Juan Maldacena Public Lecture: The Meaning of Spacetime

What is spacetime, exactly? And how does it impact our understanding of important phenomena in our universe?

According to Einstein’s theory of gravity, spacetime is both curved and dynamical. The theory had two surprising predictions: black holes and the expansion of the universe. In both cases, there are regions of spacetime that are outside the reach of the classical theory, the so-called “singularities.” To address them, we need a quantum mechanical description of spacetime.

Juan Maldacena studies black holes, string theory, and quantum field theory. In his July 27 Perimeter Public Lecture webcast, he described some ideas that arose from the study of quantum aspects of black holes. They involve an interesting connection between the basic description of quantum mechanics and the geometry of spacetime. He also delves into how wormholes are related to quantum entanglement.

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[gerardopc]

Juan Maldacena es una inspiración y un orgullo no sólo para los físicos argentinos sino también para los físicos de toda LATAM. Saludos desde México.

[quarkraven]

he is a hero and a (hidden) giant. one of the field's greatest living minds, i have no doubt.

[camielkotte]

It is a daunting task to prepare a lecture like this where you need to entertain and educate those who know next to nothing about the subject and students and graduates on this subject.
I have seen better presentation skills, but I d rather listen to him whole day than 1 minute of ND T for unlimited reasons.

[deeliciousplum]

Wonderful and enlightening talk. Thank you to PI for sharing this talk. 🌺

[pablo-jcqs]

And to think I attended higschool at Argentina with him, he liked to read a lot of Catholic philosofers. He was a kind guy, always smiled as today.

[nigelhornberry]

Can someone help me understand what he's communicating for those 30 seconds or so beginning at 20:28? The part where he puts the scale of the Planck length into perspective. I wasn't quite able to follow his analogy through to the end.

[jondor]

Apart from expositional expediency. Why does the curvature diagram show the well offset from the centoid of the mass

[maureensurdez]

Oh man not take away anything from this lecture he's very smart. I thought I understood these basic concepts space-time curvature speed of light planes in with geometry is totally confusing to me. I'm kind of bug it up with it. I'll continue to hear the rest of the lecture and see if it straightened itself out my brain.

[asherklatchko]

Philosophers, in particular Kant, argue that we understand the sentence before the words. In analogy, the emergent meaning comes before the word-bits that would imply it after some analysis.

[suhailski]

The way he explained Holographic principle made me feel for the first time that I understood it. I also get a feeling that he is someone who is bursting with a sense of humour and playfulness.

[tevatronlhc]

I find it also very interesting that the geometrical Interpretation of entanglement also matches the typical structure of many deep learning neural Networks like cnns and transformers the input and output layer correspond to the boundary, especially in encoder Decoder Systems, and the inner layers, what represent more and more abstract representation of the information the bulk

[KipIngram]

10:15: Actually you don't have to include that second postulate to arrive at Lorentz transformations. It's enough to just assume the laws of physics are the same for all inertial observers. You can then prove that there must be some "special speed" that behaves the way the speed of light does. However, one possibility is that that speed is infinite, and if you assume that then the Lorentz transformation reduces to the Galilean transformation. So Gallileo is just a special case of Lorentz. We *observe* that the special speed is finite in our universe, and that lets us detail out of own particular Lorentz transformation, gives us time dilation and length contraction, and so on.

[rickprice]

I am always at a quandary about space itself. I know that modern physics tells us how matter/energy behave in space. Yet I always consider that the time in the notion of spacetime is a product of mass/energy and how it behaves in space.
We have more data on mass/energy and just a few insights into how space itself is in its actions on those forces.
We have notions of dark matter and energy with our observations of space as mass/energy moves through it.
Mostly my quandary is that we still do not know all the properties of space, does it limit photons and other radiations to the "c" limit.
Is it expanding really? Since all observations have different values. Is dark energy a property of space, or a property of quantum space fluctuations?
My thought is space is not an emptiness, but a thing itself which we need to ponder separate from those spacetime notions which have more to do with the mass/energy that is in it.
Without a fundamental understanding of space itself, modern physics will not achieve progress.

[homomorphic]

Dang! I Just agreed to take delivery of a 1kg black hole and *now* I see this video...

[willemesterhuyse]

What happens at the top: where the red and black lines come close together? (timestamp: 38:00).

[qdygfpi]

Actually, v enlightening and enjoyable lecture!

[whirledpeas]

I have read, watched nearly every informative tool I can find in my area. I love all of learning

[PeoplesScience]

Us Latinos do not have much of a place in the pantheon of Physics history besides the good professor in this video and a couple of others, but who came from Europe or the US to Latin countries. Thus, the success and brilliance gives us Latinos to be GREAT and make our mark too in scientific history.

[JohnJonelis]

Out of respect for your speakers and for the benefit of your video audience, would you please print the speaker's name in the closing credits, along with the tiitle of any book being promoted?

[lnnkmgv]

Despite the applause at the end, I kept nodding off during the lecture.

This guy is not Nobel prize material.