Nuclear spectroscopy breakthrough could rewrite fundamental constants of nature | Hacker News Reader

Nuclear spectroscopy breakthrough could rewrite fundamental constants of nature

newsroom.ucla.edu

90 pointsgeox49 comments

Interestingly:

> One isotope, ²²⁹Th, has a nuclear isomer (or metastable state) with a remarkably low excitation energy, recently measured to be 8.35574 eV. It has been proposed to perform laser spectroscopy of the ²²⁹Th nucleus and use the low-energy transition for the development of a nuclear clock of extremely high accuracy.

-- https://en.wikipedia.org/wiki/Isotopes_of_thorium

Storage and cooling of thorium ions has also been achieved already. It's only a matter of time before a clock is built using such an ion-trap setup (and a matter of significantly more time until auch a clock can be used in real-world applications). The article is talking about avoiding this but I believe the first thorium clock will likely be an ion trap.

A nice website collecting information about this is https://thoriumclock.eu

Here's the open-access arXiv preprint:

https://arxiv.org/abs/2404.12311 ("Laser excitation of the ²²⁹Th nuclear isomeric transition in a solid-state host")

Here's an HN thread with 215 additional comments, from two months ago:

https://news.ycombinator.com/item?id=40194636 ("Atomic nucleus excited with laser: A breakthrough after decades (tuwien.at)")

(Both threads are about an optical coupling to ²²⁹Th nuclear transitions; also, the top comment of that thread links to the paper underpinning this thread).

I love how university PR departments exaggerate the importance of research to almost a comical degree

They have to. Its written for lay people where most else they read is also exaggerated marketing versus boring truths. People in the field just read the underlying paper and have the experience to put the results of it into proper context.

I don't disagree with what you meant here, but this sentence threw my mind through a loop. It shows how "have to" is a real weak point in how we communicate and think.

Maybe we should rank our "have to"s on a scale from 1 to 5, where for example:

- "objects in motion have to (1) remain in motion unless acted upon by an external force"

- "humans have to (2) eat food to stay alive"

- "developed countries have to (3) maintain a scientifically literate populace"

- "university PR people have to (4) write like that to pay for food and shelter"

- "university PR people have to (5) write like that to afford a new sports car"

I think you meant something like the example for (4), but reasonable people might see it more like (5), and in both cases it's at odds with the more fundamental "have to" (3) for society.

This constitutes a loose extensional definition of a spectrum between the positive (1) and the normative (5), or between "is" and "ought".

In the original example, it is that university research PR has to be written this way to provide the grant substantiation its existence subserves, but arguably ought to be that the PR piece could just describe the research properly and without all the exaggeration.

To be clear, I would have no quibble with such an argument and also do not care how anyone else feels about it. The point is to help demonstrate that "ought" is the domain of that which is always arguable and which must always be argued. "Is," like the gravity which holds us to the bosom of this planet, is.

Reminds me of https://en.m.wikipedia.org/wiki/E-Prime

Maybe we could invent some new verbs to delineate between the scenarios.

I could have wrote out why they have to do this. There's two reasons I think that are related. One is the readership is primed for such language and headlines. The other is I am guessing a lot of these university PR releases are written by early career people or even undergraduate interns themselves. These people are writers, they want to get a job writing and those employers expect them to talk a certain talk that their readers are primed for. University PR releases are in fact no more flowery than the sort of articles that get posted on /r/futurology for example. Its a good resume piece if your career is taking information and overembellishing and oversimplifying for people without any relevant experience to more easily digest.

We read the underlying paper while crying because we know one of our family members will come up to us talking about the incredible new world changing discovery

Unlike so-called "tech" companies who are very careful to avoid hyperbole and exaggeration.

Indeed. But maybe I am naive, but I would like to hold our universities to a higher standard.

What are the practical considerations of being able to measure time/gravity/etc more accurately?

Will this make GPS cheaper/more accurate? Will this allow better astronomical observations?

Note that I'm certainly not against blue-sky science where we don't immediately know of any practical uses. As the end of the article specifies, pure research often ends up paying dividends down the line.

But I'm curious if there are any more immediate applications.

I think currently most of these things are dominated by other sources of noise such that a more precise clock isn't that big of an improvement, but the article claims these kinds of clocks could also be smaller than an atomic one, which may make them worth using. Could be useful for things like submarine navigation via gravitational mapping or other applications where size and lifetime/maintenance requirements might favor this design over a standard atomic clock.

>> we don't immediately know of any practical uses.

A nuclear clock may be accurate enough that speed could be measured by time dilation alone. More accurate clocks could mean better calibration and more precise tools that contribute to all manner of communication techs.

> What are the practical considerations of being able to measure time/gravity/etc more accurately?

Likely nothing in the near term. Calibrating constants lets us project the limits of reality further and more confidently. The practical implications of that are in letting crazy shit get greenlit, e.g. the Manhattan project from nuclear physics or the light bulb from quantum mechanics.

> or the light bulb from quantum mechanics.

Electricity is the flow of ions, it's literally atomic science (albeit not "quantum" in the sense highly specialized sub field we know today).

Ok but so is everything? The phrasing makes it sound like they were saying that the development of the lightbulb was through understanding of quantum mechanics (which, it of course was not).

Only the LED light bulb. And then only kind of, they use approximations.

Adding more decimal points to various physical constants. Any everyday applications are far away.

Do you like having precise GPS? That requires using atomic clocks and the general theory of relativity.

We do but with breakthroughs in science, the future uses are impossible to see now, sometimes they lead to incredible things. When Maxwell confirmed that light is also electromagnetic force with much more than just visible light in it, then all the atom discoveries and after that all the texhnologies like computer and what not, or making laser led to compact disc drives for example. I think precise nuclear measurments might help someday discover/confirm something new in physics

The atomic clocks used in GPS are many orders of magnitude worse than state-of-the-art, and are not a significant limitation for the accuracy of the system.

We seem to have been able to build GPS without this breakthrough.

TFA mentions scaling atomic clocks down from room sized, which they already are according to google’s AI, but maybe the engineering tradeoffs to do so could be improved.

Yeah, tiny atomic clocks/frequency references the size of a matchbox are something you can just buy for a couple thousand dollars. Mostly useful for stuff like cellular base stations, seismic measurements, and a bunch of military applications.

* https://www.microchip.com/en-us/product/MAC-SA53#purchase-fr...

> When trapped in a transparent, flourine-rich crystal, scientists can use a laser to excite the nucleus of a thorium-229 atom.

> [...] This accomplishment means that measurements of time, gravity and other fields that are currently performed using atomic electrons can be made with orders of magnitude higher accuracy

I want to know how they trap the scientists in that crystal.

First encase them in carbonite so they’re not so wiggly.

Would it be upsetting if we sent a probe a lightyear away and found that some constant, I dunno, Planck's constant or whatever, had changed?

Not sure if upsetting is the right word, but people are looking for things like that. It would be a remarkable discovery for sure. There are markers in the spectra of distant stars that could give us a hint, so sending probes is not necessarily a requirement. So far, potential variances have been constrained to a very high degree.

Excuse me, to a very high degree? Can you elaborate?

Here's one example, where they measure the separation of spectral features from the OH molecule in a fairly distant galaxy and use that information to put a limit on how much variation there could be in the fine structure constant over the past 2.9 billion years: https://ui.adsabs.harvard.edu/abs/2018PhRvL.120f1302K/abstra...

I'm confused - is this essentially saying we haven't ruled out fluctuations but we are putting a tighter bound on the variance? But not that we actually detected variation right?

My curiosity led me down the rabbit hole of all the eras that happened before the first microsecond and to consequently learning about when the forces diverged. What is the intuition on the four forces being unified? What does that mean? Is this even a question that makes sense to ask?

Yes. If there are no variations, it's impossible to rule them out. You can only put tighter and tighter constraints on them.

Not OP, but this is talking about bounds on how different such constants can be across time and space. For example, wikipedia.org/wiki/Time-variation_of_fundamental_constants

To put another way, the amount of change in plank’s constant that could potentially happen is highly limited (based on our current methods of measuring and inferring), and only getting more limited as we improve accuracy.

Very. One consequence is that, for example, momentum might not be conserved, since according to Noether’s theorem momentum conservation is directly linked to the translation invariance of fundamental physical laws. One consequence of that in turn would be that Newton’s 3rd law, “every action has an opposite and equal reaction”, would not always hold since it’s equivalent to momentum conservation.

Stuff I've read is spectroscopy can detect molecules from billions of light years away. And if something like Planck's constant varied with time or distance the spectral properties of those would change radically.

Upsetting? Hardly, it would be exciting.

Rewriting the fine structure constant sounds dangerous.

It's generally considered unlikely that the FSC or the gravitational constant has varied through time or space.

"Nuclear spectroscopy breakthrough could rewrite fundamental constants of nature". That's UCLA's PR department in action.

I'm listening?

"Rewrite" is a misstatement; what is actually meant is "measure with greater accuracy".

Abbreviated from "Rewrite least significant digits of ..." /s

Maybe so, but the abbreviation significantly changes how the average person is going to interpret what is being done.

I agree. The /s marks end of joke/sarcasm fyi (which itself is abbreviated from <s>joke</s>).

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