Necessity of complex numbers

MIT 8.04 Quantum Physics I, Spring 2016
View the complete course: ocw.mit.edu/8-04S16
Instructor: Barton Zwiebach
License: Creative Commons BY-NC-SA
More information at ocw.mit.edu/terms
More courses at ocw.mit.edu

[@andrewchen2673]

See you all next year when the algorithm brings us back

[@m.raedallulu4166]

7:00 (When very good physicist are wrong, they are not wrong for silly reasons, but they are wrong for good reasons, and we can learn from their thinking.) I love it!

[@eloymarquez4783]

Booom

[@larrykinglk]

Love it too. Very inspiring!

[@jasonsmith4114]

When something sounds right but is also actually right, great quotes are made.

[@TruMystery]

stfu brainlet

[@declanwk1]

Einstein was not saying that QM was wrong, it gives such accurate answers it can't be wrong. He was saying that QM was incomplete. Bohr's dominant personality resulted in history recording that Einstein lost these early arguments in the interpretation of QM but many of the questions he raised are still unanswered and need to be resolved along with incompatibilities between QM and GR.

[@stm3252]

gauss hated the name imaginary, because it's confusing.He suggested to use lateral, because the complex number are represented on the lateral axis unlike all other numbers.

[@ridovercascade4551]

He sounds right, but I am not to deep in Algebra to have an opinion. Maybe Imaginary has also some point of truth? The square root of -1 is impossible, so imagine being possible. B times that imaginary square root -1. But sure for me as a student, it would be made me so much clear if it wasn't called imaginary axis.

[@Adam-rt2ir]

It's impossible in the usual high school restriction to real numbers, but then people starting to study complex numbers complain, because why study something that is impossible/imaginary, it creates a bad approach, not very open minded.

[@BlahBlahBlah13623]

@@ridovercascade4551 'imaginary' numbers are as imaginary as negative numbers.

[@roc6596]

i can be easily defined as the product between to points in a Cartesian plain which is (0;1).(0;1)=(0;-1) looking at an Argand Gauss plain it would look like i.i=-1, so we can basically multiply to real points and obtain minus one

[@Jack01010]

@@ridovercascade4551 Actually imaginary numbers are real, so it's better call them "lateral"

[@ramenmondal8342]

I am not mathematics major. But whenever I watched videos regarding math it brings Peace in heart. I don't know why

[@chiranjitray760]

That makes you a mathematician

[@antoniodiaz1998]

That's because mathematics is a gift from god

[@ergbudster3333]

Change your major. Unless you're physics or stats or social science with stats then you already in place. Continue thinking. Be the genius you were meant to be.

[@zTheBigFishz]

Music of the Spheres...

[@suyash-dwivedi]

Well you feel nostalgia, that's why.

[@luismontalvohiroyasu5814]

Barton Zwiebach is peruvian. He was born and studied school and electical engineering in Lima, Peru. As a peruvian I feel so proud of him.

[@felipetoledodiaz1928]

Que orgullo, saludos desde chile

[@mauricioaletz9694]

Wow, increíble que haya llegado tan lejos!

[@umeriqbal5406]

Peruvian flake cocaine 👍

[@dibujodecroquis1684]

Ya me di cuenta de que su acento al hablar inglés es de hispanohablante, pero ni su nombre ni su apellido son de hispanohablante...

[@luismontalvohiroyasu5814]

@Arriaga Two El Perú es un país compuesto por un crisol de razas: mestizos, nativos, blancos, negros, asiáticos, etc. PERÚ: País de cultura milenaria y de todas las sangres.

[@codeisawesome369]

If I ever strike it rich, I would love to go to MIT to study physics at leisure with amazing teachers like this...

[@VoidFame]

Tbh you could just go for free and not get credit. Make friends not money :p

[@codeisawesome369]

@@VoidFame I'm not from the States, so unfortunately I'll be stopped at the border even though I'm trying to make Friends - because I don't have Money...

[@VoidFame]

@@codeisawesome369 I see now. It's not an issue of tuition, but an issue of living arrangements. I wish you the best of luck if you decide that is your pursuit.

[@codeisawesome369]

@@VoidFame Thank you! :-) Have a great week ahead.

[@0xDEAD_Inside]

@@VoidFame What! You can?

[@stephenanastasi748]

I had to learn this by distance education (1992) before the internet and always struggled. Barton makes it seem so easy. What a fabulous lecturer.

[@vahidmirkhani]

I clicked because I thought he was a young Harrison Ford. Now I know how complex numbers are crucial part of wavefunctions in quantum.

[@eklipsegirl]

Who the fuck is that Harrison Ford? Why are people so obsessed with screen clowns and disregard quantum physics? I had to google to know who that guy is and was very disappointed to find out that it's yet another random film actor :(

[@omniyambot9876]

@@eklipsegirl yeah useless actor

[@NightmareCourtPictures]

@@eklipsegirl Relax. Some of us that like physics, also like movies. In fact some of us like physics because we picked it up from watching movies! Twister was one of the first movies i saw as a kid...I largely believe that this movie alone is one of the things that shaped my entire life to who I am today, being both a filmmaker and a hobbyist physicist.

[@melontusk7358]

@@eklipsegirl chill, mate, nobody's disregarding QM here. As a physics major who minored in other things, I love cinema. "Blade Runner" starring Harrison Ford was a bold film that dared to ask thought-provoking questions. "Interstellar" is another cerebral masterpiece that also deals with existential ideas as well as Theoretical physics, mainly General Relativity and higher dimensions. It truly sparked my interests again and inspired me to retake my Relativity course. Films have influenced many great physicists and engineers in real life, most notably Hyperspace in Superstring Theory and most recently the NASA's warp drive from "Star Trek" by Alcubierre.

[@arnabmukherjee6192]

@@eklipsegirl calm the fuck down you pseudo intellect

[@user-tt2po5wg7n]

What a great introductory video. The professor is comfortably understandable and thorough.. Fantastic, short introduction to complex numbers and their importance. Thanks for posting!.

[@timthompson468]

Great video. I’m reading Ruel Churchill’s book on complex numbers and applications. I like his introduction. Instead of starting with the definition of i as the square root of negative one, i is introduced as part of a function that is necessary for certain equations (an ordered pair with certain, somewhat unusual mathematical properties). As, I read it, the fact that it turns out to be the square root of negative one is more a consequence of the definition , rather than the basic definition of i. It’s a subtle point, but that explanation sits better with me. Most modern books start with “i is the square root of negative one,” and that’s harder to get my head around than the more fundamental definition.

[@fourier07able]

'I' is a solution of the equation: x^2+1=0,so we could take this equation as the generator of imaginary numbers, i.e. the positive square root of '-1' is the imaginary unit i=(0,1), an ordered pair.

[@akinyiomer4589]

This is actually so damn useful. I wish more instructors/professors/reference books approached the more abstract concepts from this perspective, as the majority of learners - particularly those who don't enjoy maths - will have a better chance at getting a complete and thorough understanding.

[@xqamii3862]

most of the reasons it is introduced like this is because it was used by him previously in the lecture, when talking about Motion in 1D, i think. i do agree that it is a good way at looking at i, and complex numbers as a whole instead of just defining it by itself

[@TheBeatle49]

Agreed!

[@MGHOoL5]

Exactly! That's how we should learn: why was a concept created and not 'here is a useful information to remember'. Things must be learned as they arose: out of necessity not possible utility. That's why I find it fascinating to read history which renders the present necessary or in hermeneutics (e.g. psychoanalysis) to grasp things from their fundamentals.

[@manuelignaciodelgadotalave7958]

As a peruvian I feel proud of Barton, he is the best student of the National Engineering University in Lima Peru

[@Avicenna10]

Fantastic, short introduction to complex numbers and their importance. Thanks for posting!

[@hugoaraujo3]

I am a teacher at the beginning of my career. That was a very inspiring explanation.

[@andrealeto99]

you teach in university?

[@LsPl.]

Honestly, this was probably the best introduction to quantum mechanics i'ver ever heared. Before you get to this whole superposition shit and stuff, first explaining the fundamental maths behind it, which by all means isnt that hard to not teach it to students. Great job.

[@mohamedaminechekkouri8890]

I’m actually an engineer but this is the first time I understand why we really need the complex numbers Thank you sir !

[@nyahhbinghi]

He didn't really get to a full explanation but it was a good start...a couple of identity equations doesn't explain at least for me

[@leif1075]

EXSCTLY ZHE DIDNT EXPLAIN AT ALL WHY WHY DOES TJE WAVEFUNCTION have imagonary i in there to begin with...it has partly to do with not being bale to have time move backwards but he doesn't get into that at all..

[@michaelgoldsmith9359]

We don't need complex numbers it's just a simple way of taking into account things which change with regards to the period of sin function, like ac current, or for simplifying manipulations of vectors, which can be done without complex numbers but just in a nightmarishly complex way.

[@kuldeepshukla1797]

Started with x^2 + 1 =0. People were not used to with these kind of equations

[@iamthegreatest3914]

Pure Mathematics don't search for Its applications. Pure Mathematicians do mathematics for fun & they get pleasure doing it . For example - Group Theory was Invented for Fun . But later other people found its uses in Computer Science & Quantum Physics

[@usptact]

Very nice short note on complex numbers. A great professor tells you much more than just writing down those dry equations.

[@afifakimih8823]

Very pure very clear very quality lecture series on QM and QFT...!❤💜❤

[@espi3324]

This brings me back to the good old days of engineering school. Ironically I miss it. I felt so sharp in my mathematical skills.

[@keen2461]

When I studied this subject 25 years ago, back on the engineering classes, I remember I got to understand the topic quite well as it was necessary to solve circuits problems. But I never got to use that on the real world, and now it is a "complex" concept for me. Anyway, I hope someday I have the time to brush up on my advanced maths.

[@shameelkhan8189]

Oh jee aspirant!

[@YakiOnigiriZoro]

I thought that was Harrison Ford in disguise

[@camunoz2]

Yeah right?

[@gabor6259]

Harrison Ford + Benedict Cumberbatch

[@pugboi8017]

ROFL

[@PeopleOfCasinos]

Lol I had the same thought "wtf is Harrison Ford doing at MIT????"

[@anderson.barcellos]

Dude! Tot's! 🤣

[@nathanwalker1424]

What a great introductory video. The professor is comfortably understandable and thorough.

[@zzzyzzzyzzzyxxx]

It is a tragedy that the terms _real_ and _imaginary_ were adopted to classify these numbers since: a) The origin of the terms was actually meant to be used as an insult to certain mathematicians (more in a moment), and b) It confuses students learning math who, through no fault of their own, assume the lay, or common, definition of imaginary, that being something that is “fantasy”, “make-believe” or “made up”, leading to a student’s understandable conclusion: _how can something that “doesn’t exist” be in any way useful? _ Good question! Origin and usefulness to follow, but first . . . . A side track in nomenclature . . . . In physics, there is a fundamental particle called a quark. There are 6 types of quark. These types are called flavors. The flavors of quarks are: up, down, bottom, top, strange and charmed. Why is one strange and the other charmed? Can you really taste them if they are called flavors? Nope - they are just names whose origins come from the imaginations of the physicists involved. (en.wikipedia.org/wiki/Quark#Etymology) *The origin of the terms Real Number and Imaginary Number* In the late 16th to early 17th century, when some mathematicians began developing the idea of the square root of negative numbers, other mathematicians were not too impressed. One prominent mathematician (and naysayer) of the day was Rene Descartes, who wrote, scathingly, "_These people play with their imaginary numbers while we mathematicians work with real numbers_." Herein lies the origin of both terms real and imaginary. Yes, before Descartes remark, the numbers we now call real numbers were not called real numbers by mathematicians, they were just called numbers!

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐💐

[@ezomaruzcategui80]

Thanks for the contribution. Make remember My times in Electrical Circuits with Samer Teacher.

[@lolaalsaadi5708]

Wow , such an amazing explanation, thanks lot

[@sungbeomcho3606]

How couldn't I thumbs on this lecture. Thanks professor

[@puekai]

I like his writing, elegant

[@cidorodrigues6087]

I'm Sido Rodrigues Brazil I really like Quantum Physics Classes. Very important to know quantum physics. Teach everything the universe knows and you gain self-knowledge about everything. Great series of really useful lectures on quantum mechanics. I am also very grateful to MIT OpenCourseWare and Barton Zwiebach... etc...

[@Rocket89P13.]

El legendario Barton de la UNI

[@gauravxsharma]

I really love it we need this type of teacher in india because I always think why this is required to study and he had a very clear point of it with examples i love it never in my life i had this my clear view to any chapter a lots of love from india.

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐

[@souvikdas5662]

Really awesome explanation of complex nos and necessities in qm

[@EeshwarBalageethavengateswaran]

4:24.. yes we can work and get it.. McLaurin's series is one best way to use and prove that e^ix = cos x + i sin x.. U can enjoy proving it bcoz it gives a detailed and satisfying proof. I've done many times.. it's interesting.. 😊😊😊

[@xyzct]

The most enlightening way to teach complex numbers is to show the student that from N to Z to Q to R to C is merely four different quotient set extensions designed to remove the obstructions to the inverse operations: subtraction, division, logarithms, and root extraction, respectively.

[@LarryD-ul3le]

You mean limits, not logarithms. And you should really continue on to quaternions.

[@xyzct]

@@LarryD-ul3le, no, I do not mean limits. I mean logarithms. And tell me, what obstruction to an algebraic inverse operation did the quotient set extension to form quaternions remove?

[@rafanifischer3152]

These are cool studies. The professor has a nice clear-cut way of explaining without overemphasizing the simpler parts of the mathematics.

[@thegirlwholovesmaths]

Totally agree. Clear and concise. He knows his stuff.

[@rogerarrick1907]

Oh that was very good. Brought a lot of stuff together nicely.

[@pietro5266]

Because of this lecture, I now understand the foundation of cos x + i sin x, and also how "i" came to exist and it's usefulness. Never saw these explanations before.

[@naveenkrupadas6333]

MIT is MIT. It is always absolute. Thank you, MIT

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐💐

[@pandit-jee-bihar]

He summed it all up with the statement that "complex number was needed to solve equations". That's it!

[@FunPHYSICZ]

This is excellent. One of my degrees is in Physics. I have a lot of math in my background. Complex Numbers were a necessary subject in order to do the math. The problem was that the concept of mapping complex numbers to a Cartesian Plane was just presented as a given, with absolutely no explanation why. "That's just the way it is." Dr. Zwiebach does a much better job of presenting the "why" than most professors. But the ultimate understanding for me occurred when I stopped and read the history of Rene' Descartes, one of the greatest mathematicians ever, and the reason we call this plane representation "Cartesian". If you get an understanding of Descartes's thought process and where the concept of Complex numbers comes from, you can think like a mathematician and not just depend on memorization.

[@tchevrier]

complex numbers are fundamental in electrical engineering and pretty much anything that deals with waves because that angle gives you a way to represent the phase of the wave.

[@spb1179]

Going to have to watch these lectures, this prof is amazing

[@gokurocks9]

I took a lesson on complex numbers before I took any trig, Calc. I didn't know you could use i to solve polynomials. That's incredible...

[@drania76]

That’s the correct order of learning mathematics, congratulations. Once the idea that only positive number has a root square has been internalised it really is difficult to understand complex numbers and complex numbers are another level of mathematics and that is a real magic.

[@stephenbeck7222]

The primary purpose of complex numbers in algebra is to solve polynomials. How do you solve x^2+1=0 without i?

[@no_more_spamplease5121]

​@@stephenbeck7222 Yes. Complex numbers were invented to ensure the *closure* property for solving quadratic polynomial equations, ensuring any of them will necessarily have 2 complex roots (which can be real numbers or not).

[@stassavchuk]

Well, finally, on the 27th year of my life I realized the physical sense of the complex number :)

[@srinivasg1295]

Hats of to the instructor.. Amazing brain people have.. So complex

[@ilmdost8088]

Love this, such a nicely interpretate, We really need of such great man as an teacher.

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐💐

[@springdoctor]

There is no mystery about imaginary numbers or euhler’s identity. As the exponent of e , the imaginary number causes the radius to rotate counter clockwise around the x, y axis of the unit circle sweeping out out cosine and sine values just as the good professor says. Knowing this, imaginary numbers make perfect sense and e to the i 2pi = 1

[@jonahansen]

Man, this professor is good!

[@oprahwinfrey2967]

Historically, there was sequential extension of number fields. The field of natural numbers was extended to the field of integers, then up to the field of rational numbers, then up to the field of real numbers and, at last, up to the field of complex numbers. The complex field thus has a key distinctive feature: It is algebraically closed. Restriction of physical quantities only by the field of real numbers seems logically unsatisfactory since mathematical operations often deduce them from the field of original definition.

[@MikeDbean420]

Great teacher. Thank you for video.

[@roughsharkangular2034]

I clicked because i thought it was harrison ford teaching mit class

[@FernandoVinny]

Obviously MIT students already know what are Complex Numbers

[@MetallicDETHmaiden]

you'd be surprised.

[@mohittiwari8934]

Yes

[@aperture0]

@Non sum dignus I had to 'cause it's freaking MIT!!!!

[@brandonklein1]

I agree, but perhaps it is the case that thinking of them in maybe a new more pure way as described by the professor gets some of the clutter and possible confusion about them out of mind.

[@smishdws]

At my school, introductory mathematics is a prerequisite for quantum mechanics, but I think complex numbers was still very briefly discussed. Always good to quickly put everyone on the same page to follow discussion, and emphasize some important math concepts that will connect to physics concepts later on.

[@vipuljani6027]

I am first time meeting with Walter Levin in IIT Bombay and this time I see that professors is no difference between that!!! I love tham very much in this time I am in harverd in us I am very happy too

[@NeoCynic1]

Reading Spengler and his explication of the various "mathematics" of different Cultures. This helps

[@richardhall9815]

I love how the chalk boards move up and down like window sashes.

[@andrewlankford9634]

You know it's MIT when every blackboard moves up and down like a window sash. That's reeel quality there.

[@plfreeman111]

A great professor hints at things beyond what are being taught. @2:30, "It's actually zz*, a very fundamental equation". And with year's of math under my belt now, I'm like, "Oh, man, that is a huge deal." That you can use the multiplication of a complex number with it's conjugate to get a real number that is a squared norm and generates a measure on the space of C. Mind still blown (even though I know this stuff well). But the professor just moves on and leaves it lying there. Quietly acknowledging the importance, but knowing that it's a distraction from what needs to be taught. Bravo.

[@nizarsurche]

شكرا على التقديم الرائع

[@dkarthiganesh]

Thanks Professor

[@jaacobb123]

When you're smart like these professors you can convey as much information speaking slowly as eminem rapping

[@dozog]

I like your observation. It's about the information density of this prof.'s words. An involved receiver is also a requirement. Eminem videos have more views.

[@jaacobb123]

@@dozog Exactly, and very true.

[@dozog]

@@jaacobb123 If the old adagium that repetition is the mother of learning is true, then rappers may still be great teachers.

[@pre-universitygeometricalg5862]

In Geometric Algebra (which is a development of Clifford Algebra), the unit imaginary is given a geometric interpretation that is extremely useful in formulating and solving mathematical problems that arise in a broad range of fields, including quantum mechanics. Our channel is mainly for lower-level users of GA, but some of the members of our associated LinkedIn group are GA experts, and will be happy to direct interested viewers to sources of additional information.

[@tenaciousgirl5201]

Sir, you don't know how grateful i am to you ! May the One True God bless you.

[@shubhambaidya6126]

Such good quality education to millions around the globe... *Claps claps*

[@JeffaHensley]

Decent lecture, but it begs the question of the title of the video. He just states that they’re necessary, meanders around a few examples of how we’d be lost without imaginary numbers, but other than this necessity for their existence, doesn’t explain them.

[@kingk.crimson6633]

"Other than the necessity for their existence" that is the title of the video

[@RangerCaptain11A]

probably a 1.5 hour class, so most of the content is missing.

[@ramenbroth]

You're asking for something that's not within the context of the title of the video...

[@madScientist404]

the answer to your question lies in Geometric Algebra. The result of the work of Grassmann, Clifford, Hamilton and sort of rediscovered by Hestenes. It gives you a geometric interpretation for the equation i^2= -1. It can be associated with some plane in physical space.

[@flumpyhumpy]

@4:38 "Complex numbers, you used them in electromagnetism, you sometimes used them in classical mechanics, but you always used them in an _auxiliary_ way. It was not directly relevant because the electric field is real, the position is real, the velocity is real, everything is real. And the _equations_ are real. On the other hand, in quantum mechanics the equation *already has an i* . So in quantum mechanics, psi is a complex number. _Necessary_ . *It has to be* ." This lecture is from a course on quantum mechanics. The title of the video is apposite, concise, and absolutely correct.

[@peterpetigrew2869]

"GET TO THE CHOPPER !!!" 😂😂😂😂

[@sneakytweeky7625]

Awesome teacher he really speaks a story which makes it attractive to listen to Wish my teachers spoke like this

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐💐

[@faustdownunder]

The "norm" is otherwise also denoted as the magnitude of the complex number vector. May I respectfully add that Z = cos(theta) + i * sin(theta) only if magnitude(Z) = 1. Complex number are used and have been used for a very long time in AC circuit theory. We can indeed very well measure complex numbers by simply measuring amplitude and phase of voltages, currents, field vectors.

[@joefagan9335]

Well that was begging the question!!!

[@emmanuelb.jankpolo4651]

Great teaching

[@peterkiedron8949]

Do not confuse notation with deeper meaning. The equation can stated as a set of two equations of Re and Im parts and complex numbers do not have to be invoked. So, no complex numbers are not necessary but they simplify notation.

[@fethilakhdari1078]

Great video in every respect, please keep them comming.

[@Tomahawk1999]

if i had teachers like these, maybe i would not have hated math so much and actually done well in my life.

[@AnimeCritical]

Even now it's not too late.

[@MaxPower2719]

Many people who had bad or mediocre teachers turned out really well. Your future lies in your own hands, not in the hands of some teacher. All the tools are available; you choose to pick them up or walk away. If the "1999" part in your name reflects you year or birth, you are a measly 20 years old. Your life has hardly begun. You have all the opportunities ahead of you to "do well" in your life. Or, you know, you could just sulk on in the internet and blame others for not following your hopes and dreams.

[@stuartyeo5354]

Very encouraging :)

[@thicclumber5790]

Tomahawk1999 ur a failure because of urself and nobody else, but sure blame ur teacher if it makes u feel better

[@felipeteixeira7169]

thicc lumber who the fuck are you to judge someone as a failure, though? There are n factors that may cause one to get unmotivated and bad teachers is surely one of them.

[@ffggddss]

This is really well presented! This guy ought to be teaching at MIT or the like. Oh, wait, ... Fred

[@amitabhbasu6583]

Flfoilm

[@remixex369]

I have never taken QM. However, thanks to QM we have a very VERY robust wave propagation theory. One of the most reliable ways to compute synthetic seismograms is through Normal Mode Summation. It saves you a lot of headaches to do this!

[@Larry000]

G.O.A.T. explanation of complex numbers!

[@AndreaCalaon73]

I would love to eventually hear about Geometric Algebra ...

[@RangerCaptain11A]

my professor for that class was romanian. she talked slow like this professor, so it was easy to follow. it was a good class to expand your mind.

[@AndreaCalaon73]

@Muhammad Haider No, I mean "Geometric Algebra", as proposed and first studied by David Hestenes

[@NLGeebee]

Except that i ≠ √-1. By definition i² = -1, so if anything i = ±√-1.

[@adrien8572]

No by definition i=(0,1)

[@NLGeebee]

Adrien If you mean that the coordinates of z = 0 + i in a complex plane are (0,1) then you are right, but a graphical representation is not equal to the definition.

[@adrien8572]

@@NLGeebee The way complex numbers are built is by defining two operations on the set R^2 : one addition and one multiplication. i is a notation for the couple (0,1) because it is easier two manipulate this notation. It really is just that. You can represent all complex numbers in R^2 because they are just R^2 with two operations !

[@NLGeebee]

Adrien I believe I was tought that if the complex number z = i, or z = 0 +1i, then that number z is represented in R² as the point (0,1).

[@adrien8572]

@@NLGeebee That is indeed true !

[@Alpha-wj9hb]

الراجل ده عالي فشخ ❤️

[@dearheart2]

Brings back memories.

[@williamsmith4220]

He just derived de moivre's theorem!!! Holy cow I never noticed that.

[@puru1818]

No, he didn't...

[@SuperSaltyFries]

He derived Euler's formula.

[@p27kushagra]

@@SuperSaltyFries He derived nothing. What's wrong with u people..?

[@Indic4Zone]

i should really stop binge watching science videos when i keep saying "alright just one more yt videos, and i will sleep after this"

[@flowerwithamachinegun2692]

r/iamverysmart ?

[@Indic4Zone]

@@flowerwithamachinegun2692 nah dude, i'm just wondering why these lectures videos keep appears in my reccommendation, yeah sometimes i do watch 3b1b/blackpenredpen/welch labs/ocw but most of the time, i watches family guy/simpsons/futurama/one piece/the last airbender, i just like to do it, i'm just not very sure why this video keeps appearing in my reccommendation

[@donwald3436]

MIT has the best blackboard erasers, that big boy is a dream.

[@arifulmoral]

Excellent

[@oldguy1958hk]

Good refreshing course... I make living on I... I call it "j" part of a number ...for me I stands for current, I m an electrical engineer.

[@davjdprjce]

the imaginary unit is denoted *j* in electrical engineering since *i* denotes current

[@eceakyol5857]

in turkiye we learn the complex numbers in highschool

[@jelteverhoeff]

In NL we learn nothing in highschool

[@Shrodinguer4321]

Come and take a look at the moroccann program 😂

[@ansupriyadarshi1456]

So do we in India. It’s a fascinating subject when you look back at it. At the time I thought why study when it’s all imaginary 😂

[@t_aikutsu]

In the UK usually people would start to learn it in university, but some people choose to study "further maths", which sees them learning about complex numbers from 16

[@memojedi]

Perfect explanation! Just perfect!

[@beoptimistic5853]

kzbin.info/www/bejne/joKsk6FobMmCoKc 💐💐💐

[@maggiejetson7904]

I always wonder why we need to learn complex number, but didn't understand it till 3rd year in college for electrical engineering. It makes frequency related work a lot simplier.

[@afifakimih8823]

Who says physics is boring...It's actually amazing...just see these lectures.!!absolutely Amazing.!"

[@kylewhitney2890]

While the smartest of the smart get into schools like MIT, Harvard, etc., I’d love to go there I would sit in on lectures like this for fun.

[@TheMounten1]

If you work hard enough you can get into a good uni in the us with comparable education although you may have a large debt to loans

[@CIOWhitepapers]

That's what you're doing right now. Many of the big universities have full classes on youtube now and it's quite possible that you'll get more from those courses than the freshmen who pay top dollar to attend in person.

[@kandasamym6600]

Knowledge should for knowledge only but not exami orientation The teacher is teaching very nicely

[@spacelemur7955]

All my life from ~ age 10, when in the presence of a good teacher I have always felt on the verge of understanding math, but have never had it quite click into place. Next year I turn 70, and am still trying, albeit with declining hope.

[@schmetterling4477]

Why are you telling us that you never had the intention of paying attention to mathematics? ;-)

[@stevenvanhulle7242]

"Once you invent i you don't need more numbers." Quaternion: "Am I a joke to you?"

[@maxfrankenberg8260]

Steven Van Hulle ... to solve any polynomial equation

[@2002tantry]

Does anyone else feels like you understand these things way down in your career and it just went above your head when you were actually learning in college 😂?

[@SuperSaltyFries]

It's no surprise. We hardly have any time in university to actually read the damn textbook because each professor assigns so many homework assignments each week plus the 3-4 lab reports to complete.

[@ema7956]

my favourite staff.i love maths

[@AkashGupta-yq8lx]

I love complex no.. as well as complex geometry❤️❤️

[@patrickryckman3867]

Wow Harrison Ford can do anything.

[@imonkai5210]

We believe that our existence is real in an imaginary world.😂

[@NandishPatelV]

Maya in dharma (Indian system) KeepSmiling ☺️🌺

[@Schrodinger0]

Also your pfp is imaginary (i)

[@imonkai5210]

@@Schrodinger0 BTW, you have to use calculus to prove that.🤣

[@rs324]

awesome professor!

[@jadenmax679]

great teaching.

[@jadghalayini1446]

What if we had two numbers z1 and z2 such that z1 != z2 but |z1|^2 = |z2|^2 (trivial example: z1 = 1, z2 = i). If what we're interested in is the norm squared, when it comes to measuring in quantum mechanics, then what is the difference (measurable, perhaps) between z1 and z2? Another property?

[@James__123]

I remember this being answered in my lecturers last year, but I can't remember the answer :D I'm sure he's going to mention it later in the course

[@IgorAherne]

I believe it's the "cosine similarity"

[@zoltankurti]

Good question. The answer is, you can't measure the phase alone. But if it interacts with another system, the phase difference between the two systems can be measured, roughly speaking. The interference pattern of two waves for example will depend on the phase difference of the two waves. And it's similar for all other systems, you will get an interference term in the prediction which depends on the phade difference and can be measured.

[@memelsify]

Look up Aharnov-Bohm effect.

[@zoltankurti]

@@memelsify you still need interference to measure this effect, this is not usable to measure the phase of the wave function. You always need interference with another system for that.

[@StudiesBR]

what kind of harrison ford is this?

[@tropictom5996]

The one that is starring in the upcoming math adventure film “Raiders of the Lost Quark”

[@novemberalpha6023]

Indiana Jones at University

[@GaganGrewalf095]

Imaginary

[@erniewinn2415]

He is a great lecturer.

[@rolllarry]

That was easy :-) Well done, thank you so much for clearing up that haze I had from college. It wasn't MIT, maybe that was it :-)

[@MaheshKumar-dn2hb]

0:01 Is nobody going to talk about how he wrote "couplex #'s" instead of complex #s?

[@gauravbanakar8434]

nope.

[@vicheakeng6894]

#DATA

[@Cjnw]

Pedantic perspective