Black holes

[edd]

You can't point up to the sky and say "Look, there's a light cone. Your retina isn't actually "on the surface of many light cones". It's on the inside surface of your eye, your eye is in space, and light moves through space and terminates on your retina. It's important to stay very grounded with all this.

Obviously light cones aren't physical objects - they're the locus of possible paths a light ray can take from a point, and in reality there may or may not be light rays travelling along them.

I think people might give you a funny look if you claimed the flight paths out of London Heathrow Airport don't exist, and only the planes flying along them do. Sure you might philosophically argue that point and they don't have any objective reality, but arguments like that don't help one make progress in a discussion when considering building a new runway. The light cone might not be physical but it is undoubtedly a useful concept to bring into a discussion in some physics problems.

 

[Farsight]

We normally think of the infalling observer moving faster and faster and faster as he approaches the black hole. If say he was "dropped from infinity", he'd be moving "at the speed of light" at the event horizon. However the speed of light at the event horizon is zero, and he can't be moving faster than that. So he doesn't fall faster and faster.

Forgive my uninformed interruption, but if this is true, and he can't be moving faster than c, which is zero at the EH, then his infalling speed must decrease to zero at the EH.

Yes. Hence black holes were originally called frozen stars.

To my naive logic, this suggests that from some large distance outside the EH, he is accelerated inwards by the BH gravitational field to reach a maximum velocity at some distance from the EH, and then decelerates to zero at the EH (suggesting a negative gravitational gradient extending from the EH to the point of maximum velocity).

It doesn't work like that. The gravitational gradient is positive all the way down. Imagine you had a gedanken rope with a light clock on the end of it. (Remember's Brian's gif for this). You rapidly lower the light clock to some point above the event horizon. You leave it there for a week. Then you rapidly haul it back up again and note the reading. You repeat this for various points above the event horizon. You can then plot all the readings, and draw a graph showing how the light clock goes slower and slower the closer it is to the event horizon. There is no point beyond which it starts going faster again.

This doesn't sound right, but why is it wrong (assuming c == zero at the EH) ?

There's a relationship between the infalling observer's falling speed as measured by you and the difference in your light-clock readings. It isn't a direct relationship, but for simplicity let's just say it is. Let's also say that a very long way from the event horizon at point X, your light-clock reading was 299,792,458. A little closer in at point Y your light-clock reading was 299,792,457. When your observer falls from point X to point Y, he passes point Y at 1m/s. A lot closer in at point Z, your clock reading was 149,896,229. When your observer falls from point X to point Z, he passes point Z at 149,896,229 m/s. At this point his inward journey resembles the inward journey of a beam of light. A vertical beam of light doesn't move faster and faster as it approaches a planet.

 

[Farsight]

Obviously light cones aren't physical objects - they're the locus of possible paths a light ray can take from a point, and in reality there may or may not be light rays travelling along them.

I think people might give you a funny look if you claimed the flight paths out of London Heathrow Airport don't exist, and only the planes flying along them do. Sure you might philosophically argue that point and they don't have any objective reality, but arguments like that don't help one make progress in a discussion when considering building a new runway. The light cone might not be physical but it is undoubtedly a useful concept to bring into a discussion in some physics problems.

They're all useful concepts Ed, it's just that you have to remember that they are concepts, and make sure they don't get in the way of your understanding of what's actually happening in the world. And don't forget that a light cone isn't the same thing as a light path - you can see a lightbeam. In addition I've talked about light paths being the same length in the invariant interval, hence your flight path example isn't ideal.

 

[Farsight]

dlorde: I take it it'd really bake your noodle to think of a large black hole passing at high speed through the space occupied by some lump of matter. Clearly it has to disappear from that volume and somehow be carried along by that black hole, and yet for Farsight it clearly has to remain at that fast moving event horizon.

This sort of thing gets interesting. The gravastar is somewhat similar to the old frozen star idea. Note this: "This region is called a 'gravitational vacuum' because it is a void in the fabric of space and time". Now think of the bowling-ball-on-the-rubber sheet analogy, only instead of a bowling ball at the bottom of the gravitational potential well, you've got a hole in the rubber sheet. See ordinary black hole depictions too. How do you move it? You can't put a gradient underneath it like you can with the bowling ball.

 

[dlorde]

...You can then plot all the readings, and draw a graph showing how the light clock goes slower and slower the closer it is to the event horizon. There is no point beyond which it starts going faster again.

I'm glad I didn't suggest that...

When your observer falls from point X to point Y, he passes point Y at 1m/s. A lot closer in at point Z, your clock reading was 149,896,229. When your observer falls from point X to point Z, he passes point Z at 149,896,229 m/s. At this point his inward journey resembles the inward journey of a beam of light.

At what point does his velocity begin reducing to zero?

A vertical beam of light doesn't move faster and faster as it approaches a planet.

I'm glad I didn't suggest that...

 

[Brian-M]

It doesn't work like that. The gravitational gradient is positive all the way down. Imagine you had a gedanken rope with a light clock on the end of it. (Remember's Brian's gif for this). You rapidly lower the light clock to some point above the event horizon. You leave it there for a week.

But the clock-on-a-rope would be experiencing a vast gravitational acceleration that objects in freefall towards the black hole would not be experiencing, so the results from those clocks would not necessarily be valid for in-falling objects.

It seems to me (if I'm understanding how this applies to gravity) that a falling object might experience less time dilation than a stationary object.

For someone falling into the black hole, it would appear to them that they are stationary and that your clock is accelerating at an enormous rate away from the black hole (which is accelerating towards them at the same rate).

As the infalling observer watches the clock on your rope whiz past, it'll appear to them that it's going much slower than the light clock they're holding in their hand. They are holding the fast-moving clock even when they're closer to the black hole or event horizon than your clock-on-a-rope is.

At least, that's how I understand it at the moment. Can anyone else here (apart from Farsight) tell me whether or not I'm on the right track?

 

[Farsight]

According to MTW GR, sure, but not in FGR. What I'd like to see is farsight explain what happens to an infalling observer in his reality. I don't recall him doing that, he's explained what happens at the EH (time stops) but not how you get there.

I wish you guys would stop calling it FGR. Einstein really did talk repeatedly about the speed of light varying with gravitational potential. And light clocks do go slower when they're lower. And A World Without Time: The Forgotten Legacy of Godel and Einstein is serious stuff. Knowing all that you should be able to work out for yourself that there's something very wrong with the usual story about what happens to the vertically-infalling observer. All I'm offering is a simple extrapolation based on what Einstein said and scientific evidence. Anyway, see post #842. I think that on the way into the black hole the observer's falling speed increases and increases until it's the same as the local speed of light. At that point there's an effective shockfront, and the observer breaks up spectacularly. He no longer exists as matter, and instead a part of his mass-energy continues towards the black hole in the form of light. He goes out with a bang rather than a whimper, and you should see the flash. A gamma-ray burst.

 

[sol invictus]

I wish you guys would stop calling it FGR.

Why would we? The physics of your theory don't match that of general relativity, so it needs a different name.

I think that on the way into the black hole the observer's falling speed increases and increases until it's the same as the local speed of light. At that point there's an effective shockfront, and the observer breaks up spectacularly. He no longer exists as matter, and instead a part of his mass-energy continues towards the black hole in the form of light. He goes out with a bang rather than a whimper, and you should see the flash. A gamma-ray burst.

Gamma rays! Great! FGR has just made its first unambiguous experimental prediction. Let me note two facts:

(1) That prediction is in total and complete conflict with that of GR, which predicts that the radiation emitted by an infalling observer will rapidly redshift into the infra-red and fade out with rapidly decreasing intensity, and

(2) If matter very close to the horizon emitted its rest-mass energy in gamma rays, I'm pretty sure we'd see that from super massive black holes, not to mention smaller holes. Hence FGR is probably ruled out observationally, although the astronomers should comment.

 

[Brian-M]

(2) If matter very close to the horizon emitted its rest-mass energy in gamma rays, I'm pretty sure we'd see that from super massive black holes, not to mention smaller holes.

I'm sure that Farsight will claim that light is virtually motionless at that point, so we'd never actually see the gamma-rays coming out of the black-holes.

 

[Hellbound]

I'm sure that Farsight will claim that light is virtually motionless at that point, so we'd never actually see the gamma-rays coming out of the black-holes.

Well, he did actually say we'd see a flash, so he either mis-spoke, was speaking metaphorically, or is contradicting himself again.

 

[edd]

At least, that's how I understand it at the moment. Can anyone else here (apart from Farsight) tell me whether or not I'm on the right track?

Sounds like the right track, yes. You've got to be a quite careful thinking about these things as you can easily handwave yourself to the wrong answer but the general principle of the situations not being identical is absolutely right.

 

[Farsight]

I thought you weren't going to waste any more time on this Brian? LOL, good thread through isn't it? If you want me to go back to the posts of yours I skipped, let me know.

Who said anything about length contraction? I didn't. That's not what I was talking about.

You said the distance was varying rather than the speed. It isn't. I thought that was what you were referring to.

Yes. That's exactly what I'm talking about. If you follow the mirrors so you can't see the forward/lateral/upwards/whatever motion it looks slower, but really isn't.

Agreed. You're looking into his frame from the outside, and because you're panning, the light looks slower to you. But it doesn't look slower to him. Instead when he turns the tables and pans his telescope while looking at you, your light looks slower to him. But it isn't. It's just diagonal in relation to him, but his panning removes that.

Of course it's traveling a longer distance, the clock is moving at a higher velocity and so the light is bouncing off the mirrors at a more obtuse angle in order to bounce back and forth between these rapidly moving mirrors without missing them.

It is for the moving-observer scenario where we're talking about time dilation due to relative velocity. But not for gravitational time dilation. The mirrors are just sitting there. Sure there's a bit of curvature, the light beam isn't exactly straight. But when the upper pair of mirrors are fairly close to the lower pair, you can't distinguish any difference in the curvature in the lower pair versus the upper pair. You can distinguish the clock rates, but you can't distinguish the tidal gradients at the two locations.

Since the light is now moving diagonally between parallel lines (the "lines" being the path of the mirrors) instead of at right angles, it must covering more distance, which means it must take longer to bounce back and forth between the mirrors.

See above. When we're talking about parallel-mirror light clocks losing synchronisation when separated by a foot of elevation, the left-hand mirror is tilted this way \ a little, the right-hand mirror is tilted this way / a little, and the beam arcs between them. This is really slight, and is pretty much the same for both mirrors. If it wasn't, it would be like you measuring gravitational acceleration to be 9.81m/s where one pair is located and 9.80 m/s where the other pair is located. You can't detect this. But you can detect the difference in clock rates, and you can detect things falling down.

If an observer is moving at a rate that keeps them a constant distance from the mirrors (or pans a telescope), this diagonal motion is not apparent. An illusion is created of the light bouncing back and forth off stationary mirrors at right angles at a slower rate.

Fair enough re relative velocity.

But since the mirrors are moving the light isn't actually going any slower.

As above.

In the GIF, imagine the mirrors flying away from you into the screen. The bottom pair of mirrors are flying away from you faster, so the light has to travel a longer diagonal distance to get from one mirror to the other, creating the illusion that the light is slower.

Huh? Both pairs of mirrors are just sitting there. This is no illusion.

But since you're also flying forward into the screen so that you're always a constant distance from the mirrors, it doesn't look like the mirrors are moving at different speeds, or even moving at all.

What? I'm just sitting there too.

From the viewpoint of a stationary observer floating above, it's obvious that the bottom pair of mirrors is moving faster and that the light is zig-zagging at different angles between the different pairs of mirrors.

Brian, either I've totally misunderstood you here or you're kidding yourself.

(If you're wondering how you can remain at a constant distance from the mirrors if the mirrors are moving at distant speeds, you're standing in a rotating space station. Since the top pair of mirrors are at a smaller radius from the hub, they travel at a slower speed than the lower mirrors.)

What rotating space station? We could do this parallel-mirror thing in a gravitational field regardless of rotation.

At this point I don't care if you get it or not, I'm just trying to make myself clear. If you want to know how this relates to what happens under gravity, re-read my previous point.

I'm sorry Brian, but I think you're clutching at straws here. How can I explain it? It's something like this: in the special relativity case you move fast relative to me and my light looks slower to you whilst yours look slower to me. In the general relativity case we're both just sitting there looking at those two parallel-mirror light clocks and those light pulses moving back and forth between them. Where the lower clock is, the light goes slower, and that's it.

I thought the whole point of the twins paradox was that it wasn't symmetrical. You end up with one twin older than another.

The so-called paradox is that two twins with relative velocity each sees the other one's clocks going slower than his own. That's the symmetry. It's broken when one twin turns round and comes back.

 

[edd]

(2) If matter very close to the horizon emitted its rest-mass energy in gamma rays, I'm pretty sure we'd see that from super massive black holes, not to mention smaller holes. Hence FGR is probably ruled out observationally, although the astronomers should comment.

It's not at all clear to me what Farsight's prediction here is to be honest. Astrophysical black holes can emit tens of percent of the infalling rest-mass, but I somehow suspect it'd not be consistent with this 'dematerialising' scenario.

 

[Farsight]

I was hoping Farsight might be able to explain how, despite the rapidly increasing gravitational force closer to the BH, everything comes to a halt at the EH ? and how a BH forms & grows - is the singularity always the smallest possible, if, as soon as an EH forms, nothing can get past it? And what happens when the mass of matter accreted above the EH becomes greater than the mass of a BH of that size - does a new EH form around it, or does the EH expand somehow? How can it expand if time itself has stopped at the EH? How densely can the matter above the EH be packed? etc., etc. Just curious to see how he explains it.

It forms and grows like the original frozen star. It's like you can crush snow down to make an iceball, but then you can't crush it down any more. Thereafter it grows much like a hailstone.



See post #842 where I responded to a previous question. The force of gravity is related to how different your clock readings are at different locations. Have a look at wiki and note the upturned-hat plot. If had a spaceship perched above the Earth's, you could lower clocks and plot something like this, especially if there were convenient shafts going deep into the Earth. The force of gravity is the slope of the plot. Now let's go back to the black hole, and give ourselves a bit of artistic licence: you are able to rapidly lower clocks to the event horizon and push them through. You are also then able to retrieve them rapidly and look at their readings. Once you account for your lowering and retrieval, you work out that all the readings are zero. You make a new plot, and find that you have a steeper version of the upturned hat, but the bottom region is totally flat. That's because regardless of how far through the event horizon you pushed your clocks, they all come back with the same zero reading. Clocks can't go slower than that, so once you're at the event horizon the force of gravity has vanished.

 

[edd]

It forms and grows like the original frozen star. It's like you can crush snow down to make an iceball, but then you can't crush it down any more. Thereafter it grows much like a hailstone.

I assume your analogy is not supposed to be perfect given the astrophysical evidence for a lack of a solid surface for black holes.

 

[Farsight]

As Farsight is completely ignoring me, he won't bother reading this post...

I read it.

...perhaps he also considers edd's "physics knowledge is scant", that edd "has no sincerity, and [edd's] sophistry is rubbish". I wonder if Farsight thinks he gave edd "plenty of my time, and it turned out that [edd was] being deliberately dishonest, and a deliberate timewaster"?

Edd seems to know a fair bit and is obviously honest and sincere. You should try it sometime.

 

[Farsight]

At what point does his velocity begin reducing to zero?

I'm sorry, I don't know. It's quite close in. Maybe Clinger might like to go with the flow and earn his keep by working that out for you. Or maybe somebody can point to something already online.

 

[Farsight]

But the clock-on-a-rope would be experiencing a vast gravitational acceleration that objects in freefall towards the black hole would not be experiencing, so the results from those clocks would not necessarily be valid for in-falling objects.

You just use them to plot gravitational potential. If there's a big difference in gravitational potential between point X and Y the force of gravity is strong there.

It seems to me (if I'm understanding how this applies to gravity) that a falling object might experience less time dilation than a stationary object.

Don't look at it that way. The falling object is like lowering a clock to point X, then Y, then Z, etc. It is subject to an increasing degree of time dilation at each point. If you lower it fast it still experiences the same degree of time dilation at each point. If you lower it so fast that you've effectively dropped it, the same applies.

For someone falling into the black hole, it would appear to them that they are stationary and that your clock is accelerating at an enormous rate away from the black hole (which is accelerating towards them at the same rate).

Sure. It's the same for somebody falling off a roof.

As the infalling observer watches the clock on your rope whiz past, it'll appear to them that it's going much slower than the light clock they're holding in their hand. They are holding the fast-moving clock even when they're closer to the black hole or event horizon than your clock-on-a-rope is.

Yes, an observer who flashes past me can claim that my clock is going slower than his. But I can claim that his clock is going slower too. We have to meet to decide this, and then we find that our clocks are running at the same rate. But then when he lowers his clock, we both agree that his is running slower than mine.

At least, that's how I understand it at the moment. Can anyone else here (apart from Farsight) tell me whether or not I'm on the right track?

Huh. Sadly some of the other posters here keep quiet when I'm right, even when I'm totally in line with their own understanding.

Sheesh look at the time. I'll have to love you and leave you guys. Until the next time.

 

[DeiRenDopa]

This post is a development of what's in my earlier post here (please refer to that for the full details).

In summary, Farsight's claim is this: "The best way to appreciate this is to replace the light beams with trains. The first one to hit the buffers detonates a bomb on the other one. It's always the lower train that blows up. Your motion and your distance affects the way you see things, but you don't see the upper train blow up."¹
We can test the second objective, independently verifiable part of Farsight's claim; namely, "you don't see the upper train blow up".

Let's take a point on the Earth's surface that is 6,370 km from its center. G and c have their usual values. The upper (higher elevation) train is 0.3 m distant from the lower one, vertically above it. The train tracks are 1 m in length. Each train contains a buffer detector, a bomb, and a radio trigger, wired so that the very instant it hits its buffer it sends a radio signal to trigger the bomb on the other train (the triggers work on very different frequencies, so the train doesn't blow itself up!). Once a bomb has gone off, the radio trigger is destroyed, so a blown-up train cannot blow up the other train.

OK so far? Any questions or comments²?

The time it takes light to travel 1 m is ~3.3 ns (nanoseconds). The time dilation of one train compared with the other is ~3.3 x 10^-17. So, per the Farsight diagram, the upper train hits its buffer ~10^-25 s before the lower train hits its buffer. The upper train, having hit its buffer, sends the radio trigger to the lower train. That signal takes ~1 ns to reach the lower train. By the time it does, the lower train has looooong since reached its buffer, and sent its radio trigger.

The result? The upper train blows up³.

Farsight's claim is thus falsified.

But suppose the triggers are a bit smarter; suppose that hitting the buffer also, instantly, defuses the bomb on board?

In this case we can test the first objective, independently verifiable part of Farsight's claim: "It's always the lower train that blows up".

Re-running the experiment, the upper train hits its buffer, sends its radio trigger, and turns off its bomb. It does not blow up. The lower train hits its buffer, before receiving the upper train's detonation signal (as before). It then sends its radio trigger and turns off its bomb. A looooong time later it receives the upper train's radio trigger, but it's safe, because the bomb has been defused.

The result? Neither train blows up.

Farsight's claim is thus falsified.

But maybe this is just a special case; maybe different trains, on different tracks, on different planets, at different elevations would do different things? Perhaps they would … but all we need is a single falsification; after all, Farsight did not explicitly exclude this particular case.

But maybe there's another way for the upper train to detonate the bomb on the lower train (and/or vice versa), one that does result in the detonation of the lower train but not the detonation of the upper one? Well, I guess we'll never know … unless one of you readers asks him ...

¹ Farsight does not include his signature diagram in the post from which this quote is taken. If you follow the chain backwards, you find that it's in this post:

I can see that optical clocks lose synchronisation when separated by only a foot of vertical distance. From that I know that parallel-mirror light clocks will do the same. So I know that this is what's happening:
|---------------|
|---------------|

² Not from Farsight of course, he can't even read this post.

³ Yes, the lower train blows up too, but that's not the core of Farsight's claim. Oh, and could someone please check my working? Thanks.

 

[DeiRenDopa]

This is a continuation of my last post.

Way back here, I took Farsight to task for being sloppy in the setup of his experiment:

However, I think the biggest communications failure in this post concerns the Gedankenexperiment itself ("light beams in say a smoke-filled chamber, and gave you a gedanken high-speed camera, you should be able to play back the film and see the light beams propagating in ..."). From his years of interacting with others, Farsight certainly knows that a goodly number of his audience will 'smell a rat' in the way he's presented this Gedankenexperiment. For example, many in his audience will have learned that simultaneity, of remote events, is relative; that one's everyday intuitions are unreliable when it comes to grokking relativity; and that remote records (which is what the film from the gedanken high-speed camera is) need to be analyzed very carefully, to draw sound conclusions.

But it must be said that this particular experimental setup is different from the exploding trains one. Perhaps, using this setup, it is also possible to test Farsight's objective, independently verifiable claims (and perhaps find them validated)?

Let's see.

We'll start by finding and copying all Farsight's posts in which he describes this particular setup. Here they are (I've labeled them, for easy reference)¹:

A

Regarding the main point I'm trying to convey, if I showed you two parallel cables with a different impedance, you'd expect to see some variation in the A/C signal propagation time, which we might depict like this:

|-----------------|
|-----------------|

If I replace the cables with light beams in say a smoke-filled chamber, and gave you a gedanken high-speed camera, you should be able to play back the film and see the light beams propagating in a similar fashion:

|-----------------|
|-----------------|

I would hope that you would attribute this difference to vacuum impedance rather than "time flowing slower", and conclude that c = √(1/ε₀μ₀) is not an absolute constant.

B

And that doesn't. It's science fiction, RC. It contradicts the patent evidence. Come on, you could devise an experiment with superhighspeed cameras and watch the two light beams making progress in a misted chamber:

|-----------------|
|-----------------|

You could see the top beam getting to the end first. But KS coordinates are telling you that the coordinate speed of light is the same everywhere? Come on RC, surely you can see the problem?

C

Yes. I've given it repeatedly. The speed of light varies with gravitational potential just like Einstein said. But people who are convinced that it's absolutely constant absolutely refuse to accept it. If I arranged two parallel-mirror light clocks at different elevations, you know that they won't stay synchronised. You also know that there's no literal time flowing between the mirrors, just light moving. If we used say dust in space, you'd be able to see the light beams moving like this:

|-----------------|
|-----------------|

Think of the light beams as racehorses. When one gets ahead of the other you say it's moving faster than the other. If somebody tried to tell you they were going at the same speed, you'd laugh at them.

In this last quote, below, Farsight combines his 'exploding trains' with his 'misty chamber'. He also is as clear as he's been, in any post, on what the actual empirical evidence for his claim is:

D

What different reference frames? It's just two beams of light moving through space. It's misty or smoky so you can see them. You can't see the reference frames. They're just abstract things that you derive using the motion of light.

It doesn't matter where I am, the lower beam gets to the end faster than the upper beam.

But what you can see is one light beam moving faster than the other. Don't kid yourself that it isn't because of something you can't see.

It doesn't appear to travel at a different speed. It travels at a different speed. The gedanken scenario is where you replace the light beams with trains. When one train hits the buffer the other train explodes. All observers see the lower train explode.

I have done. Now trust the evidence of your own eyes and look. Do you see time flowing? No. What you see is light moving.

You can observe the light travelling slower. You can't observe time travelling slower.

You're seeing light moving. You aren't actually seeing time elapsing. That's just what you call it.

The evidence I can see. You don't have any evidence for time passes slower. Again, I can show you light moving, you can't show me time passing.

Don't try to explain away what you can see with something you can't.

I've got to go I'm afraid. But yes I like your GIF. Just look at it. Take the evidence at face value. Which light pulse is moving faster?

Got all that?

In this 'misty chamber' setup, we have two devices which emit pulses of light, in a horizontal direction. They are in a large chamber, or room, separated in elevation by 0.3 m, as in the case of the exploding trains. The emission of the light pulses is from the left-hand "mirror". The pulses reveal their positions by lighting up some dust, or smoke, or mist. Farsight does not explain how this happens, but let's invent some magical dust which has the following properties²:

-> it is massless

-> it instantly emits light isotropically when a light pulse hits it

-> its refractive index is the same as the vacuum through which the light pulses are travelling

-> it does not change the trajectory or speed of the light pulses in any way.

The light which the magical dust gives off is detected, and recorded, by a camera.

But where is this camera located? Well, Farsight doesn't say. In fact, in one of his descriptions (B) he refers to two cameras.

So I've taken the liberty of setting up three cameras: one, called U, is in the same horizontal plane as the upper parallel-mirror light-clock; one, called L, in the same horizontal plane as the lower parallel-mirror light-clock; and one, called M, mid-way between U and L. U, M, and L are in the same vertical plane, and the same vertical plane as the two right-hand mirrors. This plane is orthogonal to the (vertical) plane containing the two parallel-mirror light-clocks.

Farsight doesn't say how he does it, but let's suppose the emission of light pulses from the two clocks (i.e. from the left-hand "mirror") is synchronized.

Rather than watch all this happen with our eyes (Farsight says we can do this – see D - but that's nonsense of course³), we'll examine frames from the "film" taken by the three cameras. Our aim, in the film analysis, is to see if there is objective, independently verifiable evidence that is consistent with Farsight's claims (as contained in the extracts of the four posts above), or falsifies those claims.

That'll be in my next post.

OK so far? Any questions or comments?

¹ If anyone has found any more, please say so
² there are probably more properties that should be listed, and some of the ones listed are, to some extent, very similar; but you get the idea, right?
³ If you can't see why, just say so; I'll be happy to explain