The Anisotropic Synchrony Convention

Summary

Nobody has ever measured the one-way speed of light.  Not once, in four hundred years of trying.  Every measurement ever made is a round trip.  Send a pulse out, bounce it off a mirror, divide the total path by the total time on one clock.  To measure a one-way speed you would need two clocks in different places already reading the same time, and to set two distant clocks to the same time you have to assume how long light takes to get from one to the other.  The circle is not a limitation of technique.  It is structural, and Einstein said so in the paper that founded relativity.

Jason Lisle's anisotropic synchrony convention (ASC) takes that gap seriously.  If the split of a round trip into an outbound half and an inbound half is a matter of definition, then a convention in which inbound light arrives instantly is as legitimate as the one physics normally uses.  On that convention there is no light travel time toward an observer, distant events are seen as they happen, and the stars made on Day Four shine on Earth on Day Four.  Lisle's summary is that the distant starlight problem "was not so much a physics problem, but an error of exegesis."¹¹

This article grades that proposal.  It is the strongest of the eight published young-earth answers to distant starlight, and it deserves to be handled carefully in both directions.  It should not be dismissed with the bad objections that circulate against it, and it should not be sold as more than it is.

Here is the verdict, stated first.

• The physics is real. Relativity fixes the round-trip speed of light in vacuum at c in every inertial frame and every direction. It does not fix the one-way speed. Einstein called the equality of the two halves "a stipulation which I can make of my own freewill,"²² and in 1905 he had already considered timing events by their arrival at a single observer, which is ASC, and set it aside not as false but as "not independent of the standpoint of the observer."³³
• The philosophical debate is genuinely open, and this article will not pretend otherwise. David Malament's 1977 theorem is the strongest argument that simultaneity is fixed by causal structure alone. The literature has not converged on it. The Stanford Encyclopedia records Roberto Torretti and John Norton reading it as decisive, and Adolf Grünbaum, Allen Janis and Michael Redhead reading it as not, with Grünbaum's rebuttal published in 2010.⁴⁴ Anyone who says "Malament settled this against Lisle" is claiming more than the field does.
• ASC's specific position, ε = 1, is stranger than Lisle's presentation admits, and it also has more independent support than his critics admit. It sits outside the open interval 0 < ε < 1 that Reichenbach's own parameterisation allows,⁴ which means the conventionalists Lisle appeals to would reject it. But two philosophers of physics reached the same relation from the other direction: Sahotra Sarkar and John Stachel showed in 1999 that dropping Malament's time-reflection requirement makes the past light cone a legitimate simultaneity relation, and Hanoch Ben-Yami argued in 2006 for extending Reichenbach's range to include ε = 1 exactly.⁵⁵⁵ A 2012 Foundations of Physics paper by Fabien Besnard proves something sharper still: give an observer only his own worldline, the light cones he can send and receive, and a time ordering, and the only simultaneity relations he can define are the past and future light cones. Standard synchrony is not among them.⁶⁶
• The ASC foliation is not exotic in mainstream physics either. Relativistic cosmologists routinely use "observational coordinates," in which "w = constant hypersurfaces are past light cones."⁷⁷ That is the ASC slicing under a different name, used for entirely secular purposes.
• And none of that buys anything observational, which is the heart of the matter. Lisle says so himself, twice. In 2010: ASC "cannot be falsified any more than the metric system can be falsified."¹ In 2025: "the difference between ESC and ASC is one of coordinates, leaving the underlying geometry and measurable observations unaffected."⁸⁸ A coordinate change cannot alter an observable. So ASC cannot be refuted by an observation, and it cannot be confirmed by one either.
• The decisive limitation is proper time. A synchrony convention assigns time labels to distant events. It does not touch the time elapsed along an object's own history, which is an invariant and is the same in every coordinate system. Every indicator of a long stellar history therefore survives untouched: main-sequence turnoffs in globular clusters, cooling white dwarfs, galaxy mergers caught mid-collision, and, cleanest of all because it is a young-earth publication, Danny Faulkner's own 2017 table of seventeen Galactic supernova remnants with ages above 7,000 years, five above a million.⁹⁹
• So ASC converts the distant starlight problem into the appearance-of-age problem. It moves the difficulty from the light beam to the object. Lisle accepts the consequence in print: "Perhaps God created galaxies with systematic differences depending on their distance from our local group. Not every sequence is a time-sequence."¹⁰¹⁰ That is the same answer created-light-in-transit gave, and it is the answer Faulkner rejected as deceptive.¹¹¹¹ This is the single most important thing in this article.
• Two common objections to ASC are simply wrong and should be retired. "Relativity says light travels at c" confuses the round-trip speed with the one-way speed; Lisle answers it directly.¹⁰ "The SN 1987A light echo disproves instantaneous inbound light" fails because the light that lit the ring travelled away from Earth first, so it is slow under ASC and the observed delay survives. Lisle works the geometry out and gets the right answer.¹⁰
• The sharpest published criticism comes from another young-earth creationist, and it half succeeds. Phillip Dennis argues in the Answers Research Journal that the ASC model is internally inconsistent.¹²¹² His central derivation is circular. He writes the spacetime interval in its Einstein-convention form and then derives the Einstein convention, which Lisle correctly identifies as begging the question.¹³¹³ But Dennis's conclusion survives his flawed proof: "The ASC convention is merely a coordinate transform that cannot alter physical quantities."¹² That is true, and Lisle agrees with it. The two men are not disagreeing about relativity. They are disagreeing about whether the light travel time problem is the kind of problem a coordinate can solve.
• The exegetical case is where ASC is weakest, and it should be said plainly. Lisle's argument that Genesis uses ASC has three parts. There is "and it was so" in Genesis 1:15, the claim that ancient cultures had no other option, and and the observation that the Einstein convention makes the creation week frame-dependent over cosmic distances.¹¹¹ The third is a genuinely good argument and is usually ignored. The first two are weaker than they look. No ancient text states a synchrony convention, and a convention that no text states, adopted because it resolves a modern difficulty, needs a reason beyond "it would help."
• Bottom line. ASC is legitimate physics, honestly presented by its author, and unrefuted. It is also observationally empty by construction, and it leaves the age evidence exactly where it was. A reader who wants a young universe should understand that ASC does not give one; it removes one argument against one, and hands the weight of the case to the appearance of age.

What relativity actually fixes, and what it leaves open

Start with the thing that is not in dispute.

The round-trip speed of light in vacuum is c in every inertial frame and in every direction.  Send a pulse from A to a mirror at B and back to A.  Time it on one clock at A.  Divide twice the A-to-B distance by the elapsed time.  The answer is 299,792,458 metres per second, always, no matter how fast A is moving, no matter which way the apparatus points.  That result is measured to extraordinary precision and nothing in this article questions it.

The one-way speed has never been measured, and there is a structural reason.  To time a one-way trip you need a clock at A to record the departure and a clock at B to record the arrival, and the two clocks have to agree on what time it is.  How do you make them agree?  The obvious method is to send a light signal from A to B carrying A's reading, and have B set his clock to that reading plus the travel time.  But the travel time is the one-way speed divided into the distance — the quantity you were trying to measure.  You cannot get out of the circle by moving a clock from A to B either, because a moving clock runs slow by an amount that depends on its velocity, and velocity is distance over time, which needs synchronised clocks again.

Einstein saw the circle immediately.  In §1 of the 1905 paper that founded special relativity he wrote that a common time for A and B "cannot be defined at all unless we establish by definition that the 'time' required by light to travel from A to B equals the 'time' it requires to travel from B to A."³  Fifteen years later, writing for a general audience, he put it in a dialogue.  He raises the objection in his own voice — how do you know the two halves take the same time? — and gives the answer he then endorses:

"That light requires the same time to traverse the path A → M as for the path B → M is in reality neither a supposition nor a hypothesis about the physical nature of light, but a stipulation which I can make of my own freewill in order to arrive at a definition of simultaneity."²

That is the entire foundation of ASC, and it belongs to Einstein, not to a creationist.

Einstein also considered ASC itself, in 1905, and rejected it for a reason that is worth reading carefully.  Two paragraphs before the "by definition" sentence, in the same section, he wrote:

"We might, of course, content ourselves with time values determined by an observer stationed together with the watch at the origin of the co-ordinates, and co-ordinating the corresponding positions of the hands with light signals, given out by every event to be timed, and reaching him through empty space.  But this co-ordination has the disadvantage that it is not independent of the standpoint of the observer with the watch or clock, as we know from experience."³

Timing every event by when its light reaches one observer is ASC.  Einstein's objection to it is not that it is wrong.  It is that it depends on where the observer stands.  Standard synchrony instead depends on how fast the observer moves.  Neither dependence is eliminable, and Einstein chose the one that suited a theory about velocity frames.  Lisle quotes exactly this passage, from Sarkar and Stachel's 1999 paper, and makes the same point about it.¹

One clarification that prevents most of the confusion.  The claim is not that the one-way speed of light might turn out to be something other than c if we measured it better.  The claim is that "the one-way speed of light" is not a fully specified physical quantity until you say how you synchronised the clocks.  Saying that is choosing a convention.  It is the same kind of statement as saying there is no fact about whether a ship is moving until you name a reference frame.  Physics is full of these.

Reichenbach's ε, and where ASC sits in it

Hans Reichenbach turned Einstein's stipulation into a parameter.

Send light from A at time t₁, reflect it at B, receive it back at A at time t₂.  Any event at B in the open interval between those two readings can be defined as simultaneous with a chosen event at A.  Reichenbach writes the choice as

t_B = t₁ + ε(t₂ − t₁)

and the conventionality thesis says the value of ε is stipulated, not discovered.⁴

• ε = ½ is Einstein synchrony (ESC). Light is equally fast both ways. It is what physics uses, because it makes the equations symmetric.
• ε < ½ makes the outbound leg slower than the inbound leg.
• ε = 1 makes the inbound leg instantaneous and the outbound leg travel at c/2. This is ASC.

The three cases worth naming:

Under ASC the speed of a light ray depends on the angle θ between the ray's direction and the direction toward the observer.  Lisle's formula is

v = c / (1 − cos θ)

so a ray aimed straight at the observer (θ = 0) arrives instantly, a ray aimed straight away (θ = 180°) travels at c/2, and a ray crossing sideways (θ = 90°) travels at exactly c.¹³  The round trip always averages to c.  Keep the transverse case in mind.  It disposes of one of the objections later in this article.

Here is a detail Lisle's presentations pass over and his critics have not exploited.  Reichenbach's range is the open interval 0 < ε < 1, and the Stanford Encyclopedia states it that way.⁴  The endpoints are excluded on purpose.  At ε = 1 the event at B that is called "simultaneous" with the reception at A is the reception event's own past light cone — which means two events that can be causally connected are being called simultaneous.  Reichenbach and Grünbaum built the conventionality thesis on the principle that only causally unconnectible events may be freely relabelled, so their own criterion rules ASC out.  The Stanford Encyclopedia says so directly:  because the half-null-cone relations "define causally connectible events to be simultaneous, it would seem that they would also be rejected by adherents of the views of Reichenbach and Grünbaum."⁵

So Lisle's position is unusual.  It is rejected by the anti-conventionalists, and it is also rejected by the classical conventionalists whose thesis he invokes.  That is a real weakness in how ASC is usually presented — and it turns out not to be fatal, for reasons that come from secular philosophy of physics rather than from creationism.

Is the conventionality thesis defensible?

This is the question critics of ASC most often get wrong, in both directions.  Popular creationist presentations treat conventionality as settled fact.  Popular critiques treat it as refuted in 1977.  Neither is true, and the actual state of the literature is more interesting than either.

Malament's theorem, stated fairly

In 1977 David Malament proved a uniqueness result.¹⁴  Suppose you want a simultaneity relation S that is definable purely from the causal structure of Minkowski spacetime — which events can influence which — relative to a single inertial observer's worldline O.  Require that S be an equivalence relation, that it not be the trivial relation holding between all events, and that it relate at least one event on O to at least one event off it.  Malament showed that S must then be standard synchrony.  There is no other option.⁴

If that holds, ASC is not a rival convention.  It is not a simultaneity relation at all.  That is why the theorem matters.

Some philosophers took it as decisive.  Roberto Torretti wrote that Malament "proved that simultaneity by standard synchronism in an inertial frame F is the only non-universal equivalence between events at different points of F that is definable … in terms of causal connectibility alone."  John Norton wrote that Malament "was able to prove that the central claim about simultaneity of the causal theorists of time was false."⁴

Others did not, and they are not cranks.  Grünbaum published a detailed critique in 2010, thirty-three years later, objecting that Malament has to assume S is an equivalence relation, and arguing that the latitude Malament's theorem leaves is the same latitude as Reichenbach's ε.  His conclusion:  "Malament's remarkable proof has not undermined my thesis that, in the STR, relative simultaneity is conventional."  Michael Redhead in 1993 and Debs and Redhead in 2007 argue similarly.⁴

Two facts should be enough to keep anyone from calling this closed.  The dispute has run for fifty years.  And the Stanford Encyclopedia's own survey, written by Allen Janis, presents it as live rather than resolved.

The result that matters most for ASC specifically

Here is the part that neither Lisle's supporters nor his critics usually mention, and it is the strongest technical support ASC has.

Malament's theorem needs one more assumption than the list above.  The simultaneity relation must be invariant under time reflection, meaning a flip in the direction of time about a point on the observer's worldline.  That requirement is what kills the light cone.  Reflect the past light cone in time and you get the future light cone, a different relation, so the past-cone relation is not time-reflection invariant and Malament's theorem excludes it.

In 1999 Sahotra Sarkar and John Stachel argued in Philosophy of Science that there is no physical warrant for that requirement.¹⁵  Drop it, and Malament's other criteria are satisfied by a relation the Stanford Encyclopedia describes plainly:

"Dropping that requirement, they show that Malament's other criteria for a simultaneity relation are then also satisfied if we fix some arbitrary event in space-time and say either that any pair of events on its backward null cone are simultaneous or, alternatively, that any pair of events on its forward null cone are simultaneous. … If the backward-cone relation were chosen, then simultaneous events would be those seen simultaneously by an observer at the cone's vertex."⁵

"Simultaneous events would be those seen simultaneously by an observer at the cone's vertex" is a definition of ASC, arrived at by two philosophers of physics with no interest in Genesis.

The same survey records what they found next, and this is the honest counterweight:  among the relations meeting these requirements, standard synchrony is the unique one independent of the observer's position, and the half-null-cone relations are the unique ones independent of the observer's motion.⁵  That is precisely Einstein's 1905 trade-off, now proved rather than asserted.  ESC and ASC are the two natural choices, and you pick according to whether you care more about position or velocity.

Sarkar and Stachel's proof was itself contested, and their key premise survived the contest.  Domenico Giulini, a relativist at Zürich, replied in 2001 that their mathematics is "incomplete."  They include scale transformations that are no more a physical symmetry than time reflection is, and one step of their inertial-frame argument does not follow.¹⁶¹⁶  But on the central point he sides with them:  "They assert – and we agree with this – that there is no physical reason to require invariance under time reflections."¹⁶  And he confirms the consequence:  without time reflections "one could still have lightlike half-cones as equivalence classes."¹⁶

Hanoch Ben-Yami reached ε = 1 from a third direction in 2006, by replacing Malament's time-symmetric causal relation with an asymmetric one, "if event e₁ is a cause of event e₂, then e₂ does not precede e₁," which allows events to be simultaneous with their causes and "consequently the range of Reichenbach's ε is extended to include both 0 and 1."⁵  That is exactly the gap identified in the previous section, closed by someone with no stake in the outcome.

The sharpest result, and its limits

In 2012 Fabien Besnard published a systematic treatment in Foundations of Physics that tries to clean the whole debate up.⁶  His framing is the useful one:  what can an observer actually build a simultaneity relation out of?

Malament gives the observer the full causal-connectibility relation κ, meaning which events could in principle influence which, everywhere in spacetime.  Besnard points out that an observer does not have that.  What an observer has is his own worldline, the light cones he can emit and receive, and a clock.  Restrict him to those, and Besnard proves:

"There is no implicitly (X, L_X)-definable equivalence relation on M satisfying (M). … The only implicitly (X, L_X, <)-definable equivalence relations satisfying (M) are Λ⁺_X and Λ⁻_X."⁶

In words:  given a worldline, the light cones centred on it, and a sense of which direction is earlier, the only simultaneity relations definable are the future and past light cone relations.  Standard synchrony is not definable from that data.  It requires the full causal structure, which the observer cannot determine.

That is a striking result and it should be reported as one.  It should also be reported with its limit, which Besnard states in the same theorem:  give the observer a clock that measures durations as well as ordering, and a large family of other relations becomes definable again, including standard synchrony.⁶  Real observers have such clocks.  So the theorem does not say ASC is forced.  It says the ASC foliation is the one available from the barest observational data, which is a considerably weaker and still interesting claim.

And the foliation is used by working cosmologists

One more piece of context that both sides of the creationist debate seem unaware of.

Relativistic cosmologists have a standard coordinate system built on exactly the ASC slicing.  It is called observational coordinates, introduced by George Temple in 1938 and developed into a research programme by George Ellis and collaborators from 1985.  A 2010 Physical Review D paper describes it this way:  the time coordinate w is "the proper time coordinate on an observer's world line (C), such that w = constant hypersurfaces are past light cones," and such coordinates "are therefore the natural framework on which electromagnetic radiation reaches an observer."⁷⁷

Nobody in that literature thinks this makes distant galaxies young.  They use it because observational data live on the past light cone, so a coordinate system adapted to it is convenient for reconstructing the metric from what telescopes actually see.  That is the whole point in miniature.  The ASC foliation is ordinary, legitimate, mainstream, and utterly without consequence for the age of anything, because ages are computed from the metric and not from the labels.

Verdict on this section

The conventionality of simultaneity is unsettled after fifty years.  ASC's particular value ε = 1 is outside the classical conventionalists' range, but three independent secular treatments put the past-light-cone relation back on the table.  Sarkar and Stachel, Ben-Yami and Besnard all reach it, and Giulini endorses the key premise.  Anyone arguing against ASC on the ground that it is not real physics is arguing against the wrong thing.

What Lisle actually proposed

Jason Lisle has a PhD in astrophysics from the University of Colorado.  He first published the proposal in 2001 in the Journal of Creation, under the pseudonym "Robert Newton,"¹⁷ and set it out at full length in the Answers Research Journal in 2010.¹

He draws a distinction that most summaries of him drop, and dropping it misrepresents him in one direction or the other.  There are two things, and only one of them is testable:

"The anisotropic synchrony convention is just that—a convention.  It is not a scientific model;  it does not make testable predictions.  It is a convention of measurement and cannot be falsified any more than the metric system can be falsified."¹

"To be clear, the ASC convention does not make testable predictions and cannot be falsified.  However, the ASC model goes beyond the mere convention and does make testable claims and is therefore falsifiable.  The essential claim of the ASC model is that the Bible uses the ASC convention."¹

Quoting either half alone gets him wrong.  Quote only the first and he looks like he is hiding behind unfalsifiability.  Quote only the second and he looks like he is claiming an empirical result.  He is doing neither.

The ASC model adds three stipulations to the bare convention.  Gravitational time dilation across the visible universe is negligible.  The stars were made on Day Four.  And the mainstream distance scale is correct, which is the stipulation most often missed:

"I will further stipulate that the consensus understanding of galactic distances, redshifts, and universal expansion is basically correct, having been established by good scientific procedures which are verifiable in the present."¹

ASC does not shrink the universe.  It does not move galaxies closer.  It does not question parallax, Cepheids, type Ia supernovae or the cosmic distance ladder.  Popular retellings that say otherwise are not describing Lisle's proposal.  The same holds for the Doppler model of galaxy redshifts, which is a separate and much more contestable proposal of his;  Lisle himself says the two are independent, because "the ASC model doesn't assume any particular metric."⁸

With those stipulations in place, the model says the universe looks about six thousand years old everywhere:

"Since the ASC model has the stars being made on the fourth day of the Creation Week, and since light travel-time is zero under the selected synchrony convention, and since we have supposed that gravitational time dilation is negligible, it follows that the universe appears at all distances as it is now, having aged an equal amount everywhere.  Therefore, when we look at any region of the universe, we are seeing it at an age of roughly 6,000 years."¹

Note what that entails, because it is counter-intuitive and it matters later:  under ASC, distant galaxies are not old.  They are young, in fact marginally younger than the Earth, because expansion produces a real cosmological time dilation.  Lisle puts it in a footnote:  "The universe will appear slightly less than 6,000 years old at extreme distance due to differential aging."¹  This is the opposite of Humphreys' white hole cosmology, which is a young-Earth old-universe model.  The two most prominent young-earth astronomers of the last thirty years contradict each other on this, and popular material routinely cites both.

The line between a coordinate and a physical claim

Before going further, one distinction has to be nailed down, because getting it wrong produces a version of ASC that really is refuted.

Andrew Repp, surveying fifty-seven years of creationist astronomy in the Creation Research Society Quarterly, draws it:

"Careful treatments of ASC present it as a redefinition of time coordinates … Other treatments seem to suggest an actual physical anisotropy in the propagation of light (i.e., that the 'one-way speed of light' toward Earth is infinite)—which would seem conclusively ruled out by electromagnetic theory."¹⁸¹⁸

His footnote gives the reason, and it is a good one:  "a physically infinite c in one direction would require a zero ε₀μ₀ in that direction, making either Coulomb's Law or Ampere's Law wildly anisotropic as well.  A mere coordinate redefinition—Newton's original proposal—would not suffer from this problem."¹⁸

If light really did propagate infinitely fast toward the Earth as a matter of physics, the vacuum's electric and magnetic constants would have to be direction-dependent, and that would show up in laboratory electromagnetism at once.  It does not.

Lisle is on the right side of Repp's line and says so repeatedly.  Replying in 2020 to a critic who called ASC a hypothesis:

"He refers to the one-way speed of light being infinite toward an observer as my hypothesis.  In reality, it is neither mine, nor is it a hypothesis.  It is a synchrony convention, one that has been used throughout history. … Peter is trying to refute a convention, a bit like arguing that the metric system has been empirically falsified.  But since conventions are defined, they cannot be falsified."¹⁰

And in 2010:  "Synchrony conventions are stipulated.  They are not a property of the universe that can be investigated."¹

Popular presentations, including some by creationists who think they are defending Lisle, say "light really does travel infinitely fast toward us."  That is the version Repp says electromagnetism rules out, and it is not what Lisle claims.

What ASC buys: nothing that a telescope can see

Now the accounting.  The same feature that makes ASC unfalsifiable makes it uninformative, and this is not a hostile framing.  It is Lisle's own.

Statement one, 2010:  ASC "cannot be falsified any more than the metric system can be falsified."¹

Statement two, 2025, in a paper defending his separate Doppler model against Luke Barnes:

"Indeed, the difference between ESC and ASC is one of coordinates, leaving the underlying geometry and measurable observations unaffected."⁸

That sentence is the whole matter.  A coordinate transformation is a relabelling of points.  It cannot change the value of an invariant, and every observation is an invariant:  a photon count in a detector, a spectral line's wavelength, an interval of proper time on a laboratory clock, the reading a telescope records.  If two descriptions differ only by coordinates, no measurement distinguishes them — in either direction.

Two consequences follow, and the young-earth reader should sit with both.

ASC cannot be refuted by an observation.  Any observational objection to ASC is answerable in principle before it is stated, because the objector is computing an invariant and the invariant is unchanged.  In practice the answers are not even hard.

ASC cannot be confirmed by an observation either.  No telescope will ever return data that favour ASC over ESC.  Nothing in astronomy is evidence for it.  It is not that kind of claim.

Two objections that fail, and should stop being made

"Relativity says light travels at c, so ASC contradicts relativity."  It does not.  Relativity fixes the round-trip speed.  Lisle answers the sharpest version of this objection, comparing round-trip times along perpendicular paths, directly:

"Peter proposes comparing the round-trip speed of light in two orthogonal directions, and showing it to be the same.  But ASC requires the round-trip speed of light to be the same in all directions.  Only the one-way speed is stipulated to be non-isotropic.  So the fact that light takes the same time to travel a round trip A to B to A in the north-south direction as it takes to travel a round trip C to D to C in the east-west direction is a prediction of both ASC and ESC."¹⁰

He is right.  This is the most common objection to ASC and it is worthless.

"The SN 1987A light echo disproves instantaneous inbound light."  This one looks decisive and is not.  A supernova exploded in the Large Magellanic Cloud on 23 February 1987.  A ring of gas around it, ejected long before, began to fluoresce about three months later and peaked at about thirteen months, because light going sideways from the star to the ring and then on to Earth travels a longer path than light coming straight here.  If inbound light is instantaneous, why the delay?

Because under ASC the light that lit the ring was not inbound.  It left the star heading away from Earth, toward the far side of the ring, and light aimed away from the observer travels at c/2.  Lisle works the geometry through and gets the observed answer:

"The equation shows that the closer the light is to being directly aimed at the observer, the faster it will be. … If you use the actual angles (which are quite small), you will find that ASC predicts that the light along AE will reach point E one year after the light moving along AB reaches point B. … Hence, the observations of the light from the supernova seen in 2014 and 2015 is exactly what ASC predicts."¹⁰

That is correct, and it has to be, because the delay is an invariant.  The general rule is worth stating once so that no reader needs to check the next objection individually:  if an argument against ASC bottoms out in something a detector measures, the argument fails before it starts.  Any objection with a chance of working has to attack the convention itself, or the exegesis, or the things the convention does not touch.

The last of those is where the real problem is.

What ASC does not buy: proper time

This is the heart of the article, and it is a point of arithmetic rather than opinion.

A synchrony convention assigns time labels to distant events.  It does not touch proper time.

Proper time is the time actually elapsed along an object's own history, the reading of a clock carried by that object.  It is computed from the spacetime metric along the object's worldline, and it is an invariant:  every coordinate system in the universe returns the same number.  That is not a claim about ASC in particular.  It is the reason relativity is a theory about geometry rather than about coordinates, and Lisle states it himself in his own textbook:  the spacetime interval "is the 'real' absolute quantity."¹⁹

So consider a star.  How long has it been burning hydrogen?  That is a question about proper time along the star's worldline.  Change the synchrony convention and the answer does not move by one second.  ASC changes what time you label the star's present state with.  It does not change how much history that state records.

Three consequences, in increasing order of severity.

Nothing local changes at all

Every age measurement that does not involve a long light path is untouched:  radiometric ages of terrestrial rocks and meteorites, counted ice-core and varve layers, the helioseismic age of the Sun.  Light from the Sun takes eight minutes to arrive.  ASC makes that eight minutes zero.  It changes nothing else about the Sun.

This is worth saying because "distant starlight" is the argument everybody has heard of, and it is not where the weight of the age evidence sits.  Winning it entirely leaves radiometric dating and the age of the solar system exactly where they were.

Objects a few thousand light years away are barely affected

For anything inside our own Galaxy the ASC/ESC difference is at most a few tens of thousands of years.  The ages in dispute are millions to billions.  The difference is negligible against the quantity being measured.

Two examples make the point without leaving the Milky Way.

Globular cluster 47 Tucanae.  Hansen and colleagues determined its age in Nature in 2013 by fitting the cooling sequence of its white dwarfs, dead stellar cores that radiate away stored heat on a well-understood schedule.  Their result:  "an absolute age of 9.9 ± 0.7 Gyr at 95% confidence," about 2 billion years younger than NGC 6397 measured the same way.²⁰²⁰  The cluster's distance modulus in the same paper is µ₀ = 13.32 ± 0.09,²⁰ which puts it about 15,000 light years away.  ASC can move that age by at most 15,000 years out of 9.9 billion — a correction of one part in 660,000.

Supernova remnants.  Here the cleanest source is a young-earth publication.  Danny Faulkner, the staff astronomer at Answers in Genesis, published a paper in 2017 titled "Are Old Supernova Remnants Really Missing?"  His abstract:

"reexamination of the data shows that there indeed are old supernova remnants, and that stage three supernova remnants have been identified.  Therefore, this may not be a good argument for recent origin, and I discourage recent creationists from using it."⁹

His table lists seventeen Galactic remnants with ages above 7,000 years.  "Five of the SNR ages are at least a million years;  the greatest is 4.5 million years," and he adds:  "It would be difficult to reduce any of these age estimates so that they to be compatible with Davies' criterion of 7000 years."⁹  These objects are a few thousand light years away.  No synchrony convention and no cosmological metric touches them.

The distant universe still has to be explained

This is the serious one.

Under ASC every visible object has aged about six thousand years in its own proper time.  That is Lisle's own figure.  But the objects do not look six thousand years old.  They show the specific signatures a long history produces:

• Main-sequence turnoffs. In a cluster of stars all born together, the massive ones burn out first. Where the turnoff falls on the colour-magnitude diagram is a clock, and for globular clusters it reads billions of years. Chaboyer and colleagues put the mean age of the oldest clusters at 11.5 ± 1.3 Gyr from turnoff fitting with Hipparcos distances.²¹²¹
• White dwarf cooling sequences. An entirely independent clock, based on heat loss rather than nuclear burning, and it agrees: 9.9 Gyr for 47 Tuc, about 12 for NGC 6397.²⁰
• Galaxy mergers caught in progress. Tidal tails, disturbed discs and double nuclei are configurations that take hundreds of millions of years to develop and disperse.
• The elements. Iron and the heavier metals are made in stars. Their abundance in any object is a record of how many generations of stars preceded it.

None of this is a light travel time problem.  Every one of these is a statement about the state of an object as we see it, and ASC does not change the state of anything.

Lisle accepts this and answers it, and the answer should be quoted rather than paraphrased.  A critic put to him that distant galaxies do not look like nearby ones, which is what an old universe predicts.  His reply:

"Peter has also made the unfounded assumption that any difference between nearby galaxies and distant galaxies is due to differential aging.  But how could anyone possibly know this?  Perhaps God created galaxies with systematic differences depending on their distance from our local group.  Not every sequence is a time-sequence."¹⁰

That is an honest answer.  It is also the moment the model stops predicting anything.  If an observed trend with distance can be absorbed as a created initial condition, the trend cannot test the model.

The upshot: ASC converts one problem into another

Put the pieces together.

ASC removes the look-back-time interpretation of distant light.  It does not remove the appearance of age.  Under ASC, a globular cluster whose colour-magnitude diagram records eleven billion years of stellar evolution has to have been created eleven billion years into that evolution, six thousand years ago.  A supernova remnant with a 4.5-million-year expansion age has to have been created part-way expanded.

SN 1987A needs care here, because the obvious version of the objection is wrong.  Under ASC the explosion happened in 1987 by our clocks, so the titanium-44 decaying in the remnant is genuinely thirty-eight years old and was not created part-decayed.  The problem is the ring.  It is 0.67 light years in radius and expanding at 10 kilometres per second, which puts its ejection about 20,000 years before the explosion — around 18,000 BC on ASC's own reckoning, roughly three times further back than Day Four.  Both inputs are measurements rather than model outputs, and the arithmetic is worked in the SN 1987A article.

That is precisely the position "light created in transit" was in, and it is the position Faulkner rejected as deceptive.  Faulkner's objection to created light is that it implies a record of events that never happened:

"However, if the light of these stars were created in transit so that the light never left the stars, then we would see evidence of events (eclipses, for example) that would have never happened.  This is deceptive."¹¹¹¹

ASC is better than created light in one important respect and no others.  Under ASC the events did happen.  The supernova really exploded;  the light really left the star.  Faulkner draws exactly this distinction when defending his own proposal:  the difference from mature creation is that "all of the processes that we see playing out, such as SN 1987A, actually happened."¹¹  So ASC does not make the universe an illusion.

But it still requires that the state of every distant object was created already carrying a history it did not live.  A star created at the main-sequence turnoff has a helium core it never fused.  That is the appearance-of-age problem, unchanged, relocated from the light beam to the object.

This is the single most important thing in this article.  Distant starlight is the famous argument.  It is not the load-bearing one.  Even a complete victory on ASC leaves the entire age case standing, and hands it over to a doctrine of mature creation that young-earth astronomy's own leading practitioner has publicly criticised.

The internal creationist dispute: Phillip Dennis

The most sustained published criticism of ASC comes from a young-earth creationist, in a young-earth journal, and it deserves its own treatment because it is technical, because it is partly right, and because it has been reported badly by both sides.

Phillip Dennis is an independent researcher with a background in relativity who published his own general-relativistic young-earth cosmology at the 2018 International Conference on Creationism.²²  He states his position at the top of his second paper:  "I am a young earth creationist who is thoroughly committed to a literal seven days of an actual Creation Week."²³²³  This is not an outside attack.

His argument

Dennis's 2024 paper is titled "An Internal Contradiction of Lisle's Anisotropic Synchrony Convention (ASC) Model."  The abstract:

"The ASC model explicitly assumes the mathematical structure of Minkowski space and the foundations of special relativity (SR).  Minkowski space presupposes an isotropic physical speed of light.  The assumption of Minkowski space, as correctly embraced by Lisle, is incompatible with the conclusions of ASC which purports that the incoming speed of light can be made arbitrarily large."¹²

The derivation is short.  Take the spacetime interval,

s² = Δx² + Δy² + Δz² − c²Δt²

set it to zero for a light ray (light always has a null interval), and solve.  For an outgoing ray you get Δx = cΔt;  for an incoming ray you get Δx = −cΔt.  Both directions give c.  Since the interval is invariant, so is the result.  Dennis concludes that "the purported speed of light is not a physical speed.  The anisotropic speed of ASC is a coordinate rate not a physical speed and the word speed in ASC is used in an equivocation."¹²

He also turns Lisle's own textbook against him.  In The Physics of Einstein Lisle writes that observers "will always agree on the spacetime interval between any two events. … The spacetime interval is the 'real' absolute quantity," and that "Relativity does have absolutes, such as the speed of light in vacuum and the spacetime interval.  These are invariant absolute quantities."¹⁹

Where the argument fails

Dennis's central derivation is circular, and Lisle identifies the circle correctly.

The equation s² = Δx² + Δy² + Δz² − c²Δt² is not the general form of the spacetime interval.  It is the form the interval takes when ε = ½.  Written without assuming a synchrony convention — the form John Winnie derived in 1970 when he reformulated special relativity for arbitrary ε — it carries two extra terms:

s² = Δx² + Δy² + Δz² − c²Δt² − (2ε−1)²Δx² + 2c(2ε−1)ΔxΔt

Set ε = ½ and the extra terms vanish, giving Dennis's equation.  Set ε = 1 and it becomes

s² = Δy² + Δz² − c²Δt² + 2cΔxΔt

which is the ASC form.  Lisle's reply, published 13 July 2024:

"That is, he assumed that ε = ½ in his attempt to prove that ε = ½.  This is the logical fallacy of a petitio (begging the question)."¹³¹³

That criticism is correct.  Dennis starts from a diagonal metric, which encodes isotropic one-way light propagation, and concludes that light propagation is isotropic.  Nothing else was going to come out.  Lisle then does the calculation Dennis omitted, plugging the ASC speed law v = c/(1 − cos θ) into the general interval, and shows that it too gives a null interval for light.¹³  The two conventions are equally consistent.

Dennis's second technical result is the one that has been quoted most and understood least.  In his Appendix A he computes the distance R′ to a reflection event measured along the ASC surface of simultaneity, and gets

R′ = 2√(ε(1−ε)) R

so that at ε = 1, R′ = 0.¹²  His Appendix B gets the same result as a metric:  restricting the Minkowski line element to a constant-ASC-time surface gives ds² = 4ε(1−ε)(dr² + r²dΩ²), whose prefactor vanishes at ε = 1.¹²

Lisle answers that Dennis has confused the spacetime interval with spatial distance, that under ASC the radial distance dρ simply equals dr, and that "the spatial geometry of ASC is perfectly Euclidean."¹³  He notes that Dennis's formula would make "all distances in ASC … zero," which he calls absurd.¹³

Both men are computing real things, and they are computing different things.  Dennis is computing the induced metric on the simultaneity hypersurface, which is what "the geometry of space at an instant" standardly means.  At ε = 1 that surface is a null cone, its induced metric is degenerate, and its radial proper length really is zero.  That is not a mistake;  it is what a null hypersurface is.  Lisle is using the ordinary radial coordinate r, which the ASC transformation leaves untouched because it only alters t.  That is also correct.

The disagreement is about which object deserves the name "distance," and neither party has persuaded the other.  But the consequence Dennis draws survives:  under ASC you cannot lay measuring rods along a surface of constant time, so the question "how far away is that galaxy right now" has no invariant answer.  ASC therefore cannot support any claim about the present size or state of the universe — in either direction.

Where Dennis is right, and it is the part that matters

Strip the failed proof away and read his conclusion:

"The ASC convention is merely a coordinate transform that cannot alter physical quantities.  The conclusion is that ASC does not alter the invariant speed of light or the time that it takes light to reach the earth and therefore does not solve the LTTP."¹²

The first sentence is true, and Lisle agrees with it.  That is what "one of coordinates, leaving the underlying geometry and measurable observations unaffected" means.⁸  The disagreement is entirely in the second sentence, and it is not a disagreement about relativity.  It is a disagreement about what the light travel time problem is.

• If the problem is "how did the photons physically get here in six thousand years," a coordinate change cannot solve it, and Dennis is right.
• If the problem is "what do Genesis's time words mean when applied to distant events," a coordinate change is exactly the right shape of answer, and Lisle is right.

Lisle takes the second view explicitly:  the starlight problem "was not so much a physics problem, but an error of exegesis."¹  So the whole dispute reduces to the exegetical question, which is treated below.

Dennis's other objections, graded

His second paper is a 30-page reply to Lisle's reply.²³  Three of its arguments are worth grading, because two of them fail in instructive ways and the third is the strongest objection to ASC in the literature.

The femtosecond photography argument fails.  Dennis analysed published Caltech "light-in-flight" movies, which photograph a picosecond light pulse travelling through water, and fitted the centroid position against frame time to get c = 2.264 × 10⁸ m/s — the speed of light in water.  He concludes:  "Thus, the Caltech experiment empirically establishes the isotropy of the one-way speed-of-light."²³

It does not, and Dennis's own paper contains the reason.  Two paragraphs later he notes that ASC "logically requires that the transverse speed of light is exactly c in every transverse direction."²³  That is right — v = c/(1 − cos 90°) = c.  A light-in-flight camera images a pulse crossing its field of view sideways, and the scattered light it records travels straight toward the camera.  Both legs are cases where ASC and ESC give identical answers.  Rotating the apparatus does not help, because ASC's anisotropy is measured from the line of sight to the observer, not from a compass direction;  every orientation that keeps the track in frame keeps it transverse.  To test ASC you would have to fire the pulse directly at or directly away from the camera, and then there is no track to photograph.

This is exactly the failure mode the Stanford Encyclopedia warns about:  "editors of respected journals continue to accept, from time to time, papers purporting to measure one-way light speeds. … Application of the procedure just described shows where their errors lie."⁴

The slow-clock-transport argument fails, but the failure is contested and Dennis declined to argue it.  Dennis points to NASA deep-space missions.  New Horizons' onboard clock lost less than half a second of proper time on a 9.5-year flight to Pluto, so it is a slowly transported clock;  compare its mission-elapsed time against ground UTC when telemetry arrives and you recover a one-way light travel time of hours.²³

This is a real and old argument, raised by Eddington in 1924, and the reply is equally old.  Converting the spacecraft's proper time into an Earth time requires assuming that a slowly transported clock stays synchronised, and that assumption is a synchrony convention.  John Winnie proved the point within his ε-formulation, and the Stanford Encyclopedia devotes a whole supplement to the hundred-year argument:⁴  "it is not possible that the method of slow-transport, or any other synchrony method, could, within the framework of the nonconventional ingredients of the Special Theory, result in fixing any particular value of ε to the exclusion of any other particular values."⁴  Redhead put it more bluntly:  "There is no absolute factual sense in the term 'slow.'"⁴

Dennis writes:  "Undeniably, there has been controversy regarding the slow clock transport method of synchronizing clocks.  I am not going to enter that controversy at this point because it is not essential."²³  It is essential.  It is the whole question.

There is nonetheless a residue worth noting on Lisle's side of the ledger.  Under ASC a slowly transported ideal clock does not keep ASC coordinate time;  it drifts from it by exactly the one-way light travel distance over c.  That is a coordinate artefact rather than a physical effect, but it means ASC has the unusual property that no physical clock, however carefully carried, ever reads the coordinate.

The general-relativity argument is the strong one.  Dennis's last section is titled "General Relativity and the Overthrow of Conventional Simultaneity," and its point is that the conventionality thesis is a special-relativity result about empty Minkowski spacetime, while the actual universe is described by a Friedmann–Lemaître–Robertson–Walker solution which has a preferred foliation:

"This is the global absolute cosmic time.  Each value of t specifies a 3D space of simultaneous events.  Thus, this solution has a global time and is a GR counterexample to the conventionalist's claim that there is no such thing as global time or a metaphysical present."²³

He is right that FLRW spacetimes have a distinguished foliation, singled out by the matter:  comoving observers all measure the same elapsed cosmic time, and the cosmic microwave background picks out the rest frame observationally.  His conclusion overreaches, though, for three reasons.  He writes:  "special relativity is not relevant to the Creation on the whole, so Lisle's ASC solution is irrelevant."²³

1. Distinguished is not obligatory. Cosmic time is the simplest and most useful slicing of an FLRW spacetime. It is not the only admissible one, and cosmologists use others. Observational coordinates, whose constant-time surfaces are past light cones, are a working tool in relativistic cosmology.⁷ Choosing cosmic time is itself a choice.
2. Dennis's own model has the same feature and needs its own stipulation anyway. His 2018 cosmology is built by cutting a hyperboloidal initial surface out of a closed FLRW spacetime, and the surface is chosen by fiat because it "supports a young earth."²²²² If a distinguished cosmic foliation settled matters, he would not need to select a different one.
3. The argument cuts against ASC's application to cosmology, not against the convention. That is a narrower and more defensible claim than the one he makes, and it is a fair criticism: Lisle develops ASC in flat spacetime and then applies it to an expanding universe, and the extension is asserted more than derived.

Overall grade on the exchange.  Dennis's headline claim of an internal contradiction is not established;  his proof begs the question and Lisle says so correctly.  His real contribution is the negative one that both men agree on — ASC is a coordinate transformation and coordinate transformations do not alter physical quantities.  His general-relativity objection is the best argument against ASC anywhere in print.  Lisle answered it on 22 May 2026, in part nine of his eleven-part reply series, by pointing out that changing the time slicing is routine in curved spacetime and citing his own peer-reviewed paper on the Gullstrand-Painlevé form of the Schwarzschild metric;  that answer is half good, because Schwarzschild is a vacuum solution with no matter to single out a foliation, which is exactly Dennis's point about FLRW.  Coordinate Cosmologies:  Dennis and Tenev grades the later instalments.  And by his second paper the exchange has largely left physics for the metaphysics of time, with Dennis arguing that Lisle's position commits him to a block universe and that this is "a serious heresy."²³  Two young-earth creationists calling each other's physics incompetent and each other's metaphysics unbiblical, across four publications, is what a field looks like when a proposal has never been examined by anyone outside it.  Faulkner noticed the same thing:  ASC, he wrote, has not received "more attention, particularly of the negative type."²⁴²⁴

Does Genesis actually use ASC?

Everything now turns on this.  ASC as a convention is unfalsifiable and, by Lisle's own account, changes no observation.  The claim that carries all the weight is the one he identifies himself:  "The essential claim of the ASC model is that the Bible uses the ASC convention."¹

That claim is not a physics claim.  It is an exegetical claim, and it is where the proposal is weakest.  This section says so plainly, because saying otherwise would be exactly the kind of thing this project exists not to do.

Lisle's three arguments

First, Genesis 1:15.  Verses 14–15 give the purpose of the celestial lights, which is to be for signs, seasons, days and years, and "to give light upon the earth."  The verse ends "and it was so."  Lisle:

"Perhaps most significantly, Scripture itself seems to suggest that the creation of the stars was nearly simultaneous with their light reaching earth. … Verse 15 also states, 'and it was so' indicating that the stars immediately functioned in their God-ordained role:  to give light upon the earth.  This strongly implies that the Bible is using the anisotropic synchrony convention—the only convention in which all events are effectively simultaneous with their light reaching the observer."¹

Second, the ancient world had no alternative.

"As far as we know, ancient cultures did not know (1) the distance to any star (aside from perhaps the sun, and then only very roughly), nor (2) the speed of light (either in one direction, or the round trip speed).  Thus, it appears that all ancient cultures on earth implicitly used ASC.  The time when a celestial event is seen was considered to be simultaneous with the time in which the event happened."¹

He adds a nice observation:  modern astronomers use ASC implicitly too, when they name supernovae.  "A supernova (such as 1987A) is always named for the year in which its light reaches earth—the anisotropic synchrony convention."¹  And he appeals to the perspicuity of Scripture — the doctrine that the Bible is meant to be understood by all cultures in all periods — which "strongly suggests a synchrony convention that would be understood by all cultures at all times, rather than a synchrony convention that would only be used by academics in the twentieth and twenty-first centuries."¹

Third, the Einstein convention makes the creation week frame-dependent.  This is the argument that deserves more attention than it gets.

Einstein simultaneity depends on the observer's velocity.  Over cosmological distances a small velocity produces an enormous shift in what counts as simultaneous.  The Earth's orbital speed alone is about 30 km/s, one ten-thousandth of c;  applied across ten billion light years, that reorders "now" by about a million years.  So under ESC, the question "which distant events happened during the creation week" has a different answer in June than in December.  Lisle:

"Thus, events that are simultaneous in one velocity frame will be spread over millions of years in another.  Even the earth's annual orbit would cause the Creation Week to become millions of years long.  There is no hint of this in Scripture, thereby suggesting that the Bible does not use the Einstein convention."¹

That argument is sound as far as it goes, and critics of ASC should stop ignoring it.  Anyone insisting that Genesis must be read in Einstein synchrony owes an account of whose Einstein synchrony — which inertial frame — and the text gives none.

Where the case is weak

Three problems, in increasing order of seriousness.

"And it was so" is a refrain, not a timing statement.  The formula appears six times in Genesis 1 (vv. 7, 9, 11, 15, 24, 30).  It marks the fulfilment of a divine command.  It cannot carry a claim about instantaneity, because in verse 11 the same formula follows "Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit" — and a fruit tree yielding fruit is not instantaneous under any synchrony convention.  If "and it was so" means "immediately" in verse 15, it has to mean something looser in verse 11, and that is special pleading.  What the formula plainly asserts is that the command was carried out, not how long it took or how the timing should be labelled.

"They had no alternative" is an argument from silence, and it proves less than it appears to.  A culture that has never heard of light travel time does not thereby adopt a synchrony convention.  It has an unexamined assumption that seeing and happening coincide.  The difference matters enormously.  A convention cannot be mistaken;  an unexamined assumption can.  If the Hebrew author simply took it for granted that a star seen tonight is shining tonight, then Genesis is not using ASC — it is silent on a question nobody had asked.  And a text silent on the question does not solve the problem;  it merely fails to create it.

Lisle's own footnote concedes the substance of this:  "The ancient Hebrews may not have known about the earth's orbit around the sun, and it is very unlikely that they could have known how large the visible universe is.  So, they may not have perceived this as a potential problem."¹  A convention nobody knew they were adopting is a strange thing to call a convention.

A convention adopted because it resolves a modern difficulty needs a reason beyond the difficulty.  This is the deepest problem and it is a problem of method rather than of Hebrew.  ASC was not read out of Genesis and then found to have a convenient consequence.  The consequence came first — a young universe cannot see distant starlight — and the convention was proposed to meet it.  That is not disqualifying;  plenty of good ideas in science and theology arrive that way.  But it does raise the standard of evidence, and the evidence offered is a stock refrain, an argument from what the ancients did not know, and a real but negative point about the alternative.

The negative point is worth isolating, because it is the strongest thing here.  Lisle's third argument shows that Genesis cannot be committed to Einstein synchrony.  It does not show that Genesis is committed to ASC.  There are infinitely many conventions, and "the text does not specify one" remains on the table.

What follows if Genesis is silent

Suppose the honest reading is that Genesis addresses the timing of distant events not at all, that it says the lights were made and they lit the Earth, without contemplating a light travel time either way.

Then two things follow, and they point in opposite directions.

The critic loses the sharpest form of his objection.  He cannot say "Genesis asserts the stars were made 6,000 years ago in the sense of Einstein synchrony," because Genesis makes no such distinction.  Lisle's charge of a "semantic anachronism fallacy" — reading a modern meaning into an ancient term¹ — lands, and it lands whether or not ASC is right.

But the young-earth advocate loses his solution.  A text that is silent does not supply a convention;  it leaves the question open, and the physical problem is untouched:  how a universe six thousand years old in proper time contains objects whose states record billions of years.  As shown above, that problem was never really about the photons.

This article's judgement:  the exegetical case for ASC is possible but not established.  It rests on more weight than "and it was so" can bear, and on an inference from ancient ignorance that does not distinguish a convention from an assumption.  A reader who already holds a young earth on other grounds may reasonably find ASC an attractive way to describe the timing.  A reader deciding whether to hold a young earth should not treat it as evidence.

The objections to ASC, graded

The rest of this article's argument, in one table.  The prose answers follow.

Objections and responses

"ASC must be wrong because relativity says light travels at c."  Relativity says the round-trip speed of light in vacuum is c in every inertial frame and every direction.  It does not fix the one-way speed, which is what ASC changes.  Lisle answers the strongest version of this — comparing round trips along perpendicular paths — and notes that equal round-trip times are "a prediction of both ASC and ESC."¹⁰  Retire this objection.

"Malament refuted the conventionality thesis in 1977, so ASC is simply wrong."  Overstated.  Malament's theorem is real and serious, and it needs an extra assumption, invariance under time reflection, that Sarkar and Stachel argued has no physical warrant and that Giulini, who is otherwise critical of them, agrees has none.⁵¹⁶  Without it, the past light cone is admissible.  The Stanford Encyclopedia presents the whole dispute as live, with Grünbaum's rebuttal published in 2010.⁴

"The SN 1987A light echo disproves instantaneous inbound light."  It does not.  The light that lit the circumstellar ring travelled away from Earth first, so it is slow under ASC, and the observed delay comes out right.¹⁰  More generally, a coordinate change cannot alter an invariant, and every observation is an invariant.

"Somebody has measured the one-way speed of light.  See the light-in-flight photography."  No.  Light-in-flight cameras image a pulse crossing the field of view sideways, and ASC gives exactly c for transverse propagation.  Rotating the apparatus does not test anything, because ASC's anisotropy is defined relative to the line of sight to the observer.  The Stanford Encyclopedia notes that papers claiming one-way measurements keep appearing and keep containing a hidden synchrony assumption.⁴

"Slowly transported atomic clocks settle it."  This is a real argument with a hundred-year history, and the reply is equally old:  calling a transport "slow" and equating the transported clock's reading with the stay-at-home clock's is itself a synchrony convention.  Winnie proved that no transport scheme can fix ε.⁴  Redhead:  "There is no absolute factual sense in the term 'slow.'"⁴

"ASC shrinks the universe, or makes distant galaxies nearby."  It does neither, and Lisle says so:  he stipulates that "the consensus understanding of galactic distances, redshifts, and universal expansion is basically correct."¹  ASC re-labels when, not where.

"ASC means distant galaxies are billions of years old, so it concedes the old universe."  The opposite.  Under ASC every visible object has aged about six thousand years, and slightly less than that at extreme redshift because of cosmological time dilation.¹  It is Humphreys' white hole cosmology that makes the distant universe old, not Lisle's.  The two models contradict each other on this and both are cited approvingly in popular creationist material.

"If ASC is unfalsifiable it is unscientific and can be dismissed."  Half right.  An unfalsifiable claim is not thereby false, and Lisle never presents the convention as a scientific result — he compares it to the metric system.  What follows is narrower and it is the point this article presses:  because it cannot be falsified by observation, it also cannot be supported by observation.  Nothing a telescope sees is evidence for it.  The same standard applies to the multiverse and this project applies it there too.

"Dennis proved ASC is self-contradictory."  He did not.  His derivation writes the spacetime interval in the form it takes only when ε = ½, then derives ε = ½.¹³  His conclusion that ASC "cannot alter physical quantities" is nevertheless correct, and Lisle agrees with it.¹²⁸

"Then ASC solves the distant starlight problem and the debate is over."  No.  It removes the look-back-time interpretation of distant light and nothing else.  Proper time is invariant, so every object we see still has to have the history its observed state records — main-sequence turnoffs, white dwarf cooling ages, expanded supernova remnants, merger morphologies.  ASC converts the distant starlight problem into the appearance-of-age problem.  That is a real change, but it is a change of address, not a solution.

"Aren't you just repeating what secular astronomers say about creationists?"  Check the sources.  The retirement of the missing-old-supernova-remnants argument is by the staff astronomer at Answers in Genesis, in an Answers in Genesis journal.⁹  The judgement that created light "is deceptive" is his too.¹¹  The technical critique of ASC is by a young-earth creationist in the same journal Lisle publishes in.¹²  The warning that popular ASC presentations state a version electromagnetism rules out is in the Creation Research Society Quarterly.¹⁸  And the defence of ASC's legitimacy in this article comes from Philosophy of Science, Foundations of Physics and the Stanford Encyclopedia, not from Answers in Genesis.

What would change this verdict

Three things, in ascending order of difficulty.

An exegetical argument that does not depend on "and it was so."  The strongest material in Lisle's case is his third argument, that Einstein synchrony makes the creation week frame-dependent, and it is stated in three sentences in a conclusion.  A serious treatment of how ancient Hebrew narrative handles the timing of remote events, by someone who works in that field rather than in astrophysics, would either strengthen the case considerably or close it.  Nothing of the kind exists.

An answer to Dennis's general-relativity objection.  ASC is developed in flat Minkowski spacetime and then applied to an expanding, matter-filled universe that has a distinguished cosmic-time foliation.  That extension is asserted rather than derived, and Dennis is right to press it.²³  The reply this article sketches is a start, not an answer:  cosmologists use past-light-cone foliations themselves.  Lisle's own 2026 reply adds a real counterexample, the Gullstrand-Painlevé slicing of the Schwarzschild geometry, but that spacetime contains no matter to pick a preferred foliation, so it does not reach Dennis's point.

A prediction that follows from ASC and from nothing else.  Lisle lists predictions of the ASC model:  ubiquitous hot blue stars, unwound spiral arms, evidence of youth in distant planetary systems.¹  Every one of them follows from the young-age stipulation, not from the synchrony convention, and he concedes as much for the solar-system cases:  "evidence of youth within our solar system does not confirm the ASC model over and above other creation models."¹  A created-light model or a miracle predicts the same list.  Until something follows from ε = 1 specifically, ASC is not doing observational work of any kind.

Closing

The anisotropic synchrony convention is the best answer young-earth astronomy has to distant starlight, and this article has tried to say why in the terms a skeptic will accept.

It is real physics.  The one-way speed of light has never been measured and cannot be, and Einstein said the equality of the two legs is a stipulation made "of my own freewill."²  He considered the ASC alternative in 1905 and rejected it for being observer-dependent, not for being false.³  Fifty years of philosophy of physics have not closed the conventionality question, and three independent secular treatments have put the past-light-cone relation back on the table after Malament's theorem seemed to remove it.  Cosmologists foliate spacetime by past light cones as a matter of routine.  Nobody arguing against ASC on grounds of physical legitimacy has a case.

It is also empty, and its author says so:  "the difference between ESC and ASC is one of coordinates, leaving the underlying geometry and measurable observations unaffected."⁸  No observation can refute it and none can support it.  Its one substantive claim — that Genesis uses this convention — rests on a refrain that appears six times in Genesis 1 marking fulfilment rather than timing, and on an inference from what ancient people did not know.

And what it leaves behind is the whole of the problem it was meant to solve.  Proper time is invariant.  A globular cluster fifteen thousand light years away, whose white dwarfs have been cooling for 9.9 ± 0.7 billion years by a measurement that has nothing to do with light travel time,²⁰ still has to be explained.  So do Faulkner's seventeen supernova remnants.⁹  Lisle's answer is that God may have created things that way — "not every sequence is a time-sequence"¹⁰ — which is the mature-creation answer, and Faulkner has said in print what he thinks of that.¹¹

So the fair summary is this.  ASC is not crankery, it has not been refuted, and the objections most often raised against it are worthless.  It also buys nothing, and the argument it is supposed to win was never the important one.  A reader who wants to know how old the universe is should look at the objects, not at the light.

Every source behind this article, with what it says and which way it cuts, is catalogued in a companion page:  the literature.

Sources