That cannot be the case; Relativity tells us that observers in different reference frames disagree on both the timing and sequence of events. So there cannot be a universal "present"; And therefore the past, or the future, or more likely both, must exist.
Well, I won’t pretend to be any kind of astrophysicist, but for shits and giggles, I would argue that’s precisely why it is the case. From your perspective the “now” would appear different from my perspective. But if we were both experiencing the same “now”—or, rather, if the “now” were some fixed point—we would indeed be experiencing the same thing, but because there are no such things as fixed points outside our maps of the external, it always appears differently.
Iow, we are the ones that fix points and perspectives, not the universe and that is why they can differ. Again, think of a burning fuse (and let’s further state it’s a five foot long fuse for the sake of the analogy). You remember it being lit; you remember seeing the flame travel along the length of the fuse; you could even remember each foot of the fuse as it existed prior to the flame consuming it.
And if I happened upon the fuse after it was already lit and had “consumed” a foot of fuse, then from my perspective I would have seen a four foot long already lit fuse, so my account of it would differ from your account.
But from the flames’ “perspective” it’s just burning in the now. There is no fuse behind it. It—the flame—did not travel along any pathway, eventhough that’s how it appeared to us (being fixed observation points relative to it). There is no past; no previous three foot point or four foot point or five foot point, etc.
Nor is there a future, in spite of the fact that there is at time T still more fuse to burn. All the flame is doing is burning, It can’t “see” anything—or experience anything—beyond that burn. I reallize this may be where the analogy breaks down, but it’s not the analogy’s fault; it’s our inability to properly conceptualize what we’re talking about precisely because we make maps; we take pictures and then animate them. But it is the animation that is the illusion.
We are—effectively—within a giant flame in the process of exploding, it’s just so tremendously large that from our perspective it takes billions of years, but just like a flame in the process of exploding, there is nothing left behind for us to travel too.
Just look up at the stars any given night. None of them exist anymore. Not in the state we currently see them. We are effectively looking at a photo of a past explosion, but even if we had the technology to instantly transport us to the spot we are looking at, when we popped out at the other end there wouldn’t be anything there (or at least not the object we had been looking at).
That “state” no longer exists. Hasn’t existed for billions of years, it just took that long for the photons to reach our eyes, so unless there is a way to instantly freeze all matter in the universe and then reverse engineer every single particle’s changes in state due to their interactions with all the other particles such that you could recreate Universe of Particles at State X—and that in turn be so finely calculated/tuned to correspond to a meaningful event like JFK being shot or the like—it’s not possible.
Even then it isn’t you traveling “through” time; it’s you recreating a previous energy state of the entire universe and then having to hit “start” to have it all become active again for you—in your quantum shield suit—to watch (not interract with, just watch somehow without needing the photons to hit your retinae) it unfold in real time, but how could you hit the “start” button if you also did not have all of the previous energy states recreated in order for the proper trajectories/momentum to all coincide/collide in the exact same way to produce the next series of state changes?
Iow, it would require a meta recording—a DVD—of the entire universe’s energy state conditions and then at best all you could do is recreate a simulation of that universe, but not the actual one. Even if you were some sort of god that could manipulate matter at will, we’re not talking about mere manipulation; we’re talking about needing to reset an entire universe of particle states to a specific condition, stepping into that universe (without causing any butterfly effect in so doing) and then “starting” the universe up again without any impact on any particle trajectories.
Ioow, you’d have to be an Omni-capable ghost observer whose observation does not collapse any waves, which would certainly seem to be a fundamental contradiction.