The Biggest Ideas in the Universe | 15. Gauge Theory

The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody.

This is Idea #15, "Gauge Theory." Here is where the last couple of ideas come together, and we see how geometry and symmetry underlie the fundamental forces of nature as they are currently understood.

#science #physics #ideas #universe #learning #cosmology #philosophy #math #gaugetheory #symmetry

[makemetoasty]

I really love how in depth you get, most science communicators stick to the fluffy, eye-grabbing, more theoretical kind of things without actually conveying much information about them or how we came to those discoveries. Not a science student but definitely an enthusiast, and I really appreciate these videos as well as the many lectures you’ve done that people post to YouTube. I finally feel like I’ve broken through that surface level knowledge that people like to spout and have become at least a little bit knowledgeable about the subject I love the most. I dunno, I’m gushing, you’re cool, hope you read comments

[shortcutDJ]

Sean, you have no idea how much i appreciate you doing this, and putting all this effort and work out. Thank you so much.

[DanielHendriks]

My conclusion is that Sean Carroll understands it.

[bruinflight]

Preemeninent physicist: "Here's 'space'. Ah, we're getting good at drawing 'space' now."

[quaereverum]

This is the first and only clear explanation of what a gauge theory is, that I have come across. I'm so glad you uploaded this. It connects many of the dots for me.

[Mrmistershesh]

I'm a 4th year physics PhD student and these videos are still interesting and illuminating. Thanks!

[feelingcreative]

*disclaimer* I am a night shift Clinical Laboratory Scientist after a long night shift. *
I watch this series after a fighting the Covid all night in Arizona. I come home, have a couple shots of Titos, and watch Sean as I "try" to fall asleep. I'm such a nerd!
My mind races as I lay here contemplating how our world works. What can I do to make it thru this weirdness? Alas, I am a mere mortal at best...
I go to the Colorado River and watch the waves on the river, the birds going about their day, and the beauty of the landscape. That's what keeps me grounded it this crazy time.
Thank you Sean for doing what you do. It's helping a lot of us.

[incoathwetrust]

Sean C. is the physicist Eric W. wishes he could have been..

[paulc]

At 27.45 Dr. Carroll says "You understand that sentence perfectly well . . . . . . . Progress is being made." Yes indeed. And I watch every episode twice (at least). But my brain still feels like it has been roasted, toasted, grilled and parallel transported in the neuron field. But seriously, these are really great lectures and I have learnt a lot. I am just worried that there's going to be an EXAM at the end.
Is there going to be an exam Prof. Carroll ? Or just a quick test perhaps ?
Please give us plenty of warning. Thanks again.

[asolarasolarasolar]

27:45: _Think about that, you totally understand that._
Oh man, if you knew...

[kobevli]

I had to watch this a few times to fully appreciate how amazingly wonderful this video is.

Thank you SO much for the lecture Dr. Carroll !!!!

Cannot even begin to imagine how you'll top this in the next video.

[drbeanut]

I don't know what it is about you Sean, but gosh darn you incite so much excitement and joy in learning this stuff!

[rc]

Tremendous payoff indeed! I love the way Sean Carroll has laid the groundwork for us to follow and receive a valid broad stroked familiarity with one of the most popular yet inaccessible (to the layperson) theories in the Standard Model, namely QCD.

[PavlosPapageorgiou]

50:00 Could you elaborate a bit more what a static electric or magnetic field looks like in terms of photons? Is there an infinite number filling space? Are they moving? If an electron passes by and is deflected does it interact with a stream of photons? How is the momentum carried?

[sachirajmishra]

Thank you sean caroll for all these things. i am a physics student from India completed my masters this year.i am enjoying your videos and also share your videos among my colleagues. I have one request for you sean Carroll. If you can upload some lecture videos at the basic level of physics I mean starting from highschool to undergraduation level physics, it would be of Great help.it will help a wide range of students.in our locality the biggest problem is undergraduation education. you are great person in physics and surely a lot of college students Will be motivated by your lectures...

[jonathansaraco]

Hey Sean, awesome video as always! I have a question that hopefully you can cover in the Q&A segment.

You said something along the lines of "unless nature forbids it, it will happen" to talk about particles having mass. That unless there is a symmetry that takes away that mass (ie. there being no operation that gives you a mass term in the Lagrangian that satisfies the symmetry) then the particle will have mass.

So my question is about neutrinos. It's an open problem as to why the neutrinos have mass, as they do not in the conventional Standard Model formalism. So, what is the symmetry that we give the neutrino field that takes away its mass that it doesn't actually have in the real world? Or is a symmetry spontaneously broken and that's why we think neutrinos have mass?

[null_carrier]

Perfect timing dr Carroll - just doing the main part of my Solid state Physics PhD experiment (magnetism) and feeling frustrated by all the complexities and intricasies of the aparatus, human nature and Nature itself. However, seeing this s*it, you theoretical folks, have to deal with I'm feeling much better about myself, my life choices and the Universe as a whole. So, thank you, thank you very much indeed. :)

[sarojinichelliah]

Sean is not just great but unbelievable too. The funny thing is I only know basic stuff but still listen to his talks again and again in the hope of understanding it.

[theosib]

I'd really like to know how it's determined that the graviton has a spin of 2.

[grahamdlawton]

I am late to this party……….. but wanted to learn about Gauge Symmetry/Theory as this was left unexplained in a more casual book I read which ended with superstring theory and GUT/M theories. So oddly, I started here and was more enlightened. But……after going back to video 1, watching them up to and including this one again (and Q&As), then doing a little more digging on spontaneous symmetry breaking and then rewatching this for a third time, I am there. Kudos Doc - you got me there and yes, it is very rewarding. I am not a physicist, but historically and engineer, so also have a certain amount of pride in finally getting it. Looking forward to the rest of the videos (not lectures)!