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Comment by oldstrangers | Hacker News Reader

To me it's pretty intuitive that time isn't real (outside of being a concept). We just use time as an elaborate way to explain our movement through distances (and how fast or slow we cover those distances), that's about it. The twin paradox[1] does a good job of explaining this.

There's no discernable difference between today and lets say, arbitrarily, 1984. The only difference is our movement through that spatial distance.

[1] https://en.wikipedia.org/wiki/Twin_paradox

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In your rebuttal, you used a concept that necessarily assumes time ("how fast or slow", i.e. speed) to argue against the existence of time?

Velocity is real, distance is real, time is how we've decided to describe their relation.

Physically and philosophically, the "idea of time" isn't real. It just helps us describe our reality.

velocity is defined as distance over unit time so I’m not sure how you square that circle

Semantics but velocity being a measurement of somethings movement through a distance is exactly what I'm saying time is. I've stated that we use time to describe stuff, like velocity. But "time" as a physical property like gravity does not exist.

You could probably replace the usage of "time" with "increase in entropy", but it just makes it harder to understand WRT velocity. As your velocity increases, the entropy in the universe has increased as a result of whatever mechanism for acceleration is being used. If it's gas, then you are going from a nice, mostly orderly/low entropy liquid in a container, to a chaotic, high entropy gas that's now in the atmosphere.

Given that the speed of light directly relates time and distance in (to the best of our extremely precise measurements to date) an absolute manner, then if time doesn't exist, neither does distance.

Also, as TFA mentions any dismissal of time as a concept must also deal with thermodynamics.

The speed of light is still just the movement of something over a measured distance.

I can flip that around and say that a distance is just the movement of something over a measured time. By your original argument, distance doesn't exist.

I get what you're saying. But the physicality of a distance seems more meaningful than our movement through that distance.

I've tried articulating this idea before but its very cumbersome: You want to go make a drink in the kitchen, the difference between the future you making that drink and right now is only your movement to get to that point. You making the drink and you not making the drink are exactly the same "points in time". But for perception, you making the drink is an idea you see as a future event as opposed to a concurrent event that involved some movement through a distance.

Given distance, velocity and time; choose any two as physical and the third will be emergent. Choose according to the view you want to explore.

The fact that the third is emergent seems to me like more evidence that it is real, rather than the opposite

c is the render speed of god's GPU

here is another way of looking at it: the speed of light actually shows us the maximum speed of causality (how fast can a change in point A in space propagate). Some might speculate that the same speed of causality is observed in everything, it just so happens that most transformation happen in place giving us the illusion that we are stationary in space.

When I was younger I imagined in my head that a specific moment in time is literally just all of the information about the observable universe -- the position, momentum, temperature, etc of all of the particles in existence relative to one another. I’m running on very little sleep right now so be prepared for a little woo here; I’m expecting someone smarter to come correct some misconceptions in my take and hoping to learn a little bit from that.

For me, that idea always been enough to get by (without existential questions), albeit it's a little bit different from the three-axis-plus-time description in the article. It explains really intuitively why reverse time travel isn't possible (non-reversible reactions, energy required to reverse the entire universe into a previous state, etc). It also makes it intuitive that time does exist, since "time" is a noun referring to the overall state of the universe - a specific state in a set of states that at least appears to progress sequentially... but perhaps does not. Actually, looking at the questions in the article, it seems to jump out that time is uncountably infinite (since "absolute time" cannot exist). Even so, the “arrow” of time would be evident from within any of these states because there is only one direction that certain starting conditions can lead. “Time” does not account for parts of the universe in isolation, but rather all of it as a whole - so there are always plenty of pointers.

Edit: This seems to be a naive/flawed way of understanding canjobear's statement: > Time is the direction in which entropy always increases. It's the most real thing there is.

I want to rephrase to, "if time doesn't exist, how do we know where things are?" or "if time doesn't exist, how do things move?" - which seem to get back to the 3-axes-plus-time description.

Agreed! In my mind, to go back in time is to put all particles or whatever fundamental components back in the same place and state as they were previously. Thus, that would include the particles that make up you as well. How would you ever do that and if you did, how would you notice and is it really the past or just now with a replicated state?

perhaps if there is order to the expansion of the universe and all its things you could contract it and theoretically cause all particles to shift back to their older states. i guess noticing is dependant on how much our consciousness is coupled to the physical

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