On Sat, Apr 9, 2022 at 11:28 AM smitra <smi...@zonnet.nl> wrote:

> On 08-04-2022 07:19, Bruce Kellett wrote:
> >
> > Permanent records do follow from entanglement and decoherence. There
> > is no reason to suppose that algorithms processing information are
> > going to produce permanent records. Unless they do, they are useless
> > as a model of observation. In the words of David Albert (paraphrased):
> > "The task of fundamental physics is to explain the manifest image ."
> >
> Decoherence is never complete it can in principle be reversed.

No. Measurements are in principle irreversible. Whenever you have a
result entangled with the environment (by decoherence) you inevitably have
low energy IR photons that escape into space. Since these vanish at the
speed of light, they cannot be reversed. The records of results are
permanent, not just FAPP, but in principle, according to the laws of

It cannot
> reasonably be the case that I can only observe something right now
> because a record of the observation is going to exist for eternity. If
> the universe were to reverse its time evolution in 10^15000 years in a
> unitary way, causing all records to be exactly erased, then we could not
> make any observations. What's the physical basis for making this
> assumption?

What's the physical basis for assuming the universe can or could reverse at
some point in the future?

> You may argue that a FAPP permanent record is good enough for
> observation, but you cannot define a physical plausible rigorous
> boundary of your FAPP criterion.

I can and have. The irreversibility occasioned by the escape of IR photons
is a rigorous boundary.

One can always subtract 1 second from
> your time limit the universe must keep on expanding before starting to
> evolve backward. One then eventually ends up with the criterion that
> there must be enough time for the brain processes that cause the
> conscious experience of the observation to be completed.

Irrelevant speculation.


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