3 ms·

2 things: 1) If we define "universe" as "everything that exists" then you cannot record everything that happens. Because the record would be part of the univer

2 things: 1) If we define "universe" as "everything that exists" then you cannot record everything that happens. Because the record would be part of the universe and would have to recorded and the record of the record would have to be recorded... 2) The "first" and "second" universes would not be universes on their own. The "second" is a continuation of what you call the "first". So the system you describe would be random. Because the "deterministic" things that happen later on are based on the random things that happened earlier.

jblow 13y ago
Just pause for a moment on "everything that exists" because that is not necessarily a useful distinction. If you think of a universe as "everything I could see/touch/etc given infinite time", someone outside the universe who was in control of it might record it with no problem because they are not subject to the constraints of the universe. e.g. imagine the universe as being like a computer simulation that you programmed. You can probably pause it in a debugger any time you want, look at whatever state variables you want, etc. So in this case the definition cannot be "everything that exists" because you have to define "exists" in the case where different sets of things may have different levels of "reality".
- no_gravity 13y ago
  Lets say we are in a "game of life" simulation on a computer. It has been proven turing complete. So you would say its deterministic because "game of life" has deterministic rules. But if the computer that runs the simulation is in a random universe, then it might happen that bits of the computer switch in a random fashion. Making our universe inside the "game of life" simulation random too. And we could touch the randomly flipping bits. So there is no point in saying something is "outside" our universe and something is "inside".
  - jblow 13y ago
    There is no point to saying something is "outside" and something is "inside" in the extreme cases of the example you just gave, which may or may not be the case. What if the outer universe is not a random universe? What if its laws of nature are so unlike ours that we do not know what to say about it? (Maybe it does not have space or time, but it has other things instead.) But I think this is a little bit beside the point, because as I mentioned in my first post, all of this is predicated on us adopting the naïve view of time in our own universe, which is maybe not the best idea, given that we have plenty of evidence otherwise. (And anyway, if you believe that "everything that exists" can be infinite, then there is no sense in saying our universe is being produced by some kind of simulation controlled in one particular other place, because of course it is, but actually this is probably happening in an infinite number of different ways from different places such that there is not really point any more in claiming that this is happening at all; the situation becomes such that you could just draw a relation between situation X and situation Y and could state that one could be causal of the other from a certain point of view.)
dmgd 13y ago
with 1) it seems like what you're saying is that given a closed system, you cannot accurately observe and record the whole state of that system within the system itself. This feels right on the surface, but is it actually true? A quine contains a complete record of itself. That's an extreme case to be sure, but it does seem to provide at least one counterexample . . . (of a system that contains itself, not necessarily a system that actually observes and records itself) A recording of a system does not need to contain everything in order for that recording to by played back, as long as the replay system is deterministic -- you just need to record the random inputs. E.g. see the way they do it in video games [http://www.gamedev.net/topic/439336-replay-system/ http://www.gamedev.net/topic/439336-replay-system/] I'm not saying that it is possible, just it shouldn't be dismissed out of hand just because it feels like it should be impossible.
barrkel 13y ago
You're caught up in a sophistry rooted in the meaning of words. It doesn't convince anyone. By assuming a different definition of "universe" to the person you're replying to, you're not actually addressing what they're saying. Assume, for the purpose of human communication, that "universe" means "a collection of all matter and space that can ever be observed or interacted with by an observer within and part of that universe".

jblow 13y ago

Just pause for a moment on "everything that exists" because that is not necessarily a useful distinction. If you think of a universe as "everything I could see/touch/etc given infinite time", someone outside the universe who was in control of it might record it with no problem because they are not subject to the constraints of the universe. e.g. imagine the universe as being like a computer simulation that you programmed. You can probably pause it in a debugger any time you want, look at whatever state variables you want, etc. So in this case the definition cannot be "everything that exists" because you have to define "exists" in the case where different sets of things may have different levels of "reality".

no_gravity 13y ago
Lets say we are in a "game of life" simulation on a computer. It has been proven turing complete. So you would say its deterministic because "game of life" has deterministic rules. But if the computer that runs the simulation is in a random universe, then it might happen that bits of the computer switch in a random fashion. Making our universe inside the "game of life" simulation random too. And we could touch the randomly flipping bits. So there is no point in saying something is "outside" our universe and something is "inside".
- jblow 13y ago
  There is no point to saying something is "outside" and something is "inside" in the extreme cases of the example you just gave, which may or may not be the case. What if the outer universe is not a random universe? What if its laws of nature are so unlike ours that we do not know what to say about it? (Maybe it does not have space or time, but it has other things instead.) But I think this is a little bit beside the point, because as I mentioned in my first post, all of this is predicated on us adopting the naïve view of time in our own universe, which is maybe not the best idea, given that we have plenty of evidence otherwise. (And anyway, if you believe that "everything that exists" can be infinite, then there is no sense in saying our universe is being produced by some kind of simulation controlled in one particular other place, because of course it is, but actually this is probably happening in an infinite number of different ways from different places such that there is not really point any more in claiming that this is happening at all; the situation becomes such that you could just draw a relation between situation X and situation Y and could state that one could be causal of the other from a certain point of view.)

dmgd 13y ago

with 1) it seems like what you're saying is that given a closed system, you cannot accurately observe and record the whole state of that system within the system itself. This feels right on the surface, but is it actually true? A quine contains a complete record of itself. That's an extreme case to be sure, but it does seem to provide at least one counterexample . . . (of a system that contains itself, not necessarily a system that actually observes and records itself) A recording of a system does not need to contain everything in order for that recording to by played back, as long as the replay system is deterministic -- you just need to record the random inputs. E.g. see the way they do it in video games [http://www.gamedev.net/topic/439336-replay-system/ http://www.gamedev.net/topic/439336-replay-system/] I'm not saying that it is possible, just it shouldn't be dismissed out of hand just because it feels like it should be impossible.

barrkel 13y ago

You're caught up in a sophistry rooted in the meaning of words. It doesn't convince anyone. By assuming a different definition of "universe" to the person you're replying to, you're not actually addressing what they're saying. Assume, for the purpose of human communication, that "universe" means "a collection of all matter and space that can ever be observed or interacted with by an observer within and part of that universe".