Evidence record

Are the constants of nature constant?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

Source checked: 35
A judgement, not a fact: 5
Partly checked: 2
Presented as open: 2

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A measurement question inside a theoretical one. Whether the constants have changed can be tested and has been, with tight null results and one disputed claim; why they have the values they do is not answered by any theory the page cites.

There is a definite list of fundamental constants to test
Open
The list is fixed by the theory in use: the review counts 22 for general relativity plus the Standard Model, and at least seven more once neutrino masses are included. A more unified theory could change the count.
A change in a constant is something an experiment can detect
Established
Only for dimensionless combinations. A change that leaves them untouched is a change of units, which is why the experiments report ratios such as the fine-structure constant.

How the question is labelled

Claim: Numbers nobody derived

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 7, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The numerical values of the fundamental constants are not determined by the laws of nature in which they appear.

Later work looked for

Crossref, 2015 on, "varying fundamental constants review" and "fine-tuning constants": no derivation of the Standard Model parameters; nothing that changes it.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Constants

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: About two dozen numbers have to be measured rather than calculated

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.1, How many fundamental constants should be considered?
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: It follows that one has to consider 22 unknown constants (i.e., 19 unknown dimensionless parameters)
Supports
Varying Constants, Gravitation and Cosmologysection 2.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Such an extension will introduce at least seven new constants (3 Yukawa couplings and 4 Maki-Nakagawa-Sakata (MNS) parameters, similar to the CKM parameters).
Supports
Varying Constants, Gravitation and Cosmologysection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Therefore, these fundamental constants are contingent quantities that can only be measured.

What this does not establish

The count depends on the theory: 22 for general relativity with the Standard Model, at least seven more for massive neutrinos, and possibly fewer if the forces are unified.

Later work looked for

How the count is defined; not a finding later work revises. Crossref, 2015 on, "Standard Model free parameters": nothing that changes it.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: and whether they have always had these values is a question a natural nuclear reactor helps to answer.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra

What this does not establish

The reactor constrains one combination of constants at one moment about two billion years ago, on nuclear-physics assumptions. It does not answer the question for every constant or every epoch.

Corrected

24 September 2026. Previously: “and whether they have always had these values is a question with an answer from a natural nuclear reactor.” Oklo bounds the fine-structure constant at one epoch, on model assumptions the review says must be considered carefully; it is one of several tests rather than the answer.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: The Standard Model and cosmology contain numbers that no theory predicts.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: We define the fundamental constants of a physical theory as any parameter that cannot be explained by this theory.
Supports
Varying Constants, Gravitation and Cosmologysection 2.1, quoting Weinberg
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: not just because the calculation is too complicated (as for the viscosity of water) but because we do not know of anything more fundamental

Later work looked for

Crossref, 2015 on, "varying fundamental constants review": nothing that changes it.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: Whether they vary over time has been tested by quasar spectra, by the isotopes in a two-billion-year-old natural reactor, and by atomic clocks.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra
Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Indeed, two billion years ago, uranium was naturally enriched

What this does not establish

These are three of the methods the review lists; it also covers meteorites, stellar physics, the cosmic microwave background and primordial nucleosynthesis.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Nothing has been established to vary, and the limits are tight.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.12, Conclusion and prospects
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: At the moment, only one analysis claims to have detected a variation of the fine structure constant (Keck/HIRES) while the VLT/UVES points toward no variation
Supports
Varying Constants, Gravitation and Cosmologysection 3.4.12
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: it is premature to conclude on the issue of this debate and the jury is still out
Context
Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515-4414abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated, yields a weighted mean Δα/α = −0.5 ± 0.5 (stat) ± 0.4 (sys) ppm at redshifts 0.6-2.4.
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v1), read 2026-09-24. The subscripts "stat" and "sys" are written in parentheses. The text as extracted reads: Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated, yields a weighted mean $\Delta\alpha/\alpha = -0.5 \pm 0.5_{\rm stat} \pm 0.4_{\rm sys}\,$ppm at redshifts 0.6-2.4.

What this does not establish

One team still reports a spatial variation from quasar spectra (claims 42 and 45). "Not established" is the state of the evidence, not a proof that nothing varies.

Later work looked for

Crossref, 2015 on, "fine-structure constant quasar absorption ESPRESSO" and "Oklo fine structure constant": the 2022 ESPRESSO measurement and the 2015 Oklo reanalysis find no variation; the 2020 high-redshift paper still marginally prefers a spatial variation. Nothing established; page updated in the quasar section.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: The strength of electromagnetism, the masses of the quarks, the strength of gravity: these are inputs, not outputs.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

In the Standard Model the quark masses enter through Yukawa couplings, and the strength of electromagnetism through the gauge couplings the review lists.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: the Newton constant G, 6 Yukawa couplings for the quarks (hu, hd, hc, hs, ht, hb) and 3 for the leptons (he, hμ, hτ)
Supports
Varying Constants, Gravitation and Cosmologysection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Therefore, these fundamental constants are contingent quantities that can only be measured.

Later work looked for

Crossref, 2015 on, "varying fundamental constants review": nothing that changes it.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: Nothing in physics says why they are what they are.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 7, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The numerical values of the fundamental constants are not determined by the laws of nature in which they appear. One can wonder why they have the values we observe.

What this does not establish

Proposals exist, from consistency conditions to a multiverse with anthropic selection; the review calls them speculative and records an ongoing debate over whether they can predict anything.

Later work looked for

Crossref, 2015 on, "fine-tuning fundamental constants": proposals continue, none accepted as a derivation; nothing that changes it.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: A weaker question is answerable: have they always been what they are now.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the rest of the page: whether the values change can be tested (claims 13 to 34), while why they have them cannot yet be (claims 55 to 58).

Claim 10 · checked 24 September 2026 · AI-assisted audit

What has been tested

Claim: What has been tested

Kind: Framing. Signposting. It asserts nothing a source could check.

The rock at Oklo

Claim: The rock at Oklo

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: About two billion years ago, uranium in a deposit in Gabon was rich enough for a natural chain reaction to start.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1, A natural nuclear reactor
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Oklo is the name of a town in the Gabon republic (West Africa) where an open-pit uranium mine is situated. About 1.8 × 10⁹ yr ago ... in one of the rich vein of uranium ore, a natural nuclear reactor went critical
Notation restored: Superscripts restored from the superscript markup in the Europe PMC full-text XML (PMC5256069), read 2026-09-24. The text as extracted reads: Oklo is the name of a town in the Gabon republic (West Africa) where an open-pit uranium mine is situated. About 1.8 × 109 yr ago ... in one of the rich vein of uranium ore, a natural nuclear reactor went critical
Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Indeed, two billion years ago, uranium was naturally enriched (due to the difference of decay rate between ²³⁵U and ²³⁸U) and ²³⁵U represented about 3.68% of the total uranium
Notation restored: Superscripts restored from the superscript markup in the Europe PMC full-text XML (PMC5256069), read 2026-09-24. The text as extracted reads: Indeed, two billion years ago, uranium was naturally enriched (due to the difference of decay rate between 235U and 238U) and 235U represented about 3.68% of the total uranium
Context
Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabonabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: the 2 billion yr old Oklo natural nuclear reactor

What this does not establish

The review dates the reactor to about 1.8 billion years ago; other work rounds to two billion. The exact date does not affect the constraint.

Corrected

24 September 2026. Previously: “Two billion years ago, uranium in a deposit in Gabon was rich enough for a natural chain reaction to start.” The review gives about 1.8 billion years; "about" makes the round figure a round figure.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: It ran, intermittently, for hundreds of thousands of years.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Well studied reactors include the zone RZ2 (about 60 bore-holes, 1800 kg of ²³⁵U fissioned during 8.5 × 10⁵ yr) and zone RZ10 (about 13 bore-holes, 650 kg of ²³⁵U fissioned during 1.6 × 10⁵ yr).
Notation restored: Superscripts restored from the superscript markup in the Europe PMC full-text XML (PMC5256069), read 2026-09-24. The text as extracted reads: Well studied reactors include the zone RZ2 (about 60 bore-holes, 1800 kg of 235U fissioned during 8.5 × 105 yr) and zone RZ10 (about 13 bore-holes, 650 kg of 235U fissioned during 1.6 × 105 yr).
Supports
Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabonabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement
The source reads: The specific isotopic structure of xenon in this mineral defines a cycling operation for the reactor with 30-min active pulses separated by 2.5 h dormant periods.

What this does not establish

The pulsing is from one study of fission xenon in one mineral, read as an abstract. The durations are for the two best-studied of sixteen reactor zones.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: The isotope ratios left behind depend sensitively on the position of a nuclear resonance, which depends on the strength of electromagnetism relative to the nuclear force.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: One of the key quantity measured is the ratio of two light isotopes of samarium, which are not fission products. This ratio of order of 0.9 in normal samarium, is about 0.02 in Oklo ores.
Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The existence of this resonance is a consequence of an almost cancellation between the electromagnetic repulsive force and the strong interaction.

Later work looked for

How the method works; not a finding later work revises.

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: Measuring them limits any change in the strength of electromagnetism since then to about one part in ten million in the standard analysis, and one part in a hundred million in a 2015 reanalysis.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3, equation 48 (arXiv version)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement
The source reads: which, once combined with the constraint on ΔEᵣ, implies −0.9 × 10⁻⁷ < ΔαEM/αEM < 1.2 × 10⁻⁷ (48) at 2σ level
Notation restored: Superscripts and subscripts restored from the glyph positions in the arXiv PDF (arXiv:1009.5514v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: which, once combined with the constraint on ∆ Er, implies − 0.9× 10−7< ∆ αEM/αEM < 1.2× 10−7 (48) at 2σ level
Supports
Reappraisal of the limit on the variation in alpha implied by Okloabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Model
The source reads: the standard estimate (due to Damour and Dyson) of the sensitivity for resonances in ¹⁵⁰Sm is increased by a factor of 2.5
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: the standard estimate (due to Damour and Dyson) of the sensitivity for resonances in ${}^{150}$Sm is increased by a factor of 2.5
Supports
Reappraisal of the limit on the variation in alpha implied by Okloabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Model
The source reads: we deduce that |αOklo − αnow| < 1.1 × 10⁻⁸ αnow (95% confidence level)
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: we deduce that $|\alpha_{\text{Oklo}}-\alpha_{\text{now}}|<1.1\times 10^{-8}\alpha_{\text{now}}$ (95\% confidence level)

What this does not establish

The 2015 bound holds "subject to a weak and testable restriction" on how the quark masses changed, and its authors vouch for its order of magnitude. Both bounds assume the rest of the nuclear physics held still. Other analyses in the review reach a few parts in a hundred million.

Later work looked for

Crossref, 2015 on, "Oklo fine structure constant variation": Davis and Hamdan (2015) tighten the standard bound to 1.1 parts in a hundred million; page updated with that figure.

Corrected

24 September 2026. Previously: “Measuring them constrains any change in that strength over two billion years to parts in ten to the eighth or better.” "Or better" overstated it: the standard Damour and Dyson bound in the review is about one part in ten million at two sigma, and one part in a hundred million comes from a 2015 reanalysis (Davis and Hamdan), now cited.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: Both lean on nuclear models, and some readings of the data allow a second solution in which the resonance did move.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: find two branches for ΔEr = Er − Er0, with one (the left branch) indicating a variation of Er.
Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: This non-zero result cannot be eliminated.
Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3, closing
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: At present, the Oklo data, while being stringent and consistent with no variation, have to be considered carefully. While a better understanding of nuclear physics is necessary to understand the full constant-dependence

What this does not establish

The review notes that the second branch disappears at higher reactor temperatures and that one analysis finds it hard to reconcile with the gadolinium data.

Corrected

24 September 2026. Previously: “” The review says the Oklo bound rests on nuclear-physics assumptions and that a non-zero branch cannot be eliminated; the page stated the bound without either.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: It is among the tightest limits on any changing constant, and it comes from a rock rather than an instrument.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: This tight constraint arises from the large amplification between the resonance energy (∼ 0.1 eV) and the sensitivity (∼ 1 MeV).
Supports
Reappraisal of the limit on the variation in alpha implied by Okloabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The corresponding bound on the present-day time variation of α is tighter than the best limit to date from atomic clock experiments.
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: The corresponding bound on the present-day time variation of $\alpha$ is tighter than the best limit to date from atomic clock experiments.
Supports
Reappraisal of the limit on the variation in alpha implied by Oklotext after equation 12
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Assuming a linear time dependence for α over the last 1.8 billion years, Eq. (12) implies that the present-day time variation of α is subject to the (95% C.L.) bound ... which is an improvement on the best limit from atomic clock experiments

What this does not establish

The comparison with clocks is the 2015 paper’s, and clock limits have tightened since (claim 34): as a rate today, the best clock bound is now the tighter one. The Oklo figure is also model-dependent (claim 17).

Corrected

24 September 2026. Previously: “It is one of the tightest limits in physics and it comes from a rock rather than an instrument.” The sources compare Oklo with other tests of varying constants, not with physics at large.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: Where the limits come from

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: 2 billion years

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Indeed, two billion years ago, uranium was naturally enriched
Context
Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabonabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: the 2 billion yr old Oklo natural nuclear reactor

What this does not establish

A round figure; the review dates the reactor to about 1.8 billion years ago.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: Oklo natural reactor

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Isotope ratios limit any drift in the electromagnetic coupling to between one part in ten million and one in a hundred million, depending on the analysis.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3, equation 48 (arXiv version)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement
The source reads: which, once combined with the constraint on ΔEᵣ, implies −0.9 × 10⁻⁷ < ΔαEM/αEM < 1.2 × 10⁻⁷ (48) at 2σ level
Notation restored: Superscripts and subscripts restored from the glyph positions in the arXiv PDF (arXiv:1009.5514v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: which, once combined with the constraint on ∆ Er, implies − 0.9× 10−7< ∆ αEM/αEM < 1.2× 10−7 (48) at 2σ level
Supports
Reappraisal of the limit on the variation in alpha implied by Okloabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Model
The source reads: we deduce that |αOklo − αnow| < 1.1 × 10⁻⁸ αnow (95% confidence level)
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: we deduce that $|\alpha_{\text{Oklo}}-\alpha_{\text{now}}|<1.1\times 10^{-8}\alpha_{\text{now}}$ (95\% confidence level)

What this does not establish

Both rest on nuclear models (claim 17).

Later work looked for

Crossref, 2015 on, "Oklo fine structure constant variation": Davis and Hamdan (2015) is the tightest reanalysis found; page updated.

Corrected

24 September 2026. Previously: “Isotope ratios constrain any drift in the electromagnetic coupling to parts in a hundred million.” The standard analysis in the review gives about one part in ten million; one part in a hundred million is the 2015 reanalysis.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Up to 13 billion years

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Four direct measurements of the fine-structure constant 13 billion years agotitle and abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Four direct measurements of the fine-structure constant 13 billion years ago ... Observations at z=7.1 probe the physics of the universe when it was only 0.8 billion years old. These are the most distant direct measurements of alpha to date
Supports
Four direct measurements of the fine-structure constant 13 billion years agomain text, first section
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Its emission redshift is z = 7.085, corresponding to a look-back time of 12.96 billion years in standard ΛCDM cosmology.

What this does not establish

The 13 billion years is one quasar, and a look-back time in the standard cosmology rather than a direct measurement of age. The large samples in the review reach redshift 4.2, and most measurements are nearer.

Later work looked for

Crossref, 2015 on, "fine-structure constant quasar absorption": the 2020 z = 7.1 measurements are the most distant found; page updated.

Corrected

24 September 2026. Previously: “10 billion years” Quasar measurements now reach a universe 0.8 billion years old (Wilczynska and others 2020, now cited); "up to" says it is the far end, not the typical case.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: Quasar absorption lines

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Atoms in distant gas clouds absorb at frequencies that depend on the same constant.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3, many-multiplet method
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: some transitions are fairly unsensitive to a change of the fine-structure constant (e.g., Mg II or MgI, hence providing good anchors) while others such as Fe II are more sensitive.

Later work looked for

How the method works; not a finding later work revises.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: Claims of variation have been reported and disputed.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Two series of analyses were performed during the past ten years and lead to contradictory conclusions.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: A few years

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisonsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Repeated measurements of both quantities over several years are analyzed for potential violations of local position invariance.
Supports
Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisonsmain text, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: comparisons between optical atomic clocks based on ytterbium ions and microwave caesium fountain clocks over a period of more than 4 years
Supports
Varying Constants, Gravitation and Cosmologysection 3.1.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: over a year allowed to set the constraint

What this does not establish

The span differs by experiment: about a year for the 2008 aluminium and mercury comparison, more than four years for the 2021 ytterbium one.

Later work looked for

Crossref and arXiv, 2015 on, "atomic clock temporal variation fine-structure constant": clock comparisons still run over a year to several years.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: Atomic clocks

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Comparing clocks based on different transitions bounds present-day drift directly, and finds none.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Review of the field
The source reads: The laboratory constraints on the time variation of fundamental constants are obtained by comparing the long-term behavior of several oscillators and rely on frequency measurements.
Supports
Varying Constants, Gravitation and Cosmologysection 3.1.2, equation 32 (arXiv version)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: = (−1.6 ± 2.3) × 10⁻¹⁷ yr⁻¹, (32) since it depends only on αEM.
Notation restored: Superscripts and subscripts restored from the glyph positions in the arXiv PDF (arXiv:1009.5514v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: = (−1.6± 2.3)× 10−17 yr−1, (32) since it depends only on αEM.
Context
Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisonsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant α to 1.0(1.1) × 10⁻¹⁸/yr
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant $\alpha$ to $1.0(1.1)\times10^{-18}/\mathrm{yr}$

What this does not establish

"Finds none" means results consistent with zero within their uncertainties.

Later work looked for

arXiv, 2015 on, "atomic clock comparisons fine-structure constant drift": Lange and others (2021) and Filzinger and others (2023) tighten the bound and still find no drift; the page adds the 2023 figure.

Claim 29 · checked 24 September 2026 · AI-assisted audit

And the clocks in the laboratory

Claim: And the clocks in the laboratory

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: The other end of the timescale is measured directly.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The laboratory constraints on the time variation of fundamental constants are obtained by comparing the long-term behavior of several oscillators and rely on frequency measurements.

Later work looked for

How the method works; not a finding later work revises.

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: Two atomic clocks built on different transitions respond differently to a change in the fine-structure constant, so comparing their ratio over months bounds any present-day drift.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The atomic transitions have various dependencies in the fundamental constants.
Supports
Varying Constants, Gravitation and Cosmologysection 3.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: offer the possibility to test a variation of various combinations of the fundamental constants.

What this does not establish

Most clock pairs are sensitive to a combination of constants; the aluminium and mercury pair is unusual in depending on the fine-structure constant alone.

Later work looked for

How the method works; not a finding later work revises.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: A 2008 comparison of aluminium and mercury ion clocks reached the seventeenth decimal place and found the ratio stable, which constrains the drift to a few parts in ten to the seventeenth per year.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Frequency Ratio of Al+ and Hg+ Single-Ion Optical Clocks; Metrology at the 17th Decimal Placeabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: We report the frequency ratio of two optical atomic clocks with a fractional uncertainty of 5.2 × 10–17.
Supports
Frequency Ratio of Al+ and Hg+ Single-Ion Optical Clocks; Metrology at the 17th Decimal Placeabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: Repeated measurements during the past year yield a preliminary constraint on the temporal variation of the fine-structure constant
Supports
Varying Constants, Gravitation and Cosmologysection 3.1.2, equation 32 (arXiv version)
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: = (−1.6 ± 2.3) × 10⁻¹⁷ yr⁻¹, (32) since it depends only on αEM.
Notation restored: Superscripts and subscripts restored from the glyph positions in the arXiv PDF (arXiv:1009.5514v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: = (−1.6± 2.3)× 10−17 yr−1, (32) since it depends only on αEM.

What this does not establish

The paper itself was read as an abstract; the review reports the same figure. The authors call the constraint preliminary, and it is consistent with zero.

Later work looked for

arXiv, 2015 on, "atomic clock fine-structure constant": superseded as the tightest bound by Lange and others (2021) and Filzinger and others (2023); the page now adds the later result as claim 34.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Comparisons of two transitions in a single ytterbium ion, repeated over six years, have since brought the bound to a few parts in ten to the nineteenth per year.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Improved Limits on the Coupling of Ultralight Bosonic Dark Matter to Photons from Optical Atomic Clock Comparisonsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Measurements of the first frequency ratio νE3/νE2 are performed via interleaved interrogation of both transitions in a single ion.
Supports
Improved Limits on the Coupling of Ultralight Bosonic Dark Matter to Photons from Optical Atomic Clock Comparisonssupplementary section on the linear drift, equation 9, and the caption of figure 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Figure 5 shows both the previously published measurement results ... between May 2016 (MJD 57527) and August 2020 (MJD 59081), as well as the new measurement data starting from September 2020. ... measured between MJD 57527 (May 19, 2016) and MJD 59900 (November 11, 2022)
Supports
Improved Limits on the Coupling of Ultralight Bosonic Dark Matter to Photons from Optical Atomic Clock Comparisonsequation 9
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: We find a linear drift of (1/α) dα/dt = 1.8(2.5) × 10⁻¹⁹/yr.
Notation restored: The fraction and the superscript restored from the glyph positions in the arXiv PDF (arXiv:2301.03433v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: We find a linear drift of 1 α dα dt = 1.8(2.5)× 10−19/yr .
Context
Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisonsabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant α to 1.0(1.1) × 10⁻¹⁸/yr
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant $\alpha$ to $1.0(1.1)\times10^{-18}/\mathrm{yr}$

What this does not establish

One laboratory, one pair of transitions. The result, 1.8 plus or minus 2.5 parts in ten to the nineteenth per year, is consistent with zero; the data run from May 2016 to November 2022.

Later work looked for

arXiv and Crossref, 2021 on, "atomic clock temporal variation fine-structure constant": Filzinger and others (2023) is the tightest drift bound found; page updated to it.

Corrected

24 September 2026. Previously: “” The 2008 figure was the page’s latest; later clock work at PTB (Lange and others 2021, Filzinger and others 2023, now cited) is about a hundred times tighter.

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: Two methods separated by two billion years, and neither has seen anything move.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 16 and 33 to 34: both give results consistent with no change.

What this does not establish

The two measure different things: Oklo a total change since two billion years ago, the clocks a rate today. Oklo also allows a non-zero solution (claim 17).

Corrected

24 September 2026. Previously: “Two methods separated by two billion years, agreeing that nothing is moving.” The methods bound change rather than establish its absence; the new wording says what was seen.

Claim 35 · checked 24 September 2026 · AI-assisted audit

What counts as a constant varying

Claim: What counts as a constant varying

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Only dimensionless combinations are meaningful.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.2, Fundamental parameters
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The values of these combinations of constants does not depend on the way they are measured ... on the definition of the units etc.… It follows that any variation of constants that will leave these numbers unaffected is actually just a redefinition of units.

Claim: Asking whether the speed of light has changed is not a well-posed question, because the answer depends on the units, and the units are defined in terms of it.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.2, Constants and metrology
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: it was decided in 1983, that the meter shall be defined by fixing the value of the speed of light to c = 299792458 m s⁻¹
Notation restored: Superscript restored from the Europe PMC full text (PMC5256069), which marks it with <sup>, read 2026-09-24. The text as extracted reads: it was decided in 1983, that the meter shall be defined by fixing the value of the speed of light to c = 299792458 m s−1
Supports
Varying Constants, Gravitation and Cosmologysection 2.1.2, Fundamental parameters
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: It follows that any variation of constants that will leave these numbers unaffected is actually just a redefinition of units.

Claim: The quantities that can be tested are ratios such as the fine-structure constant and the proton-to-electron mass ratio, which is why results are stated in terms of them.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: They have specific values (e.g., αEM ∼ 1/137, mp/me ∼ 1836, etc.) that we may hope to understand.
Supports
Varying Constants, Gravitation and Cosmologysection 3.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: we can interpret all atomic clocks results in terms of the g-factors of each atoms, gi, the electron to proton mass ration μ and the fine-structure constant αEM.

What this does not establish

Many experiments first measure an intermediate quantity, such as a resonance energy or a decay rate, and relate it to the dimensionless constants through a model.

Later work looked for

A matter of definition; not a finding later work revises.

Corrected

24 September 2026. Previously: “which is why those are what every experiment reports.” Not every experiment reports these ratios directly: the review lists intermediate observables, such as the Oklo resonance energy, that are then translated into them.

Claim 39 · checked 24 September 2026 · AI-assisted audit

What is claimed

Claim: What is claimed

Kind: Framing. Signposting. It asserts nothing a source could check.

The quasar claims

Claim: The quasar claims

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: One team has reported a slightly smaller fine-structure constant in light from distant quasars, and then a dipole across the sky.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3, Keck/HIRES data
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Using 30 absorption systems toward 17 quasars, they obtained ... This was the first claim that a constant may have varied during the evolution of the universe. ... The more robust estimates is the weighted mean ... ΔαEM/αEM = (−0.57 ± 0.11) × 10⁻⁵, 0.2 < z < 4.2
Notation restored: Superscripts and subscripts restored from the glyph positions in the arXiv PDF (arXiv:1009.5514v1, read with pdftotext -bbox), 2026-09-24. The text as extracted reads: Using 30 absorption systems toward 17 quasars, they obtained ... This was the first claim that a constant may have varied during the evolution of the universe. ... The more robust estimates is the weighted mean ... ∆ αEM/αEM = (−0.57± 0.11)× 10−5, 0.2<z < 4.2
Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: concludes that the distribution of αEM is well represented by a spatial dipole, significant at 4.1σ
Supports
Indications of a Spatial Variation of the Fine Structure Constantabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant, alpha, at high redshift. ... Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined dataset fits a spatial dipole, significant at the 4.2-sigma level

What this does not establish

The significance is the team’s own figure, and the team itself says undetected systematic effects could produce the pattern.

Corrected

24 September 2026. Previously: “Some groups have reported a small variation in the fine-structure constant across billions of years, and a spatial gradient across the sky.” The review says only one analysis claims a detection; the spatial result is a dipole, first published by the same team (Webb and others 2011, now cited).

24 September 2026. Previously: “One team has reported a small variation in the fine-structure constant across billions of years, and then a dipole across the sky.” The sources give the result as a smaller value at high redshift, from absorption systems toward quasars (redshift 0.2 to 4.2); neither states a span in years, so the page no longer does.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: Another, analysing spectra from a different telescope, found nothing, and a 2022 measurement calibrated with a laser frequency comb finds no change at the level of about a part per million.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3, Open controversy
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: since only one of them is claiming for a detection of a variation of the fine-structure constant. This discrepancy between VLT/UVES and Keck/Hires results is yet to be resolved.
Supports
Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515-4414abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: ESPRESSO's design, and calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement.
Supports
Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515-4414abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: Δα/α = 1.3 ± 1.3 (stat) ± 0.4 (sys) ppm
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v1), read 2026-09-24. The subscripts "stat" and "sys" are written in parentheses. The text as extracted reads: $\Delta\alpha/\alpha = 1.3 \pm 1.3_{\rm stat} \pm 0.4_{\rm sys}\,{\rm ppm}$

What this does not establish

The 2022 result is one absorber toward one quasar, in one direction on the sky.

Later work looked for

Crossref, 2015 on, "fine-structure constant quasar absorption ESPRESSO": the 2022 ESPRESSO result is the most precise single measurement found; page updated.

Corrected

24 September 2026. Previously: “Others analysing similar data find nothing.” The null result in the review came from a second telescope, and the page lacked the most precise later measurement (Murphy and others 2022, now cited).

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: The disagreements turn on instrument calibration and on the statistics of combining many absorption systems.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: This calibration is crucial
Supports
Varying Constants, Gravitation and Cosmologysection 3.4.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: it is indeed difficult (without having played with the data) to engage one of the parties. This exchange has enlightened some differences in the statistical analysis.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: A 2015 study found distortions in both telescopes' wavelength scales that could account for one telescope's results and part of the other's; in 2020 a new analysis still found a spatial variation marginally preferred.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectraabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: systematic errors in their wavelength scales are ubiquitous and substantial ... closely match important aspects of the VLT--UVES quasar results at all redshifts and partially explain the HIRES results ... the distortions are capable of significantly weakening the evidence for variations
Supports
Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectrasection 6, Summary and conclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Measurement
The source reads: long-range distortions of the wavelength scale identified here have the characteristics required to adequately explain the VLT–UVES quasar measurements of ∆α/α, though they cannot entirely explain those from Keck–HIRES.
Supports
Four direct measurements of the fine-structure constant 13 billion years agoabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Observational study: associations, not causes
The source reads: When the 4 new measurements are combined with a large existing sample of lower redshift measurements, a new limit on possible spatial variation of da/a is marginally preferred over a no-variation model at the 3.7 sigma level.

What this does not establish

The 2015 study found the distortions explain the VLT results closely and the Keck results only in part. The 3.7 sigma is the reporting team’s own figure.

Corrected

24 September 2026. Previously: “” The page gave neither the later calibration study nor the claimant team’s latest result, so it did not say where the dispute stands (Whitmore and Murphy 2015, Wilczynska and others 2020, now cited).

24 September 2026. Previously: “A 2015 study found distortions in both telescopes' wavelength scales that could mimic much of the signal; in 2020 the original team still found a spatial variation marginally preferred.” The 2020 abstract read does not say its authors are the team behind the first claim, so the page no longer calls them that.

24 September 2026. Previously: “A 2015 study found distortions in both telescopes' wavelength scales that could mimic much of the signal; in 2020 a new analysis still found a spatial variation marginally preferred.” "Much of the signal" was more than the 2015 study found: its distortions adequately explain the VLT results but cannot entirely explain the Keck ones, and correcting for them barely changed the dipole within the VLT data (Whitmore and Murphy 2015, section 5.1 and 6, read in full).

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: That is the pattern of a measurement at the edge of what the instrument can do.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 44 and 45: the dispute is carried by calibration and statistics rather than by the physics of the absorbers.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Why anyone expects variation

Claim: Why anyone expects variation

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Theories that unify the forces, and theories with extra dimensions, typically contain fields whose values set the effective constants.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 5.2.2, String theory
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: It follows that the 4-dimensional couplings are determined in terms of a string scale and various dynamical fields (dilaton, volume of compact space, …).
Supports
Varying Constants, Gravitation and Cosmologysection 5.2.1, Kaluza-Klein
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Such coupling terms naturally appear when compactifying a higher-dimensional theory.

What this does not establish

These are properties of the theories, none of which has been confirmed by experiment.

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: If such a field rolls slowly, the constants drift.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologyabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter.

What this does not establish

A possibility within these theories, not a prediction that the constants do drift; the review notes such a field must sit very close to a minimum today to satisfy Solar system tests.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: So a detection would be evidence for a whole class of theories, and the absence of one constrains them.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 1, Introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Detecting any such variation will indicate the need for new physical degrees of freedom in our theories, that is new physics.
Supports
Varying Constants, Gravitation and Cosmologysection 8, Conclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: this allows one to set stronger constraints and eventually to open an observational window on unification mechanisms.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: That is why the limits keep being pushed rather than being regarded as settled.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claim 50, and from the later tightening of the clock and Oklo limits (claims 16 and 34).

Claim 51 · checked 24 September 2026 · AI-assisted audit

Why these numbers

Claim: Why these numbers

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: One of the tightest limits on a changing constant comes from a rock in Gabon.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 3.2.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: This tight constraint arises from the large amplification between the resonance energy (∼ 0.1 eV) and the sensitivity (∼ 1 MeV).
Supports
Reappraisal of the limit on the variation in alpha implied by Okloabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The corresponding bound on the present-day time variation of α is tighter than the best limit to date from atomic clock experiments.
Notation restored: LaTeX in the arXiv abstract rendered as Unicode, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: The corresponding bound on the present-day time variation of $\alpha$ is tighter than the best limit to date from atomic clock experiments.
Supports
Reappraisal of the limit on the variation in alpha implied by Oklotext after equation 12
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Assuming a linear time dependence for α over the last 1.8 billion years, Eq. (12) implies that the present-day time variation of α is subject to the (95% C.L.) bound ... which is an improvement on the best limit from atomic clock experiments

What this does not establish

The comparison with clocks is the 2015 paper’s, and clock limits have tightened since (claim 34): as a rate today, the best clock bound is now the tighter one.

Corrected

24 September 2026. Previously: “One of the tightest limits in physics comes from a rock in Gabon.” The sources compare Oklo with other tests of varying constants, not with physics at large.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Why these values

Claim: Why these values

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Nothing explains the numbers themselves.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Supports
Varying Constants, Gravitation and Cosmologysection 7, opening
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The numerical values of the fundamental constants are not determined by the laws of nature in which they appear.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: Some are measured to great precision, and none is derived.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Varying Constants, Gravitation and Cosmologysection 2.1.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: the (usual) zero energy electromagnetic fine structure constant is αEM = 1/137.03599911(46)
Supports
Varying Constants, Gravitation and Cosmologysection 2.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Therefore, these fundamental constants are contingent quantities that can only be measured.

What this does not establish

Precision varies widely: the review’s Table 1 gives some light-quark couplings to within tens of per cent.

Later work looked for

Crossref, 2015 on, "Standard Model free parameters": no derivation of any of them found; nothing that changes it.

Corrected

24 September 2026. Previously: “They are measured to great precision and derived from nothing.” Not all are precise: the review’s table gives the up and down quark couplings with uncertainties of tens of per cent.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: Whether they are derivable at all, or whether they are accidents of how this region of the universe settled

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

The two options are the review’s two lines of explanation: a consistency condition that fixes the values, or an ensemble in which our region is one of many.

Supports
Varying Constants, Gravitation and Cosmologysection 7.1, Universe and multiverse approaches
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: Two possible lines of explanation are usually envisioned: a design or consistency hypothesis and an ensemble hypothesis

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: is the question the fine-tuning argument tries to get at and does not answer.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The review treats the apparent fine-tuning as what these explanations try to account for, and records a continuing debate over whether they can predict anything.

Context
Varying Constants, Gravitation and Cosmologysection 8, Conclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: We have stressed the limitations of this approach and the ongoing debate on the possibility to make it predictive.

Claim 58 · checked 24 September 2026 · AI-assisted audit

What was read

Varying Constants, Gravitation and CosmologyUzan, Living Reviews in Relativity · Living Reviews in Relativity 14:2 (29 March 2011), full text from Europe PMC (PMC5256069); equations missing from that text were read in the arXiv version, arXiv:1009.5514v1Read in full, 24 September 2026 · Copyright; quoted brieflyRead the abstract, introduction, sections 2.1, 3.1, 3.2, 3.4.3 to 3.4.12, 5.2, 7 and 8. One excerpt is an equation from the arXiv PDF text and keeps its extracted spacing.
Frequency Ratio of Al+ and Hg+ Single-Ion Optical Clocks; Metrology at the 17th Decimal PlaceRosenband and others, Science · Science 319, 1808-1812; abstract from the Crossref recordAbstract only, 24 September 2026 · Copyright; quoted brieflyThe publisher PDF refused this environment. The same result is reported, with its derivation, in the Uzan review, section 3.1.2.
Improved Limits for Violations of Local Position Invariance from Atomic Clock ComparisonsLange and others, Physical Review Letters · arXiv:2010.06620v2, full text (PDF, 7 January 2021)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence; quoted brieflyRead in full on 2026-09-24 in the integrity pass; excerpts taken from the arXiv abstract keep its text as served.
Improved Limits on the Coupling of Ultralight Bosonic Dark Matter to Photons from Optical Atomic Clock ComparisonsFilzinger and others, Physical Review Letters · arXiv:2301.03433v1 (dated 10 January 2023)Read in full, 24 September 2026 · Copyright; quoted brieflyThe drift excerpt keeps the PDF text extraction of the equation.
Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in GabonMeshik, Hohenberg and Pravdivtseva, Physical Review Letters · Abstract from the Europe PMC record (PMID 15525157)Abstract only, 24 September 2026 · Copyright; quoted briefly
Reappraisal of the limit on the variation in alpha implied by OkloDavis and Hamdan, Physical Review C · arXiv:1503.06011v2, full text (PDF, 27 May 2015)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence; quoted brieflyRead in full on 2026-09-24 in the integrity pass; excerpts taken from the arXiv abstract keep its text as served.
Indications of a Spatial Variation of the Fine Structure ConstantWebb and others, Physical Review Letters · arXiv:1008.3907v2, full text (PDF, 1 November 2011)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence; quoted brieflyRead in full on 2026-09-24 in the integrity pass; excerpts taken from the arXiv abstract keep its text as served.
Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectraWhitmore and Murphy, Monthly Notices of the Royal Astronomical Society · arXiv:1409.4467v2, full text (PDF, 18 November 2014)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence; quoted brieflyRead in full on 2026-09-24 in the integrity pass; excerpts taken from the arXiv abstract keep its text as served.
Four direct measurements of the fine-structure constant 13 billion years agoWilczynska and others, Science Advances · arXiv:2003.07627v1, full text (PDF, 17 March 2020)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence (published version CC BY-NC 4.0); quoted brieflyRead in full on 2026-09-24 in the integrity pass; excerpts taken from the arXiv abstract keep its text as served.
Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515-4414Murphy and others, Astronomy and Astrophysics · arXiv:2112.05819v1, full text (PDF, 10 December 2021)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence (published version CC BY 4.0); quoted brieflyAbstract excerpts keep the LaTeX markup of the arXiv abstract as served, with the notation restored for display.