Using fluids to model inaccessible realms of the cosmos

https://www.quantamagazine.org/she-turns-fluids-into-black-holes-and-inflating-universes-20221212/

by _aleph2c_ • 3 years ago

97 42 3 years ago

quantamagazine.org

quickthrower22• 3 years ago

I like this idea. You need bets like this to discover things, not everyone working on the same thing.

ndsipa_pomu2• 3 years ago

Certainly it's a lot easier than trying to cultivate a real black hole in your lab.

quickthrower22• 3 years ago

Well I was thinking looking through telescopes and developing theories as the alternatives!

uoaei3• 3 years ago

Bit of an aside, but:

But physicists seek the more fundamental, quantum theory of gravity that underlies Einstein’s picture; it’s this quantum gravity theory that governs extremes like the Big Bang and black holes. And one way to inch toward this complete theory is to study quantum fluctuations in the space-time fabric.

I'm uncomfortable with the implicit framing that quantum gravity is The One True Theory and we just need to figure out how to formalize it. I'm sure this comes from the author and not the researcher, maybe something was lost in translation from the technical to the colloquial, but nonetheless it is still inaccurate to say that there is any kind of certainty that this is the right path forward. (Ditto for dark matter and dark energy, though those could more accurately be described as lacks of models than models per se.)

ndsipa_pomu2• 3 years ago

What other approaches are there that wouldn't lead to a quantum theory of gravity?

uoaei3• 3 years ago

There is more focus of late on theories of "emergent gravity", i.e., that gravity is not a fundamental force. The most interesting one to me is so-called "entropic gravity", which also resolves the issues plaguing the theory of dark matter and gives credence to MOND. Such theories have been long derided by old-school physicists raised in the golden era of quantum mechanics (and their acolytes), but have surprisingly powerful explanatory power that other theories cannot achieve without tacking on seemingly arbitrary or else otherwise unmotivated factors. Dark matter especially has always been suspect to me, since even after all this time, it is defined as little more than "the gap between our models and observations" with no strong underpinnings that would explain its existence in satisfying ways.

I am not affiliated with this blog in any way but find the arguments compelling: https://tritonstation.com/

Here's an interview with a researcher who is also trying to move beyond quantum formalisms for spacetime vis a vis gravity: https://www.quantamagazine.org/the-physicist-who-bets-that-g...

klyrs• 3 years ago

My understanding is that quantum gravity is a gaping hole in our theoretical understanding of the universe, and until that hole is plugged, we have no hopes of finding a One True Theory. That's quite different from quantum gravity being The theory.

uoaei3• 3 years ago

What I was trying to get at is that gravity may not even be quantized. The insistence that it act like the other three fundamental forces is a holdover from earlier interpretations of physics but in retrospect there's still no solid reason to assume it has to be quantum at all.

pbhjpbhj• 3 years ago

Tangentially related:

When I was in uni, I did a brief informal undergrad-level paper on modelling cosmological inflation using superfluid He-4. What I hadn't realised, and perhaps was supposed to discover, was that one of the unis [past] professors, Prof JF Allen, had worked in that field. As I read now I find that he actually was a co-discoverer of superfluid He-4.

The journal Nature describes him as "the last of a generation of independent-minded classical physicists". We knew him as "god" for his mystical presence on campus and his cartoon-God appearance, whispers followed him around the physics lounge. He also taught me QFT, or tried. It wasn't until after I graduated that I learnt the building really was named after him. I do wish that I had known to interview him about this field of modelling [cosmology] using superfluids.

at_a_remove• 3 years ago

Ah, I had the guy who was the master of Helium-3. He had something like seven patents on different applications.

OldGuyInTheClub3• 3 years ago

Liquid helium 3 and 4 have been a fertile substrate for this kind of exploration. I often think that the lab scale experiments will figure it out before the ultracolliders.

This 1998 article summarizes the state of the field up to that time. The rotating cryostat they used in the experiments is a masterpiece of instrument design.

https://www.pnas.org/doi/pdf/10.1073/pnas.96.14.7760

"Vortices in rotating superfluid 3 He" by Lounasmaa and Thuneberg

Scroll to the end for

"Superfluid 3 He in Cosmology

The topological objects in the order parameter field of super- fluid 3 He, such as textural point defects, quantized vortex lines, and solitons, are in many respects similar to monopoles, strings, and domain walls in relativistic quantum field theories (3, 4, 23, 24). In high-energy physics these objects are still hypothetical, whereas in the case of superfluid 3 He they can be observed experimentally. Here we discuss just one example: an experiment modeling developments in the early universe. The study (67, 68) involves creation of vortices by absorption of neutrons in rotating superfluid 3 He-B."

OldGuyInTheClub3• 3 years ago

Addendum after the edit deadline: G.E. Volovik has an article on the theory behind this at

https://www.pnas.org/doi/epdf/10.1073/pnas.96.11.6042

"Field theory in superfluid 3He: What are the lessons for particle physics, gravity, and high-temperature superconductivity?"

I don't pretend to understand even a fraction of this but Figure 3 is a very nice Dictionary mapping the helium phenomena to the cosmological questions.

jacquesm• 3 years ago

I watched and posted a video about He-4, amazing example of what educational videos should look like. Thank you!

acqbu• 3 years ago

black holes - I've seen a few

cosmic wonders that leave me askew

they gobble up matter with voracious delight

sucking everything in, day or night

fastneutron• 3 years ago

For a highly in-depth look at the theory behind this, I can recommend “The Universe in a Helium Droplet” by Volovik [1].

1. https://academic.oup.com/book/11557

trhr2• 3 years ago

I took a bunch of mushrooms and had the same idea, but when I pitched it to my freshman Physics professor, he told me I should "take more physics."

I thought he was insulting me, but apparently I would have made a decent physicist.

Ygg2• 3 years ago

There is a chasm of difference between taking some shrooms and testing a black hole analogue.

bowsamic5• 3 years ago

Even if this is supposed to be a joke, I don't get the connection between physics and drugs that the joke implies

greazy3• 3 years ago

There's a few instances in science where ideas were borne after the researcher took drugs. A good example is PCR assay.

Mullis has credited his use of LSD as integral to his development of PCR: "Would I have invented PCR if I hadn't taken LSD? I seriously doubt it. I could sit on a DNA molecule and watch the polymers go by. I learnt that partly on psychedelic drugs."[86]

https://en.m.wikipedia.org/wiki/Polymerase_chain_reaction#Hi...

ramraj07• 3 years ago

This is like saying everyone who tripped on acid and ranted about mind body connection and oneness to the universe is now competition to Peter Singer. Coming up with the idea is only a small part of the problem. Actually pursuing it with rigor is another.

Your professor also told you to take more physics, so he did in fact suggest you could be a decent physicist?

BSEdlMMldESB• 3 years ago

in my experience, the rigorous pursuit feels like a hamster wheel

the real problem is that it moves very fast, so when I've tried jumping into this "wheel", I find it impossible to hold on on to it. I always fly out due to centrifugal forces

sparrowInHand• 3 years ago

Imagine a material capable to reflect gravity waves, amplifying it, creating a standing wave. A blackhole without mass, regarding the effects..

amelius2• 3 years ago

Couldn't these experiments be done using computer simulations?

111010100011002• 3 years ago

Sure, you can also say we start with the ZFC axioms. QED.

Calculations provide predictions, experiments provide verification.

amelius2• 3 years ago

I mean, computational fluid dynamics is pretty mature now.

And if for some reason it doesn't work here, then that would be nice to know.

Besides, the experiments themselves are simulations.

peter_d_sherman• 3 years ago

"...she has detected sound waves in fluids that resemble Hawking radiation..."

[...]

"If the wave isn’t too tall, then this wave doesn’t interact with other waves of different frequencies — you can try this in the bathtub.

But if the amplitude gets high, then the different frequencies interact."

Fascinating!

OldGuyInTheClub3• 3 years ago

Sixty Symbols did a video with Dr.Weinfurtner. Surprised it wasn't posted already!

https://www.youtube.com/watch?v=kOnoYQchHFw

"The Black Hole Machine"

Using fluids to model inaccessible realms of the cosmos

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