I am looking for examples of physical indeterminacy impacting the macroscopic world. By physical indeterminacy, I mean physical sources of randomness such as quantum indeterminacy or brownian motion.

One example is of particular interest here: whether such randomness influences which sperm cell fertilizes a particular ovum, or whether such biological systems are too large to be affected by random perturbations, either at the atomic level (quantum) or molecular level (brownian motion).

  • $\begingroup$ In discussing the question with a physicist offline (i.e., off StackExchange), a potentially related question suggests itself: if you had two identical jars, containing identical gas molecules (same states) and identical dust motes (same state), would the dust motes' brownian trajectories be identical? Or would they differ due to quantum indeterminacy influencing individual gas molecules' kinetic interactions with each dust mote? (Based on the discussion here, I may fork this into its own question. Just thought it might inform where I'm coming from.) $\endgroup$ Commented Oct 13, 2013 at 14:04
  • $\begingroup$ I think your question is unclear. Brownian motion is not necessarily related to quantum randomness. Are you implying that Brownian motion and quantum randomness are related? Or you are asking about Brownian motion and quantum randomness as two different things? $\endgroup$ Commented Oct 13, 2013 at 15:22
  • $\begingroup$ @Gotaquestion I have edited the question to clarify that I am interested in physical sources of randomness (two examples of which are quantum randomness and brownian motion) affecting macro systems, such as biological fertilization. $\endgroup$ Commented Oct 13, 2013 at 16:44
  • $\begingroup$ Any system that is chaotic is an example of such microscopic randomness affecting macroscopic properties. $\endgroup$
    – Lagerbaer
    Commented Oct 13, 2013 at 23:11
  • $\begingroup$ @Lagerbaer, I totally understand your point and agree I should have mentioned chaos in the question. However, I would like to think about true physical randomness, rather than unpredictability due to unknown initial conditions (and I do realize there are metaphysical conundrums there), which is why I mention quantum mechanics. I'm not 100% sure that brownian motion's randomness is due to chaos or "true" physical randomness, derived from quantum uncertainty. $\endgroup$ Commented Oct 15, 2013 at 1:27

1 Answer 1


Some kinds of mutation provide an example of this kind of indeterminacy. UV light can be bad for our health. One of the reasons is that, when we are exposed to sunlight, UVB photons are absorbed by double bonds in pyrimidines, which break open, become reactive, and dimerize (photo-dimerization). This damages the DNA in the same way that it would damage a zipper if 2 adjacent teeth were fused together. The cell responds to this kind of damage with a repair process that may lead to mutation. Eventually the effect of the mutation will be manifested macroscopically. The causal sequence is complex, but it starts with a photon, which has an indeterminate path due to quantum indeterminacy. It is indeterminate whether a photon will hit a particular site in the genome.


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