Here’s the thing. Lisle’s entire ASC discussion is a distraction. Despite a lot of iffy-sounding verbiage and weasel wording (which, I suspect, are more than a little intentional), Lisle advocates no departure from real physics. There is no trick; it’s just a lot of math. Just like you can transform Earth’s rotation into a fictitious vector field by coordinate transformation (which can simplify things like ballistic missile trajectories), you can perform transformations that define the speed of light as infinite relative to a given point in space.
When Lisle says “no one has ever proved an isotropic speed of light” he is obfuscating. When anisotropic synchrony is introduced, the speed of light IS a variable by virtue of the units being used. It’s like saying, “no one has ever proved that a tonne of feathers is lighter than a tonne of bricks.”
All the wool-pulling is just an excuse for Lisle to advance good old-fashioned progressive creationism. He believes God created the universe at least 45.6 billion years ago, starting at the edge of the observable cosmos and working his way in at the speed of light until reaching Earth 6,000 years ago. The trick is that Lisle claims this is still equivalent to young-earth creationism because it is possible to redefine time to make simultaneity staggered across the universe.
The problem, of course, is with another bit: gravity. The gravitational potential of all the galaxies in the universe would have arrived at our solar system 6,000 years ago and erupted in a massive gravitational tsunami, shredding everything as it moved spherically away from us.
All this talk of different speeds of light is confusing to me, because in the modern convention, we usually talk of the speed of light as constant (in fact, it defines the meter). Changes in the speed of light are then recast as changes in other fundamental constants such as fine structure constant (\alpha), which is more relevant for most experiments today. Can someone explain to me what effect do Lisle’s arguments have on \alpha? Could there be a change in what we expect to measure for \alpha if there are different conventions?
Sure, but my point is that these arguments with YECs about the speed of light changing or being different in the past (or in different directions) don’t interact much with actual experimental work on the ground which is relevant today. It sounds anachronistic. By convention, physicists no longer measure c, but \alpha and others.
They have no affects on α because his “arguments” are just obfuscation cleverly posturing as something novel.
When Lisle says “you cannot measure the one-way speed of light,” he is leaving out the key conditional: you cannot measure the one-way speed of light without specifying a synchrony convention. This is true, but not very useful; it is the same as saying that you cannot measure length without agreeing on a unit, and you cannot measure velocity without specifying a reference frame.
He is simply saying that a very old universe (a 43+ byo universe, actually) can simply be defined as a 6,000-year-old universe. Which…yeah, sure, whatever. If I get caught doing 20 mph over the speed limit, I can define a reference frame in which I was actually stationary, but it’s not going to get me out of the ticket.
What is constant is the two-way speed of light. We can measure the two-way speed of light and, in a vacuum, it is the constant c. It is impossible to measure the one-way speed of light because of difficulties involved in synchronizing distant clocks without first assuming the one-way speed of light. Since it can’t be directly measured, we are free to define it.
It must be stressed that the choice of standard synchrony, ASC or any other valid synchrony is that the choice has zero effect on the laws of physics or anything we can observe. If they did, they would cease to be conventions. As @gene pointed out, it’s just a matter of how we set clocks and isn’t much more significant than choosing a time zone. I tend to think the one-way speed of light is simply unknowable and most likely isotropic; however, that’s a matter of philosophy, not physics.
Lisle adds confusion to an idea that’s already fairly difficult to grasp by jumping up and down pointing out that we are free to synchronize our clocks in such a way as to choose a special frame (in his case, Earth) and “define” the one-way speed of light as essentially infinite “towards” that frame, at 1/2c directly away from it and somewhere in between for other angles. He’s right, we can do that, but that doesn’t give us a young universe any more than I can make myself younger by defining a “year” as 730 Earth rotations and then declaring that my age is half what it is in standard 365 day years.
I agree with your overall point, but the difficulty in measuring the one-way speed of light is more significant than choosing a unit of measure. As I understand it, it is impossible even in principle, to measure the one-way speed of light. A synchrony convention is not analogous to a unit of measure because a synchrony convention actually defines the one-way speed of light, which is the very thing we’re trying to measure. The “without specifying a synchrony convention” qualifier might be helpful to the uninitiated (which, admittedly, is probably most of his target audience), but I don’t think it’s required for the statement to be accurate.
By definition, a “convention” has no content about reality (except to say that we can’t define a single absolute “fact” for the issue at question). Whether I synchronize my clock to GMT or US Central Time is a convention. I can synchronize to either time or easily convert between the two. I can switch back and forth without time travel or adjusting my age. The only thing I change is how I describe the timing of events and, as long as I record the convention I used, fans of other conventions can easily convert to their own favorite without any distortion of information. If something that is deemed conventional ends up describing something real and verifiable, it ceases to be convention.
The thread consensus (if I understand @PdotdQ, @r_speir, @gene, etc. correctly - please clarify if I’m wrong) seems to be that synchrony conventions are valid science (if a convention can be “science”), but that Lisle’s conclusions don’t follow from that premise. Einstein himself clearly stated and even emphasized in his 1905 paper on Special Relativity that he had to define the one-way speed of light as isotropic since it could not be proven. I’ve read extensively on the subject recently and, as far as I can tell, only Lisle has managed to draw any conclusions about the Universe from it (apart from one Philosophy of Physics paper I read where the author argued that the conventionality of such fundamental values is a result of trying to describe things that are only absolute in a 4D Minkowski Space in terms of a 3D space and, therefore, the 4D space is what’s real, not the 3D space, but I digress).
Having said that, in the research I’ve done so far, I’ve gone through several stages of “wrong thinking” about this topic and, while realizing the error of each one has lead (I hope) to clearer subsequent thinking, I could still be missing something.
In dealing with certain aspects of relativity, like inertial reference frames, it is accurate to say that there is no preferred reference frame for the universe. There is no aether, no “true” zero velocity. Every inertial reference frame is equally valid; if you are in a spaceship passing me at 0.5c, then you can define a reference frame such that you are actually at rest and I am actually passing you at 0.5c.
But there is a difference between inertial and non-inertial reference frames. A non-inertial reference frame defines “zero velocity” within a rotating or accelerating system. The most common example of this would be centrifugal force: the apparent force pushing you to the edge of a rotating body (like a car navigating a turn). Another example would be the Coriolis force, which causes hurricanes to rotate and deflects ballistic missiles launched between different latitudes. Non-inertial reference frames can be extremely useful (for example, you can define a pool table as being “at rest” on a rotating spherical Earth and therefore derive the fictitious forces that would alter the path of the cue), but they are not “real” in any meaningful sense. They are a knowing and deliberate departure from inertial reference frames, used to simplify an n-body problem and achieve a particular outcome.
Forces in inertial reference frames are real; forces in non-inertial reference frames can be real or fictitious.
Synchrony conventions are like reference frames: they are ways of measuring reality. They are mathematical tools to help simplify equations. An anisotropic synchrony convention, like a non-inertial reference frame, can be a useful tool for solving certain problems. For example, astronomers use a de facto anisotropic synchrony convention in nomenclature for supernovae, identifying their age and evolution based on the date their light reached Earth (1987A, etc.) rather than the YBP when they actually exploded.
But, like a non-inertial reference frame, an anisotropic synchrony convention is a deliberate departure from the most accurate modeling of reality, used to simplify the math. They produce fictitious results. Lisle is not incorrect in stating that they are “only a convention” but I do believe he misleads, to some degree, by implying that an anisotropic synchrony convention is just as representative of reality as an isotropic one.
His “model” is that the Bible is using an anisotropic synchrony convention and creation on the “4th day” is given within an anisotropic nomenclature.
There is a very good reason to choose an isotropic convention, although one which would likely escape Lisle. If you’ll recall…our whole universe was in a hot, dense state, then nearly 14 billion years ago, expansion started. We know from the CMB that there was contact between all parts of the observable universe during the pre-inflationary epoch. This means that we started at a point in which all parts of the universe had essentially the same location, making an anisotropic convention impossible. We define comoving time relative to the Big Bang because that is how we started.
Correct me if I misunderstand, but it sounds like you’re saying that, even though it’s impossible to directly measure the one-way speed of light, we can show by observation that it must be isotropic. You mention one way that this can be shown and, I think, the fact that gravity moves at the same speed as light (and we can accurately measure distant effects of gravity) might be another way. If that is correct, could you refer to any papers (or even a Wikipedia page) discussing this idea? I ask for my own clarification more than to challenge your claim.
I’m eager to understand this topic as accurately as I can, and I’m beginning to grow inclined that I’m still missing something, but I seem to be reaching the limits of what I can glean by googling (I’ve read the Wikipedia pages and nearly every approachable paper I can find, such as https://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/significance_conv_sim/index.html). The closest I’ve found to a paper showing that the one-way speed of light must be isotropic is Malement’s Theorem, but his theorem itself seems to be in dispute.
I also realize that the Conventionality Thesis is by no means universally accepted among physicists, but it’s popularity seems to be larger than I would expect (among non-YEC) for something that has been shown to be useful, but inaccurate, unless I’m misunderstanding CT itself, which is also possible.
Let me first clarify: I believe the thread consensus is in favor of the Conventionality Thesis, not Lisle’s application of it. I, and I believe, all of the authors I quote below believe that the one-way speed of light is actually isotropic, but it cannot be proven through direct measurement (though other observations, such as the CMB or effects of distant gravity may give indirect evidence for it) and that special relativity demands that the laws of physics hold for any convention we choose (and, likewise, we cannot choose a convention that would violate the laws of physics). These are some quotes that I see leading to my conclusion of thread consensus in support of the conventionality of simultaneity (Conventionality Thesis), emphasis mine and I welcome any of the quoted authors to correct me if I misunderstand them (I think @David_MacMillan may hold that the speed of light is conventional for some math, but not for reality):
Btw, this is off-topic, but I’ve been meaning to say it: Thank you for creating this site and forum, I’m really enjoying this opportunity to explore and refine these questions of science and if/how they relate to our faith.
I support the conventionality thesis only because I have to for the time being, not because I believe it. I am quite confident that when we finally do measure the one-way speed of light – or, indirectly measure it to within an arguable degree of certainty – that Einstein’s choice of isotropy will be the overwhelming win.
I like that you are studying timing conventions and Lisle’s ASC in specific. However, as you progress, you will find that you will not beat Lisle with any argument, probably not even the appeal to gravity. Then, at some point, it will dawn on you that Lisle completely misused and misapplied an anisotropic propagation of light. It will be an aha moment. At that point you will understand that it is precisely the Conventionality Thesis which he has violated and which overthrows his entire argument.
Lisle’s ASC is not even a player in a serious discussion of timing conventions.
I agree, though I’m inclined to think it will be overthrown via indirect rather than direct measure. I think it would require the discovery of some instantaneous communication (in theory, the speed of gravitational effect would have sufficed if it had been instantaneous) to directly measure the one-way speed, but in that case, overthrowing the CT would the be the least interesting thing about it.
Thank you. I realize there’s no beating Lisle. One of his main arguments against old universe views is that we essentially can’t guess anything about the pre-historic past based on anything in the present (he argues “You’re assuming uniformity!”). If the speed of gravitational effect and the fact that we can easily detect the effects of gravity from distant objects on even more distant objects (at differences > 3000 light years) were pointed out to him, he would just argue about uniformity. Or he might argue that the gravitational effects are actually instantaneous in all directions and it coincidentally matched the anisotropic infinite speed of light towards Earth.
It’s worth noting that there is some ambiguity in how directions are defined for synchrony conventions. In a rectangular coordinate system ε = 1 has light travelling in a positive x direction at c/2 towards the observer. In a spherical system setting ε = 1 means that light moving away from the observer travels at c/2. Since Reichenbach uses the former, ε = 0 in the above for Lisle’s ASC.
Let’s try to quantify this by revisiting the supernova example. We’ll have a mirror on earth and t2 gives the time that light from the explosion reaches it (we “see the light”, so to speak). For simplicity we’ll set t1 (when the explosion occurs) = 0 and t3 (the time that the reflected light returns to the source) = 2 * 168000 = 336,000 years. As you noted, t3-t1 is the roundtrip time and will be the same in all conventions. Of course, t2 varies depending on which convention is used:
When ε = 0, t2 = 0 + (0 * 336000) = 0 years (ASC)
When ε = 0.5, t2 = 0 + (0.5 * 336000) = 168000 years (ESC)
When ε = 1, t2 = 0 + (1 * 336000) = 336000 years
Now let’s say the light source is 14 billion light years away. We get:
When ε = 0, t2 = 0 years
When ε = 0.5, t2 = 14by
When ε = 1, t2 = 28by
And all these values are correct, depending on the convention you choose.
The conventionality thesis states that we are free to choose a value of ε in order to have a definition of whether two clocks separated by a distance are synchronised (relative to a given observer). Whilst ε = 1/2 is convenient for a number of reasons (not least because it often makes the math simpler), it’s no more “correct” than the other values used above.
You have provided formulae that are pertinent to this discussion but you have not demonstrated why they invalidate Lisle’s ASC or how they show he’s misused the conventionality thesis.
The error in this thinking is that you need enough time to accommodate all conventions. If that was the case, the principle of conventionality would be redundant. The only choice available would be ε = 0 and the universe would have to be 28 billion years old.
Lisle’s claim is that the entire universe was created 6,000 years ago and that the light reached earth immediately.
The problem with this is that converting between coordinate systems does not create forces. It just marks the x, y, z and t of events.
It’s been mentioned that Lisle’s ASC is akin to redefining a year to make yourself younger or redefining a reference frame to avoid a speeding ticket. However, the legitimacy comes not from a redefinition that Lisle makes but because it follows from relativity. I think it’s notable that the majority of the ASC objections here have come from non-physicists. And you might expect that after 9 years any misuse of conventionality would have already been uncovered.
To date, the only reasonable objections to Lisle’s model have come from @PdotdQ. I was rather busy at the time and the thread seemed to go dormant so I didn’t reply. However, it seems there’s still some interest so I’ll try to respond when I’m able.
Which, by conversion from ASC to ISC, is the equivalent of claiming the edge of the universe was created 45 billion years ago, that nearer portions of the universe were created more recently, and that light moves at c. He admitted this to me outright. It is old-universe young-earth creationism.
Correct. The forces are not created by the coordinate system; the forces are created as a consequence of creating an entire universe worth of gravitational potential all “at once”.
Remember that under Lisle’s model, light traveling toward Earth moves infinitely fast, while light traveling away from earth travels at C/2. Suppose, therefore, that you could teleport (maintaining simultaneity with Earth) to a distance just over 3,011 light-years from Earth, facing Earth. You would not be able to see Earth or anything behind it, but you would be able to see all the light coming from behind yourself (since such light is traveling toward Earth and is thus infinitely fast).
Here’s the catch. At the stroke of midnight on January 1, 2020 (or whenever would be exactly 6,023 years to the minute after creation), you would not only see Earth, but you would see ALL the light from behind Earth blink into existence instantly, like someone flipped on the light. That’s because ALL that light reached Earth instantly during creation week but has been traveling at c/2 ever since. Remember, I said you teleported from Earth, so simultaneity with Earth is preserved. That is important.
It is important because light is not the only thing that reaches you in that instant. The OTHER thing that reaches you is an entire half-universe of gravitational potential in the form of a massive gravitational wave with infinite slope. You are instantly shredded, as is everything around you.
Thus if Lisle’s model for creation (not his convention, but his model) is correct, we should expect to see a spherical wave of complete destruction obliterating everything, receding away from us at a distance of roughly 3,011 light-years. We do not see this. Therefore it is not true.
The conventionality thesis demands that the universe accommodate all conventions of simultaneity. That is precisely why Lisle’s young ASC universe is a false paradigm. It doesn’t exist anywhere except in his mind.
Further, every possible Reichenbach epsilon value must be accommodated, and, in this discussion, the age of the universe must be averaged to arrive at 14 billion years.
I’m sorry @ABC but you do not seem to understand the subject matter at hand.
At the moment, I only have enough time to address this point. You misunderstand what ε represents. It represents the fraction of round-trip time used during the trip from the source to the mirror. So if we want all of the travel time to pass on the leg from the origin/observer to the mirror, ε=1. As you correctly point out, Reichenbach was using an entirely different convention where the speed of light is infinite in the positive x direction, and c/2 in the negative x direction. This just means that the observer is located to the right of the mirror, both being on the x-axis, not that ε changes value.