This discussion explores the relationship between radioactive decay and quantum mechanics (QM), emphasizing the probabilistic nature of both phenomena. Participants highlight that while deterministic equations exist for radioactive decay, the actual decay of individual atoms is inherently random, governed by probability distributions. The conversation also touches on the historical context of scientific understanding, noting that the necessity of an observer in QM was not recognized until the development of quantum formalism around 1926. Key references include Dirac's and Bell's discussions on the measurement problem in QM.
PREREQUISITESPhysicists, students of quantum mechanics, historians of science, and anyone interested in the philosophical implications of determinism and probability in modern physics.
vanhees71 said:I'd say, there's no difference between the observed randomness of quantum phenomena in general and radioactive decay probabilities.
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.“
BruteForce1 said:Explain
Lord Jestocost said: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.
Nugatory said:- the probability of it decaying at any given moment is the same for all moments.
Either I'm not seeing some posts or you're debating with yourself here.BruteForce1 said:An ever existing quantum fluctuation state generating universes in the same fashion as radioactive nucleis decaying is not random to me, however. We have a source at least.
The devil is in the details.
PeroK said:Either I'm not seeing some posts or you're debating with yourself here.
This is the case for radioactive decay. At least today there's no known way to know, when a nucleus precisely decays or why a nucleus has decayed at precisely that point in time at this place. It just happens randomly. All we have is a very precise theory predicting the probability for its decay, the Standard Model.Lord Jestocost said: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.
vanhees71 said:This is the case for radioactive decay. At least today there's no known way to know, when a nucleus precisely decays or why a nucleus has decayed at precisely that point in time at this place. It just happens randomly. All we have is a very precise theory predicting the probability for its decay, the Standard Model.
vanhees71 said:Of course, there's no reasonable doubt that the radioactive decay is the decay of a radioactive nucleus. If I have some Radium nucleus, I know it will at some time randomly emit an ##\alpha## particle (He nucleus) with a half-life of about 1600 years. I.e., investigating a large number of Ra nuclei after 1600 years I have about only half of them left. When a specific Ra nucleus decays, we cannot predict.
Were there experiments that repeatedly prepared single radioactive atoms and waited until they decayed?vanhees71 said:Of course, there's no reasonable doubt that the radioactive decay is the decay of a radioactive nucleus. If I have some Radium nucleus, I know it will at some time randomly emit an ##\alpha## particle (He nucleus) with a half-life of about 1600 years. I.e., investigating a large number of Ra nuclei after 1600 years I have about only half of them left. When a specific Ra nucleus decays, we cannot predict.
It's very difficult to affect nuclear properties like decay rates due to the typical energy scales involved (MeV rather than eV in atomic physics). The only exception are cases like bound ##\beta## decays, where it can make a huge difference whether you look at the atom or the completely ionized bare nucleus, where due to the Pauli effect the ##\beta## decay is pretty well blocked, and the half-life between the atom and the bare nucleus differs by several orders of magnitude:BruteForce1 said:And external factors like climate have no bearing on it? I'm trying to think of it like fail rates in technology. We know why some batteries fail earlier than others (storage, heating, etc).
same with genetic mutation.
I'd consider the investigations in storage rings as examples for this. This is a pretty interesting field, also for precision measurements. One fascinating example is the GSI storage-ring result on Rhenium bound ##\beta## decay quoted above. Then there was also a high-precision test for time dilation of the life-time of moving unstable nuclei (at moderate speeds of about ##\beta=1/3##), of course confirming the Lorentz ##\gamma## factor result of Special Relativity.A. Neumaier said:Were there experiments that repeatedly prepared single radioactive atoms and waited until they decayed?
In these experiments a large number of radioactive atoms are prepared simultaneously and only the number of decay product atoms counted; one does not know which atom decayed when. Thus this is not what I meant.vanhees71 said:I'd consider the investigations in storage rings as examples for this. This is a pretty interesting field, also for precision measurements. One fascinating example is the GSI storage-ring result on Rhenium bound ##\beta## decay quoted above.