Does light take all possible paths at the same time



We’re incredibly grateful to Prof. David Kaiser, Prof. Steven Strogatz, Prof. Geraint F. Lewis, Elba Alonso-Monsalve, Prof. Christopher S. Baird, Prof. Anthony Bloch, and Prof. Stephen Bartlett for their invaluable contributions to this video.

A special thanks to Mahesh Shenoy from FloatHeadPhysics for his help with this video. Check out his excellent intuitive video on the UV Catastrophe here (Sep 2024): https://www.youtube.com/watch?v=ALEDjjAVZSY

▀▀▀
0:00 What path does light travel?
2:40 Black Body Radiation
6:47 How did Planck solve the ultraviolet catastrophe?
9:42 The Quantum of Action
13:25 De Broglie’s Hypothesis
15:16 The Double Slit Experiment
20:00 How Feynman Did Quantum Mechanics
25:01 Proof That Light Takes Every Path
31:16 The Theory of Everything

▀▀▀
Sign up to our Patreon to watch the Q&A for free: https://www.patreon.com/c/veritasium

Try Snatoms! A molecular modelling kit I invented where the atoms snap together.
https://ve42.co/SnatomsV

▀▀▀
References:
Armin Hermann (Nov 1974). The Genesis of Quantum Theory (1899-1913). - https://ve42.co/genquanttheor
Richard P. Feynman (1985). QED The Strange Theory of Light and Matter. - https://ve42.co/qed
A fantastic book on the history of the Principle of Least Action: Rojo, A. and Bloch, A. The
Principle of Least Action: History and Physics. - https://ve42.co/Bloch2018
Coopersmith, J. (2017). The lazy universe: an introduction to the principle of least action. Oxford University Press. - https://ve42.co/LazyU
PBS Space Time. (Nov 2021) - https://www.youtube.com/watch?v=Q_CQDSlmboA
Sabine Hossenfelder. (May 2022) - https://www.youtube.com/watch?v=A0da8TEeaeE
Max Planck (1901). On the Law of Distribution of Energy in the Normal Spectrum. Annalen der Physik - https://ve42.co/lawdistenergy
Paul Ehrenfest (1911). Welche Züge der Lichtquantenhypothese spielen in der Theorie der Wärmestrahlung eine wesentliche Rolle?. Wiley Online Library - https://ve42.co/quantthermrad
Nils-Erik Bomark and Reidun Renstrøm (Aug 2023). The Ultraviolet myth. Proceedings of Science - https://ve42.co/uvmyth
Planck's law. In Wikipedia - https://ve42.co/planckslaw
PBS Space Time. (Jul 2017). - https://www.youtube.com/watch?v=vSFRN-ymfgE&t=10s
Einstein and The Photoelectric Effect. (Jan 2005) via APS News - https://ve42.co/einsteinphotoelec
Louis de Broglie (1924). On the Theory of Quanta. - https://ve42.co/theoryquanta
Larry Sorensen (2012). Path Integrals 1. University of Washington - https://ve42.co/pathintegrals
Feynman’s Method of “A Particle Exploring All Possible Paths”. (Mar 2018) via Pure Dhamma - https://ve42.co/allposspaths
A great intuitive video on the Feynman path integral approach - https://www.youtube.com/watch?v=Sp5SvdDh2u8&t=1253s
Origins of Quantum Theory. via University of Pittsburgh - https://ve42.co/origquanttheor

Images & Video:
Nobistor Altona 1880 via NDR - https://ve42.co/streetlight
Edison incandescent lights by William J. Hammer via Wikimedia Commons - https://ve42.co/edinclights
The full expanded form of the Standard Model Lagrangian by Chen Ning Yang et al. via Wikipedia - https://ve42.co/stmodellang
Muon Ray. (2011). https://www.youtube.com/watch?v=-QUj2ZRUa7c
Muon Ray. (2011). https://www.youtube.com/watch?v=1C7abO7LtV0
Bohrs Atomic Model via EEEGUIDE.COM - https://ve42.co/bohrmodel

▀▀▀
Special thanks to our Patreon supporters:
Adam Foreman, Albert Wenger, Alex Porter, Alexander Tamas, Anton Ragin, Autodidactic Studios, Balkrishna Heroor, Bertrand Serlet, Blake Byers, Bruce, Dave Kircher, David Johnston, David Tseng, Evgeny Skvortsov, Garrett Mueller, Gnare, gpoly, Greg Scopel, Juan Benet, Keith England, KeyWestr, Kyi, Lee Redden, Marinus Kuivenhoven, Matthias Wrobel, Meekay, meg noah, Michael Krugman, Orlando Bassotto, Paul Peijzel, qiaohui wei, Richard Sundvall, Sam Lutfi, Tj Steyn, TTST, Ubiquity Ventures, wolfee

▀▀▀
Directed by Casper Mebius
Written by Casper Mebius and Derek Muller
Edited by Trenton Oliver and Peter Nelson
Animated by Fabio Albertelli, Mike Radjabov, Ivy Tello, Andrew Neet and Emma Wright
Illustrations by Jakub Misiek, Tommy A. Steven and Cainejan Esperanza
Filmed by Derek Muller and Casper Mebius
Produced by Casper Mebius, Derek Muller, Rob Beasley Spence, Gabe Strong, Geeta Thakur, Emilia Gyles, Zoe Heron, Emily Zhang and Tori Brittain

Thumbnail contributions by Ignat Berbeci, Ben Powell, Jakub Misiek, Ren Hurley, and Peter Sheppard

Additional video/photos supplied by Getty Images and Storyblocks
Music from Epidemic Sound

Flexible Buildings: The Future of Architecture | Engineering Documentary

World's Tallest Tower: Burj Khalifa - Dubai's Vertical City: https://youtu.be/NJI8mOv4VW4

Never before have there been so many people on Earth. The new world creates new challenges for us living together, one of the biggest being the infrastructure in the world we live in.

How can we ensure that the cities anonomyzing and isolating its inhabitants become places of encounter again? How can we use technology to create new spaces in areas where there is no space left? How can sustainable construction revolutionize the construction industry? - In the search for answers, the documentary presents current concepts and implementations from the core disciplines of architecture, development of building materials, and urban design.
▬▬▬▬▬▬▬▬▬
Subscribe Free Documentary Channel for free: https://bit.ly/2YJ4XzQ
Join the club and become a Free Documentary Patron: https://www.patreon.com/freedocumentary
Facebook: https://bit.ly/2QfRxbG
Twitter: https://bit.ly/2QlwRiI
▬▬▬▬▬▬▬▬▬
#freedocumentary #documentary #flexible Buildings
▬▬▬▬▬▬▬▬▬
Free Documentary is dedicated to bringing high-class documentaries to you on YouTube for free. With the latest camera equipment used by well-known filmmakers working for famous production studios. You will see fascinating shots from the deep seas and up in the air, capturing great stories and pictures from everything our beautiful and interesting planet has to offer.

Enjoy stories about nature, wildlife, culture, people, history and more to come.

How the US used Bananas to Conquer Central America

Get a 4-week trial, free postage, and a digital scale at
https://www.stamps.com/JohnnyHarris Thanks to Stamps.com for sponsoring the show!

I will never be able to look at bananas the same way again. The history behind this fruit is filled with government coups, propaganda, and predatory corporations.
This is the story of how US imperialism gave us crappy bananas - and why the ones in your kitchen might be doomed.

Read more in a great book by Dan Koeppel: “Banana: The Fate of the Fruit that Changed the World" https://bookshop.org/books/ban....ana-the-fate-of-the-
Big thanks to Mark Whalen for his research on the topic.
Thanks to https://www.instagram.com/cent....ralamericandisruptio who covers the ramifications of this history.
And thank you to Anderson’s Tropical Fruit Farm in Florida for shipping us the Gros Michel Bananas!

- ways to support -
My Patreon: https://www.patreon.com/johnnyharris
Our custom Presets & LUTs: https://store.dftba.com/produc....ts/johnny-iz-luts-an

- where to find me -
Instagram: https://www.instagram.com/johnny.harris/
Tiktok: https://www.tiktok.com/@johnny.harris
Facebook: https://www.facebook.com/JohnnyHarrisVox
Iz's (my wife’s) channel: https://www.youtube.com/iz-harris

- how i make my videos -
Tom Fox makes my music, work with him here: https://tfbeats.com/
I make maps using this AE Plugin: https://aescripts.com/geolayers/?aff=77
All the gear I use: https://www.izharris.com/gear-guide

- my courses -
Learn a language: https://brighttrip.com/course/language/
Visual storytelling: https://www.brighttrip.com/cou....rses/visual-storytel

- about -
Johnny Harris is a filmmaker and journalist. He currently is based in Washington, DC, reporting on interesting trends and stories domestically and around the globe. Johnny's visual style blends motion graphics with cinematic videography to create content that explains complex issues in relatable ways. He holds a BA in international relations from Brigham Young University and an MA in international peace and conflict resolution from American University.

- press -
NYTimes: https://www.nytimes.com/2021/1....1/09/opinion/democra
NYTimes: https://www.nytimes.com/video/....opinion/100000007358
Vox Borders: https://www.youtube.com/watch?v=hLrFyjGZ9NU
Finding Founders: https://findingfounders.co/epi....sodes/johnny-harris-
NPR Planet Money: https://www.npr.org/transcripts/1072164745

Download a free audiobook version of "The Richest Man in Babylon" and support TED-Ed's nonprofit mission: https://www.audible.com/ted-ed

Check out our full book recommendation: https://shop.ed.ted.com/produc....ts/the-richest-man-i

--

In the 1600s, the Dutch East India Company employed hundreds of ships to trade goods around the globe. In order to fund their voyages, the company turned to private citizens to invest money to support trips in exchange for a share of the profits. In doing so, they unknowingly invented the world’s first stock market. So how do companies and investors use the market today? Oliver Elfenbaum explains.

Lesson by Oliver Elfenbaum, directed by Tom Gran & Madeleine Grossi.

Sign up for our newsletter: http://bit.ly/TEDEdNewsletter
Support us on Patreon: http://bit.ly/TEDEdPatreon
Follow us on Facebook: http://bit.ly/TEDEdFacebook
Find us on Twitter: http://bit.ly/TEDEdTwitter
Peep us on Instagram: http://bit.ly/TEDEdInstagram
View full lesson: https://ed.ted.com/lessons/how....-does-the-stock-mark

Thank you so much to our patrons for your support! Without you this video would not be possible! Lâm Nguyễn, Uirá Maíra Resende, Sebastiaan Vleugels, Adam Foreman, Jeremy Shimanek, Bethany Connor, Vivian & Gilbert Lee, Maryam Sultan, Peng, Tzu-Hsiang, Gabriel Balsa, Shafeeq Ansari, Norbert Orgován, Dowey Baothman, Amer Harb, Courtney Thompson, Guhten, Jordan Tang, Juan, Sid, Tracey Tobkin, emily lam, Kathryn J Hammond, Elliot Poulin, Noel Situ, Oyuntsengel Tseyen-Oidov, Latora Slydell, Sydney Evans, Victor E Karhel, Bernardo Paulo, Eysteinn Guðnason, Andrea Feliz, Natalia Rico, Josh Engel, Bárbara Nazaré, Gustavo Mendoza, Zhexi Shan, Hugo Legorreta, PnDAA, Sandra Tersluisen, Ellen Spertus, Fabian Amels, sammie goh, Mattia Veltri, Quentin Le Menez, Yuh Saito, Heather Slater, Dr Luca Carpinelli, Janie Jackson, Christophe Dessalles and Arturo De Leon.

Scientists like Prof Sinclair have evidence of speeding up, slowing, and even reversing aging.
Thanks to LastPass for sponsoring this video. Click here to start using LastPass: https://ve42.co/VeLP

What causes aging? According to Professor David Sinclair, it is a loss of information in our epigenome, the system of proteins like histones and chemical markers like methylation that turn on and off genes. Epigenetics allow different cell types to perform their specific functions - they are what differentiate a brain cell from a skin cell. Our DNA is constantly getting broken, by cosmic rays, UV radiation, free radicals, x-rays and regular cell division etc. When our cells repair that damage, the epigenome is not perfectly reset. And hence over time, noise accumulates in our epigenome. Our cells no longer perform their functions well.

To counter this decline, we can activate the body's own defenses against aging by stressing the body. Eat less, eat less protein, engage in intense exercise, experience uncomfortable cold. When the body senses existential threats it triggers longevity genes, which attempt to maintain the body to ensure its survival until good times return. This may be the evolutionary legacy of early bacteria, which established these two modes of living (repair and protect vs grow and reproduce). Scientists are uncovering ways to mimic stresses on the body without the discomfort of fasting. Molecules like NMN also trigger sirtuins to monitor and repair the epigenome. This may slow aging.

Reversing aging requires an epigenetic reset, which may be possible using Yamanaka factors. These four factors can revert an adult cell into a pluripotent stem cell. Prof. Sinclair used three of the four factors to reverse aging in the retinal cells of old mice. He found they could see again after the treatment.

Special thanks to:
Professor David Sinclair, check out his book "Lifespan: Why We Age & Why We Don't Have To"
Assistant Professor David Gold
Noemie Sierra (for polyp images)
Genepool Productions for telomere animations from Immortal: https://ve42.co/immortal
Epigenetics animations (DNA, histones, methylation etc) courtesy of: http://wehi.tv
Animation: Etsuko Uno
Art and Technical Direction: Drew Berry
Sound Design: Francois Tetaz & Emma Bortignon
Scientific Consultation: Marnie Blewitt
Courtesy of Walter and Eliza Hall Institute of Medical Research

Filming, editing and animation by Jonny Hyman and Derek Muller

Music from https://epidemicsound.com "Clearer Views" "Innovations" "A Sound Foundation" "Seaweed"
Additional music by Kevin MacLeod from https://incompetech.com "Marty Gots a Plan"