This is because the current position, direction, and speed of an atom (and all other measurements that can be done physically) are only possible with one and only one specific history of everything else in the universe.
This seems almost certainly false. You can measure those things to only finite precision—there is a limit to the number of bits you can get out of such a measurement. Suppose you measure position and velocity to one part in a billion in each of three dimensions. That’s only around 200 bits—hardly enough to distinguish all possible universal histories.
This is because, if we could measure them with full precision, the current position, direction, and speed of an atom (and all other measurements if we could do them physically) are only possible with one and only one specific history of everything else in the universe.
I will edit above.
Other than our ability to measure these dimensions I think that their current state is only possible with only one history of the universe since the beginning.
That is not at all true; for example, see the inverse problem (http://en.wikipedia.org/wiki/Inverse_problem). Although the atom’s position is uniquely determined by the rest of the universe, the inverse is not true: Multiple different states of the universe could correspond to the same position of the atom. And as long as the atom’s position does not uniquely identify the rest of the outside universe, there is no way to infer the state of the universe from the state of the atom, no matter how much precision you can measure it with. The reason is that there are many ways that the boundary conditions of a box containing an atom could be arranged, in order to force it to any position, meaning that there is a limited amount that the atom can tell you about its box.
The atom is affected by its local conditions (electromagnetic and gravitational fields, etc), but there are innumerable ways of establishing any particular desired fields locally to the atom.
This causes challenges when, for example, you want to infer the electrical brain activity in a patient based on measurements of electromagnetic fields at the surface. Unfortunately, there are multiple ways that electrical currents could have been arranged in three-dimensional space inside the brain to create the same observed measurements at the surface, so it’s not always possible to “invert” the measurements directly without some other knowledge. This isn’t a problem of measurement precision; a finer grid of electrodes won’t solve it (although it may help rule out some possibilities).
Since I am not a scientist I didn’t know about the inverse problem, but I had thought about that intuitively.
I think it’s true that a current state of an atom, in a 3 dimensional context, may be achieved through multiple histories or even manipulated by a living being who wants to “cheat the system”.
But in a 4 dimensional context, where the coordinates on a base field (maybe Higgs field), which could also be called time, are included, that would eliminate the possibility of recreating the same position for different stories since time happens only once, in a forward motion, and thus making that state unique and irreplaceable.
I think a position of height x, width y, and depth z is replicable the way you say above.
But, is a position of height x, width y, depth z, at time w (considering a single time line since the big bang) replicable?
If yes then the inverse problem refutes my original idea in this thread, if not IMO it is still possible to reverse-understand the universe that way.
This seems almost certainly false. You can measure those things to only finite precision—there is a limit to the number of bits you can get out of such a measurement. Suppose you measure position and velocity to one part in a billion in each of three dimensions. That’s only around 200 bits—hardly enough to distinguish all possible universal histories.
I agree, I should have written a conditional:
I will edit above.
Other than our ability to measure these dimensions I think that their current state is only possible with only one history of the universe since the beginning.
That is not at all true; for example, see the inverse problem (http://en.wikipedia.org/wiki/Inverse_problem). Although the atom’s position is uniquely determined by the rest of the universe, the inverse is not true: Multiple different states of the universe could correspond to the same position of the atom. And as long as the atom’s position does not uniquely identify the rest of the outside universe, there is no way to infer the state of the universe from the state of the atom, no matter how much precision you can measure it with. The reason is that there are many ways that the boundary conditions of a box containing an atom could be arranged, in order to force it to any position, meaning that there is a limited amount that the atom can tell you about its box.
The atom is affected by its local conditions (electromagnetic and gravitational fields, etc), but there are innumerable ways of establishing any particular desired fields locally to the atom.
This causes challenges when, for example, you want to infer the electrical brain activity in a patient based on measurements of electromagnetic fields at the surface. Unfortunately, there are multiple ways that electrical currents could have been arranged in three-dimensional space inside the brain to create the same observed measurements at the surface, so it’s not always possible to “invert” the measurements directly without some other knowledge. This isn’t a problem of measurement precision; a finer grid of electrodes won’t solve it (although it may help rule out some possibilities).
Thx so much for the link above!
Since I am not a scientist I didn’t know about the inverse problem, but I had thought about that intuitively.
I think it’s true that a current state of an atom, in a 3 dimensional context, may be achieved through multiple histories or even manipulated by a living being who wants to “cheat the system”.
But in a 4 dimensional context, where the coordinates on a base field (maybe Higgs field), which could also be called time, are included, that would eliminate the possibility of recreating the same position for different stories since time happens only once, in a forward motion, and thus making that state unique and irreplaceable.
I think a position of height x, width y, and depth z is replicable the way you say above.
But, is a position of height x, width y, depth z, at time w (considering a single time line since the big bang) replicable?
If yes then the inverse problem refutes my original idea in this thread, if not IMO it is still possible to reverse-understand the universe that way.
Ah, hmm.… Maybe! If you include the entire history of the atom, then I’m not actually sure. That’s a tough question, and a good question =)