Question About Quantum Mechanics, Relativity and Time

[RArvay]

The two aspects of time are perceptual and mathematical. We experience time as if we were traveling through it along a sort of timeline, but physics has a different description of time, in which time is relative to the observer, such that past for one observer is future for another.

If observer #1 observes event A as happening in his present moment, he might measure that event as having a certain outcome corresponding to a quantum probability collapse. For observer #2, however, that same event has not yet occurred. It is in his future, and for him, the outcome of the quantum probability collapse remains uncertain.

But if both observers see the same event, then for observer #2, the future quantum event is no longer truly random. Although he does not yet know the outcome, it has already been determined as to what that outcome will be in his future. Therefore, that outcome cannot be truly random, but only pseudorandom for observer #2.

This seems to be contrary to the quantum mechanical definition of quantum probability, which requires uncertainty until the actual moment of the quantum collapse. I understand that for observer #2 that moment has not yet arrived, and cannot be communicated to him before he observes it, but there still seems to be a predetermined outcome for observer #2 of an event that should be inherently uncertain.

How does one resolve the apparent contradiction?

Since I am not a physicist, kindly keep that in mind, please.

[muon200]

Hello RArvay,
The situation is the same for a coin toss, so the "quantum" adjective is not important in your thought experiment. Relativistic calculations are not involved but the speed of light causes some delay.

Please understand that your phrase "truly random" should never be used in public. Use the word "random".

When you described that future event as pseudo-random for observer #2, you are mistaken. A coin toss is random, whether you see it on your desk or telescopically three seconds later by observing a mirror's reflection of the coin toss reflected from the Moon.

A random "sequence" of coin tosses can be recorded and used later for applications like Monte Carlo tests of some statistical stuff. One coin toss is not a random sequence, it is one fact.

A pseudo-random "sequence" of bits can be fabricated using the 4th digits of the square roots of a counter's monotonic sequence of large numbers. (Or use Blum Blum Shub). That pseudo-random sequence does not need to be recorded, it can be recalculated from some rules about counters and square roots. A sequence of coin tosses is not pseudo-random, it is random, even if taken from a book of coin tosses published in the year 1799. Do not use that book for cryptographic randomness, toss more coins for that.

RArvay asks, “How does one resolve the apparent contradiction?”

Resolve it in your mind by understanding the meanings of the words mentioned, above. Resolve not to create quantum or relativistic complexities in a situation that can be explained by classical mechanics of the speed of light. Do not confuse “a delay from light travel times” with “past and future outcome uncertainties”.

[RArvay]

Thank you for the informative reply.

My description of so-called "true" randomness comes from the likes of Neils Bohr,
who used it to distinguish quantum randomness from, shall we say, macro appearances of randomness, such as a coin toss.

I don't fully subscribe to the notion of quantum randomness, but I use it as a conceptual starting point.

I think Bohr (and Einstein as well!) would argue that a coin toss is not random-- even though we cannot
calculate the outcome, that is due to practical limitations, not due to theoretical principle.

The exact moment of decay of a radioactive atom is, however, truly random within the bounds of half-life, IN PRINCIPLE.
That is to say, even if we know all the factors involved leading up to that decay, nothing whatsoever tells us in what particular
moment that decay will occur.

A better example than coin tosses involves the shuffling of a deck of cards, where even as a practical matter, under some conditions,
the shuffling can be so closely observed as to be predictive of the resulting order of cards.

Quantum randomness, if it were in effect for the cards, would still result in a random order of cards that would not depend on
the observed shuffle.

The kicker is that if quantum randomness holds at the atomic level, then in principle it also applies at the macro level.
Despite the drastically lowered odds, "Anything that can happen must happen, and happen an infinite number of times." Guth.

The alternative to randomness is determinism, which I regard as inherently absurd, since it reduces us all to the status of robots,
unable to control our own thoughts, words and deeds, and unaccountable for our actions.

My conclusion is that, if the universe is not absurd, then neither randomness nor determinism govern reality,
but instead some form of volition, which is presently forbidden as a causative agent in physics.
-

[Joy Christian]

The alternative to randomness is determinism, which I regard as inherently absurd, since it reduces us all to the status of robots,
unable to control our own thoughts, words and deeds, and unaccountable for our actions.

What makes you think that you are not a robot, governed by strict determinism? I think you would benefit from reading Baruch Spinoza.

Strictly deterministic account of the quantum phenomena is quite possible. One example is this simulation of the EPR-Bohm correlation.

[Q-reeus]

...The alternative to randomness is determinism, which I regard as inherently absurd, since it reduces us all to the status of robots,
unable to control our own thoughts, words and deeds, and unaccountable for our actions...
...My conclusion is that, if the universe is not absurd, then neither randomness nor determinism govern reality,
but instead some form of volition, which is presently forbidden as a causative agent in physics.

Why not settle for effective free will? Law courts are here to stay. If you think about it long enough, it should become apparent the notion of free will as an objective reality cannot even be sensibly defined in a rigorous, fully self-consistent manner. Regardless of whether the world is inherently random or deterministic.

[florence]

.
. . . A coin toss is random, whether you see it on your desk or telescopically three seconds later by observing a mirror's reflection of the coin toss reflected from the Moon.

seems like quite a few people have looked into this coin tossing business, as here for example:http://statweb.stanford.edu/~susan/papers/headswithJ.pdf
. . .so perhaps not quite as random as one might like?

[lcwelch]

Is it not true that if one had complete knowledge - which is impossible in a quantum system - of the coin toss, e.g. initial conditions, atmospheric conditions, forces/torques and the nature of the landing spot one should be able to calculate "heads" or "tails." Quantum effects for a macroscopic body like a coin are negligible. It is only called "random" only because our brain lacks the complete knowledge and the calculating ability - not because it is inherently "random' like a decaying nucleus.

[muon200]

florence wrote,
"seems like quite a few people have looked into this coin tossing business, as here for example:http://statweb.stanford.edu/~susan/papers/headswithJ.pdf
. . .so perhaps not quite as random as one might like?"

That defective paper seems to be a joke you fell for.

I looked at the Susan Holmes paper about coin tossing. It is a flawed paper with a contrived metal machine designed to make a precise toss, compared to a human hand flipping a coin with the appearance of fairness. A human hand can use skill to make a non-random toss. But when I try to be fair, my hand is not using skill for non-randomness, I try to give a fair, unskilled toss: high and fast sometimes, low sometimes.

That paper is a joke, made to fool people who do not like to read long winded math stuff. But the "search for" function (control-f) helped me find that a hand toss is never measured for a coin. When a right hand was mentioned once on page 20, section 5.1, a ribbon is attached to the coin. Quoting: "coin was given a normal flip with the right hand". This is the extent of the description of the experiment. I believe that their "normal flip" also uses the precision machine to toss the coin using a specific hand to start the precision machinery.

Icwelch asked,
"Is it not true that if one had complete knowledge - which is impossible in a quantum system - of the coin toss, e.g. initial conditions, atmospheric conditions, forces/torques and the nature of the landing spot one should be able to calculate heads or tails”?

No. But since you think “impossible” things are useful in a debate, try this: send me a thousand dollars and I will tell you how gravity works.

No. My hand is radioactive. My hand has cells that are dying because some UV photons are pushing it around. Those photons came from the sun’s nuclear fusion. My food was made using solar energy. I am made random by the sun and the Thorium on my earthly hands.

Icwelch wrote,
“Quantum effects for a macroscopic body like a coin are negligible. It is only called "random" only because our brain lacks the complete knowledge and the calculating ability - not because it is inherently "random' like a decaying nucleus.”

I am willing to neglect quantum effects, but my coin is not. The butterfly effect is as random as one might like.

Glossary
random : good
truly random : better than random
as random as one might like : rock and roll wisdom
pseudo-random : useful for Bally’s in Las Vegas
inherently random : hierarchical
quantum randomness : small
macro appearances of randomness : big
determinism : philosophy
strict determinism : approved by authority
effective free will : good enough for rock n roll
unpredictable : humans care about the meanings of predictions
negligible : humans can survive without math

[lcwelch]

...and these things (your food, solar radiation, radioactive thumb) don't manifest themselves in the initial conditions?

I don't understand your offer to give me the secret of gravity for $1000. What secret are you talking about?