koch@chopin.DEC (Kevin Koch LTN1-2/B17 DTN229-6274) (07/22/85)
It has always bothered me that unstable particles and nuclei don't have a fixed lifetime. We are taught to believe that everything has a cause, yet this seems to be ignored when saying that a particle or nucleus has a *halflife*. How can something exist for a random amount of time and then decay? It seems to me that something must trigger that decay. What is it? Kevin Koch (Koch is it!) ...decwrl!dec-rhea!dec-handel!koch // koch%handel.dec@decwrl.ARPA
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (07/23/85)
> How can something exist for a random amount of time and then decay?
I'm sure the list will be flooded with responses that the process
behind radioactive decay is inherently quantum-mechanical, and
quantum mechanics says that fundamental processes are inherently
probabilistic, with nothing "behind the scenes". It is good that
this bothers you; it bothers a lot of us. But nobody has found
any way around this yet.
matt@oddjob.UUCP (Matt Crawford) (07/24/85)
In article <3228@decwrl.UUCP> koch@chopin.DEC (Kevin Koch DTN229-6274) writes: > > It has always bothered me that unstable particles and nuclei don't >have a fixed lifetime. We are taught to believe that everything has a >cause, yet this seems to be ignored when saying that a particle or >nucleus has a *halflife*. How can something exist for a random amount >of time and then decay? It seems to me that something must trigger >that decay. What is it? > >Kevin Koch (Koch is it!) >...decwrl!dec-rhea!dec-handel!koch // koch%handel.dec@decwrl.ARPA Consider the opposite situation: If every particle of a certain type lived for a certain amount of time and then decayed, there would have to be some internal state of the particle which kept track of the passage of time. If all neutrons, for example, are to be absolutely identical (as we know they are) then it must be impossible to distinguish a brand-new neutron from an old neutron. If you can accept the fact that the interaction between two particles which pass near each other can only be described with probabilities, then just consider the decay of a particle to be an interaction between it and a swarm of virtual particles. _____________________________________________________ Matt University crawford@anl-mcs.arpa Crawford of Chicago ihnp4!oddjob!matt
mikes@AMES-NAS.ARPA (07/28/85)
From: mikes@AMES-NAS.ARPA (Peter Mikes) From: koch%chopin.DEC@DECWRL.ARPA (Kevin Koch LTN1-2/B17 DTN229-6274) Subject: \"Randomness\" query Article-I.D.: <3228@decwrl.UUCP> It has always bothered me that unstable particles and nuclei don't have a fixed lifetime. We are taught to believe that everything has a cause, yet this seems to be ignored when saying that a particle or nucleus has a *halflife*. How can something exist for a random amount of time and then decay? It seems to me that something must trigger that decay. What is it? response: Very good and indeed deep question. I will not go 'into it' but just bring in bit of relevant history and a reference(if I find it): You may recall (or look up in a text of Statistical Mechanics =SM) elegant Einstein's derivation of the law for Black Body Radiation using the radiation coeficients B and A for stimulated and spontaneous radiation respectively. Einstein modeled the A on the alfa-decay! Even though my dictionary is saying SPONTANEOUS means 'from in- ternal causes' it means here (in view of the fact that Bell's theorem killed the Hidden Parameter interpreations of the QM) 'without a cause'. Acausal action is very exceptional (any other example??) and some suspect ( I do) in conflict with current QM and of course in con- flict with CM (= Classical i.e. Newtons mechanics. So it (all) is tied back to problems of inconsistencies of the current QM theory of measu- rement and causality and concept of state and observer. This paradox is called the QM version of the ZENO's paradox. One article with a catchy name "Watched ketle never boil's" and the following two were part of discussion which was in AM.J.Phys last year: Asher Peres: Zeno Paradox in QM. " AM.J.Phys. 48(11) 1980,pp931 Ishwar Singh et al: "Role of observer.." Am.J.Phys. 50(10) 1982 pp882 In somewhat telegraphic style - to tie it to out past discussion: the current QM insists that after the 'decay' and before detection the 'state of the system' is described by a superposition of the decayed and undecayed psi function ( even though the escaped component can be already at alfa-centauri when 'detected' - so it is in a way an inverse of the 'collapse' paradox we have talked about). Interestingly, the gam- bit of "bring in the big guns of QFT" would work somewhat in this case: QED = Quantum Electro-Dynamics maintains that the A effect is due to the flucuation of the vacuum and so it DOES have a 'cause' after all. Over all (my subjective belief is that) the QFT does not solve the current problems of QM - it just hides them better becouse it's math is somewhat more complex and significantly more cumbersome and less rigorous. So - according to orthodox QM nothing really happened at the moment of the decay ( moment of the decay ? is uncertain !) and it all happened whan you detected the escaped alpha particle ( only the clicks are real remeber?).. - You find that unsatisfactory? If you do, than I would like to compliment your physical intuition: You are one of the Happy Few. Peter