March 11, 2018 — Robert Schroeder with J. Randall Murphy

[marduk]

I don't believe anything that anyone tells me - that's why I dedicated several months to studying the key features of his gravitational field propulsion physics concepts, and confirmed them on paper, before I chose to discuss them with anyone. You can check it for yourself by charting the photon emissions; a superluminal gravitational field propulsion system would in fact generate these optical artifacts. But they're no more exotic than a delayed thunderclap - it's just an optical mirage.


Like I said, both of the images are just a kind of mirage, or an echo if you prefer, so there's no causality violation involved with that - but it's a pretty cool effect.

Superluminal gravitational field propulsion doesn't in and of itself result in any causality violations, because your on-board clock is always running forward at the same rate as your departure clock. But things get more complicated when you work with a pair of superluminal Alcubierre warp ships and add a source of time dilation into the equation - then it might be possible to create a closed timelike curve (CTC). However, CTCs are a feature of general relativity anyway, as Gödel demonstrated with his brilliant rotating universe metric, and as we've seen with other concepts such as the Tipler cylinder. So it makes no sense to me to throw out the Alcubierre metric on this basis, when we didn't throw out GR on this basis. You don't hear any physicists going around saying "GR is a nice theory but I rejected it because it permits closed time-like curves." So it would be illogical to dismiss the Alcubierre metric for that reason.

But honestly I'm not convinced by the conventional explanation linking FTL travel/communication to causality violation. Because that scenario is actually a variant of the ladder paradox (aka the pole and barn paradox), and just like we find with the ladder paradox, the two reference frames disagree not only on the spatial coordinates, but they disagree on the time coordinates as well (the key features of the ladder paradox that change the game aren't represented in the Minkowski spacetime diagrams on that page - which apparently is a common mistake). When I solved that scenario by accounting for both spatial and time dilation, I found that the earliest that Alice could receive her own message back from Carol (which required instantaneous transmission, which is impossible), was simultaneous with her original transmission. So that model linking FTL travel to causality violation is false. Everett published an even more elaborate scenario linking FTL travel with causality violation, which I haven't analyzed, but I assume that it boils down to the same underlying principle. I should probably set aside a week to solve his scenario analytically, but frankly I was so pleased to find the key flaw in the prevailing argument that I chose to move on to more interesting issues instead. I'll attach the graphical depiction that I made of the ladder paradox (just read A-B-C-D as Alice-Bob-Carol-Dave, and the "Barn Frame" is the Alice-Bob reference frame, and the "Pole Frame" is the Carol-Dave reference frame), which illustrates the scenario properly and eliminates the question about causality, in case you care to look at it.

Hmmm... maybe?

Here's what I get of the FTL = time machine equivalence.

Suppose Khan Noonien Singh leaves a war-ravaged Earth in the year 1996 in a DY-100 class sublight vessel Botany Bay, headed for Alpha Centari. Let's say at sublight speeds, it's going to take him 300 years to get there.

200 years later, Kirk leaves Spacedock in the Enterprise at Warp 7, and heads to Alpha Centari, a quick 1 day trip. On the way, he detects the Botany Bay, drops out of warp, and scopes the scene out. Instead of messing with Khan, he decides to leave well enough alone, and heads on to Alpha Centuri.

From Khan's frame of reference, he first sees the Enterprise appear, then disappear, then reappear at Alpha Centari just over a year later (the time it takes the light to go 1/3 the 4LY distance remaining to Alpha Centari. Then, 3-ish years later, he sees the Enterprise leave Spacedock from Earth. It's out of sequence. He sees it here->Alpha Centari->Earth, when Kirk's frame is Earth->Khan->Alpha Centari. So causality from his frame of reference is already all mucked up.

Now here's where it gets even more squirrely.

Let's say Khan succeeds on taking over the Enterprise and then, a year later sees it in orbit of Alpha Centari? Who's future is that?

It gets even more interesting with more observers moving, and adding subspace radio.

 

[Thomas R Morrison]

Hmmm... maybe?

Here's what I get of the FTL = time machine equivalence.

Suppose Khan Noonien Singh leaves a war-ravaged Earth in the year 1996 in a DY-100 class sublight vessel Botany Bay, headed for Alpha Centari. Let's say at sublight speeds, it's going to take him 300 years to get there.

200 years later, Kirk leaves Spacedock in the Enterprise at Warp 7, and heads to Alpha Centari, a quick 1 day trip. On the way, he detects the Botany Bay, drops out of warp, and scopes the scene out. Instead of messing with Khan, he decides to leave well enough alone, and heads on to Alpha Centuri.

From Khan's frame of reference, he first sees the Enterprise appear, then disappear, then reappear at Alpha Centari just over a year later (the time it takes the light to go 1/3 the 4LY distance remaining to Alpha Centari. Then, 3-ish years later, he sees the Enterprise leave Spacedock from Earth. It's out of sequence. He sees it here->Alpha Centari->Earth, when Kirk's frame is Earth->Khan->Alpha Centari. So causality from his frame of reference is already all mucked up.

That’s not actually a causality paradox; that’s more in the realm of the relativity of simultaneity. Let’s take a simple example:

You’re at a position 4LYs equidistant from two planetary systems, when you’re informed via instantaneous subspace radio that both planets were simultaneously blown up by the Klingon Empire. You immediately activate the flashing red “alert beacon” at your space station. For you all three events are essentially simultaneous, but it will take four years for you to see the actual planet-busting explosions.

Spock happens to be on a moon around one of the planets that blew up, and Kirk is on the Enterprise near the other planet that blew up (let’s say that he arrived a moment too late to stop the massacre).

From Spock’s point of reference, his planet blew up first, then 4 years later your beacon went off, and 8 years after his planet was destroyed he sees the other planet next to the Enterprise blow up. A very young Vulcan without any knowledge of the finite propagation speed of light might deduce that it took four years for you to notice that this planet was gone, or perhaps that your red alert signaled the Klingons to blow up the other more distant planet 8 years after the first one. But Spock knows better – he knows that it takes time for light to travel through space, and in fact all three events were in fact simultaneous.

Kirk’s reference frame is completely the opposite: his planet blew up first, then the beacon went off after 4 years, and after 8 years he sees Spock’s planet blow up. The sequence is completely reversed!

Is this a causality violation? No, of course not – simultaneity and the sequence of events depend entirely upon one’s point of reference, via the finite propagation speed of light. You have to synchronize your clocks based on that factor in order to determine the actual sequence of events, which in this case, were all simultaneous. If everyone at each reference point applies that method, then they can all determine that the three events were simultaneous, so any apparent contradiction disappears.

You have to apply the same method to determine the sequence of events with superluminal warp travel. Once you do that, you see in your example that the Enterprise first left the Earth, then stopped to have a look at Khan’s situation, then moved on to Alpha Centauri. There’s no causality paradox because observers at all three reference points can account for the propagation speed of light, and they’ll all arrive at the same sequence of events.

I couldn’t understand the next part of your example because you didn’t specify when Khan takes over the Enterprise, but the same method applies – once all of the observers take into account the propagation speed of light, they all arrive at the same timeline of events. The only thing different about superluminal warp travel is that all of the observers would be able to determine that the Enterprise traveled faster than the speed of light between its destinations. But that doesn’t involve a causality violation, it just proves that Kirk has a rockin’ warp drive ship.

To establish a causality paradox, different observers who take into account the propagation speed of light, have to arrive at different timelines.

I’m not convinced that’s possible without something like a Tipler cylinder, which isn’t actually physically possible because it has to be infinitely long to create a closed timelike curve.

 

[ALPHA ROMEO UNIFORM]

Not listen to this episode yet and UFO are real what hell they are who knows. The stories with evidence which not been release is more important to all humanity.

 

[Greers Meeting Planner]

So are you claiming that:

Nothing is Unidentified? Or nothing is Flying? Or nothing is an Object?

Ok here it is.... Evidence for unidentified flying objects would exist if it could satisfy all of the three criteria in the name:

Unidentified: this would mean it is not identifiable (and not just to You this would need to be unidentifiable to the human race) beyond anything that we are currently aware of. This would include all military. We cannot reasonably provide evidence of any flying object which is truly unidentifiable.


Flying: a deliberate act of overcoming the force of gravity to maintain an altitude above ground level

Object: a material thing that can be seen and touched

There is no evidence that proves the existence of such things while satisfying all of the three criteria in unison.

My argument is not flying objects don't exist, they might do. My argument is there is no evidence for their existence, this is different.

This evidence could be garnered and with it we could truly move the field from one of fringe to one of serious scientific interest.

Here in lies a big problem. When we say a pilot has seen them: they must exist OR a radar trace was recorded: they must exist and then move on to discuss where they may be from etc etc we start overlaying assumption on top of assumption on top of assumption.

This is actively helping to keep the UFO field in the 'specialist interest' or 'fiction' section because we don't have a significant enough body of data from instrumented sources and across a range of measures.

Imagine if the field as a whole could align their collective energies and efforts to such an endeavour, the work that followed it would be exponentitally more productive than what has been done in the 'modern day era' where a case has been made with a lack of evidence.

Garbage in to the study of UFO's = garbage out and what do we have in this field so far.. a big stinking hot mess of garbage

 

[pigfarmer]

Ok here it is.... Evidence for unidentified flying objects would exist if it could satisfy all of the three criteria in the name:

Unidentified: this would mean it is not identifiable (and not just to You this would need to be unidentifiable to the human race) beyond anything that we are currently aware of. This would include all military. We cannot reasonably provide evidence of any flying object which is truly unidentifiable.


Flying: a deliberate act of overcoming the force of gravity to maintain an altitude above ground level

Object: a material thing that can be seen and touched

There is no evidence that proves the existence of such things while satisfying all of the three criteria in unison.

My argument is not flying objects don't exist, they might do. My argument is there is no evidence for their existence, this is different.

This evidence could be garnered and with it we could truly move the field from one of fringe to one of serious scientific interest.

Here in lies a big problem. When we say a pilot has seen them: they must exist OR a radar trace was recorded: they must exist and then move on to discuss where they may be from etc etc we start overlaying assumption on top of assumption on top of assumption.

This is actively helping to keep the UFO field in the 'specialist interest' or 'fiction' section because we don't have a significant enough body of data from instrumented sources and across a range of measures.

Imagine if the field as a whole could align their collective energies and efforts to such an endeavour, the work that followed it would be exponentitally more productive than what has been done in the 'modern day era' where a case has been made with a lack of evidence.

Garbage in to the study of UFO's = garbage out and what do we have in this field so far.. a big stinking hot mess of garbage

Yup. We have enough anecdotes; if they were going to solve the problem they would have already. Schroeder at least had a suggestion about what to look for that sounded plausible. Unfortunately he also dipped into the huge collection of stories to support his theories. Tedious. Of course, it was clearly more important to discuss how subspace radio, warp drive and trans-warp conduits work than get back to the topic he was invited to talk about. Uh-huh.

 

[Christopher O'Brien]

Yep - the average person in the public still thinks that we can't travel to the stars in less time than the observed distance to any given star: i.e., that it would take >4 years to travel to Alpha Centauri, for example, "because nothing can travel faster than the speed of light." So that's the erroneous basis of the commonly held and long-discredited "distance problem."

I was just pointing out that special relativity dismissed that thinking over a century ago, and that in practice, we know for a fact that you could reach any destination in the observable universe within your own lifetime if you could constantly accelerate at the modest rate of 1g.

And if gravitational field propulsion proves to be technologically possible (and I would argue that all of the most credible UFO cases seem to indicate that it is), it gets even more interesting, because in that case it's theoretically possible to travel to the Andromeda galaxy, take some selfies and perhaps collect some biological samples, and be back in time for dinner. And that doesn't require any physics more advanced or speculative than general relativity. But the technological capability to engineer with general relativity in that way is still beyond our understanding, although many bright minds are presently working to change that.

Yabut, the amount of energy required would necessitate harnessing the energy of a star... I highly doubt any species that could do that would be interested in this primitive, violent, misogynist hell-hole of degraded bio-diversity. Unless we're some alien kid's science project, or something banal like that...

 

[pigfarmer]

Yabut, the amount of energy required would necessitate harnessing the energy of a star... I highly doubt any species that could do that would be interested in this primitive, violent, misogynist hell-hole of degraded bio-diversity. Unless we're some alien kid's science project, or something banal like that...

Unless they've solved the energy issue in some way we don't understand.

Beyond that - don't hold back Chris, tell us what you really think .....

 

[marduk]

Ok here it is.... Evidence for unidentified flying objects would exist if it could satisfy all of the three criteria in the name:

Unidentified: this would mean it is not identifiable (and not just to You this would need to be unidentifiable to the human race) beyond anything that we are currently aware of. This would include all military. We cannot reasonably provide evidence of any flying object which is truly unidentifiable.

That's not what unidentified means. Unidentified and unidentifiable are two different things.

One is an existential '∃', as in !∃->Identifiable. There does not even in theory exist a way to possibly identify something.

un·i·den·ti·fi·a·ble
ˌənīˈden(t)əˌfīəb(ə)l/
adjective

1. unable to be identified.

Unidentified means that it hasn't been identified... yet.

un·i·den·ti·fied
ˌənīˈden(t)əˌfīd/
adjective

1. not recognized or identified.

My belly button was unidentified until I knew the word for belly button and knew what it was. Then it was identified.

Anything you see and don't know what it is is unidentified, at least for that moment in time.

I am not claiming that everything that is unidentified and flying and an object is extraterrestrial, or exotic, or anything in particular. Just that it hasn't been identified. Yet.

And besides, if we did determine it was extraterrestrial, it wouldn't be a UFO any more. It would be an IFO. Identified Flying Object.

 

[marduk]

That’s not actually a causality paradox; that’s more in the realm of the relativity of simultaneity. Let’s take a simple example:

You’re at a position 4LYs equidistant from two planetary systems, when you’re informed via instantaneous subspace radio that both planets were simultaneously blown up by the Klingon Empire. You immediately activate the flashing red “alert beacon” at your space station. For you all three events are essentially simultaneous, but it will take four years for you to see the actual planet-busting explosions.

Spock happens to be on a moon around one of the planets that blew up, and Kirk is on the Enterprise near the other planet that blew up (let’s say that he arrived a moment too late to stop the massacre).

From Spock’s point of reference, his planet blew up first, then 4 years later your beacon went off, and 8 years after his planet was destroyed he sees the other planet next to the Enterprise blow up. A very young Vulcan without any knowledge of the finite propagation speed of light might deduce that it took four years for you to notice that this planet was gone, or perhaps that your red alert signaled the Klingons to blow up the other more distant planet 8 years after the first one. But Spock knows better – he knows that it takes time for light to travel through space, and in fact all three events were in fact simultaneous.

Kirk’s reference frame is completely the opposite: his planet blew up first, then the beacon went off after 4 years, and after 8 years he sees Spock’s planet blow up. The sequence is completely reversed!

Is this a causality violation? No, of course not – simultaneity and the sequence of events depend entirely upon one’s point of reference, via the finite propagation speed of light. You have to synchronize your clocks based on that factor in order to determine the actual sequence of events, which in this case, were all simultaneous. If everyone at each reference point applies that method, then they can all determine that the three events were simultaneous, so any apparent contradiction disappears.

You have to apply the same method to determine the sequence of events with superluminal warp travel. Once you do that, you see in your example that the Enterprise first left the Earth, then stopped to have a look at Khan’s situation, then moved on to Alpha Centauri. There’s no causality paradox because observers at all three reference points can account for the propagation speed of light, and they’ll all arrive at the same sequence of events.

I couldn’t understand the next part of your example because you didn’t specify when Khan takes over the Enterprise, but the same method applies – once all of the observers take into account the propagation speed of light, they all arrive at the same timeline of events. The only thing different about superluminal warp travel is that all of the observers would be able to determine that the Enterprise traveled faster than the speed of light between its destinations. But that doesn’t involve a causality violation, it just proves that Kirk has a rockin’ warp drive ship.

To establish a causality paradox, different observers who take into account the propagation speed of light, have to arrive at different timelines.

I’m not convinced that’s possible without something like a Tipler cylinder, which isn’t actually physically possible because it has to be infinitely long to create a closed timelike curve.

You know, I get this stuff far easier when it's explained in Star Trek terms. Awesome.

I've been trying to state this that way, and been struggling:
Why FTL implies time travel

 

[marduk]

Yabut, the amount of energy required would necessitate harnessing the energy of a star... I highly doubt any species that could do that would be interested in this primitive, violent, misogynist hell-hole of degraded bio-diversity. Unless we're some alien kid's science project, or something banal like that...

I dunno man. Imagine what Trump would do with a Kardashev type II civilization's power.

Hell, he'd make the milky way great again.

 

[Greers Meeting Planner]

Yabut, the amount of energy required would necessitate harnessing the energy of a star... I highly doubt any species that could do that would be interested in this primitive, violent, misogynist hell-hole of degraded bio-diversity. Unless we're some alien kid's science project, or something banal like that...

That's how you see the world, others such as myself who don't watch CNN are not programmed to look at the world through the lens of victimhood

We have no idea what other life forms may or may not find interesting so to assume aliens wouldn't be interested because of "misogyny", lol c'mon dude

The aliens maybe interested to know that 85% of all consumer purchases in America are made by women. So if men are earning more it means they are handing it over to the women to decided how it gets spent. So who is really in control

 

[Thomas R Morrison]

Yabut, the amount of energy required would necessitate harnessing the energy of a star... I highly doubt any species that could do that would be interested in this primitive, violent, misogynist hell-hole of degraded bio-diversity. Unless we're some alien kid's science project, or something banal like that...

As I see it, we're in a very similar position today with regard to gravitational technology, as we were a few hundred years ago with magnetic technology. Back then, we didn't understand how magnetism really worked, we just knew that some rocks, loadstones, exhibited magnetic properties. So if we wanted to make a stronger magnetic field, all we could do is gather up more loadstone. That's pretty much exactly where we are with gravity right now - the only way we know how to make a stronger gravity field is by gathering together more mass-energy in one place.

But once we stumbled upon the discovery of the electromagnetic inductor (and the fortuitous ferromagnetic property of iron) suddenly we could generate extremely powerful magnetic fields with very little energy, and with very small lightweight devices - no loadstone required.

I think we're going to have a very similar kind of industrial and scientific revolution when we figure out how gravitation couples to spacetime - the phenomenological dynamics of it. Right now we have no idea - we know that mass-energy and the other components of the stress-energy tensor create gravity, but that's it - our understanding at this point is purely quantitative. Once we understand the underlying coupling dynamics, like we learned the underlying electrodynamics of magnetism, I expect that this idea that it takes huge magnitudes of mass-energy to create gravity, will fall behind us just as the loadstone fell behind us.

And apparently that's correct. Because if these devices were harnessing energy levels akin to the mass-energy of a celestial body - or even much less like the mass-energy equivalent of a VW Bug automobile as NASA's Harold White has calculated in recent years, then the first accident or field containment failure would've sterilized the entire planet, or perhaps even vaporized it. So to me, these devices are physical proof that a relatively low-energy gravitational field technology isn't just possible - it's inevitable for us, as long as our scientific advancement continues forward.

You know, I get this stuff far easier when it's explained in Star Trek terms. Awesome.

I've been trying to state this that way, and been struggling:
Why FTL implies time travel

And it's also a lot of fun to discuss this stuff in Star Trek terms, so we may have to do that more often, haha. Thanks for that link; I'll take a close look at it and see if it's more convincing than the page I cited earlier. It's easy to get these kinds of diagrams wrong - it's much clearer when you just illustrate these kinds of relative motion scenarios as a simple symmetric spacetime rotation between reference frames like I did with that image I uploaded yesterday,because that's all that the Lorentz transform really is, and you can easily see it that way. And when you compare both reference frames, you can actually see how an event's position in the past is just a perceptual artifact of your reference frame - in it's own reference frame, its time coordinate is actually the same as your own, so you can't actually send a message into the past even if you're moving FTL. But like I said, I'll look at it again to see if that page offers a viable model.

 

[Thomas R Morrison]

I've been trying to state this that way, and been struggling:
Why FTL implies time travel

Okay so I read that page and I don't see an actual causality violation there - that looks like another relativity of simultaneity example. Just as we saw in our simple example with Spock and Kirk and our space station equidistant from them both, different observers can report different - and even completely backwards - sequences of events. But once you account for the speed of light, and in the example on that page, for the speed of the spacecraft as well, all observers can properly reconstruct the sequence of events in the proper order, and even determine the time of each event, by making a spacetime diagram like the ones he's drawn up (but hopefully much cleaner and easier to read). The fact is - in his example, nothing actually violates the causality of the sequence. He gave us a hand-waving "you could set things up so that the spacecraft sends a message back in time, although I won't bother to actually show you that" ... but that was the whole point of this article - to show us how "FTL = time travel." All he showed us was "different observers witness the sequence differently," which we've already dealt with using the relativity of simultaneity example that we discussed.

Here are a couple of glaring empirical problems with the "FTL = casuality violation" hypothesis: 1.) the universe expanded much faster than the speed of light during the Big Bang. Where's the causality violation? 2.) The galaxies beyond the observable universe are moving away from us faster than the speed of light right now. Where's the causality violation? Just because different observers see a sequence of events differently, doesn't mean that any signals actually traveled back in time.

Let's look at a simple analogy. Let's say that we humans were all blind, and we navigated our world using sonar, like bats. In time we'd develop a physics of sonic relativity that explained that nothing could travel faster than the speed of sound, because you couldn't possibly hear anything approaching faster than the mind-boggling speed of 761 mph.

But then some clever rascal invents the electromagnetic radio - faster-than-sound (FTS) communication. And our top physicists cry out "that's impossible because FTS = causality violation!" To prove this hypothesis, they propose the following paradox: if FTS communication were possible, that would mean that a distant observer could shout in your direction, and due to the finite propagation speed of sound, it would take you say five minutes to hear him shouting at you. But that rascal with the radio set could be standing right next to him as he shouted at you, and call you up on your radio set and tell you that soon you'd hear him shouting. You'd know about an event before it happened! In fact you could even call him right back and say "tell that guy to stop shouting" before the first word arrived at your position. "Impossible!" the sonar physicists would say, "you've stopped him shouting before his shouts even reached your ears - that's a causality violation!"

No, it isn't. No signal traveled backward in time, you've simply demonstrated the utility of FTS communication - now you can put your earplugs in before some guy hollers at you.

I still haven't analyzed Alan Everett's paper that describes an elaborate method of creating a causality violation with two FTL warp ships travelling between two bodies in space undergoing relative motion; perhaps that scenario will have some merit. But I doubt it; I have yet to see a scenario that proves "FTL = causality violation" to my satisfaction, and I doubt that any exist, because everybody seems to be confusing "relative times and positions" with "proper times and positions," which represent a crucial distinction in special relativity in the first place.

By my thinking it all boils down to this: in every reference frame, time moves in the positive direction, and, no part of any light cone points in the negative time direction - in other words all slopes have a positive value. At the maximum limit of infinite velocity, time simply stops moving at all - so you'd have to travel faster than an infinite velocity to send a signal back in time, which is obviously impossible. So in reality, there's no combination of circumstances where a signal or a vehicle can move backward in time against the flat background metric of Minkowski spacetime, regardless of velocity. As we discussed previously, if you move faster than the speed of light, you can produce an optical mirage that appears to move backward in time, but that's just an illusion - even in that scenario all observations are unfolding in the positive time direction and all photons and material bodies are moving in the positive time direction, so no causality violation occurs.

 

[Randall]

"I have seen fairies. Some people who haven't seen them will say they may not exist, but not me and the other people who have seen them. We know they exist." You can see why this is a problematic position to take when making arbitrary statements such as we know "X" exists ...

Okay so far. Yes I can see the problems. They involve proving the claim to others.

... , you don't. You think you know, big difference

That's where you go off the rails.

Notwithstanding the nature of the subject matter ( which we'll return to later ), you're not using coherent logic. Most people who have had a firsthand experience sufficient for them to know something is real, do know it is real, at least to the extent that they can know most other things are real. So the actual situation with your claim is that unless a case is a proven hoax or there is sufficient evidence to the contrary, then it's you who really doesn't know whether someone else besides you knows something is real. If you assume they don't know, you could be wrong. You cannot be sure. You can't get inside a witnesses mind or travel back in time to where the experience happened.

Therefore to claim others don't know simply because they can't prove it to you is prejudicial. The best anyone who is fair minded can do is remain undecided. Now returning to the issue of the subject matter. Let's not move the goalposts or use loaded language. I've never claimed I've seen fairies, and I'm in full agreement that the nature of the claim in question needs to be reasonable. Claiming that alien craft are real is perfectly reasonable. Claiming fairies are real is farther out there. However even in fringe cases I wouldn't necessarily dismiss the reality of the experience. I would however doubt the interpretation.

I've had that discussion before as it relates to life after death. People say they know there is life after death. However logically speaking, that's impossible. Therefore in those cases you can reasonably claim those people don't know. They only think they know. Alien craft are a whole other concept. Conceptually alien craft exist in the same universe and time as we do and are as physical in nature as we are. Therefore where there is sufficient unimpaired perceptual evidence that they are real, backed by independent witnesses, and in some cases instrumented detection, it is reasonable to believe alien craft exist.

Obviously some people don't think that such evidence is reasonably good evidence. I do. But that's a whole other issue. Ultimately we can argue nothing is real. But that's just sophistry. How far down the field do you want to move the goalposts? Far enough for you to win your point or far enough for it to be reasonable? In my view requiring verifiable scientifically valid material evidence before we can validate every experience, is moving the goalposts farther down the field than is reasonable. If we had to get that level of evidence before believing everything we experience, we might as well forget believing in most of everything.

 

[Randall]

Okay so I read that page and I don't see an actual causality violation there - that looks like another relativity of simultaneity example. Just as we saw in our simple example with Spock and Kirk and our space station equidistant from them both, different observers can report different - and even completely backwards - sequences of events. But once you account for the speed of light, and in the example on that page, for the speed of the spacecraft as well, all observers can properly reconstruct the sequence of events in the proper order, and even determine the time of each event, by making a spacetime diagram like the ones he's drawn up (but hopefully much cleaner and easier to read). The fact is - in his example, nothing actually violates the causality of the sequence. He gave us a hand-waving "you could set things up so that the spacecraft sends a message back in time, although I won't bother to actually show you that" ... but that was the whole point of this article - to show us how "FTL = time travel." All he showed us was "different observers witness the sequence differently," which we've already dealt with using the relativity of simultaneity example that we discussed.

Here are a couple of glaring empirical problems with the "FTL = casuality violation" hypothesis: 1.) the universe expanded much faster than the speed of light during the Big Bang. Where's the causality violation? 2.) The galaxies beyond the observable universe are moving away from us faster than the speed of light right now. Where's the causality violation? Just because different observers see a sequence of events differently, doesn't mean that any signals actually traveled back in time.

Let's look at a simple analogy. Let's say that we humans were all blind, and we navigated our world using sonar, like bats. In time we'd develop a physics of sonic relativity that explained that nothing could travel faster than the speed of sound, because you couldn't possibly hear anything approaching faster than the mind-boggling speed of 761 mph.

But then some clever rascal invents the electromagnetic radio - faster-than-sound (FTS) communication. And our top physicists cry out "that's impossible because FTS = causality violation!" To prove this hypothesis, they propose the following paradox: if FTS communication were possible, that would mean that a distant observer could shout in your direction, and due to the finite propagation speed of sound, it would take you say five minutes to hear him shouting at you. But that rascal with the radio set could be standing right next to him as he shouted at you, and call you up on your radio set and tell you that soon you'd hear him shouting. You'd know about an event before it happened! In fact you could even call him right back and say "tell that guy to stop shouting" before the first word arrived at your position. "Impossible!" the sonar physicists would say, "you've stopped him shouting before his shouts even reached your ears - that's a causality violation!"

No, it isn't. No signal traveled backward in time, you've simply demonstrated the utility of FTS communication - now you can put your earplugs in before some guy hollers at you.

I still haven't analyzed Alan Everett's paper that describes an elaborate method of creating a causality violation with two FTL warp ships travelling between two bodies in space undergoing relative motion; perhaps that scenario will have some merit. But I doubt it; I have yet to see a scenario that proves "FTL = causality violation" to my satisfaction, and I doubt that any exist, because everybody seems to be confusing "relative times and positions" with "proper times and positions," which represent a crucial distinction in special relativity in the first place.

By my thinking it all boils down to this: in every reference frame, time moves in the positive direction, and, no part of any light cone points in the negative time direction - in other words all slopes have a positive value. At the maximum limit of infinite velocity, time simply stops moving at all - so you'd have to travel faster than an infinite velocity to send a signal back in time, which is obviously impossible. So in reality, there's no combination of circumstances where a signal or a vehicle can move backward in time against the flat background metric of Minkowski spacetime, regardless of velocity. As we discussed previously, if you move faster than the speed of light, you can produce an optical mirage that appears to move backward in time, but that's just an illusion - even in that scenario all observations are unfolding in the positive time direction and all photons and material bodies are moving in the positive time direction, so no causality violation occurs.

Fabulous post, but I'd like to say ( even if it isn't exactly relevant ) that the difference between time, light, sound, and information makes me want to point out the following: It's one thing to have information about something happening within a temporal environment, and another to change the temporal environment itself. So sure, with FTL communication, we could know in advance we'll see something, e.g. a supernova, but that won't change anything about the supernova itself.

Time is simply change. When we say time runs slower we simply mean the rate of change is longer compared to what it was before based on an independent frame of reference. We only get into big problems with temporal change when we're dealing with situations where time is said to run backward or contrary to the arrow of time. Mathematically there's no reason time can't run backward. But putting the genie back into the bottle, or in this case just a single photon, appears to be an impossible task unless every moment of existence is simply a frame stored in some vast memory bank. Even then we'd only be dealing with copies while the arrow in a lager context continues forward.

 

[Thomas R Morrison]

Fabulous post, but I'd like to say ( even if it isn't exactly relevant ) that the difference between time, light, sound, and information makes me want to point out the following: It's one thing to have information about something happening within a temporal environment, and another to change the temporal environment itself. So sure, with FTL communication, we could know in advance we'll see something, e.g. a supernova, but that won't change anything about the supernova itself.

Time is simply change. When we say time runs slower we simply mean the rate of change is longer compared to what it was before based on an independent frame of reference. We only get into big problems with temporal change when we're dealing with situations where time is said to run backward or contrary to the arrow of time. Mathematically there's no reason time can't run backward. But putting the genie back into the bottle, or in this case just a single photon, appears to be an impossible task unless every moment of existence is simply a frame stored in some vast memory bank. Even then we'd only be dealing with copies while the arrow in a lager context continues forward.

Thank you Randall. We just recorded a very interesting Physics Frontiers episode about a theory that you might enjoy quite a bit, known as retrocausality. It turns out that a clear and sensible interpretation of quantum mechanics handily resolves the issue of quantum entanglement (and others) if we set the future boundary conditions of a system equal to the past boundary conditions - in other words, if we allow the future to affect the present just as the past affects the present, in isolated quantum systems. This completely solves the mystery of instantaneous action-at-a-distance within the context of special relativity, with its limitation on information/energy traveling at the speed of light or slower. In this fascinating interpretation of quantum mechanics (which is favored in a slightly different but intimately similar way by renowned physicist Yakir Aharonov in his brilliant book Quantum Paradoxes), the "arrow of time" is a purely statistical effect that arises when a complex systems of particles interact, obscuring the underlying retrocausality of isolated quantum systems. So you may be right - at the fundamental level of reality, time may operate in both directions equally.

 

[Randall]

Thank you Randall. We just recorded a very interesting Physics Frontiers episode about a theory that you might enjoy quite a bit, known as retrocausality.

Cool. I'll have to check it out.

It turns out that a clear and sensible interpretation of quantum mechanics handily resolves the issue of quantum entanglement (and others) if we set the future boundary conditions of a system equal to the past boundary conditions - in other words, if we allow the future to affect the present just as the past affects the present, in isolated quantum systems.

Perhaps the key phrase there is "isolated systems". Depending on how we look at things, no system is completely isolated because it's always part of a larger system. There's also the issue about how it's possible for anything to actually affect anything in any temporal sense ( Arrow Paradox ). With respect to reversing time, my comment about putting a just single photon back in the bottle should be sufficient, but it could certainly be expanded on from there ( which I do briefly below ).

Also there would be no way to observe anything going backward in time because we could not observe photons going backward out of our retinas or detectors and back to the objects they are either emitted or reflected from. Detection can only work if time moves forward. Otherwise there would have to be some third party time frame moving forward and emitting light onto the scene, which in-turn would change the scene, which means that in the larger frame of reference time is still moving forward. So in fundamentally conceptual terms, reversing time isn't possible, and in real-world terms it isn't possible either. The best that can happen is for an illusion of time reversal to happen based on some sort of memory buffer, or to use our imaginations, or express it in some sort of math. But here's the real problem and why it's just impossible in the bigger picture:

Let's assume we switch a plain light bulb on for one second. In that time about a hundred billion billion photons head out in all directions in a volume the diameter of which is a distance of about 372,564 miles. So to reverse time just for that light bulb for just one second of time means reversing the direction and the effects of a hundred billion billion photons back into the lightbulb to the exact same electrons they were emitted from that are in exactly the same position they were before the light was switched on. That seems impossible enough. But how about getting just one to retrace it's exact path?

Hmm. That turns out to be more complex than we think because if the lightbulb is say, here on Earth, then in the 2 seconds it takes for the photon to go out and retrace its path back, the lightbulb will have moved along with Earth just a tiny bit. Uh oh, so now not only do we need to get the photon to somehow go back along its original path into the same electron it was emitted from, we need to put that electron exactly back in the same place in space it was when it was emitted, and seeing as that's on Earth, now we have to move the entire Earth back too. See the problem? Everything is connected. Time can't reverse for just one thing.

Ultimately, if time reverses for one thing, then for it to be consistent and really be moving backward, time has to reverse for everything. There's no escaping this logic that I can see. That is, unless, as previously mentioned, this universe in its entirety is seen as the "isolated system", in which case, from a perspective outside the system, our particular universe ( within the multiverse ) might be stopped, run in reverse, or sped up. We'd be none the wiser either way, and time would still be moving forward in the larger picture.

 

[Thomas R Morrison]

Cool. I'll have to check it out. Perhaps the key phrase there is "isolated systems". Depending on how we look at things, no system is completely isolated because it's always part of a larger system.

In the quantum mechanical regime, “isolated” typically just means “measurements taken between two specific experimental interactions without any intervening particle interactions,” such as generating a pair of entangled particles and then subsequently measuring their spins before they can collide with any other particles.

There's also the issue about how it's possible for anything to actually affect anything in any temporal sense ( Arrow Paradox ).

Apparently that paradox contains a “qualifier switch” logical fallacy, and when that’s dealt with the paradox disappears:
Zeno's Paradox of the Arrow

There’s still a paradox if we presume that space is comprised of discrete units, but astronomical techniques to detect any granularity to space have all failed to find such a thing – in other words space appears to be classically contiguous, not quantized. So again, Xeno’s arrow paradox isn’t applicable to our reality:
Atomism

Also there would be no way to observe anything going backward in time because we could not observe photons going backward out of our retinas or detectors and back to the objects they are either emitted or reflected from. Detection can only work if time moves forward. Otherwise there would have to be some third party time frame moving forward and emitting light onto the scene, which in-turn would change the scene, which means that in the larger frame of reference time is still moving forward. So in fundamentally conceptual terms, reversing time isn't possible, and in real-world terms it isn't possible either. The best that can happen is for an illusion of time reversal to happen based on some sort of memory buffer, or to use our imaginations, or express it in some sort of math. But here's the real problem and why it's just impossible in the bigger picture:

Let's assume we switch a plain light bulb on for one second. In that time about a hundred billion billion photons head out in all directions in a volume the diameter of which is a distance of about 372,564 miles. So to reverse time just for that light bulb for just one second of time means reversing the direction and the effects of a hundred billion billion photons back into the lightbulb to the exact same electrons they were emitted from that are in exactly the same position they were before the light was switched on. That seems impossible enough. But how about getting just one to retrace it's exact path?

Hmm. That turns out to be more complex than we think because if the lightbulb is say, here on Earth, then in the 2 seconds it takes for the photon to go out and retrace its path back, the lightbulb will have moved along with Earth just a tiny bit. Uh oh, so now not only do we need to get the photon to somehow go back along its original path into the same electron it was emitted from, we need to put that electron exactly back in the same place in space it was when it was emitted, and seeing as that's on Earth, now we have to move the entire Earth back too. See the problem? Everything is connected. Time can't reverse for just one thing.

Ultimately, if time reverses for one thing, then for it to be consistent and really be moving backward, time has to reverse for everything. There's no escaping this logic that I can see. That is, unless, as previously mentioned, this universe in its entirety is seen as the "isolated system", in which case, from a perspective outside the system, our particular universe ( within the multiverse ) might be stopped, run in reverse, or sped up. We'd be none the wiser either way, and time would still be moving forward in the larger picture.

That’s not how the theory of quantum retrocausality works. It works by placing the future boundary conditions on the same footing as the past boundary conditions so that both interact with the present to shape the trajectory and other fundamental properties of the particle’s wavefunction, not by changing history after it’s already happened.

Here’s an excellent paper about it:

“Time-symmetric boundary conditions and quantum foundations,” Ken Wharton, 2016
https://arxiv.org/pdf/1003.4273.pdf

 

[Randall]

In the quantum mechanical regime, “isolated” typically just means “measurements taken between two specific experimental interactions without any intervening particle interactions,” such as generating a pair of entangled particles and then subsequently measuring their spins before they can collide with any other particles. Apparently that paradox contains a “qualifier switch” logical fallacy, and when that’s dealt with the paradox disappears: Zeno's Paradox of the Arrow

The false premise is a proclamation rather than a certainty and therefore the logic is only false if it is assumed beforehand that time is not composed of a series of "nows" or as we would say "quantized". However we don't know if time is quantized and there is no way for us to tell short of somehow being able to observe time from outside the construct in which it applies. Therefore although the paradox disappears when the initial assumption is changed, it doesn't mean the initial assumption is necessarily false.

There’s still a paradox if we presume that space is comprised of discrete units, but astronomical techniques to detect any granularity to space have all failed to find such a thing – in other words space appears to be classically contiguous, not quantized. So again, Xeno’s arrow paradox isn’t applicable to our reality: Atomism

Quantization of time is different than quantization of volume ( geometric space ).

That’s not how the theory of quantum retrocausality works.

I wasn't referring to quantum retrocausality in particular. I was referring to the idea that time can run backward. I should have made that more clear.

 

[Michael Allen]

After all is said an done regarding the physics involved in this discussion, my first question would be to somehow correlate the theory (or theories in question, regarding the Kaluza Klien extension of Einstein's field equations, the "hierarchy problem," and others mentioned or alluded to in the episode...superstring theory, the standard model and quantum loop gravity, etc) to some expectation regarding the nature of of the light emissions from past and future anomalous aerial phenomena. A quick look over some of the anecdotal material around EM affects on cars, machinery as well as details regarding the color/intensity of the light when the object appears or vanishes might help.

Regarding the KK theory, the extra dimensions used (which include the 5th) -- this space doesn't sound prima facie to be the type of space one could squeeze something into and go a few kilometers and "pop" out somewhere else near Alpha Centauri (my apologies if this is a bad or misleading cariacature of the content of the episode).

And unfortunately...

No experimental or observational signs of extra dimensions have been officially reported. Many theoretical search techniques for detecting Kaluza–Klein resonances have been proposed using the mass couplings of such resonances with the top quark. However, until the Large Hadron Collider (LHC) reaches full operational power, observation of such resonances are unlikely. An analysis of results from the LHC in December 2010 severely constrains theories with large extra dimensions.[30]

Wikipedia sv. "Kaluza-Klien Theory"

Regarding the guest, Robert definitely got my brain working through the possibly hundreds of cases regarding descriptions of EM effects, color of light bursts, transparent or translucent objects etc. Interesting episode.

Edit: Perhaps the following from "Large Extra Dimensions" might indicate something useful for putting up on a pole somewhere in the San Luis valley

Analyses of results from the Large Hadron Collider severely constrain theories with large extra dimensions.[4][5][6][7][8][9]

The Fermi/LAT collaboration, in 2012, published limits on the ADD model of Large Extra Dimensions from astrophysical observations of neutron stars. If the unification scale is at a TeV, then for n < 4, the results presented here imply that the compactification topology is more complicated than a torus, i.e., all large extra dimensions (LED) having the same size. For flat LED of the same size, the lower limits on the unification scale results are consistent with n ≥ 4.[31] The details of the analysis is as follows: A sample of 6 gamma-ray faint NS sources not reported in the first Fermi gamma-ray source catalog that are good candidates are selected for this analysis, based on age, surface magnetic field, distance, and galactic latitude. Based on 11 months of data from Fermi -LAT, 95% CL upper limits on the size of extra dimensions R from each source are obtained, as well as 95% CL lower limits on the (n+4)-dimensional Planck scale M_D. In addition, the limits from all of the analyzed NSs have been combined statistically using two likelihood-based methods. The results indicate more stringent limits on LED than quoted previously from individual neutron star sources in gamma-rays. In addition, the results are more stringent than current collider limits, from the LHC, for n < 4. Further details of the analysis are found in [32].

I.e. my stupid armchair reading of the above hints at close (originating in Earth atmosphere) gamma ray bursts around UAP might indicate the propulsion using LED

Something much smaller than what is shown here (NASA) -- essentially a Cerenkov radiation detector. Sure...if we point one of these at a UAP at the right time and place (unlikely)

Depending on the energy of the initial cosmic gamma ray, there may be thousands of electrons/positrons in the resulting cascade that are capable of emitting Cerenkov radiation. As a result, a large "pool" of Cerenkov light accompanies the particles in the air shower. Air Cerenkov detectors, as the name implies, rely on the detection of this pool of light to detect the arrival of a cosmic gamma ray.

Gamma-Ray Detectors

All of this of course commits time, money and resources to looking at UAP from a purely ETH perspective.