Re: Does anybody have any evidence that all evolutionary events are

Vend wrote:

On 10 Ago, 13:45, John Harshman <jharshman.diespam...@xxxxxxxxxxx>
wrote:

Unpredictability

Chaotic systems are unpredictable unless you know the initial conditions
exactly. Are they therefore random? Not as the word is apparently being
used in this thread. Or can random events be grounded in strict causality?


Let's distinguish between epistemic and non-epistemic randomness:
Epistemic randomness is unpredictability due to our ignorance about
the system.
Non-epistemic randomness is unpredictability due to the fact that the
very mechanics of the system is non-deterministic.

Chaotic systems have epistemic randomness.
Quantum phenomena, in particular quantum wavefunction collapse,
possibly have non-epistemic randomness (it can be assumed so, although
the issue is not resolved).

Agreed.

Why do
you suppose that quantum randomness must affect selection and drift?

Because they affect all phenomena, and unless there is some
"averaging" effect, the unpredictability of quantum events will be
mantained and usually amplified in macroscopical events.

Then there appears to be an averaging effect, because macroscopic events
seem quite often to be predictable,

Some of them are.
Many interesting events are not.

Right. So we can't just say a priori that x is unpredictable or random
because it's underlain by quantum events.

and much of their unpredictability
seems to arise simply from our not having access to all the initial
conditions.

This would be the case if the underlaying laws were completely
deterministic.
If they aren't (as is appears to be the case), even perfect knowledge
of the initial conditions at some time t0 will not suffice to
accurately predict it at any t > t0 (unless t - t0 is very small).

This doesn't follow. It follows only if both of these conditions are
true: 1) the events are both underlain by quantum randomness and 2)
there is no buffering effect that insulates the phenomenon from
dependence on single quantum events. We may agree that (1) is true but
it's clear that (2) is often not true.

Let t0 < t1 < t2.
If the system is deterministic and you know the exact conditions at t0
and assuming that there are no external perturbations (or that you
know them exactly), you can predict its state at time t1 and at time
t2.
If you did your math right, it must hold that if you choose t1 as the
initial time you can calculate the state at t2 obtaining the same
result, and also, if the system is reversible, you can run it
backwards to calculate the state at t0.

But if the system is not deterministic, even with exact knowledge at
t0 you can't predict the state at t1 exactly. If you then try to
predict the state at t2 from your estimate of the state at t1, the
uncertainty about the initial conditions at t1 would add up with the
uncertainty of the non-deterministic evolution from t1 to t2.

In general, the uncertaninty will increase as time passes, unless
there is some stabilizing effect, that is, some states that "attract"
the system trajectory.

Right. Unless.

For instance, if a physical system tends to lose energy, it can be
predicted that after some time it will be in a low energy state.
Depending how those state are located in the state space, this could
make the system evolution rather unsensitive to initial conditions,
external perturbations and quantum or other kinds of noise.


In the example you provided, for instance, a large set of quantum
events would influence the path of the lightning.

This may be true, but do the influences add up to uncertainty in whether
a squirrel gets hit, assuming you knew all the deterministic factors
involved? Or do the large number of quantum events involved become
predictable in aggregate?

Lightning is an atmospheric phenomenon. Atmospheric phenomena would be
chaotic even if the underlaying laws of physics were completely
deterministic: a minmal difference of the state or the parameters at
time t0 causes a great difference at time t1, the famous butterfly
effect.

But chaos is not random, as I understand it. If the underlying laws
really were deterministic, the entire system would be deterministic
regardless of whether we were in practice able to predict it.

But the laws aren't deterministic, as far as we know.

It still doesn't follow that any given chaotic system is unpredictable
because of quantum effects. It would seem odd to me if, for example, the
orbits of the planets were dependent on quantum effects. They are
certainly highly predictable over long periods, even though the system
itsself is chaotic.

If laws are not deterministic, the small amount of unpredictability
that is introduced at every instant is not averaged away, but instead
its effect on the macroscopical outcome is amplified in a short time.

This may be true for some phenomena. It's certainly not true for others.
So there clearly are damping effects as well as amplifying ones. The
question is whether damping or amplifiying effects are operating in the
cases at hand. I don't see how you can be so certain either way.


Because we are considering systems that are chaotic, hence any
randomness is amplified.

This does not follow. It may be that the initial conditions to which the
system is so sensitive do not depend on particular quantum events, for
example.

.

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