I don’t understand the difficulty people have with time, or perhaps rather the sensationalism and shitty wording people want to use when describing time; as well as conflating what happens at quantum or light scales with anything outside those scales.
Time is because things change. That is it. That is all.
Things exist because they have motion. Existing is motion. As long as things exist, there will never be true absolute 0. For that fundamental thing of being to be, it “vibrates”. That seems to be the usual way that comes out to describe fundamental properties and the things that generate them. To vibrate, a thing must “move” back and forth, oscillate, change state. When it “moves”, when it changes state, … blam! time. When it changes state and emits photons (or whatever else), blam! it takes “time” for those photons to transmit, to “travel”, to communicate their change in state to other things with state, other things that are.
Since there are many things that might be identified as distinct from many other things, they do not exist in the same “place”. And to communicate their changes of state from one “distinct” vibrational existence to another — for other things to be affected by changes of state — those changes must generally be communicated across “place”, to those other “distinct” things. That is not instantaneous. It is not instantaneous, because those things “are” distinct in some manner of measuring existence and the interactions between determined, existing things. (This is ignoring quantum-scale anything; because quantum anything is all about potential, and base expressions of state, and something to dive into differently. Anything of the “normal”, “human” scale is now a composite, determined state of existence and undifferentiated quantum potential no longer applies to it (not significantly, anyway).)
Of course the experience or perception of time will change as the rates of interactions change, as they are affected by other fundamental interactions of existence. If the vibrations of your particles are slowed or encumbered by a heavy pull into the vibrational space of the Earth, or the Sun, or a black hole, of course you yourself will interact at a slower pace, and the experience of the sequence of changes of state will happen more slowly. Of course you will experience “time” differently. Of course these things are relative.
Time is not a particle. It has no fundamental “particle” to express it. It is something that only comes about because of the fact that things exist (“move”) and interact (communication of changes of state that must themselves “move”). Although, in that sense, all fundamental particles that interact are the fundamental “particles” of time. Because all these things interact, and because they interact on their own terms, of course time is relative to each type of interaction. Of course the rate of changes of states is relative to the affected states of things as those states are affected by gravity and other fundamental interactions.
But any talk about time being an “illusion” or not “real” is stupid, hysterical, and irrational. People do seem to be observing very odd things at the quantum level. But that’s quantum. We should absolutely keep observing, experimenting, learning what new and interesting effects we can derive from quantum interactions. But that is quantum interactions. And even if states are superimposed, or entangled at the quantum level, that doesn’t change anything about the nature of interactions or the sequentiality of it, especially at “human” levels (which are still part of physics). We may get fascinating new technologies such as instantaneous communications out of it. But, we will never be able to ignore sequentiality.
The same thing goes for light. All the theories about particles traveling near light speed and how that affects time… those are cute and all, but humans and all such things we can meaningfully interact with ever can not and will never be able to travel near those speeds. If we did, we would no longer be human to care. We would be a stream of separate particles, photons, or whatever else, that would not resume being human at the outcome of that event, nor retain any aspect of “consciousness” or sense of self or memory relative to that event.
(If you’re going to argue that making a copy of yourself, communicated to elsewhere via quantum entanglement, is travelling faster than light, I’m not interested in talking with you. You are a devil’s advocate kind of arguer who is twisting meanings of words or concepts just to win or to be contrary. There is no value in arguing with you. At least, you are arguing from such a place, unless you can point to a demonstration in physical reality that “traveling” as that term is commonly used creates “copies” every moment, however a moment is defined, that traveling occurs. And I highly doubt you can prove that. Copying != traveling, even if a lot of the distinction is moreso semantic — given that re-creating yourself somewhere else via quantum-entangled transmission of information requires destroying your current self in order to not have duplicates, and it is making a “new” you out of different matter elsewhere, not the same you materially propulsed by energetic release. And, if there are duplicates afterwards, that is distinctly copying, not traveling. So, technologies that could be theoretically derived out of quantum understanding and manipulation might create the basic effect, it is still not actually the same thing. It may be handy and astounding, but it is a manipulation, a work-around, not physically (not “physics”-ly) the same thing.)
Of course “time” doesn’t matter to quantum-scale and light-scale particles. They are simple particles. They are intrinsically not complex interactions, or systems of interactions. They simply are things affected by other things. They can’t sense; they don’t have the complex system of interactions composed of lower-level things to create “sensing”, or a sense of “caring” about time; they don’t “care” about their state being this or that, and whether this or that happened first to make their state what it is now. They just are. There is no “consciousness” to them, nor sense of self. That is an outcome of human-scale systems of interactions. They, also, therefore, don’t “perceive” time, except by the very fact they change state from this to that. They perceive in their very being, but they also can not have any memory of previous states. Therefore they can not “perceive”. Because they just are. They don’t have the complex machinery in and of themselves to generate memory. They are the pieces that compose complex machinery that generates memory, and therefore perception.
But fundamental things still go through changes of state (even states that are superimposed for a period), and those changes are always sequential. Your perception of them, or your interaction with them, could be derived to happen “out of order”, because all such perceptions are relative. But the changes still happened in a certain order. And the closer you get to the source of a set of changed states, the more you will always have to contend with a loss of manipulable relativity. The closer you get, the less relative it is. And even if it is theoretically possible to manipulate the order of your perceptions of them, that will never happen, because you are a system that can not continue being that system if you were traveling at the speeds necessary to achieve those manipulations of perception. And once you were no longer that system, you would simply be a collection of photons, or near-light-speed particles that would no longer be capable of generating a concern about the “perception” of those events. You would simply be more pool balls on the table being bounced around, still in a sequence of exchanges of energy, of information.
Whatever we may find and manipulate at the quantum level, or at light speeds, there will never be “time” travel. Not for human-scale systems. And even if someone managed to suddenly revert all energy and the direction of all interactions of all matter for the entire universe all at once (which is what would effectively have to happen to have “time travel”), you, as a participant and outcome in those interactions, would never know the difference. You would still just perceive sequences of events, and the rules of engagement, the rules of the “universe”, the physics of the universe would still all perfectly, logically support everything you experienced (if you understood the physics completely and accurately, all at once). Even if quantum variability helped throw some randomness spice into the sequences while riding the “other” directionality of experience, you would never know, see, or experience the differences in any meaningful, absolutely discernible, definable way that can’t just be boiled down to “that’s how things are”, “that’s how they turned out”.
So any garbage or hype about time being an illusion, or all things existing in all states all at once need to be shut the fuck up. Why? Because ultimately, all humans will still have to acquire energy, get food, eat it, shit it, fuck, reproduce, strive for resources, strive to get money from others, strive for control of the outcomes of their collection of systems called a body, called life, against other living things, etc. Because all the humans saying the stupid crap about time not being real will still go off and do all these things. They will still feed their babies, and try so hard to make sure their babies survive; to make sure they themselves survive. As long as you are human, time is real and exists, and sequences of changes of state and communication of those changes of state only go one way, at whatever rate they go. You as a human being, as a living thing, will always compete for energy, and will always perceive those changes of state of “energy”, and will “die” someday along with all of that. Deal with it. Time is real.