No.1: Space and Time
Did you know that space and time are really the same thing? To have space is to have time, and to have time is to have space. You can't have one without the other. Without space there is nowhere to have time, and without time there is no time to have space. We can't see timespace fully because we are functions of it. It is behind us, in a way that we can't turn around to see. We are part of a marbled edifice growing, not moving. We do not move from place to place, but grow from one place to another, but we can only see the surface, the growing tip, and not the marbled trails. We are not bodies but body-shaped tendrils trailing through the years.
It is not time travel that we need, in order to see the past, it's an additional sense. Whether it is possible to generate such an additional sense using only the ones we have to start with is a difficult question. A superior being would carry on its existence not only at the "flat" three-dimensional tip (think of two-dimensional analogy) where we exist, but simultaneously in more than one spacetime location. Therefore such a being would not need to travel in time, it would be in or span many places in time at once. Evolution doesn't look like it will ever get us there, and devices travelling at any speed couldn't get us there, because they are only trying to move from one location to another. What we need is a device that will enable us to be in more than one location simultaneously.*
Some experiments with photons and particles, e.g. sending them different ways through polarising filters and detecting where they end up, produce results indicating that a particle has gone both ways simultaneously. Also one half of a particle spins one way, the other the opposite way, no matter how far apart you separate them, when you change the spin on one of the particles the other changes too. This defies the theory of relativity, because it shows action / influence travelling faster than the speed of light, yet nothing can travel faster than the speed of light according to Relativity. But can something be in two places at once?
*The Herald would like to offer a million pound prize for the first person to build such a device. Richard Branson would you please contact us to arrange sponsorship. I think I will call this the Padre Pio project. Ed