Neutrinos in Nature: Estimating Numbers

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Discussion Overview

The discussion revolves around estimating the number of neutrinos in nature, exploring theoretical and cosmological aspects of their abundance. Participants consider various estimates and historical ideas related to neutrinos and their properties.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant estimates that there are about three times the number of neutrinos as photons, suggesting a figure of approximately 3 x 10^90 neutrinos in the observable universe, contingent on cosmological details.
  • Another participant questions what is meant by "details of cosmology," indicating a need for clarification on the factors influencing neutrino estimates.
  • A participant references a historical idea related to neutrinos, mistakenly attributing it to Feynman, which involves the notion of a single particle that can switch its direction in time, later corrected to pertain to electrons and attributed to John Wheeler.

Areas of Agreement / Disagreement

Participants express differing views on the estimates of neutrino numbers and historical concepts, with no consensus reached on the specifics of cosmological calculations or the origins of the particle idea.

Contextual Notes

The discussion includes unresolved assumptions regarding the calculations of neutrino abundance and the historical attribution of ideas, which may depend on varying interpretations of cosmological models.

randa177
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what is the best estimates on the number of neutrinos in nature?
 
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Some say about three times the number of photons, which is about 10 billion times the number of protons, which is about 10^80 in the observable universe out to about 14 billion light years. So you get about 3 x 10^90 neutrinos counting all three flavors.
A more sophisticated calculation depends on details of cosmology.

Jim Graber
 
what do you mean by details of cosmology?
 
Isn't this the particle that Feymann suggested that there may be only 1 in the whole universe, it just has the ability to switch it's direction in time at random?

Or am I thinking electrons?
 
GleefulNihilism said:
Isn't this the particle that Feymann suggested that there may be only 1 in the whole universe, it just has the ability to switch it's direction in time at random?

Or am I thinking electrons?

Yes, you are thinking of electrons, but the idea was not thought up by Feynman. Although he mentioned it in his Nobel Prize lecture, the idea actually came from John Wheeler.
 
Good to know. Thank you Cristo.
 

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