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Your position is inconsistent: the arrangement of particles changing is time, so your explanation of there not being time... asserts that time happens! Putting

Your position is inconsistent: the arrangement of particles changing is time, so your explanation of there not being time... asserts that time happens! Putting the universe back as it was except for you is time travel. You've traveled your state to a different time (previous state) of the universe. Your semantic game sounds very clever, but is actually just inconsistent and borderline ignorant of what people mean by those terms.

thinkloop 10y ago
> Putting the universe back as it was except for you is time travel. You've traveled your state to a different time (previous state) of the universe. > Your semantic game sounds very clever, but is actually just inconsistent and borderline ignorant of what people mean by those terms. I don't think that's how most people think of time travel. For example, say I proceeded to invoke reactions to get all particles back to exactly how they were on Jan.1 2000. Say this took me a year, and finally, in 2018, I execute the final reaction that places the last particle, so that the universe is exactly like it was Jan.1, 2000. Have I been time travelling for a year? Does making 2018 look like 2000 what people generally think of as time travel? What about that you yourself did not change, where are those particles coming from? What about the old you existing in that time as well, there aren't enough particles in the universe to have two you's. What about the time you travelled from remaining in existence while you're gone, and the changes you invoke in the "past" propagating there? I get that it would provide a similar experience in many ways, but it doesn't involve travelling, nor time, just changes in particle positions - which is the nuance I am highlighting.
- SomeStupidPoint 10y ago
  You have to give up the idea of a universal clock: you only have a local one. In your example: since you erased the elapsed computation in other regions, you (by putting the particles back) are literally rewinding every clock but yours. In whatever sense they were ever in 2000, they're back there, though you're in (your) 2018. Having your 2018 be their 2000 seems like a sensible definition of time travel. (And yes, you'd have spent a year time traveling, though in many senses you always are time traveling forward, and you just happened to spend a year going fast "backwards".) For the rest of your points, I agree that they're sensible objections to being able to do it, but they don't make the concept not mean anything, which was your original point. Why would the future remain? You destroyed it when you time traveled, and any changes in the future would require time traveling forward to see. (Forward is less erasure heavy, because you're just stalling instead of rewinding.) It's not just a similar experience, it's the literal definition of what that term means. > nor time, just changes in particle positions Uh... It's comments like this which makes me question your position. Changes in particle positions is time! Literally: time is just that thing a clock does, which is tick. If particles change position, that's (by definition) time.
YCode 10y ago
I think what he means is that time exists in the way that distance or speed exists. It's not a physical force like gravity or magnetism that acts upon the universe, it's just a method for us to understand and quantify what happens around us. Traveling back in time subsequently doesn't make sense because the "past" is simply what we call previous configurations of matter. You can't go back to those configurations (read: "go back in time") because they don't exist anymore. Now, I'm not a physicist so I have no idea if he's correct, but semantically it makes sense and it's something I've wondered about for a while.
- SomeStupidPoint 10y ago
  > Traveling back in time subsequently doesn't make sense because the "past" is simply what we call previous configurations of matter. So? If my future goes from the world as it is now to the world as it was in 2000, in what sense am I not in 2000? I mean, you guys seem to be under the impression that there's a single universal clock I cant reset... There's not. In whatever sense it ever was 2000, rewinding all the clocks would make it 2000 again. There's no clock besides those local ones, so if you reset them all, you're in the past (in whatever sense there was ever a past). I just find it particularly silly to have said there's no time when you keep commenting on time happening. (Also, does traveling a foot to the left not make sense because there's no distance, just past states Ive been in? Cause you said time was like distance, and you're right: both exist or neither exist in exactly the same sense.)
  - YCode 10y ago
    Unlike distance, time is unidirectional. Yes, if you could roll back all matter, energy and every other force in the universe you could "go back in time" but the point is that time is a concept and not a force of nature. It seems like you're being obtuse about the distinction.
    - SomeStupidPoint 10y ago
      Your position is just semantic games: traveling to a past state of the universe and living there is time travel -- you translated your state in to a past configuration of the universe. You're just sitting there whining how what both scientists and lay people would accept as time travel (living in the past) isnt Real Time Travel, because it's not some fictionalized Platonic ideal you've constructed and insist is the One True Meaning. Amature science people are the worst: a little knowledge keeps you from seeing the picture.

thinkloop 10y ago

> Putting the universe back as it was except for you is time travel. You've traveled your state to a different time (previous state) of the universe. > Your semantic game sounds very clever, but is actually just inconsistent and borderline ignorant of what people mean by those terms. I don't think that's how most people think of time travel. For example, say I proceeded to invoke reactions to get all particles back to exactly how they were on Jan.1 2000. Say this took me a year, and finally, in 2018, I execute the final reaction that places the last particle, so that the universe is exactly like it was Jan.1, 2000. Have I been time travelling for a year? Does making 2018 look like 2000 what people generally think of as time travel? What about that you yourself did not change, where are those particles coming from? What about the old you existing in that time as well, there aren't enough particles in the universe to have two you's. What about the time you travelled from remaining in existence while you're gone, and the changes you invoke in the "past" propagating there? I get that it would provide a similar experience in many ways, but it doesn't involve travelling, nor time, just changes in particle positions - which is the nuance I am highlighting.

SomeStupidPoint 10y ago
You have to give up the idea of a universal clock: you only have a local one. In your example: since you erased the elapsed computation in other regions, you (by putting the particles back) are literally rewinding every clock but yours. In whatever sense they were ever in 2000, they're back there, though you're in (your) 2018. Having your 2018 be their 2000 seems like a sensible definition of time travel. (And yes, you'd have spent a year time traveling, though in many senses you always are time traveling forward, and you just happened to spend a year going fast "backwards".) For the rest of your points, I agree that they're sensible objections to being able to do it, but they don't make the concept not mean anything, which was your original point. Why would the future remain? You destroyed it when you time traveled, and any changes in the future would require time traveling forward to see. (Forward is less erasure heavy, because you're just stalling instead of rewinding.) It's not just a similar experience, it's the literal definition of what that term means. > nor time, just changes in particle positions Uh... It's comments like this which makes me question your position. Changes in particle positions is time! Literally: time is just that thing a clock does, which is tick. If particles change position, that's (by definition) time.

YCode 10y ago

I think what he means is that time exists in the way that distance or speed exists. It's not a physical force like gravity or magnetism that acts upon the universe, it's just a method for us to understand and quantify what happens around us. Traveling back in time subsequently doesn't make sense because the "past" is simply what we call previous configurations of matter. You can't go back to those configurations (read: "go back in time") because they don't exist anymore. Now, I'm not a physicist so I have no idea if he's correct, but semantically it makes sense and it's something I've wondered about for a while.

SomeStupidPoint 10y ago
> Traveling back in time subsequently doesn't make sense because the "past" is simply what we call previous configurations of matter. So? If my future goes from the world as it is now to the world as it was in 2000, in what sense am I not in 2000? I mean, you guys seem to be under the impression that there's a single universal clock I cant reset... There's not. In whatever sense it ever was 2000, rewinding all the clocks would make it 2000 again. There's no clock besides those local ones, so if you reset them all, you're in the past (in whatever sense there was ever a past). I just find it particularly silly to have said there's no time when you keep commenting on time happening. (Also, does traveling a foot to the left not make sense because there's no distance, just past states Ive been in? Cause you said time was like distance, and you're right: both exist or neither exist in exactly the same sense.)
- YCode 10y ago
  Unlike distance, time is unidirectional. Yes, if you could roll back all matter, energy and every other force in the universe you could "go back in time" but the point is that time is a concept and not a force of nature. It seems like you're being obtuse about the distinction.
  - SomeStupidPoint 10y ago
    Your position is just semantic games: traveling to a past state of the universe and living there is time travel -- you translated your state in to a past configuration of the universe. You're just sitting there whining how what both scientists and lay people would accept as time travel (living in the past) isnt Real Time Travel, because it's not some fictionalized Platonic ideal you've constructed and insist is the One True Meaning. Amature science people are the worst: a little knowledge keeps you from seeing the picture.