# Determinism of Macroscopic World

• I
• bgq
In summary: This subset is determined by the principle of least action, which is deterministic. So quantum weirdness goes away at the level of the macroscopic world.
bgq
Hi,

If the microscopic world is not deterministic, then naturally the macroscopic world should also be not deterministic because it is based on the microscopic world. The problem is that the macroscopic world is deterministic; the evidence of this is that a lot of our technology and calculations assume that the world is deterministic. For example, the start and the end of the moon eclipse tonight is predicted very accurately. Such accuracy couldn't be obtained if the planets and the sun move in a non deterministic way.

The macroscopic world is indeed non deterministic and what we calculate is nothing more than the most probable value; however, for macroscopic objects the probability of the other outcomes is negligible.

Is this conclusion true?

Yes. If you add up a large number of random variables, the sum becomes (nearly) deterministic.

A measure of how nondeterministic a process is is given by the standard deviation. The standard deviation describes the typical departure of some quantity from the most likely value. If the standard deviation is high, then the quantity seems very nondeterministic, and if the standard deviation is low, then the quantity seems approximately deterministic.

Let's consider generating a "random" number ##h## in the range 0 to 1 as follows: Flip a coin ##N## times, and let ##h## be the fraction of results that are "heads" (so it's the ratio ##\frac{H}{N}## where ##H## is the number of "heads").

The most likely value for ##h## will be ##1/2##. The standard deviation for ##h## will be ##\frac{1}{2 \sqrt{N}}##

With ##N=1##, the standard deviation is 1/2, which is the same size as ##h##. So ##h## is pretty nondeterministic, it can be 0 or 1.

With ##N=## one million, ##h = 0.5 \pm 0.0005##. So ##h## is pretty certain to be very close to 1/2.

So if you are dealing with very large numbers of similarly distributed quantities, then the averages will appear deterministic even though each of the quantities contributing to the average may be nondeterministic.

Last edited:
bhobba, bgq and Demystifier
stevendaryl said:
Yes. If you add up a large number of random variables, the sum becomes (nearly) deterministic.

A measure of how nondeterministic a process is is given by the standard deviation. The standard deviation describes the typical departure of some quantity from the most likely value. If the standard deviation is high, then the quantity seems very nondeterministic, and if the standard deviation is low, then the quantity seems approximately deterministic.

Let's consider generating a "random" number ##h## in the range 0 to 1 as follows: Flip a coin ##N## times, and let ##h## be the fraction of results that are "heads" (so it's the ratio ##\frac{H}{N}## where ##H## is the number of "heads").

The most likely value for ##h## will be ##1/2##. The standard deviation for ##h## will be ##\frac{1}{2 \sqrt{N}}##

With ##N=1##, the standard deviation is 1/2, which is the same size as ##h##. So ##h## is pretty nondeterministic, it can be 0 or 1.

With ##N=## one million, ##h = 0.5 \pm 0.0005##. So ##h## is pretty certain to be very close to 1/2.

So if you are dealing with very large numbers of similarly distributed quantities, then the averages will appear deterministic even though each of the quantities contributing to the average may be nondeterministic.
Thank you very much

bgq said:
If the microscopic world is not deterministic, then naturally the macroscopic world should also be not deterministic because it is based on the microscopic world.

My view is a bit different and based on Feynman's path integral approach. At the level of the macro-world only certain paths exist - the rest cancel - giving the principle of least action (PLA).

Form the PLA and certian symmetry considerations (essay applications of Noethers Theorem) all of classical mechanics follows - and that is deterministic.

So exactly where does the quantum weirdness go? If you look closely enough, and I am not even sure with our current technology we can, we can see those paths have a bit of a 'width' so to speak. But tons of other phenomena like Brownian motion etc make detecting it very very difficult.

Thanks
Bill

## 1. What is determinism in the macroscopic world?

Determinism in the macroscopic world is the belief that all events and phenomena in the physical world are predetermined by a set of causal laws and conditions. This means that every action and outcome can be predicted if all the necessary information is known.

## 2. How does determinism differ from free will?

Determinism and free will are two opposing concepts. While determinism holds that all events are predetermined, free will suggests that individuals have the ability to make choices and decisions that are not influenced by external factors. Determinism suggests that our actions and decisions are a result of prior causes, while free will argues that we have the power to choose our own paths.

## 3. Is determinism compatible with quantum mechanics?

There is ongoing debate about whether determinism is compatible with quantum mechanics. Some scientists argue that the random nature of quantum mechanics challenges the concept of determinism, while others believe that the underlying laws and principles of quantum mechanics still uphold the idea of determinism.

## 4. How does determinism impact our understanding of causality?

Determinism has a significant impact on our understanding of causality. It suggests that all events and outcomes are caused by specific antecedent conditions, rather than being random or unexplainable. This means that there is a cause and effect relationship between all events in the macroscopic world.

## 5. What are some potential implications of determinism in the macroscopic world?

Determinism has implications for various fields, including philosophy, psychology, and physics. It challenges our notions of free will and personal responsibility, and it also has implications for our understanding of the universe and its fundamental laws. Some scientists argue that determinism can lead to a more deterministic approach to problem-solving and decision-making in various areas of science and technology.

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