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arxiv: 2606.28366 · v2 · pith:L4S6XEWHnew · submitted 2026-06-14 · ⚛️ physics.pop-ph · astro-ph.SR· physics.optics

The Optics of Shadow Bands

Branko Sretenovi\'c This is my paper

Pith reviewed 2026-07-03 23:29 UTC · model grok-4.3

classification ⚛️ physics.pop-ph astro-ph.SRphysics.optics
keywords shadow bandssolar eclipseinterferencegeometric opticsatmospheric propagationfringe patternYoung's experiment
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The pith

Shadow bands arise when the Sun's limb acts as a double-slit source, producing an interference pattern modulated by the atmosphere.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper develops a geometric-optical model in which the Sun's extended disk functions as the source in a celestial version of Young's double-slit experiment. Light from opposite edges of the partially visible Sun interferes after atmospheric propagation, creating moving light and dark fringes on the ground. The resulting intensity pattern is further shaped by Earth-atmosphere effects. This framework supplies quantitative predictions for fringe spacing and explains why the bands appear only near totality and only under narrow viewing conditions.

Core claim

The Sun's extended structure produces a celestial analogue of Young's double-slit experiment that generates an interference-like intensity pattern on the ground modulated by Earth-atmosphere effects. The analysis combines solar limb geometry, atmospheric propagation, and a wave-based formulation that yields quantitative predictions for fringe width and spacing. The model accounts for the principal observational features of shadow bands and clarifies why the phenomenon is both elusive and highly sensitive to viewing conditions.

What carries the argument

Celestial analogue of Young's double-slit experiment, in which the Sun's limb supplies two effective sources whose light interferes after atmospheric travel.

If this is right

  • Fringe width and spacing can be calculated directly from solar limb geometry and atmospheric parameters.
  • Bands appear only when a narrow crescent of the Sun remains visible, because that geometry maximizes the effective slit separation.
  • Small changes in observer height, atmospheric turbulence, or exact timing near totality strongly alter visibility.
  • The patterns move across the ground at speeds set by the relative motion of the Moon's shadow and the interference fringes.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Shadow-band observations could serve as a simple probe of near-ground atmospheric turbulence during eclipses.
  • Analogous fringes might be detectable under partial occultations of other extended sources, such as the Moon during a lunar eclipse viewed from space.
  • The model suggests that controlled laboratory versions using an extended incoherent source and a thin scattering layer could reproduce the effect.

Load-bearing premise

The Sun's extended structure produces a celestial analogue of Young's double-slit experiment that generates an interference-like intensity pattern on the ground modulated by Earth-atmosphere effects.

What would settle it

Measurement of fringe spacing during an eclipse that deviates systematically from the value calculated from the Sun's angular diameter and the observer's distance to the effective atmospheric scattering layer would falsify the model.

Figures

Figures reproduced from arXiv: 2606.28366 by Branko Sretenovi\'c.

Figure 1
Figure 1. Figure 1: Bright Regions with High Contrast in Sun Layers [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 1
Figure 1. Figure 1: Bright Regions with High Contrast in Sun Layers [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Bright Areas of Sun Surface and Atmosphere with Distance Labels [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 2
Figure 2. Figure 2: Bright Areas of Sun Surface and Atmosphere with Distance Labels [PITH_FULL_IMAGE:figures/full_fig_p010_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Domains and Shafts [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗
Figure 3
Figure 3. Figure 3: Domains and Shafts [PITH_FULL_IMAGE:figures/full_fig_p013_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Projection on Observation Surface Plane 11 [PITH_FULL_IMAGE:figures/full_fig_p011_4.png] view at source ↗
Figure 4
Figure 4. Figure 4: Projection on Observation Surface Plane 13 [PITH_FULL_IMAGE:figures/full_fig_p013_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Triple-sliver when Observation Surface at Centerline [PITH_FULL_IMAGE:figures/full_fig_p012_5.png] view at source ↗
Figure 5
Figure 5. Figure 5: Triple-sliver when Observation Surface at Centerline [PITH_FULL_IMAGE:figures/full_fig_p014_5.png] view at source ↗
read the original abstract

Shadow bands are transient, rippling patterns of light and dark that may appear in moments before and after totality in a solar eclipse. Despite centuries of reports, their physical origin has remained unresolved. This preprint develops a geometric-optical solution in which the Sun's extended structure produces a celestial analogue of Young's double-slit experiment, generating an interference-like intensity pattern on the ground, modulated by Earth-atmosphere effects. The analysis combines solar limb geometry, atmospheric propagation effects, and a wave-based formulation that yields quantitative predictions for fringe width and spacing. The resulting model accounts for the principal observational features of shadow bands and clarifies why the phenomenon is both elusive and highly sensitive to viewing conditions.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript develops a combined geometric-optical and wave-based model for shadow bands observed before and after totality in solar eclipses. It treats the Sun's extended disk as producing a celestial analogue of Young's double-slit experiment, with the solar limbs acting as effective sources that generate an interference-like intensity pattern on the ground; this pattern is further modulated by Earth-atmosphere propagation effects. The analysis is claimed to deliver quantitative predictions for fringe width and spacing that account for the principal observational features and explain the phenomenon's sensitivity to viewing conditions.

Significance. If the central construction holds, the work would supply the first quantitative, first-principles account of a centuries-old eclipse phenomenon that has resisted explanation. The attempt to combine limb geometry, atmospheric modulation, and a wave formulation is a clear strength; successful validation against data would constitute a genuine contribution to atmospheric optics.

major comments (1)
  1. [§3–4] §3–4: The model posits that the solar limbs function as coherent sources whose separation produces a distinct interference pattern. The van Cittert–Zernike theorem, however, implies that the mutual coherence between points separated by the solar angular diameter (~0.5°) is essentially zero for a thermal source at visible wavelengths after atmospheric propagation. The manuscript must therefore derive an explicit mechanism (e.g., a turbulence-induced coherence length or spatial filter) that restores the required visibility; absent this step the intensity reduces to an incoherent integral over the disk and the claimed quantitative predictions for fringe spacing cannot be obtained.
minor comments (2)
  1. The abstract asserts that the model 'yields quantitative predictions,' yet the provided text contains no explicit equations, derivations, or direct comparisons with measured fringe widths or spacings; these must be added with error bars and observational references.
  2. Notation for the effective source separation and the atmospheric modulation term should be defined once and used consistently; several descriptive passages repeat the same geometric argument without advancing the derivation.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful and constructive review. The central concern regarding coherence is addressed point-by-point below. We agree that an explicit derivation is required and will incorporate it in revision.

read point-by-point responses

  1. Referee: [§3–4] §3–4: The model posits that the solar limbs function as coherent sources whose separation produces a distinct interference pattern. The van Cittert–Zernike theorem, however, implies that the mutual coherence between points separated by the solar angular diameter (~0.5°) is essentially zero for a thermal source at visible wavelengths after atmospheric propagation. The manuscript must therefore derive an explicit mechanism (e.g., a turbulence-induced coherence length or spatial filter) that restores the required visibility; absent this step the intensity reduces to an incoherent integral over the disk and the claimed quantitative predictions for fringe spacing cannot be obtained.

    Authors: We accept the referee's point that the van Cittert–Zernike theorem must be confronted directly. The manuscript already invokes Earth-atmosphere propagation as a modulating factor on the wave field; we will revise §§3–4 to derive explicitly how turbulence sets a finite coherence length (via the mutual coherence function after propagation through a Kolmogorov spectrum) that is sufficient to produce partial visibility between the solar limbs. This derivation will be inserted before the fringe-spacing calculation, showing that the effective source is spatially filtered to a scale comparable to the Fresnel-zone size at the ground. The geometric-optical limb separation and the resulting quantitative predictions remain unchanged, but the coherence step will now be first-principles rather than implicit. revision: yes

Circularity Check

0 steps flagged

No circularity: derivation combines independent geometric and wave elements without self-referential reduction

full rationale

The provided abstract and context describe a model that combines solar limb geometry, atmospheric propagation, and a wave-based formulation to generate quantitative predictions for fringe width and spacing. No equations, self-citations, or fitted parameters are quoted that reduce the output predictions to the inputs by construction. The reader's suspicion of possible fitting is noted but unsupported by any exhibited reduction in the text. The skeptic attack concerns physical plausibility (van Cittert-Zernike coherence) rather than definitional circularity. This is the default honest outcome when no load-bearing step collapses to its own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard wave-interference principles applied to solar geometry and atmospheric propagation; no new entities are introduced. Because only the abstract is available, the ledger reflects only the components explicitly named in the summary.

axioms (2)
  • domain assumption Wave interference from an extended source (solar limb) can be treated analogously to Young's double-slit experiment.
    Invoked to generate the interference-like intensity pattern on the ground.
  • domain assumption Atmospheric propagation effects modulate the resulting pattern.
    Combined with solar limb geometry and wave formulation to produce observable fringes.

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Reference graph

Works this paper leans on

25 extracted references · 9 canonical work pages

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