> On 28 Jan 2021, at 11:32 am, Bruce Kellett <bhkellet...@gmail.com> wrote: > > On Thu, Jan 28, 2021 at 11:20 AM Pierz Newton-John <pier...@gmail.com > <mailto:pier...@gmail.com>> wrote: > On 28 Jan 2021, at 11:03 am, Bruce Kellett <bhkellet...@gmail.com > <mailto:bhkellet...@gmail.com>> wrote: >> On Thu, Jan 28, 2021 at 10:44 AM smitra <smi...@zonnet.nl >> <mailto:smi...@zonnet.nl>> wrote: >> >> FAPP, therefore not well defined at all. Sticking to FAPP you could >> never have discovered Special Relativity, General Relativity, found the >> correct way to resolve Maxwell's Demon paradox, etc. etc. >> >> FAPP is well-defined for all practical purposes. That is all that you >> require for special and general relativity, statistical mechanics, and the >> rest of physics. You cannot point me to any physical result that is not FAPP >> -- we have only limited measurement precision, after all. And that is good >> enough for real-world physics. >> > Bruno’s point IIUC is that FAPP is OK for the physics you have now, but > possibly not for the next physics. "Irreversible FAPP” means irreversible > today. It’s true that there does come a point with decoherence where the > state is irreversible, but that point is arbitrary and depends on the > technology you have available. > > That is not true. Decoherence ultimately involves the emission of IR photons > into outerspace -- through heat dissipated in the atmosphere if no other way. > Such effects are truely irreversible, not just FAPP, because once you have > lost photons to space there is no way to get them back -- you can't chase > after them and turn them around..... > > The point about decoherence is that the irreversibility is ultimately a > matter of the laws of physics. FAPP is just for laboratory purposes, but in > the wider context, the irreversibility is absolute, not just FAPP.
That’s true - decoherence by definition means something escaped the experimental boundaries and then it’s game over. I should have said that where decoherence begins is technologically determined. The point is that the bounds of what is reversible or not depend on what we are technologically capable of. After all that’s the problem of quantum computers - maintaining larger and larger superpositions in a controlled state. In the future it’s to be hoped that we can extend those bounds to the point where the question of whether QM is universal or not can be resolved. Surely that is a meaningful question and surely the only way to answer it is through something like what I am describing. If we can be confident that QM is universal, then we can get closer to an answer on whether MWI is the right interpretation. > > > Proposals for testing MWI involve extending that point further and further. > If you can reverse a quantum state that has evolved to macroscopic > complexity, you can get interference and you’re on your way to showing that > QM is indeed universal, and that MWI may be the best theory. FAPP is just > giving up on testing, say, the Frauchiger-Renner experiment, which may prove > to be tomorrow's equivalent of testing Bell’s theorem - not possible when the > theorem was created, but possible later on. > > I think you have failed to understand the physics underlying FAPP. It is not > just a matter of technology. FAPP is for laboratory convenience, but > ultimately, the irreversibility is built into the laws of physics. > > Bruce > > -- > You received this message because you are subscribed to a topic in the Google > Groups "Everything List" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/everything-list/xsl8cSDT4M8/unsubscribe > <https://groups.google.com/d/topic/everything-list/xsl8cSDT4M8/unsubscribe>. > To unsubscribe from this group and all its topics, send an email to > everything-list+unsubscr...@googlegroups.com > <mailto:everything-list+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAFxXSLQ2puatoEnK7AXL3MTyBDCuBdPg92%3D3SQuT%2Bc3szNgBdA%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAFxXSLQ2puatoEnK7AXL3MTyBDCuBdPg92%3D3SQuT%2Bc3szNgBdA%40mail.gmail.com?utm_medium=email&utm_source=footer>. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/C1C812B5-BBF7-4CC4-AA70-32A943CF0AC9%40gmail.com.
