The discussion centers on the many-worlds interpretation (MWI) of quantum mechanics, particularly addressing concerns about energy conservation across infinite universes. Participants argue that energy is conserved within each world and that the superposition of states does not lead to energy depletion. The conversation references key concepts such as decoherence, the Born rule, and the work of David Deutsch, highlighting ongoing debates about the interpretation of probability in quantum mechanics. The consensus indicates that while MWI is speculative, it provides a framework for understanding quantum phenomena without violating conservation laws.
PREREQUISITESPhysicists, quantum mechanics students, and anyone interested in the philosophical implications of the many-worlds interpretation and its impact on energy conservation discussions in quantum theory.
JesseM said:
That would be an argument for moral nihilism! Just because there is some world where you become a serial killer that doesn't mean you might as well do it here, since after all your decisions are shaped by personality and beliefs and these things make some actions far more likely than others. David Deutsch expresses his attitude towards morality in the context of the MWI http://www.kurzweilai.net/articles/art0268.html when he says "By making good choices, doing the right thing, we thicken the stack of universes in which versions of us live reasonable lives. When you succeed, all the copies of you who made the same decision succeed too. What you do for the better increases the portion of the multiverse where good things happen."vanesch said:
JesseM said:
So you think the effect of my actions on others is irrelevant? (and yes, this is drifting from the main thread topic, maybe it'd be better if the posts on morality and the MWI were split off and moved to the philosophy forum...) If so I'd disagree, whatever decisions now influence the total number of copies stemming from this moment, and can influence the number of copies of people around me who are affected positively or negatively by my choices. This is exactly David Deutsch's argument, as I understood it.vanesch said:
It's true that if you're most concerned with avoiding causing suffering, then even in a single probabilistic universe you should avoid taking risks which could lead to such suffering, so for a perfectly rational being the existence or nonexistence of other worlds shouldn't affect their moral choices. Still, the real existence of other worlds where a particular risk--say, not wearing a seatbelt on one car trip--leads to such suffering might make the issue a little more emotionally vivid for some people, and encourage them to actually try to live up to their moral standard at all times, which we as not-perfectly-rational-beings have trouble doing.vanesch said:
JesseM said:
Does that mean, for example, that you would have no problem with leaving a hidden nuclear bomb under a major city, with a timer set to make it explode in 200 years? Since you probably won't live that long (ignoring quantum immortalityvanesch said:
), the negative effects are purely hypothetical to you, but I think most people would consider this highly immoral.
I don't expect that the precise details of the MWI will survive to the "next physical theory", but in broad strokes, the violation of Bell's inequality in QM suggest only a few different options for any theory/interpretation which preserves them and still describes some sort of objective reality--"hidden" nonlocal communication between separated particles, backwards-in-time influences of the measurement on the original traits of the particles when they were created, weird conspiracies in the initial conditions of the universe, of local splits in each experimenter (with the copies of each experimenter only needing to be matched up once a signal has had time to pass between them, so that locality is actually preserved). It looks to me like the universe goes to a lot of trouble to avoid the possibility of FTL signalling at the overt level so "hidden" FTL signalling seems sort of klunky and inelegant, and conspiracies in initial conditions seem doubly inelegant, so I'd bet on either the backwards-in-time explanation or the splitting-copies explanation, and of the two the latter seems more likely to me, since there are also a lot of strong hints that chronology protection is also built into the laws of physics in a basic way (plus the difference between allowing 'hidden' backwards-in-time signals and allowing 'hidden' FTL signals seems cosmetic, since a nonhidden ability to send information backwards in time would naturally lead to a nonhidden ability to send information faster than light).vanesch said:
Wasn't Deutsch just talking about different position-states in the superposition that is a photon's wavefunction between measurements? Or different paths in the Feynman path integral for a photon, perhaps? Either way, these are standard ideas, it'd just be a philosophical question whether you choose to view them as "real" or just elements of a calculation used in predicting the photon's position when you do measure it.reilly said:
As I understand it, "many worlds" is somewhat deceptive in that there's really only one big wavefunction for the entire universe, and the appearance of different "worlds" is subjective, having to do with the notion that decoherence causes macroscopically different states in this huge superposition to no longer "interact" (i.e. interfere) in a way that's practical for anyone to detect. But they never really stop interfering even if this interference is too hard for us to measure, so they aren't really wholly separate.reilly said:
JesseM said:Does that mean, for example, that you would have no problem with leaving a hidden nuclear bomb under a major city, with a timer set to make it explode in 200 years? Since you probably won't live that long (ignoring quantum immortality
)