Sean Carroll

I'm sorry if I'm confusing. That's the term I use, usually assuming that it is obvious (like referring to C++ templates to a python developer without explaining what is that).

To be honest, it is hard to visualize, as it is counterintuitive of what we think of space. While I know many people would disagree, I really like the garden hose analogy [1]. The idea is to simply imagine a very long garden hose. From a great distance, it looks like a one-dimensional line. Now you get closer, and realize it has a second dimension, which is its circumference curled around that seemingly 1-D line. An ant walking on the hose can move along its length, but also in a circle around it. The extra dimension in KK is like this circumference. It is tiny, curled up so we don't directly notice it, but still potentially there.

[1] https://www.preposterousuniverse.com/blog/2004/06/30/extra-dimensions/

Thanks for the kind words! For anyone curious to dive deeper into the crazyness that is quantum mechanics I can highly recommend a few resources:

- Sean M Carroll's work, in particular his Biggest Ideas in the Universe books: https://www.preposterousuniverse.com/biggestideas/

- Artur Ekert, basically the father of Quantum Cryptography has an amazing course for free on youtube: https://www.youtube.com/@ArturEkert . It's a very precise and understandable explanation of quantum computing, and some of the math that is involved with quantum mechanics.

- If you have hours to spare, watch Richard Behiel's videos on Youtube. He's like the 3Blue1Brown of Quantum Physics. His latest video on superconductivity and the Higgs Field is almost 5 hours long (!!!) https://youtu.be/DkH1citHtgs?si=-yQNYDu9TlTpE1A0 . It builds on his other videos, so I'd recommend starting at the beginning.

I believe the community consensus (based on surveys) is that there aren't enough microlensing events to explain the amount of dark matter we see, using MACHOs.

You can read this even at: https://en.wikipedia.org/wiki/Massive_compact_halo_object

I believe that I most recently heard it from Lina Necib's appearance on Sean Carroll's podcast ... that would be this episode: https://www.preposterousuniverse.com/podcast/2020/05/11/96-lina-necib-on-what-and-where-the-dark-matter-is/

Recommended, if you go for that sort of thing.

[Edited to add: OK, turns out the consensus is unstable. There appears to be a window of BH mass range which has not been observationally excluded. See, e.g.https://en.wikipedia.org/wiki/Primordial_black_hole#Theoretical_history]

As a layman, I can't follow, but the paper [1] references AQUAL [2] "This systematic deviation agrees with the boost factor that the AQUAL theory predicts." But that theory doesn't agree with observation? And I'll paraphrase Sean Carroll [3] as saying something like Scalar-vector-tensor theories are just dark matter theories in disguise. Positing an noninteracting energy density, is just positing dark matter.

1 https://arxiv.org/pdf/2305.04613.pdf

2
https://en.wikipedia.org/wiki/AQUAL#:~:text=AQUAL%27s%20failure%20to%20predict%20the%20amount%20of%20gravitational%20lensing%20actually%20observed

3 https://www.preposterousuniverse.com/podcast/2023/07/31/245-solo-the-crisis-in-physics/

On "not the path to AGI": Gary Marcus on the Mindscape podcast is worth a listen.

https://www.youtube.com/watch?v=ANRnuT9nLEE&list=PLrxfgDEc2NxY_fRExpDXr87tzRbPCaA5x&index=23

Transcript: https://www.preposterousuniverse.com/podcast/2022/02/14/184-gary-marcus-on-artificial-intelligence-and-common-sense/

"...And then there’s natural language understanding and reasoning, and I would say we have not really made progress at all. GPT-3, which we may wanna talk about, gives the illusion of having natural language of understanding, but I don’t really think that it does. And we are nowhere near, for example, an all-purpose general assistant. ..."

It is well possible that GPT-4.1 references Sean Carroll, either directly or by regurgitation.

> One sometimes hears the claim that the Big Bang was the beginning of both time and space; that to ask about spacetime “before the Big Bang” is like asking about land “north of the North Pole.”

Source: https://www.preposterousuniverse.com/writings/dtung/

I'm a regular listener of his Mindscape podcast, and that's where I got this phrase. I can highly recommend his podcast: https://www.preposterousuniverse.com/podcast/