The Core Question

Modern astronomy no longer listens to the universe through light alone. It now listens through multiple messengers: electromagnetic radiation, gravitational waves, neutrinos, cosmic rays, and transient events that appear across several channels at once. This is what makes multi-messenger astronomy so powerful. When a neutron star merger or black hole collision happens, the universe can send more than one kind of signal toward Earth.

The ArcSecs question explored here is direct: do gravitational waves and electromagnetic light truly behave identically across cosmic distance?

In the standard model, the answer is essentially yes in vacuum. Gravitational waves and photons are both expected to propagate at the same invariant speed, commonly represented by c, while redshift is explained by the expansion of space. Arrival-time differences between a gravitational-wave signal and an electromagnetic counterpart are usually attributed to source physics: jet breakout, ejecta opacity, accretion-disk diffusion, viewing angle, or local environmental effects.

The alternative model explored here separates those messengers. It treats gravitational waves as the cleaner baseline clock and treats electromagnetic light as a signal that may experience cumulative slowing and energy degeneration over distance. In simpler terms:

• Gravitational waves are modeled as traveling at a constant invariant speed.
• Electromagnetic radiation is modeled as gradually slowing through a cosmic medium or vacuum-like substrate.
• Photon energy is modeled as degenerating with distance, producing redshift without requiring expansion of space.
• Observed delays are separated into intrinsic source delay plus propagation delay.

This is not a minor adjustment. If even partly correct, it would change how redshift, distance, supernova time dilation, Hubble tension, gravitational lensing, and electromagnetic counterpart searches are interpreted.

The Standard View: Light, Gravity, and Expanding Space

In mainstream cosmology, gravitational waves are ripples in spacetime produced by accelerating masses, such as merging black holes or neutron stars. Electromagnetic radiation is carried by photons. Although these messengers interact with matter very differently, both are expected to travel at the same speed in vacuum.

The standard interpretation of cosmological redshift is geometric. Space expands, and as light crosses that expanding space, its wavelength stretches. A photon emitted as blue or ultraviolet light can arrive as red, infrared, microwave, or radio radiation depending on the distance and expansion history involved.

This view is extraordinarily successful. It organizes the cosmic microwave background, the large-scale distribution of galaxies, supernova observations, gravitational lensing, baryon acoustic oscillations, and many other measurements into a single framework. Any alternative model must therefore clear a very high bar.

The tired-light family of ideas has historically failed that test. Classical tired light proposed that photons lose energy while traveling, causing redshift without expansion. But standard tired-light models have several major problems. They do not naturally explain observed time dilation in distant supernova light curves, they can imply image blurring if scattering is involved, and they struggle to reproduce the full precision structure of modern cosmological observations.

The ArcSecs model is an attempt to revisit that failure point by coupling photon energy degeneration with photon velocity attenuation. Instead of saying only “light loses energy,” it asks whether a deeper propagation model could make light both redshift and arrive with stretched timing.

The ArcSecs Decoupled Propagation Model

The proposed model begins with a separation:

Gravitational waves define the cleaner propagation baseline, while electromagnetic light carries a path-dependent history of interaction with the cosmic medium.

In this framework, gravitational-wave velocity is treated as constant:

vGW = c0

Electromagnetic velocity is instead modeled as a distance-dependent quantity:

vEM(x) = c0 × e^(-αx)

In that expression, x is distance traveled and α is a velocity attenuation coefficient. The larger the coefficient, the more strongly light slows over distance.

Photon energy is modeled with a similar attenuation form:

E(x) = E0 × e^(-βx)

Here, β is an energy degeneration coefficient. If photon energy decreases with distance, the observed wavelength increases. That gives the model a redshift mechanism without requiring metric expansion.

The most interesting version of the model appears when the velocity attenuation coefficient and energy attenuation coefficient are linked:

α ≈ β

That coupling is the key move. It means photon energy loss and photon timing stretch are not separate coincidences; they are two expressions of the same deeper propagation effect.

The model then divides any observed electromagnetic delay into two major components:

Observed Delay = Intrinsic Source Delay + Propagation Delay

Intrinsic source delay includes ordinary astrophysics: gamma-ray jet breakout, kilonova opacity, accretion disk diffusion, viewing angle, and local matter density. Propagation delay is the additional delay caused by light traveling more slowly than the gravitational-wave baseline.

A critical prediction follows. If light slows continuously while gravitational waves do not, the electromagnetic delay should grow nonlinearly with distance. In the simplest approximation, the extra delay scales roughly with distance squared. That gives the model a sharp test: multi-messenger events at greater distances should show a detectable distance-dependent delay after local astrophysical delays are modeled out.

GW170817: The Anchor Event

The strongest anchor for this discussion is GW170817, the binary neutron star merger observed on August 17, 2017 by LIGO and Virgo. It was followed by the short gamma-ray burst GRB 170817A, observed roughly 1.7 seconds after the gravitational-wave signal.

This event matters because it gave astronomy one of its cleanest side-by-side comparisons between gravitational waves and electromagnetic radiation. The source was localized to the galaxy NGC 4993, roughly 40 megaparsecs away. That is distant by human standards, but relatively nearby by cosmological standards.

In the ArcSecs model, GW170817 acts as the local calibration point. The observed 1.7-second delay is not treated as pure propagation delay. Most of it is assigned to intrinsic source physics. In standard astrophysical language, the gamma-ray signal may have required time to emerge after the neutron star merger because a relativistic jet had to break out through merger ejecta before gamma rays could escape cleanly.

The ArcSecs calculation described in the underlying model assigns only a small fraction of the 1.7-second delay to vacuum-scale electromagnetic slowing. The estimated propagation component is about 0.020 seconds across 40 Mpc, with the rest attributed to the merger environment and gamma-ray production mechanism.

This is important because it keeps the model close to the tight constraints produced by GW170817. The gravitational-wave and gamma-ray arrival times strongly restrict large deviations between the speed of gravity and the speed of light at relatively nearby cosmic distance. Any alternative model that produces huge local delays would already be in trouble.

GW150914: The Problem Case

GW150914 was the first direct gravitational-wave detection, produced by the merger of two black holes. In mainstream astrophysics, black hole mergers are not usually expected to produce bright electromagnetic counterparts unless they occur in a special environment with surrounding matter.

A weak gamma-ray transient reported near GW150914 has been debated. Some analyses considered it potentially associated; others treated it as likely unrelated background. That uncertainty makes GW150914 a stress test rather than a clean calibration case.

If the reported gamma-ray signal were associated with GW150914 and if the simple ArcSecs attenuation coefficient from GW170817 were applied uniformly, the model would predict a larger propagation delay than the reported gamma-ray offset. That creates a contradiction.

The model therefore faces two possible interpretations:

1. The reported electromagnetic signal was not physically associated with GW150914.
2. The attenuation coefficient is not universal, but depends on the line-of-sight environment.

The second option is more interesting for ArcSecs. If light slowing is caused by interaction with a cosmic medium, then the effect should not be perfectly uniform. It should depend on density, structure, plasma environment, gravitational environment, and possibly the large-scale distribution of matter between the source and observer.

That turns the model from a simple one-constant tired-light theory into a path-integral theory:

Total EM delay = ∫ path-dependent optical resistance dx

In this version, a photon crossing a deep cosmic void would experience less slowing and energy degeneration than a photon crossing dense filaments, halos, clusters, or active galactic environments.

GW190521: Environmental Delay and AGN Diffusion

GW190521 was a massive binary black hole merger and one of the most unusual gravitational-wave events detected. A candidate optical flare, ZTF19abanrhr, was reported from an active galactic nucleus environment at redshift z ≈ 0.438.

The candidate electromagnetic counterpart appeared on a much longer timescale than the gamma-ray signal associated with GW170817. The ArcSecs source model discusses an observed delay on the order of 34 days.

In the decoupled propagation model, a key separation must be made again:

• Vacuum-scale propagation delay is the delay caused by electromagnetic slowing across distance.
• Environmental diffusion delay is the delay caused by the source environment before light can escape.

GW190521 is not treated as a case where the full 34-day delay comes from light slowly crossing intergalactic distance. Instead, the dominant delay is assigned to local source physics. If the merger occurred inside or near an active galactic nucleus disk, electromagnetic radiation could be delayed by disk interaction, shock breakout, opacity, and diffusion through dense matter.

That matters because it shows the model cannot simply plot every electromagnetic delay against distance and call the result propagation delay. It must first subtract or model the astrophysical environment.

The Supernova Time-Dilation Problem

Any modern tired-light model has to face the supernova problem. Distant Type Ia supernovae appear time-dilated: their light curves are stretched by a factor related to redshift. In the standard expanding-universe interpretation, this is expected. As space expands, wavelengths stretch and observed time intervals stretch too.

Classical tired light has trouble here. If photons merely lose energy while traveling through static space, the photon color changes, but the spacing between arriving photons does not automatically stretch in the same way. That is one of the major reasons tired-light cosmologies are not accepted as mainstream cosmology.

The ArcSecs model attempts to repair this by coupling energy degeneration with velocity attenuation. If later-arriving light is traveling through a propagation state in which electromagnetic velocity has degraded relative to the gravitational baseline, then the arrival interval between photons can stretch.

In simplified form:

Energy loss creates redshift. Velocity attenuation creates arrival-time stretching. If both share the same attenuation structure, redshift and time dilation become linked.

This is the central theoretical claim. The model does not merely revive tired light; it modifies it. It argues that tired light failed because it treated energy loss without a corresponding propagation-time effect.

Whether that is enough to match actual supernova data is a separate and difficult question. The model must not only reproduce the rough 1 + z time-dilation trend, but also match luminosity distances, spectra, surface brightness relations, the cosmic microwave background, baryon acoustic oscillations, and the structure-growth record.

Hubble Tension as Optical Resistance

The Hubble tension is one of the major open problems in modern cosmology. Local distance-ladder measurements using Cepheids and Type Ia supernovae tend to produce a higher value for the Hubble constant than values inferred from cosmic microwave background measurements interpreted through ΛCDM.

In the standard view, this may indicate unknown systematics, new early-universe physics, evolving dark energy, modified gravity, or some other correction to the model.

In the ArcSecs interpretation, the tension is reframed. The local distance ladder and early-universe CMB inference may not be measuring one identical expansion parameter. Instead, the local measurement could be partly measuring electromagnetic optical resistance: the amount of energy degeneration light experiences through the particular cosmic structures between source and observer.

Under that interpretation, redshift is not pure expansion. It is a composite observable:

Observed redshift = source motion + gravitational effects + propagation energy loss + possible expansion-like terms

This would make the Hubble constant less like a single universal expansion speed and more like an effective optical parameter inferred from light. Different distance methods would disagree because they depend on different epochs, wavelengths, environments, and propagation paths.

This is speculative, but it produces a clear research direction. Instead of asking only “what is the expansion rate?”, the model asks:

How much of the redshift-distance relation is geometry, and how much could be accumulated electromagnetic propagation history?

Gravitational Lensing as a Future Test

Strong gravitational lensing may become one of the cleanest ways to test the model. In standard general relativity, gravitational waves and electromagnetic waves from the same lensed event should follow equivalent null paths, with lensing delays determined by geometry and gravitational potential.

In the ArcSecs decoupled model, electromagnetic light experiences an additional refractive or attenuation-like effect that gravitational waves do not. That creates a possible differential-lensing signature.

A strongly lensed neutron star merger with a confirmed electromagnetic counterpart could therefore be decisive. If gravitational-wave image delays and electromagnetic image delays differ after all normal source and lensing effects are modeled, the result would demand explanation.

Falsifiable Predictions

A useful alternative cosmology must risk being wrong. The ArcSecs light-slowing and energy-degeneration model makes several predictions that can be attacked with future data:

1. Distance-dependent EM lag: After intrinsic source delays are modeled out, electromagnetic counterparts should show a residual delay relative to gravitational waves that grows nonlinearly with distance.
2. Path-dependent redshift scatter: Lines of sight through dense filaments, halos, clusters, or AGN environments should show stronger attenuation-like behavior than paths through voids.
3. Different lensed timing: In strongly lensed multi-messenger events, gravitational-wave and electromagnetic image delays may not match exactly.
4. Environmental counterpart suppression: Some missing electromagnetic counterparts may not be purely absent at the source; they may be shifted, dimmed, or delayed below instrument thresholds.
5. Frequency-dependent observational bias: Highly attenuated events may be easier to recover in infrared, microwave, or radio channels than in optical surveys.

The LIGO-Virgo-KAGRA observing runs, Rubin Observatory, Zwicky Transient Facility, gamma-ray monitors, radio surveys, and future gravitational-wave detectors provide the kind of dataset needed to test these ideas. The key is not a single spectacular event. The key is a population: many events, many distances, many environments, and careful separation of source delay from propagation delay.

What This Does Not Prove

This model should not be oversold. It does not prove that spacetime is false. It does not prove that the universe is static. It does not prove that ΛCDM is wrong. It does not prove that tired light has solved all historical objections.

What it does provide is a structured alternative hypothesis:

• Use gravitational waves as the cleaner timing baseline.
• Treat electromagnetic redshift as a possible propagation-history observable.
• Separate intrinsic source delay from distance-dependent propagation delay.
• Look for path-dependent residuals that correlate with cosmic structure.
• Make predictions that can fail.

That is the scientific value of the model. Its strength is not that it avoids criticism, but that it can be translated into observational tests.

Conclusion: A Testable Alternative, Not a Finished Theory

The ArcSecs light-slowing and energy-degeneration model is a speculative attempt to reinterpret redshift, electromagnetic delay, and multi-messenger timing. It begins by decoupling gravitational waves from electromagnetic light: gravity provides the clean timing baseline, while light carries the accumulated history of its journey.

GW170817 provides the local anchor. GW150914 exposes the danger of assuming a universal attenuation coefficient. GW190521 shows how source environments can dominate electromagnetic delay. Supernova time dilation remains the central obstacle that any tired-light-derived model must address. Hubble tension becomes a question of whether distance-ladder light is measuring expansion alone or some mixture of geometry and optical resistance.

The model may be wrong. But it is useful if it leads to sharper questions:

Are gravitational waves and light truly equivalent messengers across cosmic distance, or does light arrive carrying measurable evidence of energy loss, velocity attenuation, and path-dependent interaction with the universe itself?

That is a question worth modeling, simulating, and testing.

References and Further Reading

1. LIGO Document Control Center: GW170817 Observation of Gravitational Waves from a Binary Neutron Star Inspiral
2. arXiv: GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
3. NASA GCN Circulars for GW170817 / GRB 170817A
4. LIGO-Caltech: LIGO-Virgo-KAGRA Complete Fourth Observing Run
5. LIGO-Caltech: LIGO-Virgo-KAGRA Announce the 200th Gravitational Wave Detection of O4
6. GW190521: A Binary Black Hole Merger Inside an Active Galactic Nucleus?
7. Electromagnetic Flares Associated with Gravitational Waves from Binary Black Hole Mergers in AGN Accretion Disks
8. NASA: Hubble Constant and Tension
9. Planck 2018 Results. VI. Cosmological Parameters
10. Ned Wright: Errors in Tired Light Cosmology
11. Rubin Observatory: Multi-Messenger Astronomy
12. Challenges and Opportunities for Time-Delay Cosmography with Multi-Messenger Gravitational Lensing