# How The Most Useless Branch of Math Could Save Your Life

TLDRKnot theory, a branch of mathematics, explores the properties and distinctions of various knots. It has practical applications in fields like chemistry, where knotting molecules can alter material properties, and biology, where enzymes untangle DNA knots to enable cell replication. The study also informs the design of stronger materials and has implications in medical treatments like chemotherapy. Simple everyday tasks, such as tying shoelaces, illustrate the theory's relevance, highlighting the superiority of the square knot over the granny knot for security.

###### Takeaways

- 📚 Knot theory is a branch of mathematics that studies the properties and classification of knots, discovering over 352 million distinct knots so far.
- 🧬 The field has practical applications in various scientific areas, including the structure of proteins and DNA, material science, and medical treatments like chemotherapy.
- 🪢 The difference between a granny knot and a square knot lies in the direction of the wrapping around the loop: counterclockwise for the former and clockwise for the latter, with the square knot being more secure.
- 🔍 Distinguishing knots can be challenging, but invariants (properties that remain constant regardless of the knot's projection) and Reidemeister moves are key tools in knot identification.
- 🌀 The discovery of knot theory's applications in molecular knots has opened up possibilities for creating new materials with unique properties by tying molecules in specific knots.
- 🧬 Bacterial DNA replication requires the action of enzymes like type two topoisomerase, which use knot theory principles to manage the knotted structure of the DNA.
- 💊 Understanding knot theory helps in the development of antibiotics and chemotherapy drugs by targeting the knot-like structures in bacterial or cancer cells' DNA.
- 🪀 The study of knot formation in real-world scenarios, such as tangled headphones, has led to insights on how to prevent or reduce knotting in everyday objects.
- 🌟 The concept of p-colorability and polynomial invariants like the Alexander and Jones polynomials are advanced tools in the knot theorist's arsenal for knot classification.
- 🔗 The history of knot theory dates back centuries, with contributions from famous mathematicians and scientists, including Lord Kelvin and Alan Turing, reflecting its enduring intellectual appeal.
- 🎓 The complexity and beauty of knot theory exemplify how mathematical concepts can transcend their abstract origins to become essential tools in understanding and manipulating the world around us.

###### Q & A

### What are the two common methods of tying a shoelace knot?

-The two common methods are going counterclockwise around the loop, which forms two identical trefoils on top of each other, also known as a granny knot, and going clockwise, which results in mirror-imaged trefoils on top of each other, known as a square knot.

### Why is knot theory important in mathematics and other fields?

-Knot theory is important because it helps identify, categorize, and understand every possible knot that could exist. It has applications in various fields such as the structure of proteins and DNA, development of new materials, and even in the creation of medicines that save millions of lives.

### What is the knot equivalence problem?

-The knot equivalence problem, also known as the problem of distinguishing knots, is the challenge of determining whether two knots are the same or different without breaking the loop. This problem has propelled the field of knot theory for over 150 years.

### How do mathematicians study knots without them falling apart?

-To study knots without them falling apart, mathematicians connect the two ends of the rope to form a closed loop. This allows them to tease the knot apart for study without it fundamentally changing.

### What is the simplest knot after the unknot?

-The simplest knot after the unknot is called the trefoil knot, which cannot be turned back into a circle without breaking it open, taking out the knot, and then closing it up again.

### How do you tell two knots apart using invariants?

-Invariants are properties of a knot that never change, no matter how much the knot is twisted or tangled. By comparing these invariants, such as crossing number, tricolorability, p-colorability, and polynomials like the Alexander polynomial and the Jones polynomial, one can determine if two knots are different.

### What is the significance of the Perko pair in knot theory?

-The Perko pair is significant because it consists of two knots that were listed as separate in Tait's knot tables for over 75 years. Kenneth Perko discovered in 1973 that they are actually the same knot, leading to a single correction in the long-standing knot tables.

### How do chemists create synthetic knotted molecules?

-Chemists create synthetic knotted molecules by tying molecules around ions or by designing molecules to self-assemble into knots. These knots change the properties of the molecules, potentially creating new materials with unique characteristics.

### What role does knot theory play in biological processes?

-Knot theory is crucial in understanding biological processes such as DNA replication and protein structure. Enzymes like type two topoisomerases use knot theory principles to manage knots in DNA, allowing for proper cell replication and functioning. Knots in proteins can also affect their function, and understanding these knots helps in their potential repair or utilization.

### How can you prevent knots from forming in items like headphones or strings?

-To prevent knots from forming, one can confine items like headphones or strings to as small a space as possible to restrict motion. Alternatively, increasing the stiffness of the string or wire can also help, as it reduces the likelihood of the free end braiding into loops and forming knots.

### What is the current total number of known prime knots?

-As of 2020, the total number of known prime knots is 352,152,252, as calculated by mathematician Ben Burton for up to 19 crossings.

###### Outlines

##### 🪢 The Fascinating World of Knot Theory

This paragraph introduces the concept of knot theory, a branch of mathematics that studies the properties and classification of knots. It explains that there are two common ways to tie shoelaces, which look similar but have different properties. The paragraph delves into the history and applications of knot theory, highlighting its relevance in various fields such as the structure of proteins and DNA, material science, and even medicine. It also touches on the discovery of the first 352,152,252 knots and the challenge of distinguishing between different knots, known as the knot equivalence problem.

##### 🧶 The Evolution of Knot Theory and Its Pioneers

This section discusses the evolution of knot theory, focusing on the contributions of Scottish physicist Peter Guthrie Tait and his interactions with William Thomson, later Lord Kelvin. It describes Tait's demonstration of vortex rings and Kelvin's subsequent hypothesis that atoms are made of vortex rings of ether. The paragraph also covers Tait's efforts to categorize knots based on their crossing numbers and his collaboration with James Clerk Maxwell. It concludes with the impact of Tait's work on the field and the challenges faced in distinguishing between knots.

##### 🔄 Reidemeister Moves and the Knot Equivalence Problem

This paragraph explains the concept of Reidemeister moves, which are three types of manipulations that can be used to transform any two identical knots into each other. It discusses the knot equivalence problem, which is the challenge of proving whether two knots are different or the same. The paragraph highlights the work of mathematician Wolfgang Haken, who created a computer algorithm to solve the knot equivalence problem for distinguishing any knot from the unknot, and the subsequent advancements that led to the solution of the entire knot equivalence problem using a specific upper bound on the number of Reidemeister moves.

##### 🎨 Invariants: The Key to Distinguishing Unique Knots

This section introduces the concept of invariants, which are properties of knots that remain unchanged regardless of how the knot is twisted or tangled. It explains how invariants can be used to uniquely identify knots and discusses the tricolorability invariant as an example. The paragraph also covers more powerful invariants like p-colorability and polynomial invariants, such as the Alexander polynomial and the Jones polynomial, which have significantly contributed to the understanding and classification of knots.

##### 🧬 Knot Theory's Impact on Chemistry and Biology

This paragraph discusses the practical applications of knot theory in chemistry and biology. It explains how knot theory has been used to understand the structure of synthetic knotted molecules, which can lead to the creation of new materials with unique properties. The section also highlights the role of knot theory in understanding the mechanisms of enzymes like type two topoisomerase, which are crucial for DNA replication in bacteria and humans. It emphasizes the importance of knot theory in the development of antibiotics and chemotherapy treatments.

##### 🎓 The Future of Knot Theory and Its Broader Implications

This final paragraph reflects on the journey of knot theory from a standalone mathematical field to a tool with applications in various scientific disciplines. It discusses the computational challenges involved in knot tabulation and the methods used to generate and classify knots. The paragraph also touches on the potential of knot theory in material science, with the example of creating stronger fabrics. It concludes with a nod to the curiosity-driven origins of knot theory and its potential to unlock mysteries in various fields.

##### 🏅 Sponsorship and Learning Opportunities with Brilliant

This section acknowledges the sponsorship of the video by Brilliant, an online learning platform that offers courses in math, data science, programming, and more. It highlights the platform's interactive and visual content, which makes complex concepts easier to understand. The paragraph encourages viewers to explore Brilliant's offerings, including a course on computational biology and a new course on data science, to enhance their skills and understanding of the modern world.

###### Mindmap

###### Keywords

##### 💡Knot Theory

##### 💡Trefoil Knot

##### 💡Unknot

##### 💡Invariants

##### 💡Reidemeister Moves

##### 💡Polynomial Invariants

##### 💡Knotted Molecules

##### 💡Type Two Topoisomerase

##### 💡Protein Knots

##### 💡耳机线缠绕

###### Highlights

Most people tie their shoe laces incorrectly, leading to knots that easily come undone.

There are two primary methods for tying a shoelace knot: counterclockwise and clockwise around the loop.

Knot theory is a branch of mathematics that studies the properties and classification of knots.

Mathematicians have discovered and catalogued over 352 million knots, each with unique characteristics.

Knot theory has practical applications in various fields, including the structure of proteins and DNA, new materials, and medicine development.

The concept of a knot involves a closed loop of rope that cannot be untangled without breaking the loop.

The simplest knot after the unknot is the trefoil knot, which cannot be transformed into an unknot without breaking and rejoining the rope.

Distinguishing between different knots is challenging and is known as the knot equivalence problem.

The crossing number is a way to categorize knots, representing the minimum number of crossings in the simplest form of a knot.

Prime knots are knots that cannot be decomposed into simpler knots, and they form the basis for understanding composite knots.

The knot equivalence problem has been partially solved using Reidemeister moves and computer algorithms.

Invariants are properties of knots that remain constant regardless of how the knot is twisted or tangled.

The tricolorability invariant can be used to distinguish between the unknot and the trefoil knot.

Polynomial invariants, such as the Alexander polynomial and the Jones polynomial, provide more detailed information for distinguishing knots.

Knot theory has been applied to create synthetic knotted molecules, which can have unique properties and potential applications in materials science.

Type two topoisomerases are enzymes that help manage knots in DNA, and their inhibition is the basis for some chemotherapy drugs.

Knot theory is used to understand and potentially repair misknotted proteins, which can be crucial for their proper functioning.

The correct way to tie shoelaces to prevent them from coming undone easily is by tying a square knot with a clockwise loop direction.

Knot formation in real-world scenarios, such as tangled headphones, can be modeled and mitigated with specific strategies.

Knot theory has evolved from a pure mathematical pursuit to a field with practical applications across various scientific disciplines.

###### Transcripts

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