Can the probability of an event ever be exactly zero?

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Discussion Overview

The discussion centers on the concept of probability in relation to continuous random variables, specifically whether the probability of an event occurring at an exact moment in time can ever be zero. Participants explore the implications of continuous time, mathematical modeling, and the nature of events in a probabilistic framework.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants argue that in a continuous time framework, the probability of an event occurring at an exact moment is zero due to the infinite divisibility of time.
  • Others suggest that while mathematically the probability can be zero, there exists a specific instant when an event occurs, raising questions about the relationship between mathematical models and reality.
  • A participant highlights the distinction between continuous and discrete random variables, noting that a probability of zero does not imply impossibility.
  • Some participants discuss the implications of defining events in terms of exact moments versus durations, questioning whether anything occurs at an exact instance in reality.
  • There is mention of mathematical theories, such as Cantor's proof and sigma-additivity, which relate to the treatment of events with zero probability in uncountable collections.
  • One participant references Bayesian statistics and its approach to probability, suggesting that not all intervals of time are equally likely, although they express skepticism about this perspective.

Areas of Agreement / Disagreement

Participants express a range of views, with no clear consensus on whether the probability of an event occurring at an exact moment can be considered zero in practical terms. The discussion remains unresolved, with competing interpretations of mathematical principles and their implications for real-world events.

Contextual Notes

Participants acknowledge limitations in their understanding of the relationship between mathematical models and physical reality, as well as the nuances of defining events in continuous time.

  • #61
quadraphonics said:
Indeed, the cost of including infinity in a number system is that certain basic expressions must remain undefined, when they include infinity. But so what? They're still defined as usual for every finite number, and the expressions where infinity is sensible (like 1/\infty=0) are still well defined.

There is also a finite number that does not work in many basic algebraic manipulations, but is nevertheless included in many standard number systems.

Can you give me an example of a finite number that I can't multiply both sides of an equation by?

I'm not trying to be a brat. I'm just not seeing this.

I would agree that the limit as n -> infinity of 1/n = zero

But I'm having a hard time with this 1/infinity = 0 thing...
 
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  • #62
Archosaur said:
Can you give me an example of a finite number that I can't multiply both sides of an equation by?

No, but there is a finite real number that you can't divide both sides of an equation by :]

Archosaur said:
I would agree that the limit as n -> infinity of 1/n = zero

But I'm having a hard time with this 1/infinity = 0 thing...

\infty, as it is used in the extended reals, is essentially a shorthard for that type of limit expression.
 
  • #63
quadraphonics said:
\infty, as it is used in the extended reals, is essentially a shorthard for that type of limit expression.

I am totally okay with this! I'll sleep easy tonight, thanks!
 

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