32 ms·

The first nuclear clock will test if fundamental constants change

288 points by beefman 2y ago

1970-01-01 2y ago
Matter in other galaxies would behave differently from matter in the Milky Way if fundamental constants are not always true. I argue about this sometimes. Others keep stating that the wavelengths are equal, so everything else must be.
- gmueckl 2y ago
  I think the better way to ask this question is: how much large scale spatial variation can there be in the laws of physics so that the observable behavior doesn't contradict existing observations? As far as I remember, this has been studied, but I can't find a reference right now.
  - canadianfella 2y ago
    [dead]
  - jepler 2y ago
    wikipedia has a high level review of current constraints: https://en.wikipedia.org/wiki/Time-variation_of_fundamental_constants https://en.wikipedia.org/wiki/Time-variation_of_fundamental_... fine-structure constant: less than 10^−17 per year gravitational constant: less than 10^−10 per year proton-electron mass ratio: less than 10^−16 per year
- rkagerer 2y ago
  What's meant by "the wavelengths are equal"? (And have we measured comparable wavelengths in other galaxies?)
  - fnordpiglet 2y ago
    Presumably they mean propagating EM radiation we observe from earth appears to behave the same on earth as we observe from distant galaxies since the event that created them happened at a time much different than ours and a distant region of space.
    - saalweachter 2y ago
      I mean, technically the EM radiation we observe from distant galaxies does look different than the EM radiation we observe locally: it's red-shifted. I'm sure someone has proposed this is due to physical constants changing over time, rather than the expansion of space-time, and I'm sure someone else has explained why this is wrong.
  - itishappy 2y ago
    The wavelengths of physical processes are equal. If fundamental constants changed, we'd expect, say, the Lyman series to change too.
  - analog31 2y ago
    Yes, we've measured comparable wavelengths. It's one way we can measure the red shift. Not just (red shifted) absolute wavelengths, but the relative spacing between them are quite sensitive to physical constants. These spectra can also be used for identifying the elemental composition of stars.
  - cryptonector 2y ago
    > What's meant by "the wavelengths are equal"? Absorption lines of the elements in the stars whose starlight we observe. THey are the same after correction for redshift.
- mysecretaccount 2y ago
  If the fundamental constants are not constant, why not expect them to change in this galaxy as well? The appeal to "other galaxies" seems suspect to me, a way to evade falsifiability.
  - itishappy 2y ago
    "A way to evade falsifiability" is the goal of the statement, given that we've been searching for evidence to the contrary for as long as we've been able. We haven't found any, and we've searched close-at-hand the most thoroughly.
  - 1970-01-01 2y ago
    The idea is they're fixed/set by the overall size of the galaxy.
  - mbrubeck 2y ago
    If the constants change over very long time spans, we could observe this by looking at distant galaxies from billions of years ago. We don’t have a way to make similar observations within our own galaxy.
    - lupusreal 2y ago
      What if the constants only changed over incredibly small scales, vibrating back and forth between two very similar numbers like a standing wave with extremely small amplitude and wavelength, such that any measurement done on even small scales has trouble seeing anything but the average?
      - raattgift 2y ago
        Let's start with the universe since the ignition of the first stars. Your question is also super-interesting in the context of the very early universe, so I'll come back to that further below. Depending on the constants, with significant fluctuation of them you'd expect spectral line broadening rather than the sharp lines we see in precision interferometry, violations of local Lorentz invariance, different structures in "stacked" spectra (like the Lyman-alpha forest), and instabilities in Keplerian orbits. Present measurement precision of subatomic transition spectra has really boxed you in on this: many physical constants have relative standard uncertainties on the order of 10^-10 or better. > any measurement ... [sees only] the average So you'd start wondering: in the limit of infinitesimal fluctuations, is a fluctuating constant just constant rather than an "effective constant"? Where's there's still wiggle room is in the exact masses of heaver generation standard model particles (top quark, tau mass, W-to-Z mass ratio for example) and somewhat frustratingly Newton's gravitational constant, all of which have relative standard uncertainties worse than 10^-5. (There's a quick explanation of standard uncertainty and relative standard uncertainty at <https://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/definitions.html https://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/defi...>) However, assuming cosmic inflation, one might expect incredibly small scale fluctuations in physical constants to be stretched, just like incredibly small scale fluctuations in the densities of matter and radiation. This could lead to later-universe regions of arbitrary size with a significantly different value for one or more physical constants, just like we see regions relatively stuffed with galaxies (filaments) and regions that are relatively empty (supervoids). We'd expect that when we look at different parts of the sky we'd see differences in things like the Lyman-alpha forest, the population and/or spectra and/or light curves of quasars/supernovae/variables, and so on. So, in order to have the apparently constant physical constants we observe, while keeping your idea that there are tiny fluctuations in them, you'd have to suppress high frequency fluctuations in the constants in the very early universe, because otherwise you'd have to suppress gross effects like different gas and dust chemistry when comparing one galaxy cluster to another. And we are looking: https://cen.acs.org/physical-chemistry/astrochemistry/Scientists-find-complex-organic-molecules-young-galaxy-12-billion-light-years-away/101/web/2023/06 https://cen.acs.org/physical-chemistry/astrochemistry/Scient... (The cosmic inflation epoch predates the "freezing-out" of some of the physical constants, so my thinking is that during inflation there must be some precursor constant(s) that determine(s) the mass of the electron (for example) once there are electrons after the electroweak epoch. Even after inflation the ordinary expansion of the universe can stretch fluctuations enough that (assuming your idea) there is likely to be a directional dependence on precision extragalactic astronomy.)
- renewiltord 2y ago
  One thing I have been arguing for a long time is that the fundamental constants are different until we observe them. i.e. if we don't observe it, it's possible for a tennis ball to travel through a wall. But in the universal program, if we will now or later observe the result, then it won't happen. But it'll happen so long as we will never observe the result. In fact, it's probably happened many times. No one has proven that this is impossible, AFAIK.
  - ezrast 2y ago
    What does "impossible" mean to you if not that a thing and it's consequences can never be observed?
    - renewiltord 2y ago
      Impossible means it does not happen, not that it does not happen only when we look. Just because we can't see it doesn't mean that it doesn't happen. After all, as the comment I replied to pointed out, other galaxies can have different constants. We have to be humble and admit we just don't know.
      - jiggawatts 2y ago
        The problem with these type of arguments is rigorously defining “we” and “look”. Turns out that our gaze has no effect on anything and we’re uninteresting squishy bags of mostly water as far as physical processes are concerned.
        renewiltord 2y ago
        Yeah, but no one has proven that this is impossible so it's still possible. Just like OP comment.
        wizzwizz4 2y ago
        https://www.smbc-comics.com/comic/2014-03-25 https://www.smbc-comics.com/comic/2014-03-25
- gitaarik 2y ago
  Well, if you think about it, on a large scale of the universe, our laws are helped by our mathematical inventions of dark matter and dark energy. So is there really dark matter and dark energy, or is our understanding of the laws of the universe incomplete?
  - thewarpaint 2y ago
    > So is there really dark matter and dark energy, or is our understanding of the laws of the universe incomplete? These propositions are not mutually exclusive, the former implies the latter, right?
  - foxyv 2y ago
    As I understand it, dark matter and dark energy are just placeholders for discrepancies between our current physical model and observations made by telescopes like Hubble and Kepler. This could mean either that our measurements are inaccurate, or that the model is incomplete. Honestly, I think that both are extremely likely.
    - AlexAndScripts 2y ago
      Dark matter (matter that has mass but does not interact in any other way) might be the literal solution. But there are also other suggestions (MOND is a big one). The https://en.m.wikipedia.org/wiki/Bullet_Cluster https://en.m.wikipedia.org/wiki/Bullet_Cluster is pretty interesting.
    - BurningFrog 2y ago
      "Dark matter" and "dark energy" could just as well be called "unexplained matter" and "unexplained energy". These terms are mostly placeholders for things we don't understand.
      - cowl 2y ago
        not even that. "unexplained matter" implies that there is some matter to explain (what type etc) when in reality is an unexplained observation that could be explained by current laws/constants if only there was some more (actually a lot more) matter. is a pure mathematical construct and mathematically it wold be just as valid to ad "dark constant modifier"
- cryptonector 2y ago
  Not necessarily. We have redshift and we use that to measure distance (in space and time). If fundamental constants were different in the past that might merely change only what distances we measure.
  - analog31 2y ago
    That would probably require quite a coincidence, since the redshift and the spacing between wavelengths both depend on the same constants but in different ways.
mseepgood 2y ago
They probably do change, but extremely slowly. It would feel strange if there were something fixed in the universe.
- bitmasher9 2y ago
  If they changed in a way to have meaningful impacts on how astronomical bodies operate we should be able to observe the change as some of the oldest light we observe is billions of years older than the newest light. In fact, based on this we can tell that the fundamental constant the speed of light has not changed which I agree is very strange.
  - vl 2y ago
    It comes down to what time is. I.e. what was before the Big Bang? If time didn’t exist before big bang, then speed of light emerged after big bang, and as such “changed”.
- psychoslave 2y ago
  Either there is some unversal constants, or everything constantly change.
  - hughesjj 2y ago
    Could be both. Some things determined by some mathematical constraints will always be followed. Ex things like group theory and statistics will always be followed by any object subject to them, but how that manifests if the objects those rules act upon changes in form
- kimixa 2y ago
  Why would it be "strange"? What reference can we possibly use to compare? This sort of thing tends to be so far from "common sense" it probably doesn't make sense to try to reason about it from that perspective.
  - gus_massa 2y ago
Bluestein 2y ago
"When you absolutely, totally, fundamentally, have to, fundamentally be sure" :)
User23 2y ago
It’s still something of an open question whether or not G is actually constant. Not only that, but the results differ depending on whether atomic or dynamical time is used! In the latter case no change is measured using lunar reflectors.
- ForOldHack 2y ago
  Remind me what are the dimensions of G?
BurningFrog 2y ago
If the laws of physics can drift over time, might that explain the Big Bang?
- __MatrixMan__ 2y ago
  I don't think so. There was no time before the Big Bang, so it's not like the laws of physics have anywhere to drift from such that they're in a bang-causing configuration at t=0.
  - vlovich123 2y ago
    I think that’s an overly strong statement. There’s a theory that the Big Bang followed a Big Crunch from a “previous” universe [1]. Or our universe is a black hole within another higher dimension universe since the edge of our universe looks a lot like what we would think the event horizon looks like within a universe [2] It’s correct to say that the time of our universe begins at the Big Bang, at least as far as we can measure it in any way and according to the currently dominant theories, but there are ways that it would make sense to talk about a time before the Big Bang and what caused it to happen. [1] https://www.universetoday.com/38195/oscillating-universe-theory/ https://www.universetoday.com/38195/oscillating-universe-the... [2] https://www.discovery.com/science/Universe-Inside-Every-Black-Hole https://www.discovery.com/science/Universe-Inside-Every-Blac...
    - toenail 2y ago
      > There’s a theory that the Big Bang followed a Big Crunch Does that theory come with a testable hypothesis?
      - vlovich123 2y ago
        Yes and it’s likely to be falsified. But us living within a singularity I believe is a consequence of string theory if I recall correctly.
      - ForOldHack 2y ago
mikewarot 2y ago
Let's assume they manage to make a nuclear clock out of this, with an Allan drift that's low enough to be useful. Once that's done, it'll take years of observation to measure any meaningful differences and gather enough data to notice something. Meanwhile, moving the height of anything a centimeter, the position of the moon, and a whole other host of noise sources have to be canceled out. I have no doubt this will be done... and it will be awe inspiring to hear it all told after the fact. While you're waiting... I found this really cool meeting documented on YouTube[1] that has the clearest explanation of how Chip Scale Atomic clocks work I've ever seen. I look forward to Chip Scale Optical Lattice clocks [1] https://www.youtube.com/watch?v=wHYvS7MtBok https://www.youtube.com/watch?v=wHYvS7MtBok
- incompatible 2y ago
  > Meanwhile, moving the height of anything a centimeter, the position of the moon, and a whole other host of noise sources have to be canceled out. Because time runs slower the stronger gravity becomes? I don't think it would be a problem, as long as the entire experimental apparatus is within the same gravity field for the duration of a particular measurement.
  - wongarsu 2y ago
    The gravity field we are in isn't that constant. The gravitational influence of the moon is strong enough to move a lot of water here on Earth. The other planets are a lot further away, but not completely without gravitational influence. Earth's orbit around the sun isn't a perfect circle and has ~3% difference between lowest and highest point. The seasonal shift in mass distribution on Earth is big enough that we used to correct for it in astronomical time observations (the up to 30ms or so between UT1 and UT2). On the other hand, I don't think this experiment is really all that sensitive to gravity since we aren't really measuring time.
    - incompatible 2y ago
      But it would depend on how long it takes to make a single measurement. Perhaps the moon wouldn't move far.
qsdf38100 2y ago
If fundamental constants could change, this would violate energy conservation, and the second law of thermodynamics. Someone once said, if your pet theory violates the second law, there is no hope. Or am I missing something?
- tines 2y ago
  Energy conservation isn't as sacred as many people (including me) assume. See for example https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-...
  - kibwen 2y ago
    Conservation of energy is the first law. I don't suppose anyone has any doubts about the second law?
    - tines 2y ago
      The second law is not a law in the same way like the law of gravity is, it’s more a statistical statement. It simply states that more probable things will happen more often. How do we know what’s more probable? It’s what happens more often. It’s only inviolable insofar as we presume we know all the laws of nature. Also, the second law is only applicable to closed systems. The universe may not be a closed system in the way we normally think of it.
      - ForOldHack 2y ago
        The second law may be in a way we must evolve to conceive it, or may be in a way that we may never conceive it, or we are acting in ideas that are as distant as friction creating fire. We crawled, the we walked, then we ran, rode, motored, flew, rocketed, got stuck in orbit... My college physics professor once said, "if in order to make progress we must leave reality, by all means let's leave reality." He also pointed to three red volumes on his shelf, and said those may interest you, and they did. (Richard Feynman)
elihu 2y ago
> Lots of nuclei have similar spin transitions, but only in thorium-229 is this cancellation so nearly perfect. > > “It’s accidental,” said Victor Flambaum(opens a new tab), a theoretical physicist at the University of New South Wales in Sydney. “A priori, there is no special reason for thorium. It’s just experimental fact.” But this accident of forces and energy has big consequences. ... > Physicists have developed equations to characterize the forces that bind the universe, and these equations are fitted with some 26 numbers called fundamental constants. These numbers, such as the speed of light or the gravitational constant, define how everything works in our universe. But lots of physicists think the numbers might not actually be constant. Putting these things together, if the physical constants do change over time, then perhaps there really isn't anything special about thorium-229, it's just that it's the one where the electrical repulsion and strong nuclear forces balance out right now. In a billion years maybe it would be some other element. Maybe we're just lucky to be alive at a time when one of the isotopes of an existing element just happens to line up like this. Perhaps too there's an optimal alignment that will happen or has already happened when those forces exactly balance out, and maybe that would be an ideal time (or place, if these constants vary by location) to make precise measurements in the changes to these constants, much like a solar eclipse was an ideal opportunity for verifying that light is bent by gravity.
- vlovich123 2y ago
  You’re assuming a monotonous linear change. It could be periodic or jumping between discontinuous values.
- benreesman 2y ago
  Not a physicist, just a passionate layperson. AFAIK real practitioners choose their units such that a lot of things are unity: speed of light is 1 (hence E = M), h-bar is 1, etc. There are some numbers like the “fine structure constant” (which I think is tantalizingly close to 1/137) that do seem difficult if not impossible to derive from others. The pop-science explanation for this that a layperson like myself would know about is the “anthropic” principal, they are such because only in such regimes would anyone ask the question. I don’t know what real scientists think about this.
- 2y ago
deleted 2y ago
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chadrustdevelo 2y ago
If it does change, for what ever reason, like, what does it actually mean? Someone big brain explain to me why this is a big deal.
- jasekt 2y ago
  It basically invalidates modern science in the same way Einstein invalidated Newtonian physics. It would mean we have pretty good approximation on how things work, but we are fundamentally wrong. So it would be an exciting time to be a physicist, as it would force us to rethink how things really are from atoms, to stars and the beginning of the universe.
  - shiroiushi 2y ago
    Doesn't the fact that both General Relativity and Quantum Mechanics don't make correct predictions at all scales already show we're fundamentally wrong?
    - cthalupa 2y ago
      Maybe. Maybe not. There might not be a Universal Theory of Everything. Everyone hopes there's something and most scientists do believe that something is out there, but the idea that there might be reasons we can't unify them or that there are physical limits that prevent us from gathering the information we need to fully suss things out isn't exactly fringe science.
  - left-struck 2y ago
    It does not invalidate science. The scientific method is the process by which we build gradually towards a clearer picture of the ground truth if there is one. Even if by “science” you just meant our current understanding of the universe as opposed to the method we gain that understanding, then this would not invalidate that, it only invalidates a small part. Yes, we are fundamentally wrong, I would hope that all physicists recognise that we don’t have a perfect explanation for how things work yet, this would be just another step in that process, but an exciting one indeed.
heisenzombie 2y ago
I think you might mean the one _electron_ conjecture. It’s fun because you have anti-electrons whose Feynman diagrams look like electrons going backwards in time. So you could conceivably be observing the tangled world line of a single electron bouncing back and forward in time — sometimes observing it as an antielectron. Doesn’t work with photons because there’s not an anti-photon. Anyway it’s sort of a fun “woah!” moment that Feynman was so good at producing, but I don’t think it’s taken particularly seriously as a theory.
- gradschool 2y ago
  The version of that story I remember is that John Wheeler said to Feynman that the reason all electrons are alike is that there's only one electron, which we perceive as a positron when it's going backwards in time. Feynman instantly refuted the idea by pointing out that there are more electrons than positrons.
  - heisenzombie 2y ago
    Yes I think I probably saw/read Feynman retelling the story. And yes, where’s all the antimatter, right!?
- cvoss 2y ago
  Positrons don't merely look like time-reversed electrons, and it's not limited to Feynman diagrams. Everything we know about those particles, experimentally and in our best theory, says that they literally are identical but for a minus sign on the time variable. And it does work for photons because there is an anti-photon: the photon itself. The particle is symmetric under time reversal.
  - heisenzombie 2y ago
    Of course you’re right about photons!
FollowingTheDao 2y ago
This always seems like a logical error to me and perhaps someone can explain: To measure a constant, you need something constant, but you do not know if something is constant if you do not have something constant to measure it against. (False premise?) I believe we can only assume things are constant, but they only appear constant. I you read the work of the physicist Julian Barbour regarding time I think you will be in for some remarkable insights. "Time arises out of change". https://www.youtube.com/watch?v=GoTeGW2csPk https://www.youtube.com/watch?v=GoTeGW2csPk
- gus_massa 2y ago
  It's possible to measure the ratio of some values that we think are constants https://en.wikipedia.org/wiki/Dimensionless_physical_constant#Examples https://en.wikipedia.org/wiki/Dimensionless_physical_constan... and see if they are the same here now and in old far away galaxies.
- jjk166 2y ago
  It's okay to measure one thing with something else that's variable. For example let's say I want to determine aluminum's coefficient of thermal expansion. I have a block of aluminum which I am measuring with a steel ruler. Both objects will change size if I vary the temperature, but by measuring both at several temperatures I can determine the ratio of their coefficients of thermal expansion. Funnily enough, if I'm using a mercury thermometer I'm really measuring everything relative to mercury's coefficient of thermal expansion.
lo_fye 2y ago
Seems like a case of premature naming to me! If we have to test whether or not they change, they shouldn't already be called "constants".
- datavirtue 2y ago
  They are definitely used as constants. A static agreed-upon number is assigned to a CONST and used in calculations.
klasko 2y ago
Maybe Boards of Canada was right, and constants are changing.
nyc111 2y ago
The article mentions 26 constants but it seems there is more than that https://en.wikipedia.org/wiki/List_of_physical_constants https://en.wikipedia.org/wiki/List_of_physical_constants And I think if the constant is a ratio, like the fine structure constant, https://en.wikipedia.org/wiki/Fine-structure_constant https://en.wikipedia.org/wiki/Fine-structure_constant no change can be detected, even if there were a change because the ratio will stay the same. Likewise a constant like pi will stay the same because it is a ratio.
- jjk166 2y ago
  There are 26 fundamental constants, ie values that can not be determined from theory alone and need to be experimentally measured, which all other constants can be written in terms of. And it's not even a specific 26; 1/c is just as valid a constant as c, and you could rewrite any equation to use that instead of c. For ratios, the constancy of the ratio is exactly what they seek to test.
jnewbert 2y ago
this is mind blowing to see
MoSattler 2y ago
Possibly a dumb question: How do you determine the accuracy of the most precise clock? You don’t have anything more accurate to measure it against, right?
thomassmith65 2y ago
These numbers, such as the speed of light or the gravitational constant, define how everything works in our universe. But lots of physicists think the numbers might not actually be constant. In my ignorant, non-physicist head, gravity always struck me as a force that would make sense as variable. Maybe that would explain all the missing 'dark matter', or even provide an alternate explanation as to why so many species on our planet were larger millions of years ago (assuming an explanation for these two phenomena isn't self-contradictory, which, given my lack of physics background, it might well be!)

288 points by beefman 2y ago

1970-01-01 2y ago

Matter in other galaxies would behave differently from matter in the Milky Way if fundamental constants are not always true. I argue about this sometimes. Others keep stating that the wavelengths are equal, so everything else must be.

gmueckl 2y ago
I think the better way to ask this question is: how much large scale spatial variation can there be in the laws of physics so that the observable behavior doesn't contradict existing observations? As far as I remember, this has been studied, but I can't find a reference right now.
- canadianfella 2y ago
  [dead]
- jepler 2y ago
  wikipedia has a high level review of current constraints: https://en.wikipedia.org/wiki/Time-variation_of_fundamental_constants https://en.wikipedia.org/wiki/Time-variation_of_fundamental_... fine-structure constant: less than 10^−17 per year gravitational constant: less than 10^−10 per year proton-electron mass ratio: less than 10^−16 per year
rkagerer 2y ago
What's meant by "the wavelengths are equal"? (And have we measured comparable wavelengths in other galaxies?)
- fnordpiglet 2y ago
  Presumably they mean propagating EM radiation we observe from earth appears to behave the same on earth as we observe from distant galaxies since the event that created them happened at a time much different than ours and a distant region of space.
  - saalweachter 2y ago
    I mean, technically the EM radiation we observe from distant galaxies does look different than the EM radiation we observe locally: it's red-shifted. I'm sure someone has proposed this is due to physical constants changing over time, rather than the expansion of space-time, and I'm sure someone else has explained why this is wrong.
- itishappy 2y ago
  The wavelengths of physical processes are equal. If fundamental constants changed, we'd expect, say, the Lyman series to change too.
- analog31 2y ago
  Yes, we've measured comparable wavelengths. It's one way we can measure the red shift. Not just (red shifted) absolute wavelengths, but the relative spacing between them are quite sensitive to physical constants. These spectra can also be used for identifying the elemental composition of stars.
- cryptonector 2y ago
  > What's meant by "the wavelengths are equal"? Absorption lines of the elements in the stars whose starlight we observe. THey are the same after correction for redshift.
mysecretaccount 2y ago
If the fundamental constants are not constant, why not expect them to change in this galaxy as well? The appeal to "other galaxies" seems suspect to me, a way to evade falsifiability.
- itishappy 2y ago
  "A way to evade falsifiability" is the goal of the statement, given that we've been searching for evidence to the contrary for as long as we've been able. We haven't found any, and we've searched close-at-hand the most thoroughly.
- 1970-01-01 2y ago
  The idea is they're fixed/set by the overall size of the galaxy.
- mbrubeck 2y ago
  If the constants change over very long time spans, we could observe this by looking at distant galaxies from billions of years ago. We don’t have a way to make similar observations within our own galaxy.
  - lupusreal 2y ago
    What if the constants only changed over incredibly small scales, vibrating back and forth between two very similar numbers like a standing wave with extremely small amplitude and wavelength, such that any measurement done on even small scales has trouble seeing anything but the average?
    - raattgift 2y ago
      Let's start with the universe since the ignition of the first stars. Your question is also super-interesting in the context of the very early universe, so I'll come back to that further below. Depending on the constants, with significant fluctuation of them you'd expect spectral line broadening rather than the sharp lines we see in precision interferometry, violations of local Lorentz invariance, different structures in "stacked" spectra (like the Lyman-alpha forest), and instabilities in Keplerian orbits. Present measurement precision of subatomic transition spectra has really boxed you in on this: many physical constants have relative standard uncertainties on the order of 10^-10 or better. > any measurement ... [sees only] the average So you'd start wondering: in the limit of infinitesimal fluctuations, is a fluctuating constant just constant rather than an "effective constant"? Where's there's still wiggle room is in the exact masses of heaver generation standard model particles (top quark, tau mass, W-to-Z mass ratio for example) and somewhat frustratingly Newton's gravitational constant, all of which have relative standard uncertainties worse than 10^-5. (There's a quick explanation of standard uncertainty and relative standard uncertainty at <https://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/definitions.html https://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/defi...>) However, assuming cosmic inflation, one might expect incredibly small scale fluctuations in physical constants to be stretched, just like incredibly small scale fluctuations in the densities of matter and radiation. This could lead to later-universe regions of arbitrary size with a significantly different value for one or more physical constants, just like we see regions relatively stuffed with galaxies (filaments) and regions that are relatively empty (supervoids). We'd expect that when we look at different parts of the sky we'd see differences in things like the Lyman-alpha forest, the population and/or spectra and/or light curves of quasars/supernovae/variables, and so on. So, in order to have the apparently constant physical constants we observe, while keeping your idea that there are tiny fluctuations in them, you'd have to suppress high frequency fluctuations in the constants in the very early universe, because otherwise you'd have to suppress gross effects like different gas and dust chemistry when comparing one galaxy cluster to another. And we are looking: https://cen.acs.org/physical-chemistry/astrochemistry/Scientists-find-complex-organic-molecules-young-galaxy-12-billion-light-years-away/101/web/2023/06 https://cen.acs.org/physical-chemistry/astrochemistry/Scient... (The cosmic inflation epoch predates the "freezing-out" of some of the physical constants, so my thinking is that during inflation there must be some precursor constant(s) that determine(s) the mass of the electron (for example) once there are electrons after the electroweak epoch. Even after inflation the ordinary expansion of the universe can stretch fluctuations enough that (assuming your idea) there is likely to be a directional dependence on precision extragalactic astronomy.)
renewiltord 2y ago
One thing I have been arguing for a long time is that the fundamental constants are different until we observe them. i.e. if we don't observe it, it's possible for a tennis ball to travel through a wall. But in the universal program, if we will now or later observe the result, then it won't happen. But it'll happen so long as we will never observe the result. In fact, it's probably happened many times. No one has proven that this is impossible, AFAIK.
- ezrast 2y ago
  What does "impossible" mean to you if not that a thing and it's consequences can never be observed?
  - renewiltord 2y ago
    Impossible means it does not happen, not that it does not happen only when we look. Just because we can't see it doesn't mean that it doesn't happen. After all, as the comment I replied to pointed out, other galaxies can have different constants. We have to be humble and admit we just don't know.
    - jiggawatts 2y ago
      The problem with these type of arguments is rigorously defining “we” and “look”. Turns out that our gaze has no effect on anything and we’re uninteresting squishy bags of mostly water as far as physical processes are concerned.
      - renewiltord 2y ago
        Yeah, but no one has proven that this is impossible so it's still possible. Just like OP comment.
        wizzwizz4 2y ago
        https://www.smbc-comics.com/comic/2014-03-25 https://www.smbc-comics.com/comic/2014-03-25
gitaarik 2y ago
Well, if you think about it, on a large scale of the universe, our laws are helped by our mathematical inventions of dark matter and dark energy. So is there really dark matter and dark energy, or is our understanding of the laws of the universe incomplete?
- thewarpaint 2y ago
  > So is there really dark matter and dark energy, or is our understanding of the laws of the universe incomplete? These propositions are not mutually exclusive, the former implies the latter, right?
- foxyv 2y ago
  As I understand it, dark matter and dark energy are just placeholders for discrepancies between our current physical model and observations made by telescopes like Hubble and Kepler. This could mean either that our measurements are inaccurate, or that the model is incomplete. Honestly, I think that both are extremely likely.
  - AlexAndScripts 2y ago
    Dark matter (matter that has mass but does not interact in any other way) might be the literal solution. But there are also other suggestions (MOND is a big one). The https://en.m.wikipedia.org/wiki/Bullet_Cluster https://en.m.wikipedia.org/wiki/Bullet_Cluster is pretty interesting.
  - BurningFrog 2y ago
    "Dark matter" and "dark energy" could just as well be called "unexplained matter" and "unexplained energy". These terms are mostly placeholders for things we don't understand.
    - cowl 2y ago
      not even that. "unexplained matter" implies that there is some matter to explain (what type etc) when in reality is an unexplained observation that could be explained by current laws/constants if only there was some more (actually a lot more) matter. is a pure mathematical construct and mathematically it wold be just as valid to ad "dark constant modifier"
cryptonector 2y ago
Not necessarily. We have redshift and we use that to measure distance (in space and time). If fundamental constants were different in the past that might merely change only what distances we measure.
- analog31 2y ago
  That would probably require quite a coincidence, since the redshift and the spacing between wavelengths both depend on the same constants but in different ways.

mseepgood 2y ago

They probably do change, but extremely slowly. It would feel strange if there were something fixed in the universe.

bitmasher9 2y ago
If they changed in a way to have meaningful impacts on how astronomical bodies operate we should be able to observe the change as some of the oldest light we observe is billions of years older than the newest light. In fact, based on this we can tell that the fundamental constant the speed of light has not changed which I agree is very strange.
- vl 2y ago
  It comes down to what time is. I.e. what was before the Big Bang? If time didn’t exist before big bang, then speed of light emerged after big bang, and as such “changed”.
psychoslave 2y ago
Either there is some unversal constants, or everything constantly change.
- hughesjj 2y ago
  Could be both. Some things determined by some mathematical constraints will always be followed. Ex things like group theory and statistics will always be followed by any object subject to them, but how that manifests if the objects those rules act upon changes in form
kimixa 2y ago
Why would it be "strange"? What reference can we possibly use to compare? This sort of thing tends to be so far from "common sense" it probably doesn't make sense to try to reason about it from that perspective.
- gus_massa 2y ago

Bluestein 2y ago

"When you absolutely, totally, fundamentally, have to, fundamentally be sure" :)

User23 2y ago

It’s still something of an open question whether or not G is actually constant. Not only that, but the results differ depending on whether atomic or dynamical time is used! In the latter case no change is measured using lunar reflectors.

ForOldHack 2y ago
Remind me what are the dimensions of G?

BurningFrog 2y ago

If the laws of physics can drift over time, might that explain the Big Bang?

__MatrixMan__ 2y ago
I don't think so. There was no time before the Big Bang, so it's not like the laws of physics have anywhere to drift from such that they're in a bang-causing configuration at t=0.
- vlovich123 2y ago
  I think that’s an overly strong statement. There’s a theory that the Big Bang followed a Big Crunch from a “previous” universe [1]. Or our universe is a black hole within another higher dimension universe since the edge of our universe looks a lot like what we would think the event horizon looks like within a universe [2] It’s correct to say that the time of our universe begins at the Big Bang, at least as far as we can measure it in any way and according to the currently dominant theories, but there are ways that it would make sense to talk about a time before the Big Bang and what caused it to happen. [1] https://www.universetoday.com/38195/oscillating-universe-theory/ https://www.universetoday.com/38195/oscillating-universe-the... [2] https://www.discovery.com/science/Universe-Inside-Every-Black-Hole https://www.discovery.com/science/Universe-Inside-Every-Blac...
  - toenail 2y ago
    > There’s a theory that the Big Bang followed a Big Crunch Does that theory come with a testable hypothesis?
    - vlovich123 2y ago
      Yes and it’s likely to be falsified. But us living within a singularity I believe is a consequence of string theory if I recall correctly.
    - ForOldHack 2y ago

mikewarot 2y ago

Let's assume they manage to make a nuclear clock out of this, with an Allan drift that's low enough to be useful. Once that's done, it'll take years of observation to measure any meaningful differences and gather enough data to notice something. Meanwhile, moving the height of anything a centimeter, the position of the moon, and a whole other host of noise sources have to be canceled out. I have no doubt this will be done... and it will be awe inspiring to hear it all told after the fact. While you're waiting... I found this really cool meeting documented on YouTube[1] that has the clearest explanation of how Chip Scale Atomic clocks work I've ever seen. I look forward to Chip Scale Optical Lattice clocks [1] https://www.youtube.com/watch?v=wHYvS7MtBok https://www.youtube.com/watch?v=wHYvS7MtBok

incompatible 2y ago
> Meanwhile, moving the height of anything a centimeter, the position of the moon, and a whole other host of noise sources have to be canceled out. Because time runs slower the stronger gravity becomes? I don't think it would be a problem, as long as the entire experimental apparatus is within the same gravity field for the duration of a particular measurement.
- wongarsu 2y ago
  The gravity field we are in isn't that constant. The gravitational influence of the moon is strong enough to move a lot of water here on Earth. The other planets are a lot further away, but not completely without gravitational influence. Earth's orbit around the sun isn't a perfect circle and has ~3% difference between lowest and highest point. The seasonal shift in mass distribution on Earth is big enough that we used to correct for it in astronomical time observations (the up to 30ms or so between UT1 and UT2). On the other hand, I don't think this experiment is really all that sensitive to gravity since we aren't really measuring time.
  - incompatible 2y ago
    But it would depend on how long it takes to make a single measurement. Perhaps the moon wouldn't move far.

qsdf38100 2y ago

If fundamental constants could change, this would violate energy conservation, and the second law of thermodynamics. Someone once said, if your pet theory violates the second law, there is no hope. Or am I missing something?

tines 2y ago
Energy conservation isn't as sacred as many people (including me) assume. See for example https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-...
- kibwen 2y ago
  Conservation of energy is the first law. I don't suppose anyone has any doubts about the second law?
  - tines 2y ago
    The second law is not a law in the same way like the law of gravity is, it’s more a statistical statement. It simply states that more probable things will happen more often. How do we know what’s more probable? It’s what happens more often. It’s only inviolable insofar as we presume we know all the laws of nature. Also, the second law is only applicable to closed systems. The universe may not be a closed system in the way we normally think of it.
    - ForOldHack 2y ago
      The second law may be in a way we must evolve to conceive it, or may be in a way that we may never conceive it, or we are acting in ideas that are as distant as friction creating fire. We crawled, the we walked, then we ran, rode, motored, flew, rocketed, got stuck in orbit... My college physics professor once said, "if in order to make progress we must leave reality, by all means let's leave reality." He also pointed to three red volumes on his shelf, and said those may interest you, and they did. (Richard Feynman)

elihu 2y ago

> Lots of nuclei have similar spin transitions, but only in thorium-229 is this cancellation so nearly perfect. > > “It’s accidental,” said Victor Flambaum(opens a new tab), a theoretical physicist at the University of New South Wales in Sydney. “A priori, there is no special reason for thorium. It’s just experimental fact.” But this accident of forces and energy has big consequences. ... > Physicists have developed equations to characterize the forces that bind the universe, and these equations are fitted with some 26 numbers called fundamental constants. These numbers, such as the speed of light or the gravitational constant, define how everything works in our universe. But lots of physicists think the numbers might not actually be constant. Putting these things together, if the physical constants do change over time, then perhaps there really isn't anything special about thorium-229, it's just that it's the one where the electrical repulsion and strong nuclear forces balance out right now. In a billion years maybe it would be some other element. Maybe we're just lucky to be alive at a time when one of the isotopes of an existing element just happens to line up like this. Perhaps too there's an optimal alignment that will happen or has already happened when those forces exactly balance out, and maybe that would be an ideal time (or place, if these constants vary by location) to make precise measurements in the changes to these constants, much like a solar eclipse was an ideal opportunity for verifying that light is bent by gravity.

vlovich123 2y ago
You’re assuming a monotonous linear change. It could be periodic or jumping between discontinuous values.
benreesman 2y ago
Not a physicist, just a passionate layperson. AFAIK real practitioners choose their units such that a lot of things are unity: speed of light is 1 (hence E = M), h-bar is 1, etc. There are some numbers like the “fine structure constant” (which I think is tantalizingly close to 1/137) that do seem difficult if not impossible to derive from others. The pop-science explanation for this that a layperson like myself would know about is the “anthropic” principal, they are such because only in such regimes would anyone ask the question. I don’t know what real scientists think about this.
2y ago

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chadrustdevelo 2y ago

If it does change, for what ever reason, like, what does it actually mean? Someone big brain explain to me why this is a big deal.

jasekt 2y ago
It basically invalidates modern science in the same way Einstein invalidated Newtonian physics. It would mean we have pretty good approximation on how things work, but we are fundamentally wrong. So it would be an exciting time to be a physicist, as it would force us to rethink how things really are from atoms, to stars and the beginning of the universe.
- shiroiushi 2y ago
  Doesn't the fact that both General Relativity and Quantum Mechanics don't make correct predictions at all scales already show we're fundamentally wrong?
  - cthalupa 2y ago
    Maybe. Maybe not. There might not be a Universal Theory of Everything. Everyone hopes there's something and most scientists do believe that something is out there, but the idea that there might be reasons we can't unify them or that there are physical limits that prevent us from gathering the information we need to fully suss things out isn't exactly fringe science.
- left-struck 2y ago
  It does not invalidate science. The scientific method is the process by which we build gradually towards a clearer picture of the ground truth if there is one. Even if by “science” you just meant our current understanding of the universe as opposed to the method we gain that understanding, then this would not invalidate that, it only invalidates a small part. Yes, we are fundamentally wrong, I would hope that all physicists recognise that we don’t have a perfect explanation for how things work yet, this would be just another step in that process, but an exciting one indeed.

heisenzombie 2y ago

I think you might mean the one _electron_ conjecture. It’s fun because you have anti-electrons whose Feynman diagrams look like electrons going backwards in time. So you could conceivably be observing the tangled world line of a single electron bouncing back and forward in time — sometimes observing it as an antielectron. Doesn’t work with photons because there’s not an anti-photon. Anyway it’s sort of a fun “woah!” moment that Feynman was so good at producing, but I don’t think it’s taken particularly seriously as a theory.

gradschool 2y ago
The version of that story I remember is that John Wheeler said to Feynman that the reason all electrons are alike is that there's only one electron, which we perceive as a positron when it's going backwards in time. Feynman instantly refuted the idea by pointing out that there are more electrons than positrons.
- heisenzombie 2y ago
  Yes I think I probably saw/read Feynman retelling the story. And yes, where’s all the antimatter, right!?
cvoss 2y ago
Positrons don't merely look like time-reversed electrons, and it's not limited to Feynman diagrams. Everything we know about those particles, experimentally and in our best theory, says that they literally are identical but for a minus sign on the time variable. And it does work for photons because there is an anti-photon: the photon itself. The particle is symmetric under time reversal.
- heisenzombie 2y ago
  Of course you’re right about photons!

FollowingTheDao 2y ago

This always seems like a logical error to me and perhaps someone can explain: To measure a constant, you need something constant, but you do not know if something is constant if you do not have something constant to measure it against. (False premise?) I believe we can only assume things are constant, but they only appear constant. I you read the work of the physicist Julian Barbour regarding time I think you will be in for some remarkable insights. "Time arises out of change". https://www.youtube.com/watch?v=GoTeGW2csPk https://www.youtube.com/watch?v=GoTeGW2csPk

gus_massa 2y ago
It's possible to measure the ratio of some values that we think are constants https://en.wikipedia.org/wiki/Dimensionless_physical_constant#Examples https://en.wikipedia.org/wiki/Dimensionless_physical_constan... and see if they are the same here now and in old far away galaxies.
jjk166 2y ago
It's okay to measure one thing with something else that's variable. For example let's say I want to determine aluminum's coefficient of thermal expansion. I have a block of aluminum which I am measuring with a steel ruler. Both objects will change size if I vary the temperature, but by measuring both at several temperatures I can determine the ratio of their coefficients of thermal expansion. Funnily enough, if I'm using a mercury thermometer I'm really measuring everything relative to mercury's coefficient of thermal expansion.

lo_fye 2y ago

Seems like a case of premature naming to me! If we have to test whether or not they change, they shouldn't already be called "constants".

datavirtue 2y ago
They are definitely used as constants. A static agreed-upon number is assigned to a CONST and used in calculations.

klasko 2y ago

Maybe Boards of Canada was right, and constants are changing.

nyc111 2y ago

The article mentions 26 constants but it seems there is more than that https://en.wikipedia.org/wiki/List_of_physical_constants https://en.wikipedia.org/wiki/List_of_physical_constants And I think if the constant is a ratio, like the fine structure constant, https://en.wikipedia.org/wiki/Fine-structure_constant https://en.wikipedia.org/wiki/Fine-structure_constant no change can be detected, even if there were a change because the ratio will stay the same. Likewise a constant like pi will stay the same because it is a ratio.

jjk166 2y ago
There are 26 fundamental constants, ie values that can not be determined from theory alone and need to be experimentally measured, which all other constants can be written in terms of. And it's not even a specific 26; 1/c is just as valid a constant as c, and you could rewrite any equation to use that instead of c. For ratios, the constancy of the ratio is exactly what they seek to test.

jnewbert 2y ago

this is mind blowing to see

MoSattler 2y ago

Possibly a dumb question: How do you determine the accuracy of the most precise clock? You don’t have anything more accurate to measure it against, right?

thomassmith65 2y ago

These numbers, such as the speed of light or the gravitational constant, define how everything works in our universe. But lots of physicists think the numbers might not actually be constant. In my ignorant, non-physicist head, gravity always struck me as a force that would make sense as variable. Maybe that would explain all the missing 'dark matter', or even provide an alternate explanation as to why so many species on our planet were larger millions of years ago (assuming an explanation for these two phenomena isn't self-contradictory, which, given my lack of physics background, it might well be!)