3 ms·

Seems like a lot of the problem with "time" is semantic. Do things change? Yes, and if that's the definition then it certainly exists. But people don't general

Seems like a lot of the problem with "time" is semantic. Do things change? Yes, and if that's the definition then it certainly exists. But people don't generally see time like that, they think of it as some medium, or 4th dimension, that can possibly be traveled through. This kind of time does not exist (as much as anything can't exist). There are only particles and their positions. Traveling back in time would require moving every particle in the universe back to the state you want to experience. But this is not "traditional" time travel, just god-like influence over particles. Traveling back in time, in how people fantasize about it, would require copies of the universe being made every plank-time, that you can visit. And even that is just another 3d space that happens to look like one you saw before. Time is chemical and physical reactions. The minimum amount of time (sorry) a reaction can take to happen is possibly plank-time. Nothing can "happen" faster than plank time. So time is possibly granular. If reactions stopped happening, time would stop. That's one set of views.

timcederman 10y ago
Time is very much a dimension. You should read up on relativity.
- semi-extrinsic 10y ago
  In relativity we can model time as a dimension, with great success. But even there it is always evident that the time dimension is very different from the spatial ones; for one, we cannot travel in it. I believe GP is only saying this is the problem, ignoring that the time dimension is very special.
  - witty_username 10y ago
    We can travel in it. We all are travelling in time and at different rates depending on our speed and gravity.
    - thinkloop 10y ago
      That's the sci-fi terminology and view that complicates and confuses the issue. Can reactions happen faster or slower, yes. No need to say "travel", that word has distinct meaning and connotations that lead to incorrect possibilities.
      - baytrailcat 10y ago
        You have unknowingly stumbled into the heart of Special Relativity :) "travel" is the same all dimensions. If you think you are moving from (x1,y1,z1) to (x2,y2,z2) you are actually moving from (x1,y1,z1,t1) to (x2,y2,z2,t2). If you think you are staying put at (x1,y1,z1), then you are continuously moving from (x1,y1,z1,t1) to (x1,y1,z1,t2) to (x1,y1,z1,t3) and so on. The more you move in space, the less you move in time. Also, when you put General Relativity in the picture, any sort of movement within this 4D space is possible (because the geometry of this space is wrapped) go to past, future, anything.
        thinkloop 10y ago
        Your comment perfectly crystalizes everything I'm trying to say. You explain the relationship of time to space very nicely and succinctly and correctly, however you decided to use the word "move", which comes with a lot of 3d baggage, which leads you to start thinking that "any sort of movement within this 4D space is possible". Nothing in relativity shows that freely moving back and forward in the time dimension is possible. The closest semblance is slowing your own time relative to other things you care about, so that, for example, you can have the body of a 30yr-old while earth is at 3000AD, but again that's not "traveling" around time, it's closer to putting food in the fridge so it spoils slower.
- thinkloop 10y ago
  I don't know if physicists do it on purpose to get published, or whether they've drank too much of the kool-aid, but "dimension" is another one of those terribly overloaded terms. String theorists say that the universe may have 11 dimensions. So cool! I wonder what's in them!? Maybe my childhood puppy is there! But do you know what they mean? Only that one or more of their equations had an exponent of 11. That's it. There is no correlation or evidence of that translating to physical, or interesting, dimensions that we think of.

timcederman 10y ago

Time is very much a dimension. You should read up on relativity.

semi-extrinsic 10y ago
In relativity we can model time as a dimension, with great success. But even there it is always evident that the time dimension is very different from the spatial ones; for one, we cannot travel in it. I believe GP is only saying this is the problem, ignoring that the time dimension is very special.
- witty_username 10y ago
  We can travel in it. We all are travelling in time and at different rates depending on our speed and gravity.
  - thinkloop 10y ago
    That's the sci-fi terminology and view that complicates and confuses the issue. Can reactions happen faster or slower, yes. No need to say "travel", that word has distinct meaning and connotations that lead to incorrect possibilities.
    - baytrailcat 10y ago
      You have unknowingly stumbled into the heart of Special Relativity :) "travel" is the same all dimensions. If you think you are moving from (x1,y1,z1) to (x2,y2,z2) you are actually moving from (x1,y1,z1,t1) to (x2,y2,z2,t2). If you think you are staying put at (x1,y1,z1), then you are continuously moving from (x1,y1,z1,t1) to (x1,y1,z1,t2) to (x1,y1,z1,t3) and so on. The more you move in space, the less you move in time. Also, when you put General Relativity in the picture, any sort of movement within this 4D space is possible (because the geometry of this space is wrapped) go to past, future, anything.
      - thinkloop 10y ago
        Your comment perfectly crystalizes everything I'm trying to say. You explain the relationship of time to space very nicely and succinctly and correctly, however you decided to use the word "move", which comes with a lot of 3d baggage, which leads you to start thinking that "any sort of movement within this 4D space is possible". Nothing in relativity shows that freely moving back and forward in the time dimension is possible. The closest semblance is slowing your own time relative to other things you care about, so that, for example, you can have the body of a 30yr-old while earth is at 3000AD, but again that's not "traveling" around time, it's closer to putting food in the fridge so it spoils slower.
thinkloop 10y ago
I don't know if physicists do it on purpose to get published, or whether they've drank too much of the kool-aid, but "dimension" is another one of those terribly overloaded terms. String theorists say that the universe may have 11 dimensions. So cool! I wonder what's in them!? Maybe my childhood puppy is there! But do you know what they mean? Only that one or more of their equations had an exponent of 11. That's it. There is no correlation or evidence of that translating to physical, or interesting, dimensions that we think of.