Modulus for X Axis: Can You Stop Negative Values?

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Discussion Overview

The discussion revolves around the concept of modulus functions, particularly in relation to the x-axis and negative values. Participants explore whether a modulus can be defined to prevent negative x-values, with applications mentioned in contexts like radioactive decay.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that the modulus function y = |x| cannot go below the y-axis, questioning if a modulus could be created to prevent negative x-values, particularly in scenarios like radioactive decay.
  • Another participant argues that negative time is a valid concept, stating that one can choose a reference point for time (t=0), and that negative values of time can represent moments before this reference point.
  • A further reply highlights that taking negative time in the context of radioactive decay could yield a mass greater than the initial mass, which is considered reasonable by some participants.
  • One participant questions the validity of having a mass greater than the initial mass unless it was produced by a nuclear reaction at some point.
  • A later post expresses a desire to understand if there exists an "opposite" of the modulus function.

Areas of Agreement / Disagreement

Participants express differing views on the concept of negative time and its implications in mathematical models, particularly in physics. The discussion remains unresolved regarding the existence of a modulus that prevents negative x-values.

Contextual Notes

Participants have not reached a consensus on the implications of negative time or the existence of an opposite modulus function. The discussion includes assumptions about the nature of time and mass in physical contexts.

madmike159
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y = |x| can't go below the y-axis because a Modulus is always positive, but can you get a modulus that stops x going negitive? Could this be used for things like radioactive decay where the graph should go in -x but doesn't because you can't have - time?
 
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x, as a function of y, x= |y| does that. I am not clear why you say "you can't have negative time". There is no such thing as an "absolute" time. In any application of mathematics, to, say, physics, you are free to choose which moment you will call "t= 0". Negative values of t simply mean times before your chosen starting point.

For example, if I have a radioactive substance, with half-life [itex]\lambda[/itex], that, at time 0 (say, when I start the experiment) has mass m= A grams, then as time t, it will have mass [itex]m= A(1/2)^{\lambda t}[/itex]. Taking t< 0 will give a mass greater than A, which is a perfectly reasonable answer: before time t= 0, it had greater mass than at time t= 0.
 
"Taking t< 0 will give a mass greater than A, which is a perfectly reasonable answer: before time t= 0, it had greater mass than at time t= 0."

Unless it was created at some time as a by-product of a nuclear reaction.
 
Really all I wanted to know is if there is an opposite of the modulus function.
 

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