I'm so agnostic concerning the concept of time itself at the end of the day.
I feel that we're so busy struggling to find a way to make time travel work, that we forget that time itself isn't a mechanism of the universe, and that it's just a word we use to describe some sort of effect or bi-product that we're observing.
Here's a can of worms... Compare the concept of time travel to something like 'smell travel'. Is it really that different? We are conditioned to know what smell is because our body has a mechanism to "interpret" particles and send signals to our brain which we 'remember'... How do we know that Time is any different? Perhaps travelling back in time is a flawed concept in itself, in the same way that "travel back in hearing" or "travel back in smell" makes little sense at all because we're just describing an effect or mechanism of our biology, rather than an effect or mechanism of the universe.
I think you partly misunderstood his comment. Basically instead of time we can look at it as a change of states, just a linear process. There is no time. If you place something on a table (in a perfect environment with no decay) you can't tell how much time it sat there. It could have sat there for 1 hour or 1 million years. It just didn't move and no one tracked the "time". Time is just a concept in our minds to track changes in space (or state of space). Special relativity I think doesn't contradict this. It just says that the "speed" of the state changes (e.g. you go from A to B) is relative. But this speed can't go negative. There is no trace of previous events where you could go back to.
My thought is that in special relativity, there is no absolute present, only the present from different reference frames. Essentially, “now” isn’t an objective thing. “Happen simultaneously” is not an observer-independent equivalence relation, and so there is no observer-independent way of splitting things into “the present (which exists)” vs “the past” vs “the future”.
If you want to refer only to that which you presently observe as “existing”, then there is only the boundary of your past light cone, but this would be a bit solipsistic imo, as any other person you observe, the boundary of their past light cone would mostly not be part of the boundary of yours (it would be in it, just not on the boundary of it), and so they would seem to see things that “don’t exist”. This doesn’t seem sensible to me.
I don’t see any good alternative to treating the past and future as being fully real.
Here's a can of worms... Compare the concept of time travel to something like 'smell travel'. Is it really that different? We are conditioned to know what smell is because our body has a mechanism to "interpret" particles and send signals to our brain which we 'remember'... How do we know that Time is any different? Perhaps travelling back in time is a flawed concept in itself, in the same way that "travel back in hearing" or "travel back in smell" makes little sense at all because we're just describing an effect or mechanism of our biology, rather than an effect or mechanism of the universe.