Biggest Ideas in the Universe

The Biggest Ideas in the Universe | 16. Gravity

Gravity! This one’s sure to be a crowd-pleaser. We take advantage of some of our previous discussion of curvature and spacetime, but we also talk about Einstein’s physical motivations for inventing general relativity, and the origin of gravitational time dilation and the like.

The Biggest Ideas in the Universe | 16. Gravity

And here is the associated Q&A video. Distinguished mostly by a deeper dive into black holes, including the information-loss puzzle.

The Biggest Ideas in the Universe | Q&A 16 - Gravity

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The Biggest Ideas in the Universe | 15. Gauge Theory

Finally a reward for the hard work we did in the last few videos! (Not that hard work isn’t its own reward.) This week we talk about Gauge Theory, explaining how the forces of nature arise because of local symmetries in quantum fields.

The Biggest Ideas in the Universe | 15. Gauge Theory

And here is the Q&A video, where we go into more specifics about the Higgs mechanism, how it gives mass to particles, and how that plays out in the Standard Model of particle physics.

The Biggest Ideas in the Universe | Q&A 15 - Gauge Theory

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The Biggest Ideas in the Universe | 14. Symmetry

Symmetry is kind of a big deal in physics — big enough that the magazine jointly published by the SLAC and Fermilab accelerator laboratories is simply called symmetry. Symmetry appears in a variety of contexts, but before we dive into them, we have to understand what “symmetry” actually means. Which is what we do in this video, where we explain the basic ideas of what mathematicians call “group theory.” By the end you’ll know exactly what is meant, for example, by “SU(3)xSU(2)xU(1).”

The Biggest Ideas in the Universe | 14. Symmetry

And here is the associated Q&A video:

The Biggest Ideas in the Universe | Q&A 14 - Symmetry

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The Biggest Ideas in the Universe |13. Geometry and Topology

Cheating by having two ideas this week. But they are big ones. We talk about how “parallel transport” of vectors allows us to define curvature intrinsically, and leads us to the Riemann curvature tensor. Then we move to topology, in particular homotopy groups, which show up in physics all the time.

The Biggest Ideas in the Universe | 13. Geometry and Topology

And here is the associated Q&A video, where we talk a bit about embeddings, tensor components, topological defects, and more.

The Biggest Ideas in the Universe | Q&A 13 - Geometry and Topology

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The Biggest Ideas in the Universe | 12. Scale

After three videos in a row about quantum field theory, we bring things a bit more down to earth by talking about the sizes of things. Mostly about particles and atoms; the sizes of people and planets will have to come later.

The Biggest Ideas in the Universe | 12. Scale

And here is the associated Q&A video:

The Biggest Ideas in the Universe | Q&A 12 - Scale

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The Biggest Ideas in the Universe | 11. Renormalization

The third installment of a little trilogy about the basics of quantum field theory. First we explained free fields, and why they led to particles; then we added interactions and used Feynman diagrams to calculate them; and today we’re going to deal with pesky infinities by introducing effective field theories. A wild ride!

The Biggest Ideas in the Universe | 11. Renormalization

And here is the associated Q&A video:

The Biggest Ideas in the Universe | Q&A 11 - Renormalization

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The Biggest Ideas in the Universe | 10. Interactions

Last time we figured out that when you start with a theory of noninteracting fields and quantized it, you could think of the result as a theory of noninteracting particles. Now we let those particles interact, and describe what happens using Feynman diagrams.

The Biggest Ideas in the Universe | 10. Interactions

And here is the associated Q&A video:

The Biggest Ideas in the Universe | Q&A 10 - Interactions

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The Biggest Ideas in the Universe | 9. Fields

We’ve talked about the quantum mechanics of particles, now it’s time to apply those ideas to fields. It requires a bit of effort to understand how a quantum field — which is really a wave on top of a wave, when you think about it — ends up looking like particles in the right circumstances. But it’s worth it.

The Biggest Ideas in the Universe | 9. Fields

And here is the Q&A video. I talk a bit about different kinds of fields, and why the Dirac or Klein-Gordon equations are not relativistic versions of the Schrödinger equation.

The Biggest Ideas in the Universe | Q&A 9 - Fields

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The Biggest Ideas in the Universe | 8. Entanglement

Entanglement is one of the most important features — arguably, when you get down to it, the most important feature — of quantum mechanics, but it’s often glossed over in how we introduce the subject to students. Here we dive in, and I use this as an excuse to eventually talk about some of the different physical theories vying to be a complete formulation of quantum mechanics.

Update: I originally uploaded the wrong file, this should be the right one!

The Biggest Ideas in the Universe | 8. Entanglement

And here is the associated Q&A video. (Sorry I was in a hurry and didn’t do the lighting correctly … I’ll never make it big in Hollywood at this rate.)

The Biggest Ideas in the Universe | Q&A 8 - Entanglement

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The Biggest Ideas in the Universe | 7. Quantum Mechanics

I thought about making the title for this week’s Idea simply “Quantum,” since one-word titles are kind of cool, but ultimately decided that accuracy was a higher priority than coolness. That’s why I’ll never be cool.

Anyway, quantum mechanics! This installment runs down the basic ideas; we’ll leave the conceptual heavy lifting for next week.

The Biggest Ideas in the Universe | 7. Quantum Mechanics

And here is the Q&A video. Mostly I talk about the double-slit experiment, and how it implies that the wave function is something other than simply a stand-in for our lack of knowledge about where the particle is.

The Biggest Ideas in the Universe | Q&A 7 - Quantum Mechanics

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