This is a Wix version of Time University.
Unwritten Entangled Histories
In quantum physics retro causation usually applies to entangled states where whether a spin is up or down (or a cat is alive or dead) may depend on what happens later.
If it is possible to influence the past we might assume that the past is not set in stone or that certain parts of history are not yet written.
In Many Worlds (and related Many Minds) models alternate timelines may have wavelike properties including the possibility of negative wove interference and negative probability of events. In Real numbered math we only get chances between 0 and 100%. Any other values are normally meaningless.
The inclusion of complex numbers, waves and discrete numbered outcomes from quantum and digital math, all lead to complexities outside our normal common sense ideas. E.g. Just as electron paths seem to be influenced by alternate possible pathways so our lives may also be influenced by what lives our alternate selves might lead in alternate timelines.
In Einstein's 4D Spacetime model the imaginary numbers cause some changes in direction involving hyperbolic functions such as Sinh Cosh and Tanh rather that circular functions like Sin Cos and Tan.
Changing spatial directions in allow you to "circle" back to your original direction. You can also do 180 degree turns and revisit a place in space that you visited before. Change of directions inside a U shape such as a parabola act differently. The end result is no matter how far we spin ourselves around we are unlikely to find ourselves doing 180 turns in time.
Consistent Histories and Futures
In classical Newtonian particles based physics if you know everything about the present all future events might be predicted. Similarly with imperfect knowledge we can explore what past timelines are consistent with what we know of the present. In some models the present is not only not perfectly known but also in flux or incomplete. In ny our knowledge of things is limited. Based on this limited knowledge we have a set of possible alternate timelines. Those histories that are consistent with present knowledge lead to alternate possible futures. Surprisingly some models seem to allow us to manipulate some past events as easily as future events.
Delayed Choice
Delayed choice is where we seem to be able to make a choice of action that seems to influence events that could be construed as being in our past.
Time is no longer universal but relative in most modern theories. THE past and THE future do not exist. In such topologies the ability to influence your past or future may be equally easy. If free will exists. If we have a strict mechanical world we may need to have a pat that is open to change, in order to have a open ended future. In some models it is in theory just as easy to change aspects of our past as it is to change our future.
In some models free will choice itself is somehow integral to the direction of time. In many ideas Time is more something we experience rather than something the universe needs.
The inclusion of aspects of mind, free-will, personal perspective etc. tends to mix science and mystic ideas. This can sometimes cause controversies with those with strong philosophical viewpoints, such as the universe being totally mechanical or those looking to include ideas from religious beliefs.
Some of John Archibald Wheeler's ideas included delayed choice and other aspects of the mix of Time and free will. For more details Google "JA Wheeler + Consciousness" or "Participatory Universe". These concepts can lead us to question how real our universe may be and lead to ideas that our world may be in some ways similar to a dream or computer simulation. Although Wheeler was not afraid to explore "crazy" ideas to explain the weird nature of quantum and spacetime physics, he believed in using firm foundations to base such speculations.
John A Wheeler
http://homepages.spa.umn.edu/~larry/CLASS/CATASTROPHE/anthropic.html
http://nautil.us/issue/9/time/haunted-by-his-brother-he-revolutionized-physics
Backward causation - Stanford - https://plato.stanford.edu/entries/causation-backwards/
https://futurism.com/john-wheelers-participatory-universe/
http://discovermagazine.com/2002/jun/featuniverse
Tachyon Universes and Many Worlds
Tachyon Universes are inertial frames where time flows in the opposite direction to your view of time.
Reaching such a "parallel" world may need a person to travel faster than light. This site in the past has put forward the idea that slower than light travel causes people of different velocities in space to have different directions in time and existing in different inertial frames. After chatting with ChatGPT4 it appears that time dilation and warping of spatial distances may change for different observers the order of events in time remain the same. Presumably the positional relationships in space may also be constant for other observers that we interact with. If we assume that superluminal speeds are impossible, travelling between theoretical parallel worlds resulting from inertial frames may be impossible. I.e. even if tachyon universes exist they may be "firewalled" to prevent us to visit them.
