3 ms·

> are traveling through a 4D space Huh? My standard interpretation of "4D" in this kind of context is spacetime. But one doesn't "travel" through spacetime; o

> are traveling through a 4D space Huh? My standard interpretation of "4D" in this kind of context is spacetime. But one doesn't "travel" through spacetime; one's entire journey "just is". https://en.wikipedia.org/wiki/Slaughterhouse-Five#Tralfamadorian_philosophy https://en.wikipedia.org/wiki/Slaughterhouse-Five#Tralfamado...

denton-scratch 2y ago
Hey, vote me down to oblivion if you want; I don't care. But I think it's nice to say why. What have I misunderstood? Is this a 4D space in a 5D spacetime? Is "block spacetime" discredited? I thought the parent comment sounded weird, as if I'd missed some important context.
- dsabanin 2y ago
  To me the main problem with “traveling through 4D” is the fact that “traveling” is happening in the 4-th dimension.
  - merely-unlikely 2y ago
    Isn’t traveling happening in all 4 dimensions?
    - lazide 2y ago
      Well, one of them (time) is moving forward at a steady yet unchanging rate. It’s rare to call that ‘traveling’ since it isn’t meaningfully in control of the traveler. More like ‘bring drug along in’
      - nordsieck 2y ago
        > Well, one of them (time) is moving forward at a steady yet unchanging rate. If you want to be technically correct, my understanding is that everything moves through spacetime with a constant vector - the faster you move through space, the slower you move through time and vise versa. We just don't notice (typically) because the effect isn't particularly pronounced below 0.01C. But I believe that GPS satellites do take this effect into account.
        lazide 2y ago
        Would you describe our current level of technology as allowing controlled travel in this vector (say, being able to ‘go back’, or ‘go forward’), or merely notice and account for side effects in it related to things they are already doing for other reasons?
        nordsieck 2y ago
        > Would you describe our current level of technology as allowing controlled travel in this vector (say, being able to ‘go back’, or ‘go forward’), or merely notice and account for side effects in it related to things they are already doing? 1. You can only go forward in time to varying degrees, never back. 2. Like I said above, we are technically always varying our speed through time. It's just that the effect is difficult to notice because the size of the effect is small.
        lazide 2y ago
        And you get back to my comment.
        denton-scratch 2y ago
        > 1. You can only go forward in time to varying degrees, never back. That's what we seem to observe; but I'm not aware of any reason why that should be so a priori, and I don't know what kind of evidence would be conclusive, either this way or that.
        nordsieck 2y ago
        > That's what we seem to observe; but I'm not aware of any reason why that should be so a priori, and I don't know what kind of evidence would be conclusive, either this way or that. This is my personal opinion, not an "official" physics opinion, but I think that the second law of thermodynamics creates a ratchet that prevents movement backwards in time.
        2y ago
jerf 2y ago
The big thread arguing about "travelling" through 4D is missing the point. The point I was making is, accounting for the fact everything is travelling does not make their footprint particularly larger, because then you also have to account for time in the total spacetime they could be in instead of just the space they could be in. Arguing about the English for a case English doesn't have words for anyhow is not particularly relevant.

denton-scratch 2y ago

Hey, vote me down to oblivion if you want; I don't care. But I think it's nice to say why. What have I misunderstood? Is this a 4D space in a 5D spacetime? Is "block spacetime" discredited? I thought the parent comment sounded weird, as if I'd missed some important context.

dsabanin 2y ago
To me the main problem with “traveling through 4D” is the fact that “traveling” is happening in the 4-th dimension.
- merely-unlikely 2y ago
  Isn’t traveling happening in all 4 dimensions?
  - lazide 2y ago
    Well, one of them (time) is moving forward at a steady yet unchanging rate. It’s rare to call that ‘traveling’ since it isn’t meaningfully in control of the traveler. More like ‘bring drug along in’
    - nordsieck 2y ago
      > Well, one of them (time) is moving forward at a steady yet unchanging rate. If you want to be technically correct, my understanding is that everything moves through spacetime with a constant vector - the faster you move through space, the slower you move through time and vise versa. We just don't notice (typically) because the effect isn't particularly pronounced below 0.01C. But I believe that GPS satellites do take this effect into account.
      - lazide 2y ago
        Would you describe our current level of technology as allowing controlled travel in this vector (say, being able to ‘go back’, or ‘go forward’), or merely notice and account for side effects in it related to things they are already doing for other reasons?
        nordsieck 2y ago
        > Would you describe our current level of technology as allowing controlled travel in this vector (say, being able to ‘go back’, or ‘go forward’), or merely notice and account for side effects in it related to things they are already doing? 1. You can only go forward in time to varying degrees, never back. 2. Like I said above, we are technically always varying our speed through time. It's just that the effect is difficult to notice because the size of the effect is small.
        lazide 2y ago
        And you get back to my comment.
        denton-scratch 2y ago
        > 1. You can only go forward in time to varying degrees, never back. That's what we seem to observe; but I'm not aware of any reason why that should be so a priori, and I don't know what kind of evidence would be conclusive, either this way or that.
        nordsieck 2y ago
        > That's what we seem to observe; but I'm not aware of any reason why that should be so a priori, and I don't know what kind of evidence would be conclusive, either this way or that. This is my personal opinion, not an "official" physics opinion, but I think that the second law of thermodynamics creates a ratchet that prevents movement backwards in time.
        2y ago

jerf 2y ago

The big thread arguing about "travelling" through 4D is missing the point. The point I was making is, accounting for the fact everything is travelling does not make their footprint particularly larger, because then you also have to account for time in the total spacetime they could be in instead of just the space they could be in. Arguing about the English for a case English doesn't have words for anyhow is not particularly relevant.