5 ms·

Drifting off topic but something about that comic is confusing. Surely by putting down rocks to represent the computation is he is not simulating the Universe,

Drifting off topic but something about that comic is confusing. Surely by putting down rocks to represent the computation is he is not simulating the Universe, only describing a simulation of it. In the case of the cardboard and marbles there is a physical process by which the program is executed, in this case the only way it is executed is in the mind of the guy. Or is that the point?

simcop2387 10y ago
I think the simulation is as much in the rocks as it is in the head of the guy doing it. The rocks would have an infinite size but it doesn't need to be in the head of the guy for him to compute it.
zeroer 10y ago
The question you're asking is essentially the same as the Chinese room thought experiment. My interpretation is that the system of the stones plus the mind of the guy together make up the program, when neither alone can.
seiferteric 10y ago
You could just as easily say a computer simulation is only describing a simulation by holding bits in memory.
fizixer 10y ago
One row represents one instant of "the machine". By adding another row below it, the human is doing the execution very very very slowly. Actually, depending on the rules, there is no need for more than one row to be present at any time. When the human starts working on the next row, (s)he can remove the rocks from the previous row after using up its information. "Depending on the rules" means the future state (next row) is completely defined by one previous state (one previous row). This still allows one to make a turing machine. An example where one previous state is not enough is Newtonian mechanics, where you need, not just previous positions, but also previous velocities, or, equivalently, the second to last row as well. (note: the physics in the comic is being simulated on top of the turing machine, so it's not a problem for this comic). Minor nitpick: Someone who is smart enough to crack quantum mechanics, and build a "manual" computer when alone, should be smart enough to figure out a way to find a source of energy so the computation happens automatically.
- j1vms 10y ago
  > Minor nitpick: Someone who is smart enough to crack quantum mechanics, and build a "manual" computer when alone, should be smart enough to figure out a way to find a source of energy so the computation happens automatically. Not to take this xkcd too seriously but: if he were truly there for infinity (that is, the duration of his existence is infinite), then he wouldn't be in any hurry. Another way to put it is that, in the steady-state sense of things, no means of computation is "noticeably" faster to him than any other (only relatively faster). Consider that any time difference between events (e.g. the termination of the same calculation performed by different mechanisms) would be infinitesimal compared to the duration of his infinite existence. Also, interestingly, since he is there for eternity then his existence does not really have a start time or end time, as far as he's concerned. If he wanted to have some real fun with infinity, he might kick off a couple of interacting harmonics in the sand, maybe watch them interact, as anything else - finite - cannot last.
industriousthou 10y ago
I got the impression that he was simulating _our_ universe, not _the_ universe. In other worlds, the laws of physics, etc, in our universe might only exist in a rock simulation in some other universe with very different properties (unlimited spaces and time, etc).

simcop2387 10y ago

I think the simulation is as much in the rocks as it is in the head of the guy doing it. The rocks would have an infinite size but it doesn't need to be in the head of the guy for him to compute it.

zeroer 10y ago

The question you're asking is essentially the same as the Chinese room thought experiment. My interpretation is that the system of the stones plus the mind of the guy together make up the program, when neither alone can.

seiferteric 10y ago

You could just as easily say a computer simulation is only describing a simulation by holding bits in memory.

fizixer 10y ago

One row represents one instant of "the machine". By adding another row below it, the human is doing the execution very very very slowly. Actually, depending on the rules, there is no need for more than one row to be present at any time. When the human starts working on the next row, (s)he can remove the rocks from the previous row after using up its information. "Depending on the rules" means the future state (next row) is completely defined by one previous state (one previous row). This still allows one to make a turing machine. An example where one previous state is not enough is Newtonian mechanics, where you need, not just previous positions, but also previous velocities, or, equivalently, the second to last row as well. (note: the physics in the comic is being simulated on top of the turing machine, so it's not a problem for this comic). Minor nitpick: Someone who is smart enough to crack quantum mechanics, and build a "manual" computer when alone, should be smart enough to figure out a way to find a source of energy so the computation happens automatically.

j1vms 10y ago
> Minor nitpick: Someone who is smart enough to crack quantum mechanics, and build a "manual" computer when alone, should be smart enough to figure out a way to find a source of energy so the computation happens automatically. Not to take this xkcd too seriously but: if he were truly there for infinity (that is, the duration of his existence is infinite), then he wouldn't be in any hurry. Another way to put it is that, in the steady-state sense of things, no means of computation is "noticeably" faster to him than any other (only relatively faster). Consider that any time difference between events (e.g. the termination of the same calculation performed by different mechanisms) would be infinitesimal compared to the duration of his infinite existence. Also, interestingly, since he is there for eternity then his existence does not really have a start time or end time, as far as he's concerned. If he wanted to have some real fun with infinity, he might kick off a couple of interacting harmonics in the sand, maybe watch them interact, as anything else - finite - cannot last.

industriousthou 10y ago

I got the impression that he was simulating _our_ universe, not _the_ universe. In other worlds, the laws of physics, etc, in our universe might only exist in a rock simulation in some other universe with very different properties (unlimited spaces and time, etc).