Parallel Worlds Probably Exist. Here’s Why
 Published on: 06 March 2020
 The most elegant interpretation of quantum mechanics is the universe is constantly splitting
A portion of this video was sponsored by Norton. Get up to 60% off the first year (annually billed) here: https://bit.ly/32SM0yd or use promo code VERITASIUM
Special thanks to:
Prof. Sean Carroll https://www.preposterousuniverse.com
His book, a major source for this video is 'Something Deeply Hidden: Quantum Worlds and The Emergence of Spacetime'
Code for solving the Schrödinger equation by Jonny Hyman available here: https://github.com/jonnyhyman/QuantumWaves
I learned quantum mechanics the traditional 'Copenhagen Interpretation' way. We can use the Schrödinger equation to solve for and evolve wave functions. Then we invoke waveparticle duality, in essence things we detect as particles can behave as waves when they aren't interacting with anything. But when there is a measurement, the wave function collapses leaving us with a definite particle detection. If we repeat the experiment many times, we find the statistics of these results mirror the amplitude of the wave function squared. Hence the Born rule came into being, saying the wave function should be interpreted statistically, that our universe at the most fundamental scale is probabilistic rather than deterministic. This did not sit well with scientists like Einstein and Schrödinger who believed there must be more going on, perhaps 'hidden variables'.
In the 1950's Hugh Everett proposed the Many Worlds interpretation of quantum mechanics. It is so logical in hindsight but with a bias towards the classical world, experiments and measurements to guide their thinking, it's understandable why the founders of quantum theory didn't come up with it. Rather than proposing different dynamics for measurement, Everett suggests that measurement is something that happens naturally in the course of quantum particles interacting with each other. The conclusion is inescapable. There is nothing special about measurement, it is just the observer becoming entangled with a wave function in a superposition. Since one observer can experience only their own branch, it appears as if the other possibilities have disappeared but in reality there is no reason why they could not still exist and just fail to interact with the other branches. This is caused by environmental decoherence.
Schrodinger's cat animation by Iván Tello
Wave functions, double slit and entanglement animation by Jonny Hyman
Filming of opening sequence by Casey Rentz
Special thanks to Mithuna Y, Raquel Nuno and Dianna Cowern for feedback on the script
Music from https://epidemicsound.com "Experimental 1" "Serene Story 2" "Seaweed" "Colorful Animation 4"  Runtime : 20:
 veritasium science physics quantum mechanics many worlds Schrodinger Schrodinger's cat shrodinger cat Sean Carroll Everett norton 360 norton lifelock norton antivirus norton security norton secure vpn norton vpn cyber quantum multiverse parallel universe universes superposition entanglement branching wave function decoherence security cyber safety
COMMENTS: 40

addzsss bsss 3 hours ago
So can universes merge? Was there a point where there was only 1 universe, many billions of years ago?

Kerem Anani 4 hours ago
I don't exactly understand quantum tunneling, isn't that about things that have zero probability in shroedinger's equations happenings sometimes anyway. So wouldn't that suggest that anything is possible, just very very very unlikely

wefinishthis now 8 hours ago
Reality is a bunch of fields interacting. 'observation' is simply the interaction of certain quantum fields that cause the wave function to collapse under certain circumstances. That isn't what points to parallel universes, it's the probabilistic nature of the quantum world that does.

ryan seitz 12 hours ago
I believe Many Worlds is true, and it will be proven someday, or at least a modified version of it. Ask yourself the most basic question: What should exist? 3 possible answers: 1. Nothing 2. Everything, or 3. Something in between. We know option 1 is wrong because we exist. Option 3 implies a creator, someone or something to CHOOSE what exists and what doesnt (such as an electron, quark, or elephant), and a creator implies a simulation of which you can simply wind back the question to: Well what created the creator's "universe"? So all we're left with is option 2: Everything exists. All possible particles and combinations of masses, properties, and rules. I think this is whats going on, and similar to Many Worlds, it does explain the double slit experiment. It also explains why we appear to be in such a finely tuned universe. It also solves the Fermi Paradox. (we are truely RARE) I believe it also implies quantum immortality, which sounds awesome at first, until you really think about it  then, its horrifying. How do we test it? Im not sure. In theory, there should be a way to prove it  just to one person in one branch of universe at a time. And there's surely a nobel prize waiting for the person who does.

aquabery 19 hours ago
When I heard "This video is sponsored by Norton 360" my jaw dropped. How could you possibly have taken a sponsorship from Norton when you can find out with minutes of research that Norton not only has better alternatives that are free, but it also is infamous abo..snejejwm.........

Sweaty Albama 20 hours ago
if there were an infinite number of parallel universes there would be an infinite number of people or aliens crossing into our universe since they are infinite and with infinity all possibilities can occur. Either there is no way to travel between universes or there aren’t an infinite number of universes

RitaSijelmass 21 hours ago
I thoroughly recommend Carlo Rovelli's book Helgoland for anyone wanting to learn more in an accessible way

Neil Libertine 1 days ago
Is there elliptical orbit possible for any object or system at atomic level to cosmic level. If not then this is apparent and not actual, why it appear so is another question but forces deals with actual and not apparent motion.In any orbit which is closed path, there are two forces acting. One is inertia and other is toward centre acting force that may be electrical, magnetic or gravitational force. Though there is no such force as gravity clearly provable, so it could kind of mechanical force.Two forces acting on orbitting object are centripetal toward centre and binding, and other is centrifugal away from centre. Centripetal work as potential so distance dependent and centrifugal is kinetic. Both are equal in circle but in ellipse at apogee and perigee, centripetal is more than centrifugal.But how centripetal force depending on distance act with same strength with two different distance. Both central force theory as Newton's theory or spacetime curvature of relativity agrees that at more the distance, less the force. Earlier it was said that at perigee, nearest point, speed is more but that is not well explained with any present theory. So there is no elliptical orbit possible in nature.

Chem Man Dan 1 days ago
I'd like to believe that the number of branching universes at any given time is still finite, but like the universe itself, the number of branched universes are infinitely increasing just as the universe is infinitely expanding.

Bob Walden 1 days ago
And hopefully, at the end of this life on Judgement Day, every version of you will have been pleasing to God for the decisions you've made in those many universes! Theology meets Science.

Steve Carras 2 days ago
Cat in a box..a.Nice Rube Goldberish thing..b.Cats do have nine lives .. (both being lighthearted here, b.being of course not true..)(sadly)

Michael B 2 days ago
I don't know if Dereck realizes, but he just said something really deep: the entire universe (and everything in it) is really just one wave function.Put that in your pipe and smoke it.

Arcane Turbulence 3 days ago
Superpositioning is NOT proven by the double slit experiment. It only proves that we don't totally understand the correct fundamentals of electrons. The problem is that we see everything on the atomic level through a mathematical lens. We can never truly observe what is really going on. We can only see the result, and speculate.

Sivas 3 days ago
It took 13 billion years for the formation of our current universe , and you're saying that an another will be created all of a sudden when a cat dies!

P45 Nokota 2019 3 days ago
If we keep screwing around with this quantum decohearing we might just use up all the VRAM in this simulation or just flat out brake it.. I hope it’s not bc this is heavy math and iv heard $10k computers chugging to run hard math.

Dagmar Holíková 3 days ago
So we are bacically in the branches with biggest propabilities to happen and biggest impact of energy of the whole universe. Did I get it right?

Neil Libertine 3 days ago
Expression for doppler shift in frequency of light is, f' = ((c +/ v)/c)/f = (c'/c)fwhere, c' = c +/ v is relative speed of light to observer, v is relative speed of source and observer, c is speed of light at rest in free space, f' is shifted frequency of light, f is frequency of light at restFrom above expression, c'/f' = c/f = constant = wavelength, wSo it is clear that wavelength of light or any wave remain same when there is relative speed between source and observer of light, only frequency and speed of light undergoes change. Thus speed of light not remain constant in relative motion and that is reason of red or blue shift of light.Experience with relativists was worse because they used twisted arguments without logic and proof that change in frequency is due to change in wavelength but speed remain constant. This is falsified by other arguments also like nature of wavelength and frequency of wave.

no name 3 days ago
is it weird if me being a 16yr old somewhere in asia at home making food while watching this understood everything lil thing they mentioned?🤦🏻♀️🙂👀

Head Communications 4 days ago
If quantum superposition supports the multiverse theory, than it should be reasonable to expect that each person (and every other physical entity) has an almost infinite number of branches in their world lines with subtle variations in each when observed. Since the world line represents where and when you are along your entire lifespan, each of our world lines would then be formed by those branches in every version of the 'universe' within the multiverse. Schrödinger must have won many poker games : )

Alvin Augustine 5 days ago
Superposition only live in our imagination. It is not real. There is only you and only you exist in the universe. If superposition apply to the so called bing bang theory. Meaning there are two outcome, the other one is no big bang, no universe, and we dont exist. And the facts that we exist meaning, there is one universe we exist. And only one event occurs that is the big bang or the creation of the universe. Multiverse doesn't exist. Its all about choices, cause and effect in parallel to space and time. Once done its done.There is no version of you that live forever. Everything has come to and ends.

Joseph Oakley 5 days ago
It seems Mathematics as a whole is Time based because in order for Math to exist, Time must exist as "right now" and Math as a whole needs the "right now" as a static point to use as reference in Equations, right?. All I know is that I have these questions and they seem valid. The one thing that all Parallel worlds share is the fact that they are all "Worlds" right? What if Mathematics as a whole is based on "This 3D reality" or in simple terms..... "The Physical" instead of the "right now" that is always changing... "The physical" has always, is and will always be stable. Will always be constant and never change, meaning it will always be "the physical" Common sense has no equation and is rarely mentioned but "having" common sense and applying it in this physical world "works", yet we shy away from what works in favor of making "definitions" true. Trying to direct "what is real" with "opinions". ..... But just like every other time I talk about this.. Nothing but Crickets. We'll see

Neil Libertine 6 days ago
If speed of light is constant then why there is blue and red shift of light.

ayan javed 1 weeks ago
So the scientists who believe in parallel universe have another version of them who believes that there are no parallel universe???
Veritasium would be the best physics teacher.