Black holes

[Farsight]

No, it's an emergent property of entropy. Motion is not actually required, though entropy accounts for it.

I'm afraid it isn't, Zig. Entropy isn't something fundamental. It's a measure of "sameness". Think about a system containing gas molecules. You start off with some fast-moving molecules and some slow. You end up with all your molecules moving at a similar speed.

When a nurse uses a standard alcohol thermometer, what is it that she's actually measuring? The volume of alcohol inside the thermometer. The temperature of the thermometer is inferred from this, but the actual measurement is a volume measurement. There's a further step required to relate this thermometer temperature to the patient's temperature, which I'll let you puzzle out on your own if you're able to. The nurse may not care about these distinctions, but they are still real.

She's measuring the patient's temperature. When you measure the temperature of a container of gas, no one gas molecule has any property of temperature or heat, it's either moving fast or it isn't. Collectively the gas molecules in the system have an average speed and an average kinetic energy, and when we measure the thing we call the temperature, that's what we're measuring.

You know far less about thermodynamics than I do. You really don't want to play this game with me, because you're in far over your head.

No I'm not.

That red hot poker has lots of internal energy. But how do you determine the temperature from the thermal energy? Why, you need to use a theory which relates the two.

No you don't, you just look at it. When it's glowing and red, it's hot, and you make sure you don't grab it by the wrong end.

You have made exactly the wrong conclusion here. The truth is not that abstract theory-defined quantities don't have physical consequences, the truth is that they do.

It's the other way round. Physical things have physical consequences. They can be described using abstract theory, but it's important to remember that the abstract theory is abstract.

Oh, and that's a great display of class too, Farsight. Keep it up and you'll deprive us all of your insight by getting banned. That seems to happen to a lot of internet cranks when they get frustrated at their inability to convince people of their pet theories and start lashing out.

You're lashing. I was just emphasising the obvious.

If everyone you meet is crazy, perhaps it's you.

Yeah yeah.

Next!

 

[Farsight]

When you feel like you're the only sane one and everyone else is crazy... well, I hope you're not so far gone you can't draw the obvious conclusion from that.

Ah, more abuse I see. Tell me about those trains, sol, and the light beams going at the same speed:

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I'm still waiting for you to explain why you are so confident you understand the Schwarzschild metric and that every GR textbook is wrong...

I've explained it to you. The Schwarzschild metric accurately reflects reality in that light goes slower where gravitational potential is lower. Our vertical light beam at the event horizon doesn't curve round, it doesn't slow down, and it doesn't fall back. It doesn't get out because the light has stopped, and there we have it, the original frozen star black hole interpretation.

and yet you can't answer even the most basic questions about a simpler metric - one that coincides with Schwarzschild near-horizon

You still haven't told me what that metric represents. Tell me. What's the problem?

 

[Farsight]

You haven't done that either. You can't point to a single person who has made a prediction which contradicts your evidence.

Hawking predicted Hawking radiation, decades ago.

Except that it doesn't, because the basis for your claim (the increasing redshift observed at a distance of an object approaching the event horizon) matches exactly the prediction one would get using alternative coordinates in which the speed of light remains constant.

No problem with that.

You claim that conversion to Kruskal coordinates is invalid, but you have no basis for this claim: its predictions agree exactly with the predictions from Schwarzchild coordinates for what a distant observer will see.

But not with what the infalling observer sees. Your textbook says he sees nothing unusual, I say he sees nothing.

Hawking radiation isn't strictly general relativity. If we restrict ourselves to general relativity alone, then Hawking radiation wouldn't exist.

OK.

But you are claiming that general relativity itself, as taught, is wrong. That claim goes beyond a disbelief in Hawking radiation.

I'm not saying GR is wrong. It's a well-tested theory, one of the best theories we've got. What I'm saying is that the way it's taught now is not in line with Einstein's original in some important ways. The teaching contains errors that have created an impasse. You know, general relativity is the sleeping beauty of contemporary physics and all that.

He isn't at your beck and call. Perhaps he's busy, perhaps he's simply bored with you. What I know he isn't is scared of you. Nobody with a clue about general relativity is.

Sol is fighting shy of telling me what the expression describes. He's afraid to do so, because he's afraid I'll point out a logical flaw.

My name, for these purposes, is Ziggurat. I value my anonymity on this board for a variety of reasons, none of which have any bearing on this conversation, and I'm not going to give up my anonymity to try to prove something to you. You aren't worth it to me, and it would prove nothing even if I did.

Noted.

 

[sol invictus]

Ah, more abuse I see. Tell me about those trains, sol, and the light beams going at the same speed:

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What?

I've explained it to you. The Schwarzschild metric accurately reflects reality in that light goes slower where gravitational potential is lower. Our vertical light beam at the event horizon doesn't curve round, it doesn't slow down, and it doesn't fall back. It doesn't get out because the light has stopped, and there we have it, the original frozen star black hole interpretation.

That doesn't answer the question, which was how you can be confident about that, and yet admit that you do not understand the theory well enough to even attempt the same "analysis" on another, simpler metric.

You still haven't told me what that metric represents. Tell me. What's the problem?

The problem is that everything you've said about the Schwarzschild metric, every property it has that you've made use of, holds true for that metric... but that metric is empty, flat, spacetime.

 

[Farsight]

I don't think you quite grasp the concept that units of measurement are purely arbitrary by nature. The duration of the second isn't the product of some law of nature. It's something humans have invented for our own convenience.

I know this.

The number of cycles are an observable phenomenon, the subject of what you refer to as a counting exercise.
But seconds are made up. Invented. Arbitrary.

No problem.

We can make the duration of the second whatever we want to. As long as everyone uses the same value, it makes no difference what value we assign it.

True.

If we want to say that the duration of one second is equal to the duration of X cycles of radiation Y, we can. There's no logical reason why we shouldn't. We don't need to know what the frequency of radiation Y is, we just have to be able to identify it.

But we don't. What we say is that the second is "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". Cycles aren't used in the definition. You don't use cycles per second to define the second.

But saying that one second is equal to X cycles is exactly the same thing as saying X cycles per second, and cycles per second is frequency.

Which is why we don't use cycles-per-second in the definition of the second.

So we're essentially calculating seconds from a signal with an arbitrarily assigned frequency.

No, you're defining the second, then after you've defined the second, you can ascribe a frequency to the radiation.

My clock hasn't slowed down, you've just changed my frame of reference to one where the pulsar oscillates at a faster rate.

Your clock has slowed down because I moved you to a lower location. The pulsar hasn't changed a jot. And your frame of reference is an artefact of measurement. You now measure things differently because the environment you're now in different to the environment you were in.

 

[Farsight]

Basically, you're saying that the rate at which physical processes or events occur is reduced, or slowed down. But the sequential occurrence of physical processes and events is what the rest of us call the passage of time. So what you're saying translates as the passage time slows down, which is what we've been saying all along. The only difference (to this particular aspect of the myriad of things we're arguing about) is that you're saying time slows down because light is slower, while we're saying that light slows down because time is passing slower.

Yes. It's an importance difference though. It's the empirical view, what you see when you look at the actual scientific evidence. You can't see time passing, or passing slower. But you can see things moving. Then when you read A World Without Time: The Forgotten Legacy of Godel and Einstein you appreciate it's in line with Einstein. In a nutshell you switch from an eternalism to a presentism view of relativity, which leads to a different understanding of the nature of black holes.

 

[Farsight]

Quote:

''A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle.''

If that came from a book then Farsight will ignore it. Books!? We doan need no stinkin' books!

I haven't ignored it. I've pointed out that negative-energy particles don't exist. Photons have positive energy, so do electrons and positrons, and so on. And conservation of energy applies. So when I see In order to preserve total energy, the particle that fell into the black hole must have had a negative energy I'm raising a challenge immediately. Frankly I'm amazed that anybody swallows stuff like that.

 

[Farsight]

Farsight, I haven't seen your response to this. Given that your argument is (a) "my coordinate system shows real things, and other coordinates systems show meaningless nonsense" and (b) "I'm using uncorrupted ideas of Einstein's" ... well, perhaps ignoring it is the best you can do.

I haven't deliberately ignored it, I just thought it unremarkable. Here's the English translation again:

"The general laws of nature are to be expressed by equations which hold good for all the systems of coordinates, that is, are covariant with respect to any substitutions whatever (generally covariant)."

Einstein isn't saying anything special. He initially called relativity the principle of invariance, such that when you're in a black box, all your experimental results are unchanged. You can't tell if that box is moving fast or is stationary. Since you will practically adopt a coordinate system relevant to your motion and situation, you don't want to be expressing "the laws of nature" particular to any one coordinate system.

 

[Farsight]

I want to highlight another problem Farsight hasn't responded to. Farsight, when you've claimed that you have "experimental evidence" against mainstream MTW-style GR, what exactly are you referring to? There was a some sort of hint about clock-comparison-at-different-heights, but since those experiments agree with the standard MTW calculation (section 38.5) you can't have meant that, could you? Or maybe you're ignoring this on purpose.

No. The evidence of optical clocks running at different rates at different heights tells you the speed of light isn't constant. They're optical clocks. Light moves in them. You can simplify them to parallel-mirror light clocks. Where the light moves slower the clock goes slower. There is no time flowing through those clocks.

Any coordinate system you adopt is defined by you using your rods and clocks, calibrated from the motion of light. It's wrong to use something derived from the motion of light to dismiss the evidence you can see with your own eyes: the light goes slower when it's lower. It isn't just "the coordinate speed of light" that varies. It's the speed of light. Like Einstein said.

 

[Farsight]

You skipped most of the main points I made in the post you replied to here, which is a pity. I'm particularly disappointed by your apparent non-answer to my pointing out your error regarding the relationship between c and Z₀. You keep asking for people to try to shoot your arguments down, yet when I pointed out a logical problem with your claim you were less than receptive.

I said in one reply that the permittivity and permeability of space are two aspects of the nature of space, where the best word I could find was "strength". Maybe an analogy will help. Imagine you're holding a spring steel bar. Think of permittivity a "how easy it is to bend it". Think of permeability as "how hard it springs back". Space is the way that it is, it sustains waves and fields. I can't alter the nature of it by changing only one side of the coin. If, say, I replaced your steel bar with a lead bar, it doesn't spring back. That means waves won't propagate through it. So by throwing away the permeability I've lost c too.

I won't bother to go over all my points again though, or press you for answers, since it's obvious to me that we'd just end up going round in circles and, in any case, others here are covering most of the same questions better than I would. Perhaps they can help you bridge the gap.

I'm pushed for time, but please don't hesitate to point out any post that you feel I haven't addressed.

When you return, I'd like to focus on the following issues in particular.

First, it is a fact (that anyone can verify) that "MTW"-style black holes are valid solutions of the mathematical model we've been calling "MTW" GR. On the other hand, you assert (without details) that this is incompatible with FGR, which advocates a frozen star picture.

I keep showing you how the speed of light really does vary with position, like Einstein said. And I've given lots of details. Pay careful attention to my conversation with Brian about the NIST clock and how we define the second.

I'm going to anticipate the answer to ben m's question above, and say that there is no available evidence which favours FGR over "MTW" GR on this issue. In fact I will go further and bet that there is no empirical evidence whatsoever that favours FGR over "MTW" GR (feel free to prove me wrong). Given that, on what rational basis are you actually rejecting the one and embracing the other?

That I can see that the speed of light varies with gravitational potential:

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These two light beams are not going at the same speed.

Second, the "details" issue. You claim that FGR can be understood in terms of vacuum permittivity and permeability varying through space. You further claim that the predictions of FGR are in accord with the predictions of "MTW" GR when it comes to the classical tests of general relativity, but disagree in some other areas (e.g. black hole interiors and Hawking radiation). However, you have not given us any details; you have not shown us any quantitative laws. You are just asking us to take your word for it.

I'm asking you to look at the evidence and think for yourself.

Indeed, in light of the demonstrated inequivalence of certain other similar-sounding models to GR there is every reason for a good skeptic to assign a very low prior probability to the truth of your claims. Given the lack of detail you have provided there is no way to know if they are even self-consistent.

Whoa. I'm the skeptic here. Not you.

 

[Farsight]

But what if two spaceships are accelerating at slightly different rates? The people on each ship will feel the force pulling them "down" as slightly differently, exactly the same as people at different altitudes on a planet.

No problem.

If we turn the ships around periodically so we can take a peek at each-other's clocks as we pass, we'll see that the clock on the ship with the lower rate of acceleration is faster than the clock on the ship with the higher acceleration.

You and I will. But the people on spaceship A will see clocks on spaceship B going slower than their own, and the people on spaceship B will see clocks on spaceship A going slower than their own. That's a bit like two distant observers each seeing the other as smaller than themself.

Exactly what we see on earth, the clock with the lower acceleration (lower gravity) goes faster than the clock with the higher acceleration (higher gravity).

Clock rate is a function of gravitational potential. The "force" of gravity is a function of the local slope in gravitational potential. There's no force of gravity in a gedanken void at the centre of the earth, but that's where gravitational potential is lowest and clocks go slowest.

Okay. The speed of light is not truly, absolutely constant. It's just locally constant.

I'm afraid it isn't, not really. It's only "locally constant" in an infinitesimal region, which is a region of zero size. If there was some place in the room you're in where the speed of light was constant, light would go in a perfectly straight line and things wouldn't fall down.

That's why we use coordinate systems that correspond to the real world.

Sure. I use a map of the earth to find my way around, but it would be of limited use if I was in a spaceship.

Okay, let's entertain the possibility that it's truly light, and not time that's changing.

OK.

But what you've described before as the consequence of light changing speed is exactly the same thing as what we mean by time slowing down.

Not exactly. It leads you to different conclusions about a lot of things

Can you explain to us what the difference is between our concept of time slowing down and your concept of light slowing down? Because if there is no difference, you've just wasting our time with a mangled attempt to describe the same thing with different words.

There's a lot of differences. You appreciate that gravity is there because space is inhomogeneous so light "veers", not because spacetime is curved. That's the effect, not the cause. Time travel is totally out of the window, CTCs get junked. Black holes go back to being frozen stars, you then liken them to the early universe expanding at a constant rate, but because everything in it is moving in slow slow motion that gets less and less slow, from inside the universe the expansion looks as if it's initially very rapid. That's inflation. And the black hole is also like an inside-out universe, there is no outside to it, and it doesn't curve round on itself, it's expanding because stress-energy is like pressure, so the universe has to have an edge. You realise that the so-called constants aren't really constant, so all that anthropic "goldilocks" multiverse stuff gets the boot. And it dawns on you what Minkowski was on about with "Then in the description of the field produced by the electron we see that the separation of the field into electric and magnetic force is a relative one with regard to the underlying time axis; the most perspicious way of describing the two forces together is on a certain analogy with the wrench in mechanics, though the analogy is not complete". And Maxwell when he said "A motion of translation along an axis cannot produce a rotation about that axis unless it meets with some special mechanism, like that of a screw". You can relate it to the frame-dragging of gravitomagnetism and then Thomson and Tait's vortex atoms, only you're then into soliton elementary particles appreciating what TQFT is all about, wherein massive stable particles are like chiral stress-energy "knots" and antimatter particles are like you tying your shoes right-over-left instead of left-over-right. (See this essay for an intro. I must look at this video by the way). Then you understand the photon-in-the-box and the radiating body losing mass, and see the symmetry between momentum and inertia aka mass. The list goes on. It's like you pull a thread with Einstein's name on it and out comes this string of pearls, pop pop pop, one after the other. That one little shift changes so much.

 

[Farsight]

So... there's no way to measure vacuum impedance except by measuring the speed of light? In that case, why did you even bring up the subject of vacuum impedance way back in post 290?

Because it isn't uniform in a gravitational field.

Skipping a few sentences:

Oh my [Insert fictitious deity here].
This one literally made me laugh out loud.

(The humor lies in the fact that you begin by claiming it's ironic that he should be accusing you of ignorance... and then unwittingly and indisputably prove him right while attempting to prove the opposite.)

Farsight, I'm done wasting my time on you.

OK Brian, we're done. You carry on believing in photons annihilating one another.

(You might want to look up some information on interference patterns, and the double slit experiment, before you make yourself appear even more foolish.)

They interfere. Waves do that. And once they've ridden over one another with their superposition, you've still got waves. They didn't annihilate one another. The sun shines. But nevermind, we're done.

 

[Farsight]

Comment from the gallery: time-reverse, for example, electron–positron annihilation^WP and you get... photon-photon annihilation, though it's not typically called that. It is a completely normal process that does happen in the universe (including the lab). Photons are their own antiparticles. Neutral pions are another example of particles that are their own antiparticles.

It's typically called two-photon photon physics. When you start with one photon interacting with a nucleus, it's typically called pair production. You typically create an electron and a positron, which are antiparticles of one another. If they don't have enough separating motion they're attracted to each other and they annihilate. You're typically left with two photons. You can do the same sort of thing with low-energy proton-antiproton annihilation, also yielding photons. Neutral pions have a mean lifetime of 8.4×10^−17 s and as "transient hadronic debris" are of less interest.

 

[Farsight]

What?

Tell me how two trains moving like this, or two light beams, are moving at the same speed.

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You won't.

I've explained it to you. The Schwarzschild metric accurately reflects reality in that light goes slower where gravitational potential is lower. Our vertical light beam at the event horizon doesn't curve round, it doesn't slow down, and it doesn't fall back. It doesn't get out because the light has stopped, and there we have it, the original frozen star black hole interpretation.

That doesn't answer the question, which was how you can be confident about that, and yet admit that you do not understand the theory well enough to even attempt the same "analysis" on another, simpler metric.

I can see that the light goes slower where it's lower.

You still haven't told me what that metric represents. Tell me. What's the problem?

The problem is that everything you've said about the Schwarzschild metric, every property it has that you've made use of, holds true for that metric... but that metric is empty, flat, spacetime.

No, that's not the problem, now is it? Just tell me what that metric represents, and we'll see what the problem is. But you've refused to do so, and I don't expect that's going to change.

Let's call it a day too sol. I've given you a lot of my time, and we aren't getting anywhere.

Everybody, let's wrap it up here, I've got work to do.

 

[sol invictus]

Tell me how two trains moving like this, or two light beams, are moving at the same speed.

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You won't.

You need to describe the setup in more detail.

I can see that the light goes slower where it's lower.

And yet, that metric is flat, empty space. See the problem? You can't distinguish coordinates from physics.

The problem is that everything you've said about the Schwarzschild metric, every property it has that you've made use of, holds true for that metric... but that metric is empty, flat, spacetime.

No, that's not the problem, now is it? Just tell me what that metric represents, and we'll see what the problem is. But you've refused to do so, and I don't expect that's going to change.

What in the world are you talking about? Did you even read my post?

Let's call it a day too sol. I've given you a lot of my time, and we aren't getting anywhere.

Everybody, let's wrap it up here, I've got work to do.

So you're "doing a runner"?

 

[sol invictus]

No. The evidence of optical clocks running at different rates at different heights tells you the speed of light isn't constant. They're optical clocks. Light moves in them. You can simplify them to parallel-mirror light clocks. Where the light moves slower the clock goes slower. There is no time flowing through those clocks.

"The evidence of optical clocks running at different rates at different heights" is in full agreement with standard, MTW general relativity, Farsight.

You've repeatedly failed to produce any experimental evidence that isn't in full agreement with standard, MTW general relativity. Why is that?

 

[Ziggurat]

But not with what the infalling observer sees. Your textbook says he sees nothing unusual, I say he sees nothing.

So what contradicts the textbook? We don't have any observers who have fallen through an event horizon that we can quiz. Hell, we don't even have any observers who have fallen towards an event horizon. All we have are theoretical predictions for what would happen. The entire basis for your claim that an infalling observer would see nothing is that a distant observer will see any signal from the infalling observer red shifted. But standard textbook theory predicts exactly the same red shift for a distant observer. So we're back to you not having a single piece of evidence to actually support your contention that standard texbook GR is wrong.

I'm not saying GR is wrong. It's a well-tested theory, one of the best theories we've got. What I'm saying is that the way it's taught now is not in line with Einstein's original in some important ways. The teaching contains errors that have created an impasse. You know, general relativity is the sleeping beauty of contemporary physics and all that.

And yet, you cannot point to a single example of a testable prediction where there is any disagreement between Einstein's original formulation and current textbooks. So how exactly are they any different, if they make the same predictions for everything that can be tested? And how can one be wrong and the other right if all testable predictions are the same?

Your insistence that there is a difference reminds me of a story about pickle bugs. Pickle bugs are a kind of insect that lays its eggs in cucumbers. When the eggs hatch, the larva starts to eat the cucumber from inside. Eventually, the entire cucumber is digested, and the larva enters a metamorphosis stage. During this stage, the larva remains attached to the cucumber plant, and in fact looks externally just like a cucumber. Unsuspecting farmers will often pick these pickle bug larva, and pickle the larva along with the ordinary cucumbers. But when someone bites into a pickle bug larva, they will discover that pickle bug larva taste just like... pickles!

Essentially, you're telling me that pickle bugs are real.

 

[Farsight]

You need to describe the setup in more detail.

I've described it in ample detail. It's two parallel-mirror light-clocks at different elevations, held flat. They don't stay synchronised. There's no time flowing between the mirrors, just light moving.

And yet, that metric is flat, empty space. See the problem? You can't distinguish coordinates from physics.

And you still won't say what it represents. I've already said that if the spacetime is flat the speed of light is uniform. It isn't like the black hole situation.

What in the world are you talking about? Did you even read my post?

You still won't say what [latex]$ds^2 = -(r-r_0) dt^2 + dr^2/(r-r_0) + dy^2 + dz^2$[/latex] represents. Again, what's the problem?

So you're "doing a runner"?

No, I'm giving up on you. You aren't being sincere, you're being evasive.

 

[Farsight]

So what contradicts the textbook? We don't have any observers who have fallen through an event horizon that we can quiz. Hell, we don't even have any observers who have fallen towards an event horizon. All we have are theoretical predictions for what would happen. The entire basis for your claim that an infalling observer would see nothing is that a distant observer will see any signal from the infalling observer red shifted. But standard textbook theory predicts exactly the same red shift for a distant observer. So we're back to you not having a single piece of evidence to actually support your contention that standard texbook GR is wrong.

How many times do I have to offer the evidence of the Shapiro delay and the optical clocks at different elevations losing synchronisation? How many times do I have to show you the parallel-mirror light clocks and say that the vertical light beam doesn't bend, doesn't slow down, and doesn't fall back. So it has to have a zero speed, that's the reality underlying infinite gravitational time dilation, ergo the Schwarzschild "coordinate singularity" should not be ignored. A stopped clock doesn't start ticking because you put a stopped observer in front of it.

And yet, you cannot point to a single example of a testable prediction where there is any disagreement between Einstein's original formulation and current textbooks. So how exactly are they any different, if they make the same predictions for everything that can be tested? And how can one be wrong and the other right if all testable predictions are the same?

Because the patent evidence tells you that the speed of light isn't constant.

Your insistence that there is a difference reminds me of a story about pickle bugs. Pickle bugs are a kind of insect that lays its eggs in cucumbers. When the eggs hatch, the larva starts to eat the cucumber from inside. Eventually, the entire cucumber is digested, and the larva enters a metamorphosis stage. During this stage, the larva remains attached to the cucumber plant, and in fact looks externally just like a cucumber. Unsuspecting farmers will often pick these pickle bug larva, and pickle the larva along with the ordinary cucumbers. But when someone bites into a pickle bug larva, they will discover that pickle bug larva taste just like... pickles! Essentially, you're telling me that pickle bugs are real.

Forget it Zig. This is a black hole thread, they used to be called frozen stars, the issue is the reality of Kruskal-Szekeres coordinates, and you think negative carpets are real. Meanwhile I'm in the situation I've been in when arguing with young-earth creationists. Show them a fossil and that's not evidence. Show them carbon dating, strata, glaciation, magnetic reversals, and that's not evidence either. And then they come out with cargo-cult science, and nobody has the honesty to put them straight. Wince. Time to call it a day.

 

[edd]

You're inadvertently attributing the words of Ziggurat to sol invictus. I'm sure it's unintentional (given you refer to Zig in the last bit) but you might want to change it if it's not too late.