- #1

BruteForce1

- 36

- 1

We still have deterministic equations for both ofc but they are limited to probability values. That is all we can know.

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter BruteForce1
- Start date

In summary: The thing that is random is the lifetime of any particular radioactive atom or molecule. The decay follows a "distribution", which is an overall pattern, but it doesn't tell you at which particular time a particular atom will decay. It...

- #1

BruteForce1

- 36

- 1

We still have deterministic equations for both ofc but they are limited to probability values. That is all we can know.

Physics news on Phys.org

- #2

gleem

Science Advisor

Education Advisor

- 2,578

- 2,026

- #3

BruteForce1

- 36

- 1

gleem said:

Would it be fair to say that both QM measurement and radioactive decay exhibits information loss, or would this be misuse of the term? You have information that gets embedded into probability amplitudes. I don't believe it

- #4

gleem

Science Advisor

Education Advisor

- 2,578

- 2,026

Sorry, I am not well versed in issues regarding information so I will not comment.

- #5

Vanadium 50

Staff Emeritus

Science Advisor

Education Advisor

2023 Award

- 34,735

- 21,443

There was nothing like information theory in 1900.

- #6

atyy

Science Advisor

- 15,168

- 3,378

BruteForce1 said:

We still have deterministic equations for both ofc but they are limited to probability values. That is all we can know.

The problem with QM is not that it is random. The problem is that it requires something that is traditionally called an observer or a measurement device that is "macroscopic" or "classical". It would seem that we should be able to describe the observer using quantum mechanics, but if we do so, then we need another observer to observe the observer. This is traditionally called the measurement problem.

It is discussed briefly by Dirac.

https://blogs.scientificamerican.com/guest-blog/the-evolution-of-the-physicists-picture-of-nature/

"And when this new development occurs, people will find it all rather futile to have had so much of a discussion on the role of observation in the theory, because they will have then a much better point of view from which to look at things."

And in a long article by Bell.

https://m.tau.ac.il/~quantum/Vaidman/IQM/BellAM.pdf

Against ‘measurement’

- #7

BruteForce1

- 36

- 1

atyy said:The problem with QM is not that it is random. The problem is that it requires something that is traditionally called an observer or a measurement device that is "macroscopic" or "classical". It would seem that we should be able to describe the observer using quantum mechanics, but if we do so, then we need another observer to observe the observer. This is traditionally called the measurement problem.

It is discussed briefly by Dirac.

https://blogs.scientificamerican.com/guest-blog/the-evolution-of-the-physicists-picture-of-nature/

"And when this new development occurs, people will find it all rather futile to have had so much of a discussion on the role of observation in the theory, because they will have then a much better point of view from which to look at things."

And in a long article by Bell.

https://m.tau.ac.il/~quantum/Vaidman/IQM/BellAM.pdf

Against ‘measurement’

Radioactive decay is not random either. It also has a differential equation behind it.

- #8

- 27,628

- 19,155

BruteForce1 said:Radioactive decay is not random either. It also has a differential equation behind it.

The thing that is random is the lifetime of any particular radioactive atom or molecule. The decay follows a "distribution", which is an overall pattern, but it doesn't tell you at which particular time a particular atom will decay. It gives you only a probability for each individual atom.

I don't know the answer and I'm sure you could find out with your own research what, if any, theories there were to explain the (apparent) randomness of radio-active decay. My guess is that there was an assumption that once you knew enough about a particular atom, you could determine when it was going to decay. In the same way that you could study a macroscopic process that followed a statistical law. By looking closely enough you could explain the apparent randomness, perhaps by a distribution of initial conditions or the randomness of external influences.

The difference with QM is that it postulated a fundamental randomness (i.e. only probabilities) at the lowest level: probabilities that, according to the theory, could never be explained in terms of a more fundamental deterministic model. That said, the Bohmian interpretation of QM tries to do just that.

The short answer to your question is perhaps simply that everyone thought the probabilities of radioactive decay could eventually be explained by a deterministic theory. It would be interesing to know whether anyone took the randomness at face value and postulated that atoms might decay according to fundamentally probabilistic laws.

- #9

BruteForce1

- 36

- 1

PeroK said:The thing that is random is the lifetime of any particular radioactive atom or molecule. The decay follows a "distribution", which is an overall pattern, but it doesn't tell you at which particular time a particular atom will decay. It gives you only a probability for each individual atom.

I don't know the answer and I'm sure you could find out with your own research what, if any, theories there were to explain the (apparent) randomness of radio-active decay. My guess is that there was an assumption that once you knew enough about a particular atom, you could determine when it was going to decay. In the same way that you could study a macroscopic process that followed a statistical law. By looking closely enough you could explain the apparent randomness, perhaps by a distribution of initial conditions or the randomness of external influences.

The difference with QM is that it postulated a fundamental randomness (i.e. only probabilities) at the lowest level: probabilities that, according to the theory, could never be explained in terms of a more fundamental deterministic model. That said, the Bohmian interpretation of QM tries to do just that.

The short answer to your question is perhaps simply that everyone thought the probabilities of radioactive decay could eventually be explained by a deterministic theory. It would be interesing to know whether anyone took the randomness at face value and postulated that atoms might decay according to fundamentally probabilistic laws.

I don't view this as a problem of determinism since we have the equations which are unambigious and deterministic. A random theory of both would be that they are sometimes trajectory specific, sometimes probabilistic, and sometimes none of the above.

QM measurements are

Why do we have a very good model for only half a theory (probabilities) that are just as reliable as the macroscopic determinism, but confined to deterministic probabilities? It was initially believed determinism and probabilities were oxy morons, but scientists have learned to live with both existing simultaneously, only that the "flight path Newtonian determinism" breaks down in lower scales.

Last edited:

- #10

- 27,628

- 19,155

You get an answer and then you say "no, that's not it it's ...".

- #11

BruteForce1

- 36

- 1

PeroK said:

You get an answer and then you say "no, that's not it it's ...".

Because we are not discussing the threads question. My question was about the reception among scientists back then. I simply gave an account of why I don't view it as problematic to speak of determinism and probabilities in the same breath. The math works. In the area of physics back then it had to be more controversial since it was a long held view that flight path determinism rules. If you our current understanding is correct, then the universe at smaller scales is a clockwork not open for full scrutiny.

- #12

atyy

Science Advisor

- 15,168

- 3,378

BruteForce1 said:Radioactive decay is not random either. It also has a differential equation behind it.

Radioactivity is random (the differential equation describes the probability of decay), and quantum mechanics is also random. Quantum mechanics describes radioactive decay. However, the necessity for an observer in quantum mechanics was not apparent around 1900, as quantum mechanical theory was not yet developed. The necessity for an observer in quantum mechanics was only understood later from around 1926, after the quantum formalism was more developed.

- #13

BruteForce1

- 36

- 1

atyy said:Radioactivity is random (the differential equation describes the probability of decay), and quantum mechanics is also random.

Neither one is random. When I use the word random I go by the Merriam Websters definition of : 1a :

- #14

mfb

Mentor

- 37,240

- 14,078

Quantum mechanics is probabilistic in some interpretations and deterministic (but still appearing random to observers) in others. It doesn't make sense to say it has to be one or the other as interpretations are a matter of taste (and shouldn't be discussed here, we have a separate forum for them).

- #15

BruteForce1

- 36

- 1

- #16

BruteForce1

- 36

- 1

mfb said:The decay of an individual atom doesn't have a plan, purpose, or pattern,

A probability distribution is a pattern.

- #17

BruteForce1

- 36

- 1

- #18

mfb

Mentor

- 37,240

- 14,078

People didn't stop working on it in 1940. And differential equations are older than 1940.BruteForce1 said:

- #19

WWGD

Science Advisor

Gold Member

- 7,327

- 11,169

The Mathematical/Scientific description that applies here is: ( specific outcomes/values) not being predictable but following or being described by a probability distribution. Just like being given a fair coin. Outcome cannot be predicted but expected to follow a distribution over the long run.BruteForce1 said:Neither one is random. When I use the word random I go by the Merriam Websters definition of : 1a :lacking a definite plan, purpose, or pattern

- #20

BruteForce1

- 36

- 1

WWGD said:The Mathematical/Scientific description that applies here is: ( specific outcomes/values) not being predictable but following or being described by a probability distribution. Just like being given a fair coin. Outcome cannot be predicted but expected to follow a distribution over the long run.

Probability distribution is a prediction based on a pattern of behavior. This is elementary.

- #21

BruteForce1

- 36

- 1

mfb said:People didn't stop working on it in 1940. And differential equations are older than 1940.

I'm talking about the theoretical frame work. I didn't say differential equations started in 1940. What I found so far researching it, suggests that the differential equations of radioactive decay began in 1940, unless 1940 is referring to something else.

- #22

WWGD

Science Advisor

Gold Member

- 7,327

- 11,169

Then why are you using the everyday definition?BruteForce1 said:Probability distribution is a prediction based on a pattern of behavior. This is elementary.

- #23

BruteForce1

- 36

- 1

WWGD said:Then why are you using the everyday definition?

The everyday definition states that randomness is a patternless behavior.

The following is a pattern in my book:

"given a sample of a particular radioisotope, the number of decay events −dN expected to occur in a small interval of time dt is proportional to the number of atoms present N"

- #24

Nugatory

Mentor

- 15,063

- 9,760

However, that statement is equivalent to stating that a single atom’s decay is patternless and completely random - the probability of it decaying at any given moment is the same for all moments.BruteForce1 said:The following is a pattern in my book:

"given a sample of a particular radioisotope, the number of decay events −dN expected to occur in a small interval of time dt is proportional to the number of atoms present N"

It appears to me that you have adopted a definition of “pattern” is inconsistent, in that that there s something that you consider a pattern in patternless behavior. Such inconsistencies are generally a hint that the terms need to be defined more carefully.

- #25

- 24,488

- 15,026

I think the apparent problems people have with irreducible randomness is a cultural phenomenon, i.e., it's hard to accept that nature behaves deterministic on a fundamental level, but nature doesn't care for some philosophical prejudices of humans but just behaves as she does ;-).

- #26

Lord Jestocost

Gold Member

- 1,058

- 954

BruteForce1 said:Neither one is random. When I use the word random I go by the Merriam Websters definition of : 1a :lacking a definite plan, purpose, or pattern

True randomness means that an event occurring in space and time can on principle never be undone.

- #27

hutchphd

Science Advisor

Homework Helper

- 6,716

- 5,779

Is this formulation your own or can you ascribe it? ... I rather like it.Lord Jestocost said:True randomness means that an event occurring in space and time can on principle never be undone.

- #28

BruteForce1

- 36

- 1

Lord Jestocost said:True randomness means that an event occurring in space and time can on principle never be undone.

Explain

- #29

hutchphd

Science Advisor

Homework Helper

- 6,716

- 5,779

If you wish to play semantic games, I will point out that the definition you misquote several times after this is "lacking aBruteForce1 said:Neither one is random. When I use the word random I go by the Merriam Websters definition of : 1a :lacking a definite plan, purpose, or pattern

- #30

Lord Jestocost

Gold Member

- 1,058

- 954

hutchphd said:Is this formulation your own or can you ascribe it? ... I rather like it.

My formulation is based on the following sentence in Sir Arthur Stanley Eddington’s book „THE NATURE OF THE PHYSICAL WORLD“ (which I highly recommend): „

- #31

BruteForce1

- 36

- 1

- #32

BruteForce1

- 36

- 1

vanhees71 said:I'd say, there's no difference between the observed randomness of quantum phenomena in general and radioactive decay probabilities.

One difference is that QM is deterministic when you're not measuring.

- #33

BruteForce1

- 36

- 1

Lord Jestocost said:My formulation is based on the following sentence in Sir Arthur Stanley Eddington’s book „THE NATURE OF THE PHYSICAL WORLD“ (which I highly recommend): „This follows at once if our fundamental contention is admitted that the introduction of randomness is the only thing which cannot be undone.“

So he views randomness as noise. I don't see how deterministic systems could be undone either, however.

- #34

Lord Jestocost

Gold Member

- 1,058

- 954

BruteForce1 said:Explain

It means: You cannot trace back along a causal chain in space and time why a true random individual event has occurred at a certain space-time coordination.

- #35

BruteForce1

- 36

- 1

I don't know if radioactive decay and QM really fits that.

- Replies
- 4

- Views
- 1K

- Replies
- 2

- Views
- 1K

- Replies
- 6

- Views
- 1K

- Replies
- 10

- Views
- 1K

- Replies
- 21

- Views
- 3K

- Replies
- 14

- Views
- 2K

- Replies
- 143

- Views
- 8K

- Replies
- 25

- Views
- 12K

- Replies
- 36

- Views
- 7K

Share: