Yes, well... the past, present and future cannot just exist side by side, without believing the past and future are misnomers for just other present moments. While this could be true, I would never look too deep into it because sometimes physics can chase idea's like ghosts to over-simplify the dynamic structure around us.
If you consider Minkowski spacetime, every spacetime event is designated by four coordinates: three of space and one of time.
With respect to space, no one has any problem with the idea that “here” is an indexical — i.e., a point of view. “Here” is where I am. But I acknowledge that there are other “heres”, it is just that, from my point of view, I call them “theres.”
If Minkowski spacetime is real, as opposed to a mathematical model, then what is true for space, must be true for time as well. What I call “now” is when I happen to find myself. But, just as with space, I can acknowledge that there are other extant “nows” relative to me, only I call them “earlier” and “later.”
If we return to Einstein’s original relativistic train though experiment, it seems we have powerful evidence that the future must exist, relative to our own present. The rider on the train sees the lightning flash first at the front of the train, but sometime later, in his/her own future, sees the lightning flash at the back of the train. Meanwhile, the observer on the ground has seen both flashes simultaneously.
What are we to conclude? Although the rider on the train doesn’t it know it yet, he/she is guaranteed, sometime later, to see a lightning flash at the back of the train. The conclusion seems inescapable: The future is not open. It is just as fixed as the past.