[HN Gopher] Atomic nucleus excited with laser: A breakthrough af...
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Atomic nucleus excited with laser: A breakthrough after decades
Author : geox
Score : 405 points
Date : 2024-04-29 05:01 UTC (17 hours ago)
(HTM) web link (www.tuwien.at)
(TXT) w3m dump (www.tuwien.at)
| danans wrote:
| > This makes it possible to combine two areas of physics that
| previously had little to do with each other: classical quantum
| physics and nuclear physics.
|
| Is quantum physics now considered part of classical physics? If
| so then man, time flies!
| dxuh wrote:
| There is a big difference between "classical" quantum mechanics
| (about 100 years old now!) and quantum field theory (~50 years
| old). Maybe that's what they mean?
| snthpy wrote:
| When I was at university about 25 years ago, QM was about
| electron transition energies, with QED being a refinement of
| that for things like fine structure. In experimental HEP you
| had QCD and quark gluon plasma which informs things like the
| LHC experiments at CERN.
|
| IIRC nuclear physics was largely phenomenological with a lot
| of observations that had simple models fit to them without
| being able to reduce those to the particle physics models.
| This might be about establishing a link between the
| phenomenological nuclear models and the fundamental QM
| models.
| scotty79 wrote:
| I think they want to convey that nucleus is a really weird
| place so quantum physics of everything else is classical by
| comparison.
| emblaegh wrote:
| Classical there is used in the sense of "non relativistic".
| denton-scratch wrote:
| I thought relativistic quantum physics was not a thing (yet).
| itishappy wrote:
| Nope, it's a thing! The Dirac Equation is one example. It
| explains the Pauli exclusion principle and predicts anti-
| matter.
|
| > It is consistent with both the principles of quantum
| mechanics and the theory of special relativity, and was the
| first theory to account fully for special relativity in the
| context of quantum mechanics.
|
| What we don't have is a grand unified theory (a single set
| of rules that generates both theories), but we can consider
| relativistic effects in QM theories, and (I assume) vice
| versa.
|
| https://en.wikipedia.org/wiki/Dirac_equation
| omnicognate wrote:
| Special vs general. Quantum field theory is special
| relativistic and quantum mechanical. The grand unified
| theory stuff is about uniting general relativity and
| quantum mechanics.
| JanisErdmanis wrote:
| We currently don't know how to calculate the nucleus's bound
| state despite a thorough understanding of individual pieces
| that make it together, as explored in colliders like CERN and
| others. The problem is similar to telling at what temperature
| water is boiling, freezing, and its density from knowing the
| properties of a single water molecule. We understand quantum
| mechanics and Columb forces govern the properties; it is
| incredibly hard to renormalise the system from an energy scale
| of a gas to a liquid or solid. Similarly, it is for a quark-
| gluon plasma; thus, phenomenological models are used, like how
| the nuclear potential could look and the masses for different
| combinations of nuclei.
| tlb wrote:
| From the paper, the light is UV-C at around 140nm or 8.4 eV. But
| it has to be very precisely the right energy to cause the
| transition, since nuclear states don't have any place to dump
| excess energy to.
| jhart99 wrote:
| Ahhh thank you! I was wondering why the energy had to be so
| precise. That makes a ton of sense why it has to be so
| accurate. What makes this transition so low energy? The only
| other atomic excited state I have any knowledge of is the iron
| excited state used in Mossbauer spectroscopy. That transition
| is much higher energy. Also that one has some coupling to the
| electronic state of the nucleus. Does this Thorium transition
| have some special reason that it isn't coupled to the
| electronic state?
| adrian_b wrote:
| The radiation emitted when nuclei transition between their
| internal energy levels is known as gamma rays.
|
| The gamma rays normally have energies per photon many orders
| of magnitude greater than for visible light and also much
| greater than for X-rays (which are produced by electrons
| accelerated by very high voltages when hitting a target).
|
| The thorium 229 nucleus is the only one that can emit gamma
| rays that are so low in energy that their energy is not only
| lower than for X-rays, but it is also lower than for many
| sources of ultraviolet light. For instance the ultraviolet
| light used in state-of-the-art lithography for semiconductor
| manufacturing has much higher frequency (shorter wavelength),
| by about ten times.
|
| These gamma rays of the Th229 have a wavelength that is not
| much shorter than the 184-nm ultraviolet light that can be
| obtained with a mercury-vapor lamp.
|
| What is important is that for such a frequency/wavelength it
| is possible to build laser sources, which enables the design
| of an atomic clock that will use thorium 229 nuclei instead
| of neutral atoms or ions of other elements (like ytterbium,
| lutetium, strontium, aluminum).
| bawana wrote:
| Arent gamma, x, and uv ALL em radiation? What makes a gamma
| with a wavelength near uv still allow it to be called
| gamma? Why dont we say the nucleon emits uv at 148 when it
| transitions to its ground state?
| twic wrote:
| I found a paper which measured the energy of the transition
| [0], but it doesn't talk about why it's so low. Might be a
| starting point if you have more time to read than i do,
| though!
|
| EDIT Hmm [1]:
|
| > Interestingly, the existence of a nuclear excited state of
| such low energy seems to be a coincidence and there is
| currently no conclusive theoretical calculation that allows
| to predict nuclear levels to this precision.
|
| And there is a paper with a ton of detail and some nice
| diagrams of energy levels [2], but i'm not sure it really
| gets at "why".
|
| [0] https://arxiv.org/abs/1905.06308
|
| [1] https://link.springer.com/article/10.1140/epja/s10050-020
| -00...
|
| [2]
| https://iopscience.iop.org/article/10.1088/1361-6455/ab29b8
| pfdietz wrote:
| The Q of nuclear transitions is just insane (as reflected by
| their long half life, something in excess of 1700 seconds here
| for free atoms.) The uncertainty relationship is normally
| written as delta-p delta-x > hbar/2, but it can also be written
| as delta-t delta-E > hbar/2. So, if the half life is very long,
| delta-E can be very small.
|
| This fact is used in Mossbauer spectroscopy (recoilless gamma
| emission in solids). The peak is so sharp that it was famously
| used by Pound and Rebka to detect the gravitational red shift
| in the lab at Harvard in 1960, reaching 1% accuracy by 1964.
|
| https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment
| andrewflnr wrote:
| Where do electron transitions usually dump excess energy?
| ChrisClark wrote:
| Don't they usually create a photon with that energy?
| infogulch wrote:
| In general it's possible for electrons to jump to sub-
| orbitals which gives them a wider band of wavelengths that
| they can emit and absorb photons. The jumps between sub-
| orbitals are usually in microwave or radio bands.
| fsh wrote:
| The measurement was already confirmed by a different group:
| https://arxiv.org/abs/2404.12311
|
| This is important since impurities in the crystals used lead to
| all kinds of fluorescence that could be mistaken for a signal
| from the Thorium ions. Now two groups have seen exactly the same
| signal in different Thorium-doped crystals which is very
| covincing that they have found the actual nuclear transition.
| dguest wrote:
| I went looking for an arXiv link for this paper and found the
| one you linked.
|
| Kind of weird that this new paper is only on the group's
| website [1] and not on the arXiv.
|
| [1]: https://www.tuwien.at/fileadmin/Assets/tu-
| wien/News/2024/Tho...
| data_maan wrote:
| Who will claim priority now?
| jahnu wrote:
| As I understand it, that is not an independent discovery but
| rather replication/confirmation of the results described in
| the original 14th of March paper by PTB & TU Wien.
| tromp wrote:
| I find it satisfying to see a researcher called THORsten SchUMm
| devoting his research to THORiUM.
| lordfrito wrote:
| Lol that's a comic book name if I ever heard one. He's only
| one lab accident away from becoming a super hero/villain.
| pfdietz wrote:
| And he's working with a dangerous radioactive isotope!
| kingkawn wrote:
| We're so close! Send some spiders into the reaction
| chamber!
| AnimalMuppet wrote:
| But then _I 'm_ only a name change and a lab accident away.
| And a name change isn't that hard...
| deepsun wrote:
| It doesn't work with name changes, unfortunately.
| mananaysiempre wrote:
| For what it's worth, the names of both the element and the
| researcher do in fact refer to the Norse god of thunder Thor.
| twic wrote:
| Even better, Thorsten = Thor's stone!
| davnicwil wrote:
| Nominative determinism :-)
|
| https://en.m.wikipedia.org/wiki/Nominative_determinism
| tomxor wrote:
| Frequency illusion :-P
|
| https://en.wikipedia.org/wiki/Frequency_illusion
| ChuckMcM wrote:
| Thanks for that, I wondered if it had been confirmed.
|
| I am always in awe of folks who come into the lab every day and
| work on figuring out the one thing. I envy that level of focus.
| cantrevealname wrote:
| > _If the wavelength of the laser is chosen exactly right ...
| then maybe a special atomic nucleus could be manipulated with a
| laser, namely thorium-229. On November 21, 2023, the team was
| finally successful: the correct energy of the thorium transition
| was hit exactly, the thorium nuclei delivered a clear signal for
| the first time._
|
| So what's the wavelength? I felt like the article left me
| hanging.
|
| The answer is: 148.3821 nm
|
| Yes, I admit that it's meaningless to me. It's sort of like a big
| news story announcing that Malaysia Airlines MH-370 has been
| located somewhere in the world's oceans, but not saying where
| because a number like 148.3821 km SSE of the Cocos Islands is
| going to be meaningless to most people.
| colecut wrote:
| I guess they could have said the laser frequency is about 2.02
| petahertz
| infogulch wrote:
| Oh that's about 0.0000000014 football fields.
|
| More seriously, apparently it takes a photon with a wavelength
| of 92nm to eject an electron from a hydrogen atom. Maybe this
| is a reasonable reference/refresher:
| https://web.archive.org/web/20210413042937/https://www.nagwa...
| thebruce87m wrote:
| American football or European football? This is like the
| gallon thing all over again.
| lionkor wrote:
| standard football field size, or empirical average?
| defrost wrote:
| I suspect the average football field size across the
| former British Empire is close to the FIFA standard.
|
| Throw in Australian Rules Football fields if you're
| looking for a maximum, particularly if orginal marn-grook
| is in the mix.
| Someone wrote:
| > suspect the average football field size across the
| former British Empire is close to the FIFA standard.
|
| The FIFA standard
| (https://downloads.theifab.com/downloads/laws-of-the-
| game-202...) leaves a lot of leeway:
|
| _"3. Dimensions
|
| The touchline must be longer than the goal line.
|
| * Length (touchline): minimum 90 m (100 yds), maximum
| 120m (130 yds)
|
| * Length (goal line): minimum 45 m (50 yds), maximum 90m
| (100 yds)"_
|
| So, a field can be almost square at 90m x 89m or
| approaching thrice as long as wide, at 120m x 45m.
|
| Reason for this is prior art that can be hard to change
| (if there's a stadium around your field, and it's deemed
| too small, you'd have to demolish it to make the field
| fit the standard)
|
| Various competitions restrict this, though.
| defrost wrote:
| Interesting .. I hadn't realised there'd be so much give
| in the FIFA specs!
|
| Thankyou for looking that up.
| wil421 wrote:
| Laden or unladen?
| passwordoops wrote:
| Or Canadian or Aussie rules football?
| greggsy wrote:
| Gaelic, obviously
| tzs wrote:
| Note: I will use the term "soccer" for the most common
| football of Europe, "Association football", and "football"
| for American football. And before anyone says that soccer
| fields should be called "pitches" not "fields" I will note
| that FIFA's "Laws of the Game" call it "field" 184 times.
| They only mention "pitch" in the glossary where the heading
| for "field" is "Field of play (pitch)".
|
| Generally you want to use American football fields for this
| because American football fields have a standard size, 100
| yards x 160 feet (91.44 x 53.3 meters). That size field is
| used in professional, college, and high school football.
|
| Soccer fields on the other hand not only vary from country
| to country, they aren't even always all the same size
| within a league. The English Premier League for example is
| trying to standardize on 105 x 68 meters but several clubs
| are not yet there: Brentford (105 x 65), Chelsea (103 x
| 67), Crystal Palace (100 x 67), Everton (103 x 70), Fullham
| (100 x 65), Liverpool (101 x 68), and Nottingham Forest
| (105 x 70).
|
| For international play the standard is a range. 100-110
| meters length and 64-70 meters width.
|
| There are parts of soccer fields that are standardized to
| specific values rather than ranges so would be good for
| unambiguous length or area comparisons. The amusing thing
| is that those all have fractional values in metric but
| integer values in Imperial/US units:
|
| * Radius of circle around center mark: 10 yards.
|
| * Penalty area: 44 x 18 yards.
|
| * Distance from penalty mark to goal: 12 yards.
|
| * Goal area: 20 x 6 yards.
|
| * Distance between goal posts: 8 yards.
|
| * Height of crossbar: 8 feet.
| airstrike wrote:
| _> I will use the term "soccer" for the most common
| football of Europe, "Association football", and
| "football" for American football._
|
| I appreciate your valiant efforts but to my mind this is
| extra confusing because "soccer" is short for
| "association football"
|
| Time to rename American Football to "handegg" once and
| for all. Ok, ok, I'll settle for "American Rugby"
| smegger001 wrote:
| Or just go back to calling it gridiron football.
| vonzepp wrote:
| Or just American Handball
| thehappypm wrote:
| I've heard "handegg" before but a football is not shaped
| like an egg, it's vaguely egg-like but the teardrop shape
| of an egg is distinctly not what a football looks like.
| Galatians4_16 wrote:
| European soccer, or American soccer? (there are
| significant differences)
| megous wrote:
| Ah, imperial units...
| shiandow wrote:
| More to the point >400nm is visible light, this puts 148nm
| well within the ultraviolet range. Though it's not too far
| removed from the visible spectrum, wouldn't surprise me if
| some animals could see it.
| LeifCarrotson wrote:
| 148 doesn't feel too far removed from the visible spectrum,
| but it's in the wrong direction for animals to make use of
| it. I'm no biologist, but I'd be shocked if there were any
| animals that had adapted sensitivity to a type of radiation
| that they are never exposed to in nature. The sun doesn't
| really emit much UV-C light:
|
| https://en.wikipedia.org/wiki/Solar_irradiance#Absorption_a
| n...
|
| and the light that is emitted is absorbed by the
| atmosphere:
|
| https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet
|
| It's useful to be able to see a little UV-A, perhaps, and
| very useful for predators to see 'heat' into the IR range,
| but if your eyes were sensitive to 148nm, the world would
| be pretty dark.
|
| Maybe after a few million years, in the grinding dust in
| the back of my shop, something will evolve that has a
| symbiotic relationship to arc welders...
| shiandow wrote:
| Ah, yeah makes sense that animals couldn't see it if it's
| not really part of sunlight. I was thinking it was not
| physically impossible, but it would be remarkably
| pointless if the light is simply not there.
| pfdietz wrote:
| I don't see how it could get into an organism if it's
| absorbed by air and water.
| twic wrote:
| Also, even if there was some advantage to doing so, i'm
| not sure how animals could see a wavelength that short.
| They would need a photoreceptor protein which can absorb
| photons of that wavelength and turn them into some sort
| of chemical change which can trigger a signalling
| cascade. That protein would have to have a pair of
| molecular orbitals which are h * 148 nm apart. What can
| give you that?
|
| The ethene double bond absorbs at ~165 nm, a benzene ring
| at ~180 nm, and building things out of those tends to
| increase the wavelength, not decrease it. 148 nm is
| single bond territory - could you have a chromophore
| which uses photons of the right wavelength to break a
| bond, and then somehow react to the presence of free
| radicals?!
| narag wrote:
| A long time ago I saw some UV photos of flowers, compared
| to visible and IR. There were some distinct features.
| That suggests some insects could see them, but of course
| it's just speculation.
| BenjiWiebe wrote:
| That would be UV-A, I believe. Not UV-C.
| blincoln wrote:
| It's not speculation. Bee eyes have receptors for green,
| blue, and UV-A light, for example. But as BenjiWiebe
| mentioned, that's not the same as being sensitive to
| UV-C.
|
| I'm sure there would be some value in seeing others parts
| of UV. Some minerals fluoresce from one type of UV light
| but not another, so they'd be dark in the bands that
| cause them to fluoresce. Mantis shrimp can apparently see
| into UV-B, but I'm not aware of anything living that can
| see UV-C.
| nullc wrote:
| Many animals do have more UV extension than you might
| initially assume useful: due to scattering following the
| inverse fourth power of wavelength the sky is lit in the
| UV a long time before sunrise.
|
| Presumably wouldn't apply anywhere near as far as 148nm
| since as you note that light doesn't make it to earth.
| M95D wrote:
| They could at least say it was a UV laser.
| whatshisface wrote:
| 148nm is on the lower end of UV-C. It's higher-energy than the
| furthest ultraviolet light that the sun produces (200nm). If it
| were produced artificially, it'd be heavily absorbed by the
| atmosphere to the point of near opacity. If the visible
| spectrum was an octave, where the "tone" of a color wrapped
| around from red back to blue the way G wraps to A, it'd be the
| blue one octave above visible blue.
| pmayrgundter wrote:
| Nice to hear the octave relation used!
|
| "blue above visible blue" is a good name.. hmm, a little web
| tool to name these would be neat ;)
| beretguy wrote:
| > "blue above visible blue"
|
| Good name for a rock band. Or some tv series.
| NateEag wrote:
| But better would be a prog-rock album named:
|
| Supravisiblue
| adrianmonk wrote:
| Surely it would be a blues band.
| ethbr1 wrote:
| Joni Mitchell - Blue (Blue)
|
| https://m.youtube.com/watch?v=MvR7Dkg4NQU&t=820s
| Cthulhu_ wrote:
| Out of curiosity I googled to see if there's formal names
| to things beyond UV and a SO question came up saying
| Klingon has a word for a color that falls within the UV
| spectrum, Amarklor; it "falls between violet amarklor (dark
| violet or purple) and amaklor-kalish (almost black)".
|
| Else there's Octarine from the Discworld books, it's the
| colour of magic.
|
| Another one in that same SO thread is err, quantifying
| synesthesia in the study of "chromophonics", where sound is
| assigned a color and vice-versa, that is, one could name a
| colour after a sound, which matches up with the earlier
| "octave" analogy.
| Cthulhu_ wrote:
| It looks like "chromophonics" is a thing to link colors with
| tones (synesthesia)
| ngoldbaum wrote:
| Teeny nit, the sun produces light well into the x-rays
| (mostly from the corona though). You're probably talking
| about sunlight making it through the atmosphere.
| whatshisface wrote:
| I'm talking about the blackbody radiation of the sun's
| surface, which accounts for almost all of the light. The
| X-ray flux at earth is 11 orders of magnitude lower than
| the blackbody-related flux.
| roenxi wrote:
| Physics like this (really I'd call it materials science; it
| isn't but it has immediate practical applications on building
| things) is a bit of a sleeper in terms of importance. Small
| improvements in tolerances and materials drive huge changes in
| what is economically feasible at the other end of the science-
| engineering-machining pipeline. "We've built a higher precision
| thing" is usually huge news. Take semiconductors, where the
| entire industry is driving crazy value entirely from getting
| better at moving atoms around by a few nanometers.
|
| Missing out on the magic number does seem like a bit of a
| problem, but really the expectations on the audience are
| already quite low. That number could easily turn out to be
| worth more than a trillion dollars to humanity at large, but
| I'd bet most readers just think of it as a party factoid.
| adrian_b wrote:
| This actually has significant practical importance, because
| it is hoped that using this transition of the thorium nucleus
| it will be possible to build atomic clocks even better than
| those using transitions in the spectra of ions or neutral
| atoms, because the energy levels of the nucleus are less
| sensitive to any external influences.
|
| While in the best atomic clocks one must use single ions held
| in electromagnetic traps or a small number of neutral atoms
| held in an optical lattice with lasers, in both cases in
| vacuum, because the ions or neutral atoms must not be close
| to each other, to avoid influences, with thorium 229 it is
| hoped that a simple solid crystal can be used, because the
| nuclei will not influence each other.
|
| The ability to use a solid crystal not only simplifies a lot
| the construction of the atomic clock, but it should enable
| the use of a greater number of nuclei than the number of ions
| or atoms used in the current atomic clocks, which would
| increase the signal to noise ratio, which would require
| shorter averaging times than today, when the best atomic
| clocks require averaging over many hours or days for reaching
| their limits in accuracy, making them useless for the
| measurement of short time intervals (except for removing the
| drift caused by aging of whatever clocks are used for short
| times).
| WitCanStain wrote:
| What could we do with more accurate atomic clocks that we
| cannot do with current ones?
| defrost wrote:
| For interest, Precision Vs Accuracy, Atomic Clocks Vs
| Sapphire Oscillator
|
| https://news.ycombinator.com/item?id=28232645
|
| Detecting gravity waves with _large_ laser triangles
| required a few advances in technology - precision clocks
| was one.
|
| Not so long ago had you asked your question the answer
| would have been "detect gravity waves".
| fanf2 wrote:
| Most units of measurement are derived from the second, so
| the more precise our frequency standards, the more
| precise everything else can be. Things like
| interferometry and spectroscopy depend directly on very
| precise frequency standards.
| btilly wrote:
| The article points to a use I wouldn't have thought of.
|
| The deeper you go into a gravitational field, the slower
| time goes. Therefore comparing clocks in different places
| gives a way to measure gravity. These clocks could be
| sufficiently precise to find mineral deposits underground
| from their gravity signature.
| defrost wrote:
| > These clocks could be sufficiently precise to find
| mineral deposits underground from their gravity
| signature.
|
| We've been doing that since the 1960s at least with such
| things as the LaCoste & Romberg gravimeter (1936).
|
| You can download, see online the "Geoid"
|
| https://americanhistory.si.edu/collections/nmah_865074
|
| https://en.wikipedia.org/wiki/Gravimetry
|
| https://en.wikipedia.org/wiki/Geoid
|
| Magnetic anomalies also highlight inteesting places for
| minerals, the issue with both magnetic and gravity fields
| variations lies with determining the "true" depth to
| target (medium sized shallow target, or massive deep
| taget?) which is known as an inversion problem.
| btilly wrote:
| Yes, but a better clock means more precise measurements,
| means we can locate smaller masses to higher precision.
| defrost wrote:
| Does it?
|
| Inversion is rarely unique, and it's not due to the
| precision with which the field is measured.
|
| https://earthsciences.anu.edu.au/study/student-
| projects/nove...
|
| https://inside.mines.edu/~rsnieder/snieder_trampert_00.pd
| f
|
| Epilogue: Linear inverse problem theory
| is an extremely powerful tool for solving inverse
| problems. Much of the information that we currently have
| on the Earth's interior is based on linear inverse
| problems Despite the success of linear
| inverse theory, one should be aware that for many
| practical problems our ability to solve inverse problems
| is largely confined to the estimation problem.
| btilly wrote:
| Yes, inverse problems are hard. And not always possible
| in practice. See, for example,
| https://www.ams.org/publicoutreach/feature-
| column/fcarc-1997... for a case where one isn't possible.
|
| That said, the gravity technique is one that actually
| gets used today. With better precision, it can be even
| more useful than it already is.
| JanisErdmanis wrote:
| The problem is that the planet could be hollow and
| produce the same gravitational measurements on the
| surface and outside. It needs to be coupled with a model
| that introduces constraints for the inverse problem to be
| defined.
| blincoln wrote:
| Since mining is only concerned with material that's
| within maybe 0.1% of the distance from the surface to the
| core, seems like you'd just need to move the sensor
| around and make sure the signal changes about where you'd
| expect for a mass of X Kg at a depth of Y meters instead
| of a supermassive chunk of dense material much deeper.
| Or, to put it another way, build a grid map of the area
| and subtract any background signal. Would that not work
| for some reason?
| btilly wrote:
| Consider the special case of a spherical deposit. You can
| find the center and mass of the deposit, but not its
| volume or density.
|
| But now that you know it is there, you can use other
| techniques, like seismic measurements, to nail that down.
| JanisErdmanis wrote:
| In practice, that's what would happen. Move around until
| seeing some larger gravitational pull, likely indicating
| some deposit. However, formally, this is not correct due
| to the mere fact that the gravitational force is
| proportional to 1/R^2, just like a Columb force. Thus,
| there are infinite numbers of mass distributions that
| produce the exact same gravitational field on the
| surface. The planet could be hollow, and we would not
| know it only from the field measurements.
|
| A practical constraint is mass density, which has maximum
| and minimum values. We can make a crude approximation
| that the planet's density is constant, evaluate the field
| on the surface from the planet's shape and compare it
| with measurement. This would be more useful, but still,
| it wouldn't tell us whether there is a combo of water
| reservoir and a large massive deposit below it.
| denton-scratch wrote:
| > clocks even better than those using transitions in the
| spectra of ions or neutral atoms
|
| I'd be interested to know _how much_ more accurate a
| nuclear-state-transition clock might be than a conventional
| Caesium or Rubidium clock.
|
| TFA seems to make the point that a nuclear clock would be
| more resistant to external influences, such as EM
| radiation, than an atomic clock, and so could be used in
| experiments where such influences might introduce unwanted
| uncertainty. But I'd like to know what the claim for
| greater accuracy is based on, rather than simply greater
| reliability.
| wbl wrote:
| You have the math turned around. Because the nuclear
| resonance is much more stable and high frequency the Q
| factor and accuracy of the measurement is higher. With a
| cesium or rubidium clock it's very difficult to control
| all the influences on how tightly the nominal resonance
| is achieved and the Q while impressive is a bit less.
|
| There are some real challenges in realization: this will
| take optical combs and all sorts of other stuff to really
| take advantage of.
| pfdietz wrote:
| They also point out that because the thorium atoms can be
| embedded in a solid, and have motion << the wavelength of
| the radiation, the emission and absorption are largely
| recoil-free. This eliminates Doppler broadening. What
| broadening there could be was below the resolution of
| their pump beam.
| fanf2 wrote:
| For comparison, over the last several years there has been a
| lot of research into optical frequency standards. Because they
| run at a higher frequency than (microwave) caesium frequency
| standards, optical frequency standards can be more precise. The
| current candidates
| https://iopscience.iop.org/article/10.1088/1681-7575/ad17d2
| have wavelengths between 750nm and 250nm. Caesium frequency
| standards use a wavelength of 32.6mm, so about 100,000x bigger
| than optical frequency standards.
|
| Based on just the frequency, I dunno what makes the thorium
| nuclear transition much better than optical transitions. Unless
| the excitement (as it were) is about scaling up to even higher
| frequencies.
| CamperBob2 wrote:
| The key factor is the line width, or the range of frequencies
| over which the transition can be stimulated. The ratio of the
| stimulus frequency and line width is one way of expressing
| the resonator Q factor. In general, the lower the line width
| for a given transition, the higher the Q, the better the
| signal-to-noise ratio, and the more stable the resulting
| clock. (Imagine how much more precisely the frequency of a
| large bell could be measured compared to a cymbal or
| something else with a broader acoustical spectrum.)
|
| Cs or Rb clocks give you a line width of a few hundred Hz at
| 9 GHz (Q=roughly 100 million), while quantum transitions in
| optical clocks can achieve line widths on the order of 1 Hz
| in the PHz region (equivalent Q in the quintillions.) There
| is a lot more to building a good clock than high Q, but it's
| a very important consideration (
| http://www.leapsecond.com/pages/Q/ ).
|
| What caught my eye is the ringdown time of the stimulated
| optical resonance, apparently in the hundreds of seconds.
| They talk about line widths in the GHz range, but that seems
| to refer to the laser rather than the underlying resonance
| being probed. It would have been interesting to hear more
| about what they expected regarding the actual transition line
| width. Probably the information is there but not in a form
| that I grokked, given insufficient background in that field.
| dtx1 wrote:
| What does "exciting a nucleus" mean?
| atoav wrote:
| Not a physicist but "exciting" a thing means to make it
| oscillate e.g. by adding energy into the system. A violin
| player is exciting the string of her instrument using a bow.
|
| Now in this case they use lasers. I suspect if you choose the
| right wavelenght (=frequency) of light there is some sort of
| resonance phenomenom.
| sebws wrote:
| The article mentions switching between "energy states":
|
| > This nucleus has two very closely adjacent energy states - so
| closely adjacent that a laser should in principle be sufficient
| to change the state of the atomic nucleus.
|
| > the correct energy of the thorium transition was hit exactly,
| the thorium nuclei delivered a clear signal for the first time.
| The laser beam had actually switched their state.
|
| I don't know enough to explain any further.
| gilgoomesh wrote:
| Applying energy to lift its electrons across a band gap. In
| this case, applying 8.35574 electron volts.
| mypalmike wrote:
| I thought this was an excitation of the state of the nucleus
| rather than that of electrons.
| popol12 wrote:
| You're right, parent read too fast
| Turneyboy wrote:
| We know how to do this and have observed this tons of times
| at this point. This would not be novel in any way. This is
| about exciting the nucleus which is completely different.
| guidedlight wrote:
| Thorium-229 has two energy states. A ground state, and an
| excited isometric state.
|
| The laser is used to transition the nucleus from the ground
| state to the excited isometric state.
| bboygravity wrote:
| And then?
| topspin wrote:
| And then the nuclei return to the ground state. That
| process is probabilistic and measured in half-lives. The
| key point is that the decay back to ground state happens at
| a very precise rate that is not influenced by effectively
| anything, and can be measured accurately. Thus, a clock.
| dtx1 wrote:
| > That process is probabilistic and measured in half-
| lives
|
| > The decay back to ground state happens at a very
| precise rate that is not influenced by effectively
| anything
|
| That sounds contradictory to me.
| topspin wrote:
| I suppose it could: the term "probabilistic" applies to
| the quantum probability of any one metastable isomer
| (excited nucleus) decaying to ground state. In
| application you measure large numbers of decays, and in
| great numbers the decay curve is extremely precise.
| phendrenad2 wrote:
| Isometric? Like, is the nucleus gaining a virtual proton or
| something?
| nullc wrote:
| Nucleons occupy orbital energy states like electrons. The
| application of energy can shift the state of the nucleus,
| and some of these alternative states are relatively stable.
|
| https://en.wikipedia.org/wiki/Nuclear_shell_model
| pfdietz wrote:
| The correct word is "isomeric", as in the state of a
| nuclear isomer.
| tinco wrote:
| Not a physicist, so this comment is more of a guess with the
| intention of someone correcting me, but I think the thing all
| the physicists leave out because it's probably very obvious
| is that when an excited nucleus returns to its ground state,
| it will emit radiation.
|
| So they hit their thorium with a laser, and then instead of
| the laser passing through, it gets absorbed, and then they
| get a flash of radiation back, letting them know the thorium
| was excited. The delay between the laser pulse and the flash
| of radiation is a property of the particular thorium nucleus,
| and is not affected by environmental circumstances like
| temperature or electric/magnetic fields, so can be relied on
| as a very precise measurement of time.
| zackmorris wrote:
| 25 years ago, there were experiments to move element 72
| hafnium (Hf) between its low and excited isomer states, which
| would allow for the creation of a nuclear battery that could
| store 100,000 times more energy than a chemical battery, with
| a 31 year half life, but without neutron release:
|
| https://en.wikipedia.org/wiki/Hafnium_controversy
|
| This would be Iron Man and Star Wars tech if it worked.
| Unfortunately experiments went dark after 2009, probably
| because it worked haha, but maybe because Hf is too rare to
| make a practical battery. So it looks like they tried
| spalling element 73 Tantalum (Ta), 74 Tungsten (W) and 75
| Rhenium (Re) with protons at 90-650 MeV to create 72 Hf with
| atomic masses 178, 179 and high spin 178m2, 179m2 isomers if
| I read this right:
|
| https://publications.jinr.ru/record/151982/files/071%28E6-20.
| ..
|
| https://apps.dtic.mil/sti/tr/pdf/ADA525435.pdf
|
| There's a lot here though, so I can't really get a clear
| picture of what the yields are, or simply how many joules it
| takes to store one joule in an excited isomer. Which is of
| course all that matters, but papers often leave off the one
| part we're curious about, forcing us to learn nearly the
| entirety of the subject matter to derive it ourselves.
| Although on the bright side, maybe that protects us from
| nuclear armageddon and stuff.
|
| Maybe someone can fill us in?
|
| Edit: dangit _Microft beat me by 17 minutes, please answer
| there :-)
| cshimmin wrote:
| It means getting the nucleus to absorb a certain energy above
| its ground state. Since it is a quantum object, it can only
| absorb/emit energy in very specific amounts at once ("quanta").
|
| The details of how the nucleus manifests that extra energy are
| complicated, but you can imagine it as like, picking up a
| certain vibrational frequency.
| euroderf wrote:
| With enough absorptions, can the nucleus tear itself apart
| (i.e. fission) ?
| the8472 wrote:
| Yes, that's one possibility[0]. Or the energy can be
| sufficient to alter the decay rates of other nuclear
| reactions (alpha/beta decay, etc.) compared to the base
| isotope. A weird example: Excited tantalum-180[1] is more
| stable than its base state.
|
| [0] https://en.wikipedia.org/wiki/Photofission [1] https://
| en.wikipedia.org/wiki/Isotopes_of_tantalum#Tantalum-...
| huytersd wrote:
| But then what happens? Does it expel an electron/release
| energy etc.?
| greenbit wrote:
| Probably just emits another photon of the exact same
| wavelength a short time later. The time would be
| probabilistic, like 50% chance of emission in X amount of
| time.
| graycat wrote:
| Physics does not emphasize this, but the _half life_
| concept essentially assumes a Poisson process (Cinlar,
| _Stochastic Processes_ ) which has a Markov (past and
| future conditionally independent given the present,
| details from the Radon-Nikodym theorem, with a cute von
| Neumann polynomial proof, Rudin, _Real and Complex
| Analysis_ ) assumption.
|
| The half life concept seems to be standard over much of
| physics.
|
| That a Markov assumption could hold might suggest some
| _new physics_.
| gwd wrote:
| > It could be used, for example, to build an nuclear clock that
| could measure time more precisely than the best atomic clocks
| available today.
|
| Are today's atomic clocks really so imprecise? Without further
| explanation of this, it reminds me of this comic (which is alas
| showing its age both by mentioning flash, and by implying that
| 1024 is already a uselessly high number of cpus to support):
|
| https://xkcd.com/619/
| fancy_pantser wrote:
| Intel GPU joke in the alt text, truly timeless.
| nullc wrote:
| Now how the heck do you generate ~148.38nm light with a narrow
| linewidth? Their approach using four-wave mixing inherently
| results in short pulses.
|
| .. and given that it decays through gamma emission, does this
| mean we could now build an optically pumped gamma ray laser?
| M95D wrote:
| The gamma emission would have to re-excite other atoms in a
| cascade to create a laser. Since the exciting energy is UV, not
| gamma => no cascade amplification.
|
| A "wavelength converter" might be possible.
|
| PS: Are you sure it's gamma emission? That takes more energy
| than the exciting UV photon.
| karma_pharmer wrote:
| > PS: Are you sure it's gamma emission? That takes more
| energy than the exciting UV photon.
|
| Apparently it is neither:
|
| _Decay of the 229Th isomeric state of the neutral thorium
| atom occurs predominantly by internal conversion (IC) with
| emission of an electron_
|
| https://www.nature.com/articles/nature17669
|
| https://en.wikipedia.org/wiki/Internal_conversion
|
| This is pretty weird. You shine UV light (with _exactly_ the
| right wavelength) on 229Th, and it spits out electrons. But
| not like the photoelectric effect, where the electrons stop
| as soon as you turn off the light. No no. The Thorium keeps
| spitting out an exponentially-decaying stream of electrons
| for _hours_ after you stop illuminating it.
|
| Almost like an exponentially-discharging solar-powered
| current source (for a very specific wavelength of "solar").
| nullc wrote:
| Apparently in some ionized states it can't produce the
| electron and will instead produce the gamma, I'm unclear
| where the extra energy comes from.
|
| > Almost like an exponentially-discharging solar-powered
| current source (for a very specific wavelength of "solar").
|
| If one could make the UV source highly efficient perhaps it
| could be used as a battery with extremely good energy
| density.
| karma_pharmer wrote:
| The last sentence of the paper seems to imply that this result
| will give people a reason to want to develop those:
|
| _The development of dedicated VUV lasers with narrow linewidth
| will make it possible to access a new regime of resolution and
| accuracy in laser M"ossbauer spectroscopy and to perform
| coherent control of a nuclear excitation "_
|
| Previously, if you wanted to manipulate nuclear states, you
| needed a synchrotron. Now, you need an infinitely less
| expensive instrument. I suppose the idea is that that will
| generate a lot of interest in improving the less-expensive
| instrument.
| bawana wrote:
| What i was wondering...exactly... how do you make this kind of
| a laser? And imagine an xray laser... you could fry the
| guidance system of drone very precisely
| yread wrote:
| Is there some direct application? Like using the excitation
| states of different atoms for storing information?
| irjustin wrote:
| The article directly stated more precise atomic clocks.
| pzs wrote:
| Not a physicist, so I am asking out of curiosity and to
| learn: have the limitations to the precision of current
| atomic clocks posed any problems?
| huytersd wrote:
| If I remember correctly GPS is effected but the ultra
| precise version the gov uses can error correct pretty well.
| I would think greater GPS precision at a lower cost?
| sgt101 wrote:
| synchronization of compute across data centers is something
| I've used atomic clocks for, precision and cost are an
| issue.
| Dibby053 wrote:
| Sounds interesting. If you don't mind me asking, what
| sort of computation requires synchronization across data
| centers? And why couldn't it be done with NTP?
| nullc wrote:
| We derrive most of our other units from time, so
| differences in time accuracy translate into metrology
| improvements more generally.
|
| Existing atomic clocks based on electrical interactions are
| extremely sensitive to the surrounding magnetic and
| electrical environment-- so for example accuracy is limited
| by collisions with other atoms, so state of the art atomic
| clocks have optically trapped clouds in high vacuums.
| Beyond limiting their accuracy generally makes the
| instruments very complex.
|
| One could imagine an optical-nuclear atomic clock in
| entirely solid state form on a single chip with minimal
| support equipment achieving superior stability to a room
| sized instrument.
| was_a_dev wrote:
| If atomic clocks become a few orders of magntidude better
| than the current state of the art (see atomic lattice
| clocks) then such clocks would do direct gravitational wave
| measurements and measure some fundemental constants.
|
| The latter is important in physics to determine if these
| constants are truly constant in space and time. Which is a
| large assumption we have about the universe.
| raverbashing wrote:
| Usually these application, while they're good, they're just
| the initial idea people have given the current understanding
|
| The cool applications usually come later (or they're more
| esoteric). The researchers were more excited to determine the
| actual frequency than think about clocks
| limbicsystem wrote:
| I >think< that this will enable more accurate magnetometers
| (see OPM-MEG and atomic clock magnetometers). Which can be
| used, among other things, for measuring neuronal activity.
| nebben64 wrote:
| Can you explain your reply a bit; how will MEG tech evolve
| from this breakthrough?
| limbicsystem wrote:
| I'm still reading the paper but I think it might enable
| better versions of this sort of thing:
| https://www.nist.gov/noac/technology/magnetic-and-
| electric-f...
| sharpshadow wrote:
| That's great news! As far as I understand constants are not an
| easy topic and being able to analyse more precisely is a big win.
| Geenkaas wrote:
| My high school physics class flashes back to me, I don't think I
| understand a fraction of it but it seems very exciting (pun
| intended).
|
| I was reading up on this (now outdated) wiki page:
| https://en.wikipedia.org/wiki/Isotopes_of_thorium#Thorium-22...
|
| And it mentions the application as qubit for quantum computers.
| If the state change is relatively simple, cheap and stable, what
| could this do for quantum computing? I picture a crystalline
| processor holding Thorium nuclei as the brains of a new
| supercomputer? Would that be viable?
| bamboozled wrote:
| _For example, the Earth 's gravitational field could be analyzed
| so precisely that it could provide indications of mineral
| resources_
|
| Resources companies are salivating
| worldsayshi wrote:
| It wouldn't be precise enough to measure things like what type
| of rock you have underneath when you're thinking about digging
| a tunnel or to find land mines in dirt right?
| alexey-salmin wrote:
| Did anyone understand how they hold a nucleus (not an atom) in a
| crystal? Nucleus is charged and seeks electrons, I thought you
| need an electromagnetic trap for that (which the article says
| they don't use).
| spuz wrote:
| They use Th4+ ions, not nuclei. The lack of 4 electrons in the
| Th cations is compensated for by the surrounding F- anions.
| rsfern wrote:
| They grew CaF2 crystals with a small amount of thorium, which
| take the place of some of the Ca atoms in the crystal lattice.
| There's an illustration in fig 1 of the preprint of what the
| substitutional defects look like
|
| Like the other poster mentions, CaF2 is an ionic crystal, but I
| don't think that's an important detail because you wouldn't
| expect a nuclear transition to be affected by the bonding state
| of the electrons. My guess is it's just a convenient way to get
| a very dilute collection of thorium atoms without using an ion
| trap
| est wrote:
| > But it is not just time that could be measured much more
| precisely in this way than before. For example, the Earth's
| gravitational field could be analyzed so precisely that it could
| provide indications of mineral resources or earthquakes
|
| This has military applications as well, right?
|
| Replacing GPS for nuclear submarines.
|
| https://news.ycombinator.com/item?id=29213751
|
| https://news.ycombinator.com/item?id=36222625
| hargup wrote:
| My buddy works for such a company, https://www.atomionics.com/
| and they are doing pilots with mining companies.
| lifeisstillgood wrote:
| >>> For example, the Earth's gravitational field could be
| analyzed so precisely that it could provide indications of
| mineral resources
|
| Hold on how does that work?
|
| I have had a sort of sci-fi idea that sufficiently sensitive
| gravitational field measurements coukd detect the passing of
| submarines (I am not sure on the maths tbh) - which would render
| a lot of nuclear strategy moot.
|
| Just need to get a grasp on the maths
| meindnoch wrote:
| https://apps.dtic.mil/sti/pdfs/AD1012150.pdf
|
| Gravitational Detection of Submarines, PM Moser 1989
| moffkalast wrote:
| That then makes single SLBM drone swarms the new meta. Spread
| them over a large enough area and it'll just seem like
| tectonic activity.
| perihelions wrote:
| Look at what paper actually says: flat "not achievable" in
| the abstract; and the scaling laws on page 4 are third- and
| fourth- inverse powers of distance (!!!!); and on page 7
| they're considering ranges of the same length scale as a
| submarine itself (few hundreds of meters), and _even there_
| it 's hopeless.
|
| This one's never going to happen.
|
| Geologic mass concentrations are an entirely different story:
| you get a gravitational monopole, which is a more reasonable
| inverse square law. (No monopoles for a submarine, because by
| design they have a mean density equal to water--as the paper
| explains).
| Eliezer wrote:
| What an excellent retrospectively obvious point!
| rpastuszak wrote:
| Check out quantum navigation systems. They're not used to track
| submarines, but rather as an alternative to GPS for submarines
| (using tiny differences in the Earth's gravitational field to
| determine position).
|
| (IIRC) Royal Navy trialed it (officially) for the first time
| last year.
| fodkodrasz wrote:
| Actually the method of detecting mineral deposits by mapping
| gravitational field is already in use since a long time!
|
| The Eotvos pendulum (an instrument aka. Eotvos torsion balance)
| designed in 1888 started this kind of measurement. It was used
| commonly by the 1920s by geophysicist for mapping underground
| deposits by measuring the gradient of the gravitational field
| very precisely.
|
| This instrument was deprecated later by even better tools for
| surveying.
|
| The instrument was initially constructed for the experiment
| showing that inertial and gravitational mass are the same
| (well, linearly correlated) to a great precision:
| https://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_experiment
|
| https://www.nature.com/articles/118406a0 (pretty useless link,
| but a famed periodical)
|
| Detecting submarines is way harder, practically impossible. as
| others have already pointed out.
| limbicsystem wrote:
| Sufficiently accurate clocks can act as 'relativity sensors' -
| measuring changes in the 'time' bit of spacetime due to small
| changes in gravity.
| MadnessASAP wrote:
| If you didn't know, deflections in earth's magnetic field are
| already used to detect submarines, amongst other things. Any
| large ferrous object will cause a small but detectable
| deflection in the magnetic field.
|
| Range is pretty short but still large enough that you can do it
| from an airplane flying over.
| rbanffy wrote:
| Professor Thorsten discovering a mystery of Thorium... How
| appropriate. Thor must be proud.
| v3ss0n wrote:
| Odin must be proud.
| B1FF_PSUVM wrote:
| This is where I slip in my recommendation of the little book
| titled Votan, by John James.
| galangalalgol wrote:
| Also, it was submitted on the 18th, which was a Thorsday...
| femto wrote:
| An obvious question is whether this be used to build a nuclear
| analogue of a laser, using nuclear transitions instead of
| electron transitions. It turns out to have already been asked:
|
| https://physics.stackexchange.com/questions/296237/nuclear-t...
|
| In summary, the answer seems to be "maybe, but why?". The laser
| was originally called "a solution in search of a problem", which
| would suggest that "why" isn't really a reason not to.
|
| https://ask.metafilter.com/148055/Who-first-called-lasers-a-...
| jncfhnb wrote:
| 1) does this have any relevance to thorium as nuclear fuel? Looks
| like no.
|
| 2) is there any significance to the units of the wave length?
| Like they've narrowed it down to a number. Does that granularity
| map to anything? Some sort of discrete scale? Or is there going
| to be a range of values that work +/- a super tiny value.
| adrian_b wrote:
| This has indeed no relationship with nuclear energy, except
| that thorium 229 is produced in nuclear reactors.
|
| This achievement is a step (the most important one) towards the
| goal of making an atomic clock that uses thorium 229 (which has
| important advantages mentioned in another posting).
| acidburnNSA wrote:
| Not yet. But if someone could condition nuclear fuel atoms so
| that when they do fission, they consistently break into one
| delayed neutron precursor and one stable or near stable atom
| with no long-term afterglow heat, that could revolutionize
| nuclear power. I've been told that this dream is impossible but
| it's still my 1 genie wish. Right now they break into 50% of
| the periodic table and cause all sorts of grief.
| dharma1 wrote:
| What stocks do I long, armed with this information :)
| avsteele wrote:
| Nice to see this happen! When this was attempted with trapped
| ions, I and my colleagues at GaTech were the first to trap and
| laser cool Th(232) 3+
|
| https://sites.lsa.umich.edu/kuzmich-lab/wp-content/uploads/s...
| ISL wrote:
| No time to elaborate at the moment. Just want to say that this is
| extremely exciting news.
|
| Finding the thorium line is one of the most important open
| problems in precision/fundamental measurement.
| einpoklum wrote:
| > this is extremely exciting
|
| That's what the Thorium said! [rim shot]
| einpoklum wrote:
| > For the first time, it has been possible to use a laser to
| transfer an atomic nucleus into a state of higher energy and then
| precisely track its return to its original state.
|
| We've known about photon-atom interactions for well over 100
| years, with excitation of electrons which are either released or
| drop back to the original orbit, right?
|
| So, ok, the Nucleus is smaller and the energies to alter the
| quantum state are probably higher, but - why is this so special,
| and why Thorium in particular rather than any old nuclei?
|
| Disclaimer: I'm not a physicist.
| was_a_dev wrote:
| The energy required to alter nuclear states is often in the MeV
| energy range, where Thorium is a rare example that has a very
| close state to the ground state, seperated by 8.4eV (100,000
| less energy)
|
| This means that to exicte to this nuclear state is possible
| using an ultraviolet laser
|
| It has important applications for nuclear theory, nuclear
| atomic clocks and fundemental constant metrology.
| enslavedrobot wrote:
| Very cool. Probably impossible but I wonder if you could see non-
| linear nuclear effects if you hit it with enough intensity.
|
| Laser induced fission anyone?
| _Microft wrote:
| Look up ,,hafnium controversy":
| https://en.m.wikipedia.org/wiki/Hafnium_controversy
| davidwritesbugs wrote:
| Would this have any relevance to inertial navigation sensors?
| cwillu wrote:
| Literally over 50% of the viewport is taken up by sticky toolbar
| crap, depending on the window size.
| MilStdJunkie wrote:
| When you stop and look at QCD in the big picture, it's sort of
| shocking how little we know - like, really, _really_ know - about
| the internal structure of the proton, or even the nucleon!
|
| It's the curse of "probing" with massive energies. No one's a
| hundred percent certain of whether they're detecting something
| that's actually _there_ - like _there_ there - or whether they
| 're looking at by-product of enormous collision energies.
|
| Physicists are smart people! I could never do what they do. But
| there's a limit to certainty, and inside the proton especially
| there's unknown first principles at work. Bringing the precision
| of photons and lasers into this nucleon party is going to be
| _huge_. I can 't wait!
| javajosh wrote:
| Yeah and maybe we could do GR experiments on a table top.
| Gravity goes as 1/r^2 so a small r might make the mass terms
| irrelevant, and you could check GR in various ways [1]
| especially Shapiro delay[2]. This would, in turn, give a way to
| probe quantum gravity effects.
|
| 1 - https://en.wikipedia.org/wiki/Tests_of_general_relativity
|
| 2 - https://en.wikipedia.org/wiki/Shapiro_time_delay
| blackoil wrote:
| > it's sort of shocking how little we know
|
| To my feeble mind, it's shocking how much we know.
| swamp40 wrote:
| _> thorium crystal clock_
|
| Take note, science fiction writers.
| ThinkBeat wrote:
| Is this of any value when it comes to nuclear energy creation?
| m3kw9 wrote:
| The way to know if a "breakthrough" could be legit is by
| observing the comment count of a post that says breakthrough
| shadowtree wrote:
| Man, Vienna is killing it in physics.
|
| Nobel in 2022 for Zeilinger
|
| Nobel in 2023 for Kraus, who did his work at TU Wien
|
| Now this. Giving a lot of other unis a run for their money.
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