Dmitriyevich Novikov derived the principle of self-consistency from the principle of minimal action for situations where closed timelike curves exist. Such spacetimes are allowed by general relativity, but usually such regions where they may exist are believed to be causally disconnected from regions where they cannot exist. This principle is called “cosmic censorship”. Examples are rotating black holes as they exhibit closed timelike lines, but only inside their event horizons. So even if they exist, they cannot be observed from the outside. However, cosmic censorship is unproven and thus remain a matter of belief since as of now no counter-example has been found.
Under the Novikov principle however cosmic censorship is no longer needed. Time travel may just happen anywhere anytime, but the principle of self-consistency means that only those time travels are possible that do not violate causality. From the viewpoint of physics this does not cause any problems, it is only an issue for those humans who want to believe in free will. Neuroscientists tend to dissent the concept of free will anyway. So, the existence and finding of time travel may ultimately proof that free will is a mere illusion created by our brain to comfort us.
This poses the question if we could even detect and observe time travel, if it is so contra-indicative to our so comfortable illusion of free will? Maybe it already happens all around us, just our mind is blind to it? If so, maybe the nature of time is already full of time travel all over, like a foam connecting future and past, but this property of spacetime is fundamentally unobservable to us because our brain requires us to believe in free will to maintain our mental comfort?
Gravity as Entropic Force
In 2009, Erik Verlinde presented his theory that gravity is not a fundamental force but a consequence of differences in entropy. What we experience as gravity is nothing but nature trying to reach an equilibrium same as semipermeable membrane separating regions of salty and clear water experiences a force due to both fluids trying to reach the same level of salinity.
- Original Article: On the Origin of Gravity and the Laws of Newton – https://arxiv.org/abs/1001.0785
- Wikipedia article: https://en.wikipedia.org/wiki/Entropic_gravity
Deterministic Quantum Mechanics
… to be done …
