Taken as a whole Everett’s multiverse, where all things happen, probability is not a useful concept and everything is deterministic. However for observers like us trapped in a single branch of the multiverse, observers who do not have access to the entire wave function and all the information it contains but only a small sliver of it, probability is the best we can do.
I am unable to imagine an interpretation of this paragraph that makes it true.
Probability would be necessary for belief formation even if reality consisted of only a single world. More generally, the usefulness of probability to belief formation does not depend on any particular features or properties of the reality the belief-forming agent (or collection of agents, e.g., the people having this conversation) happens to find itself in (except for the trivial consideration that some realities cannot contain belief-forming agents).
Also, I am extremely skeptical that literally all things happen in the Everettian multiverse. For example, I would be extremely surprised if there exists or will ever exist a branch in which the law of the conservation of momentum is violated. The principle of charity demands that I assume that the OP (johnclark) knows that, but I have been in enough conversations on LW about many worlds to have strong evidence that some of the readers will take “all things happen” literally.
I consider it true that probability is in the mind and that when taken as a whole, reality does not contain probabilities. In that sense, John Clark’s statement, “Taken as a whole Everett’s multiverse . . . probability is not a useful concept and everything is deterministic,” is true. What I am extremely skeptical of is whether that truth depends somehow on the fact that our reality consists of branches that are constantly splitting or depends somehow on that fact that Schroedinger’s equation applies to our reality.
Some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant. The speed of light. The gravitational (big G) constant. The mass of the electron, proton, and neutron. The electrical charge on the proton and electron.
The inverse square law of gravity and electromagnetism. The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge.The relative strength of the 4 forces of nature. The number of large dimensions in a universe.
The Hubble constant.
The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
Some of the laws of physics could change from universe to universe
I will assume that by “universe” here you mean “Everett branch”.
I agree that they could (with low probability), just as they could slowly change over time or be different billions of light years away. This is a possibility because our reality has a property that physicists call locality. What I object to is the belief, which more than a handful of LW and SL4 participants hold, that there is something about many worlds (or about quantum mechanics for that matter) that increases the probability of stuff like that happening above what it would be if our reality had this locality property but no Everett branching.
should increase the probability we assign to stuff like that happening.
I understand that some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant.
The speed of light.
The gravitational (big G) constant.
The mass of the electron, proton, and neutron.
The electrical charge on the proton and electron.
The inverse square law of gravity and electromagnetism. The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge.
The relative strength of the 4 forces of nature.
The number of large dimensions in a universe.
The Hubble constant.
The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
Some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant.
The speed of light.
The gravitational (big G) constant.
The mass of the electron, proton, and neutron.
The electrical charge on the proton and electron.
The inverse square law of gravity and electromagnetism. The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge.
The relative strength of the 4 forces of nature.
The number of large dimensions in a universe.
The Hubble constant.
The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
I am unable to imagine an interpretation of this paragraph that makes it true.
Probability would be necessary for belief formation even if reality consisted of only a single world. More generally, the usefulness of probability to belief formation does not depend on any particular features or properties of the reality the belief-forming agent (or collection of agents, e.g., the people having this conversation) happens to find itself in (except for the trivial consideration that some realities cannot contain belief-forming agents).
Also, I am extremely skeptical that literally all things happen in the Everettian multiverse. For example, I would be extremely surprised if there exists or will ever exist a branch in which the law of the conservation of momentum is violated. The principle of charity demands that I assume that the OP (johnclark) knows that, but I have been in enough conversations on LW about many worlds to have strong evidence that some of the readers will take “all things happen” literally.
Clarification of parent:
I consider it true that probability is in the mind and that when taken as a whole, reality does not contain probabilities. In that sense, John Clark’s statement, “Taken as a whole Everett’s multiverse . . . probability is not a useful concept and everything is deterministic,” is true. What I am extremely skeptical of is whether that truth depends somehow on the fact that our reality consists of branches that are constantly splitting or depends somehow on that fact that Schroedinger’s equation applies to our reality.
Some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant. The speed of light. The gravitational (big G) constant. The mass of the electron, proton, and neutron. The electrical charge on the proton and electron. The inverse square law of gravity and electromagnetism. The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge.The relative strength of the 4 forces of nature. The number of large dimensions in a universe. The Hubble constant. The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
John K Clark
I will assume that by “universe” here you mean “Everett branch”.
I agree that they could (with low probability), just as they could slowly change over time or be different billions of light years away. This is a possibility because our reality has a property that physicists call locality. What I object to is the belief, which more than a handful of LW and SL4 participants hold, that there is something about many worlds (or about quantum mechanics for that matter) that increases the probability of stuff like that happening above what it would be if our reality had this locality property but no Everett branching.
should increase the probability we assign to stuff like that happening.
There is also the
I understand that some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant. The speed of light. The gravitational (big G) constant. The mass of the electron, proton, and neutron. The electrical charge on the proton and electron. The inverse square law of gravity and electromagnetism.
The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge. The relative strength of the 4 forces of nature. The number of large dimensions in a universe. The Hubble constant. The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
John K Clark
Some of the laws of physics could change from universe to universe, but there must be some laws that remain invariant across the entire multiverse because without rules it would behave chaotically and if the multiverse behaved that way so would all the universes in it, including ours. However there is order in our universe, but what is fundamental and what is not? I think we probably all agree that purely mathematical things like pi or e would remain constant in all universes, but consider some of the physical things that might change:
The Planck constant. The speed of light. The gravitational (big G) constant. The mass of the electron, proton, and neutron. The electrical charge on the proton and electron. The inverse square law of gravity and electromagnetism.
The conservation of Mass-energy, momentum, angular momentum, spin and electrical charge. The relative strength of the 4 forces of nature. The number of large dimensions in a universe. The Hubble constant. The ratio of baryonic matter to dark matter and dark energy.
It seems to me that the speed of light and Planck’s constant may be more fundamental than other “constants” and the basic structure of the laws of physics may be more fundamental than the constants they use. But I could be wrong, perhaps the things that always remain the same are none of the above and we haven’t even discovered them yet.
John K Clark