so theoretically it is possible to loosen c and find a determinant for displacement in time (bidirectionally)
For, if d is negative then t is negative, this is merely a descriptor at first glance but in delineating the other variables' relations we progress in our quest to unravel time travel.
One can easily understand from this equation that when mass increases greatly, such as the gas giants, time must also increase but in a power relationship, it being more costly in mass but still buys more time. If the vector follows through with design, large life forms must needs live longer too.
Also, with mass, small objects, ie if there were worlds within an atom true, have relatively shorter lifespans, but remember the power relationship holds again. To find the vector that spans from our knowledge in an einstein-newtonian universe to a polyverse experiments are in order... any useful extrapolations suggested in neutrino math?
Perhaps you could begin by collapsing our maths down a bit, and lock into a common interdimensional relationship, pi. As the point to the sphere, expanding ever 'ere, pi-based maths it is then.