In your example about the two physics theories, it seems that you don’t really need observers. Indeed, simply replace observers by blue warbles.
Suppose T1 predicts trillion trillion blue warbles in the universe and T2 predicts trillion trillion trillion blue warbles (but both theories are agnostic about how and where they occur). Now, you send an expedition to Mars and find that Mars has several billion blue warbles. What does that mean for T1 vs T2? I would say that T2 is more likely as it assigned a higher prior probability that you’d generally find blue warbles.
I may be wrong, but it seems to me that blue warbles on Mars is entirely symmetrical to observers on Earth.
Not quite. T2 presumably predicts more warbles because it is bigger. If so, encountering some concentration of warbles doesn’t distinguish between the two, because they have the same warble-density.
On the other hand, if T2 predicts a billion times the density, then you might use local concentration as evidence, but it could go either way depending on predicted densities.
The thing is… Only one of the potential universes has any observers. Hypothetical observers have dont actually observe anything, which means that you cannot reason backwards from the number of observers each universe would in theory have.
If what the super-theory predicted was that both universes existed, but was agnostic about which bit of the multiverse you were in? Then you could make a guess based on the numbers (and a very large absolute number of observers would get it wrong). But that is not how this problem was posed. And given the way it was posed, at most one of the theories can be correct, and will be observed to be so by whichever percentage of its inhabitants get to that stage of understanding. The hypothetical inhabitants of the other universe have no bearing on the matter due to not existing.
In your example about the two physics theories, it seems that you don’t really need observers. Indeed, simply replace observers by blue warbles.
Suppose T1 predicts trillion trillion blue warbles in the universe and T2 predicts trillion trillion trillion blue warbles (but both theories are agnostic about how and where they occur). Now, you send an expedition to Mars and find that Mars has several billion blue warbles. What does that mean for T1 vs T2? I would say that T2 is more likely as it assigned a higher prior probability that you’d generally find blue warbles.
I may be wrong, but it seems to me that blue warbles on Mars is entirely symmetrical to observers on Earth.
Not quite. T2 presumably predicts more warbles because it is bigger. If so, encountering some concentration of warbles doesn’t distinguish between the two, because they have the same warble-density.
On the other hand, if T2 predicts a billion times the density, then you might use local concentration as evidence, but it could go either way depending on predicted densities.
The thing is… Only one of the potential universes has any observers. Hypothetical observers have dont actually observe anything, which means that you cannot reason backwards from the number of observers each universe would in theory have.
If what the super-theory predicted was that both universes existed, but was agnostic about which bit of the multiverse you were in? Then you could make a guess based on the numbers (and a very large absolute number of observers would get it wrong). But that is not how this problem was posed. And given the way it was posed, at most one of the theories can be correct, and will be observed to be so by whichever percentage of its inhabitants get to that stage of understanding. The hypothetical inhabitants of the other universe have no bearing on the matter due to not existing.
And hypothetical blue warbles don’t actually warble. What’s your point?