# Why -1/12 is a gold nugget | Summary and Q&A

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March 18, 2014
by
Numberphile
Why -1/12 is a gold nugget

## TL;DR

Divergent series, which typically blow up to infinity, can be assigned a meaningful value of -1/12 in certain mathematical contexts.

## Key Insights

• 😘 Divergent series, which blow up to infinity, have traditionally been ignored in mathematics.
• 🍹 In certain regularized contexts, such as the sum of natural numbers, assigning meaningful values to divergent series, like -1/12, is possible.
• 🍹 Mathematicians, such as Leonhard Euler, ventured into exploring these series and made significant contributions to the understanding of divergent sums.
• 🍹 The concept of regularized sums extends beyond mathematics and finds applications in physics, especially in quantum calculations.
• ❓ The value of -1/12 assigned to some divergent series may seem counterintuitive, but it represents the finite part of the series after removing the infinite portion.
• ❓ While manipulating divergent series may initially appear arbitrary, finding rigorous justifications and explanations is an integral part of mathematics.
• 🤞 The understanding of divergent series and their assigned values is an ongoing area of research, with the hope of deeper insights and explanations.

## Transcript

Is this good? The position? More like this, right? O, it was you who made that video? I see. Okay. Well, I think that mathematicians learn this stuff at some point. And I learned it at some point. And then you kind of forget. So you kind of put it in a box somewhere and you put it in a closet. And you classify it under stuff which you have alrea... Read More

### Q: Why are divergent series traditionally ignored in mathematics?

Divergent series are ignored because they have no defined answer and continuously increase in value.

### Q: How is it possible to assign a value to a divergent series?

In certain regularized contexts, mathematicians replace the series with a "regularized" value, which represents the finite portion of the infinite series. In the case of the sum of natural numbers, the value assigned is -1/12.

### Q: Can the value of -1/12 be obtained in different ways?

Yes, there are multiple approaches to obtaining the value of -1/12 for certain divergent series. Leonhard Euler and Bernhard Riemann provided different methods, and complex numbers play a role in Riemann's approach.

### Q: Is manipulating divergent series against the rules in mathematics?

Manipulating divergent series may seem arbitrary or against the rules in traditional mathematics. However, in the context of regularized sums, where the infinite part is removed, these manipulations become justified and can provide valuable insights.

## Summary & Key Takeaways

• Traditionally, divergent series are ignored in mathematics because they have no defined answer and blow up to infinity.

• However, in certain regularized contexts, such as the sum of natural numbers, mathematicians have found it meaningful to assign a value of -1/12 to the series.

• The concept of regularized sums has been developed through various mathematical frameworks and is useful in solving problems in physics and mathematics.