What is Braess's Paradox?

Braess's Paradox is a finding in network theory where adding capacity, like a new road to a traffic network, can unexpectedly increase congestion and travel time for everyone.

How did closing a street in New York improve traffic?

During Earth Day 1990, closing 42nd Street in New York unexpectedly improved traffic. This was an instance of Braess's Paradox, where removing a seemingly beneficial route led to a more efficient overall traffic flow.

Can Braess's Paradox apply to systems other than traffic?

Yes, Braess's Paradox can apply to almost any network system, including power grids, food chains, blockchains, and the internet. Adding elements can sometimes destabilize or worsen the performance of these networks.

How can I protect my personal data online?

Services like Incogn can help protect your data. They track down data brokers holding your information and automate requests to remove it from the internet, reducing spam and improving privacy.

What is 'counter-snapping' and how does it differ from normal snapping?

Normal snapping involves a material giving way and moving in the direction of the applied force, like an umbrella flipping inside out. Counter-snapping is the opposite, where a mechanism shrinks or contracts when pulled, moving against the applied force.

What makes the counter-snapping mechanism unique?

This specific mechanism at the AMOLF Institute is unique because it exhibits force jumping – a sudden increase in stiffness when it switches states. This allows it to change its natural frequency without changing its length, unlike other snapping structures.

Key Moments

This mechanism shrinks when pulled

Veritasium

Education3 min read24 min video

Jun 30, 2025|11,346,564 views|254,407|10,758

veritasium science physics math maths traffic Braess’s paradox Braess game theory springs hooke’s law dynamic traffic

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Key Moments

TL;DR

A mechanism shrinks when pulled due to a physics paradox, with applications in traffic, power grids, and anti-vibration systems.

Key Insights

A novel mechanism shrinks when pulled, defying typical material behavior.

This counterintuitive effect is governed by a physics paradox, described as 'counter snapping'.

The paradox, known as Braze's paradox, applies to various network systems, including traffic, power grids, and even food chains.

Modifying networks by adding elements can paradoxically worsen performance, such as increasing traffic congestion or destabilizing power grids.

The mechanism's ability to switch between series and parallel configurations is key to its behavior.

This 'counter snapping' can be harnessed to control stiffness without changing length and to actively reduce vibrations in structures.

THE PARADOXICAL MECHANISM

The video introduces a remarkable mechanism that exhibits an unusual property: it shrinks when stretched. When tension is applied, instead of elongating further, it contracts. This counterintuitive behavior defies common expectations, as observed when adding weight causes a structure to contract rather than sag. This effect, initially appearing to violate physics, is rooted in a fundamental paradox that governs a wide range of systems.

UNDERSTANDING SERIES VS. PARALLEL CONFIGURATIONS

At the heart of this phenomenon lies the concept of how springs (or similar elastic components) are connected. When springs are in series, they share the load equally, and the total extension is the sum of individual extensions. However, when springs are arranged in parallel, each spring supports only a portion of the load, leading to a smaller combined extension. The paradox arises when a system that is initially configured in series is forced into a parallel configuration.

BRAZE'S PARADOX AND ITS REAL-WORLD IMPLICATIONS

This paradoxical behavior is formally known as Braze's paradox, named after mathematician Dietrich Braze. It was famously observed in traffic management, where closing a busy street paradoxically improved overall traffic flow. The principle extends to networks like power grids and even biological systems, where adding elements can degrade performance. In essence, for these networks, 'less can be more'.

THE EARTH DAY TRAFFIC EXPERIMENT

A striking example of Braze's paradox occurred during New York City's Earth Day in 1990. The closure of 42nd Street, a heavily trafficked area, was predicted to cause chaos. However, the opposite happened: traffic in surrounding areas improved significantly. This was later modeled and explained by Braze's work, which illustrated how seemingly counterintuitive changes in network topology could lead to better outcomes, contrary to individual rational choices.

MECHANICAL IMPLEMENTATION: COUNTER SNAPPING

The physical mechanism demonstrating this paradox is built from components that, individually, stretch normally. However, when combined in a specific topology, they exhibit 'counter snapping' – shrinking when pulled. This contrasts with 'snapping,' where materials suddenly deform beyond a certain force threshold. The mechanism flips between series and parallel states, leading to its unique length-changing behavior under tension.

APPLICATIONS IN STIFFNESS CONTROL AND VIBRATION DAMPING

The counter-snapping mechanism has significant potential applications. It allows for the control of stiffness without altering the overall length of the structure by switching between series and parallel states. Furthermore, it can be used to actively mitigate vibrations. By dynamically changing its natural frequency, the mechanism can counteract resonance, preventing excessive oscillations in structures and potentially simplifying vibration damping systems.

FUTURE POTENTIAL AND DATA PRIVACY

While still in early stages, the principle of counter snapping is being explored with different variables, aiming for even more counterintuitive behaviors like a balloon deflating when inflated. The video also touches upon data privacy, drawing a parallel between the paradox and the idea that less personal data online generally leads to better security, referencing a sponsor that helps remove personal information from data brokers.

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Common Questions

This phenomenon, often called counter-snapping, occurs when a system changes its configuration from a series to a parallel state under tension. This transition causes the individual components to adjust in a way that makes the overall mechanism shorter.