The Extraterrestrial Hypothesis : Fact and Fallacy

[marduk]

The way time travel seems to distill down is that, like afterlives, it isn't possible in the usual sci-fi sense we usually see it portrayed. Or more accurately, it's only possible in that way if whatever is able to do it has full control of our universe and is able to undo and redo everything that's ever happened right to the precise point they emerge. But if that's the case then the ramifications are that nothing is real in the sense we think of it either.

Everything would have to be a copy stored in some vastly powerful buffer, and of necessity the aliens would have to be from some other universe that runs on the same system as this one, or they couldn't exist concurrently in this one with us. The only other option is a situation where the timeline can branch, but even then we're dealing with the spontaneous creation of a copied universe, in which case they're not really changing time in the original universe at all.

The YouTube videos I've seen on time ( and I've watched many ) generally don't take enough into consideration and tend not to differentiate between relative rates of aging or localized reverse aging, and time travel in the sci-fi sense used here to suggest that some alien race could control the timeline on macro levels. Maybe I'm missing something in the logic though. If so maybe someone can help me see where I've made the error.

I think a very real problem with time travel backwards may be entropy.

Entropy might actually be what time is. Travelling backwards in time might be extremely problematic if that’s true.

 

[marduk]

I don't get why people have such a hard time with this. Conceptually it's as simple as digital editing. The whole thing is basically cut and/or copy/undo/paste. The interesting thing is that this whole line of reasoning also suggests that time is quantized. Each moment we think of as reality is essentially a still frame that the big system created according to the content of the previous frame and the rules that govern how change is made when compositing the next frame. And this suggests that nobody ever really lives, at least not the way we normally think of it. It's all an illusion.

​

Keep talking, I’m not picking up what you’re laying down.

 

[marduk]

Apples and oranges. As I wrote before, ULTRA remained secret for thirty years after there was no longer any real need for secrecy. By 1975 the axis had been history for three decades; revealing the secret cracking of their codes was of no real importance at all. In sharp contrast, proof that ET is here and generally far ahead of us could have serious consequences, if revealed. Can the government reassure us it could deal with an invasion, overt or otherwise? Maybe at some future point but, not now so disclosure could result in panic. There is a very compelling reason to keep it under wraps.



Oh they can keep secrets especially if there's a strong incentive.

I’m not arguing there wasn’t a reason to keep it under wraps.

I’m arguing they were incapable of doing so.

Interestingly - as a shout out to our resident physicist here - for stochastic reasons.

You just can’t herd that many cats.

 

[marduk]

Seems hardly plausible given Malmstrom and other evidence of ET-government adversarial relations instead of cooperation. ET probably keeps quiet because his agenda is nefarious, and the government keeps quiet because as long as it can't match ET, disclosure would only make things worse.

Or they keep quiet because they just don’t care.

 

[marduk]

Right.



Inasmuch as Roswell has no earthly explanation, there's a pretty good chance it does.



But there's no need to invoke it at all. While the government may have ET technology it doesn't necessarily follow that it has mastered it. There's no good evidence I'm aware of.
But never mind some foreign country, or a scheming US, ET clearly does have such technology. Since we're all but defenseless, for now, disclosure could invite panic.




Why not just annihilate us themselves? Btw Roswell may have involved just escape pods, as the main craft was completely destroyed. So having ET technology doesn't necessarily mean having the gravitational field propulsion.

If you had gravity field propulsion and wanted us dead, just pull a medium sized asteroid out of the belt and let it de-orbit into Earth’s path.

Done like dinner.

 

[Trajanus]

I’m not arguing there wasn’t a reason to keep it under wraps.

I’m arguing they were incapable of doing so.

If they could keep ULTRA secret for three decades without any compelling reason, they could keep ET secret given the great need. Btw hundreds or thousands were privy to ULTRA.

 

[Trajanus]

If you had gravity field propulsion and wanted us dead, just pull a medium sized asteroid out of the belt and let it de-orbit into Earth’s path.

Done like dinner.

ET is by far the greatest reason to maintain secrecy, not the possibility of foreign governments finding out about technology or ours waging war with it.

 

[Trajanus]

Or they keep quiet because they just don’t care.

If you mean the government they must care given the potential risks, of ET attack and of disclosure.

 

[marduk]

If they could keep ULTRA secret for three decades without any compelling reason, they could keep ET secret given the great need. Btw hundreds or thousands were privy to ULTRA.

And yet it was leaked and blown wide open.

 

[marduk]

If you mean the government they must care given the potential risks, of ET attack and of disclosure.

No I mean whatever is behind the phenomena.

 

[Thomas R Morrison]

I'm not going to pretend to be able to do the math, nor am I going to bother. All that seems to matter is that in these sorts of explanations time is reduced to a variable rather than a real-world concept. As soon as that happens it becomes an abstract mathematical model that might be internally coherent to mathematicians, but that doesn't mean it remains coherent with respect to the real world, or even what we're talking about here with respect to some craft coming back in time from some future point on our timeline, if that is even possible, which I seriously doubt.

But whatever the case, the cut & paste analogy seems to work just as well and isn't that hard to visualize. It doesn't need more spatial or time dimensions either. It just requires that we look at time a bit differently, from a sort of God's eye view outside this timeline. Maybe that's what they mean by other "dimensions". I don't know. BTW I say "cut & paste" as a convenience term, but as I alluded to it's more complex and a closer analogy would be full editing capability including compositing, and beyond that to include dynamically generated content.

Time travel does seem counterintuitive to us, but we really do have to reckon with it in real-world terms – here’s a mundane example that we absolutely know is real: the twin paradox (it’s not really a paradox, btw – it’s just kinda strange).

I think most people already know the scenario: an astronaut departs from the Earth and travels in space near the speed of light for awhile, leaving his identical twin brother behind on the Earth. The traveling astronaut twin is traveling through space at relativistic speed, which slows his rate of motion through time relative to his initial rest frame at the Earth (this conjoined space and time geometry is the key feature of special relativity). So when he gets back to the Earth, his brother is an old man, but only some smaller interval, perhaps mere days, have passed for the travelling astronaut twin. It seems unrealistic to our human intuition that a pair of identical twins could end up at different physical ages, standing side by side, simply by moving one of them through space at a high rate of speed, but it’s an absolutely proven scientific fact that this actually happens in physical reality. And gravity has the same effect of aging you more slowly, just like high-speed travel does.

Incredibly, general relativity gives us an even stranger possibility, which was discovered by Kurt Gödel back in 1949. Gödel noticed that if the universe is spinning (the entire spacetime structure itself, not just the matter within), certain trajectories through spacetime result in “closed timelike curves,” i.e., you could travel on a curving trajectory through spacetime and circle back to an earlier point on your own timeline. We published a Physics Frontiers episode called The Physics of Time Travel about this stuff. Most physicists were relieved that they could write this off as a mathematical abstraction since we have no empirical reason to think that the universe is spinning, because closed timeline curves result in the grandfather paradox in 4D spacetimes. But in 1974 Frank Tipler discovered that closed timelike curves can arise in a non-rotating universe, if you have a rotating cylinder of matter of infinite length. This provoked a harder look at closed timelike curves, and not long after that people like Kip Thorne realized that if negative spacetime curvature is permitted in general relativity (which we now know that it is), a finite Tipler cylinder can generate closed timelike curves, and stable wormholes can in theory actually be constructed. However, the three known solutions to the grandfather paradox are all pretty awful – Stephen Hawking called his solution to the problem the “chronology protection conjecture,” because that’s all it is, a conjecture.

So travel in time may seem like an abstraction, but it’s not. Special relativity shows us that it would be quite feasible to travel hundreds or thousands+ years into the future, by simply moving really fast. And general relativity extends that prospect to gravitational fields, which is also a proven fact – time is actually passing more slowly on the Earth than in space. But GR also permits closed timelike curves, and every objection that’s been raised to the real-world physical prospect of CTCs have all failed.

So now we’re confronted with the physical possibility that a sufficiently advanced civilization that has attained “applied general relativity” technology, could not only fly circles around our fastest aircraft in space, but they could fly circles around us in time as well.

I’m not sure that I understand your cut/paste analogy, but it sounds like you’re postulating an extra dimension of time – a reference frame to cut/paste from. But in 4D physics, time is just a one-dimensional line, so you can’t “rise above” that line to do any cutting or pasting - you’re stuck on that line with the only options being to move forward or backward along it - so you’re saddled with causality paradoxes like the grandfather paradox.

 

[Thomas R Morrison]

Btw Roswell may have involved just escape pods, as the main craft was completely destroyed. So having ET technology doesn't necessarily mean having the gravitational field propulsion.

Eh, maybe. I remember seeing a Richard Dolan talk where he showed infrared footage of a TR-3B-looking craft zooming around the upper atmosphere on an odd sort of meandering trajectory, with no observable emissions or turbines – it sure looked like field propulsion of some kind, and if I had to guess, I would guess that it was US military tech. I’d love to really know how much progress we’ve made in those directions. I sort of assume that we’ve made some progress, though perhaps only at the lab level, but I very much doubt that we can produce anything like the dramatic leaps from a dead hover to over the horizon in a second or two, which we seem to hear about often.

Ya, I’m pretty much with you.

The MWI is so entertaining though.

The MWI is arguably the best thing to happen to science fiction since The Time Machine. But it’s also probably the worst thing to happen to physics since the god-awful Copenhagen interpretation that spawned it.

The observer problem is pretty funny the way it’s misinterpreted. The observer doesn’t have to be a conscious entity at all - just a device capable of measurement.

If we create reality, then so does my nest cam.

That’s right; I’m glad somebody gets it. Any physical interaction qualifies as a “measurement” - the “observer” has nothing to do with any of it. But the “wavefunction collapse” malarkey with the “measurement problem” – all of that stuff slithered out of the Copenhagen interpretation, which is when quantum physics jumped the rails and plunged down a bottomless rabbit hole. Basically Bohr decided to browbeat everyone into abandoning physics in favor of mathematics, and at that point the mathematicians took control of the global physics community, so sensible explanations were replaced by mere calculations. Physics still hasn’t fully recovered from that absurd blunder into darkness.

I think a very real problem with time travel backwards may be entropy.

I don’t think that’s a problem – locally time is always moving forward (positive) with all of the approaches to time travel that I’ve seen, so your entropy is always increasing (positive) in that reference frame. And with respect to an external observer, your entropy is decreasing (negative) but your time direction is also negative, so the product is still positive. I think if there were an entropic argument against time travel, physicists would’ve jumped on it – most of them will leap at any opportunity to reject the prospect of backward travel in time.

Entropy might actually be what time is. Travelling backwards in time might be extremely problematic if that’s true.

I’ve seen an entropic model of gravity, but not of time itself. Entropy defines the direction of time, but I don’t see how it can be time, because it’s a purely statistical concept. If you have a reference I’d like to read up on it; perhaps I’m missing something.

A coupe off months ago we published a Physics Frontiers episode called “A Gravitational Arrow of Time” about this fascinating paper that identifies a gravitational arrow of time by modeling the evolution of the universe with novel concepts like complexity, information, and structure. It kind of blows my mind to see a paper that completely reframes the way we think about physics, yet is internally consistent, and offers new explanations – that’s very rare to see in academic physics papers.

 

[marduk]

Time travel does seem counterintuitive to us, but we really do have to reckon with it in real-world terms – here’s a mundane example that we absolutely know is real: the twin paradox (it’s not really a paradox, btw – it’s just kinda strange).

I think most people already know the scenario: an astronaut departs from the Earth and travels in space near the speed of light for awhile, leaving his identical twin brother behind on the Earth. The traveling astronaut twin is traveling through space at relativistic speed, which slows his rate of motion through time relative to his initial rest frame at the Earth (this conjoined space and time geometry is the key feature of special relativity). So when he gets back to the Earth, his brother is an old man, but only some smaller interval, perhaps mere days, have passed for the travelling astronaut twin. It seems unrealistic to our human intuition that a pair of identical twins could end up at different physical ages, standing side by side, simply by moving one of them through space at a high rate of speed, but it’s an absolutely proven scientific fact that this actually happens in physical reality. And gravity has the same effect of aging you more slowly, just like high-speed travel does.

Incredibly, general relativity gives us an even stranger possibility, which was discovered by Kurt Gödel back in 1949. Gödel noticed that if the universe is spinning (the entire spacetime structure itself, not just the matter within), certain trajectories through spacetime result in “closed timelike curves,” i.e., you could travel on a curving trajectory through spacetime and circle back to an earlier point on your own timeline. We published a Physics Frontiers episode called The Physics of Time Travel about this stuff. Most physicists were relieved that they could write this off as a mathematical abstraction since we have no empirical reason to think that the universe is spinning, because closed timeline curves result in the grandfather paradox in 4D spacetimes. But in 1974 Frank Tipler discovered that closed timelike curves can arise in a non-rotating universe, if you have a rotating cylinder of matter of infinite length. This provoked a harder look at closed timelike curves, and not long after that people like Kip Thorne realized that if negative spacetime curvature is permitted in general relativity (which we now know that it is), a finite Tipler cylinder can generate closed timelike curves, and stable wormholes can in theory actually be constructed. However, the three known solutions to the grandfather paradox are all pretty awful – Stephen Hawking called his solution to the problem the “chronology protection conjecture,” because that’s all it is, a conjecture.

So travel in time may seem like an abstraction, but it’s not. Special relativity shows us that it would be quite feasible to travel hundreds or thousands+ years into the future, by simply moving really fast. And general relativity extends that prospect to gravitational fields, which is also a proven fact – time is actually passing more slowly on the Earth than in space. But GR also permits closed timelike curves, and every objection that’s been raised to the real-world physical prospect of CTCs have all failed.

So now we’re confronted with the physical possibility that a sufficiently advanced civilization that has attained “applied general relativity” technology, could not only fly circles around our fastest aircraft in space, but they could fly circles around us in time as well.

I’m not sure that I understand your cut/paste analogy, but it sounds like you’re postulating an extra dimension of time – a reference frame to cut/paste from. But in 4D physics, time is just a one-dimensional line, so you can’t “rise above” that line to do any cutting or pasting - you’re stuck on that line with the only options being to move forward or backward along it - so you’re saddled with causality paradoxes like the grandfather paradox.

For those that have any math scratches to itch, I highly recommend digging into Godel. He is the reason I got into pure math, and the reason I got back out of it when I was considering a master's in it.

The stuff he's talking about are well discussed here:
Gödel metric - Wikipedia

You can skip the math if it gives you a headache, the important bit is here:

Because of the homogeneity of the spacetime and the mutual twisting of our family of timelike geodesics, it is more or less inevitable that the Gödel spacetime should have closed timelike curves (CTCs). Indeed, there are CTCs through every event in the Gödel spacetime. This causal anomaly seems to have been regarded as the whole point of the model by Gödel himself, who was apparently striving to prove, and arguably succeeded in proving, that Einstein's equations of spacetime are not consistent with what we intuitively understand time to be (i.e. that it passes and the past no longer exists, the position philosophers call presentism, whereas Gödel seems to have been arguing for something more like the philosophy of eternalism), much as he, conversely, succeeded with his Incompleteness Theorems in showing that intuitive mathematical concepts could not be completely described by formal mathematical systems of proof.

and

Following Gödel, we can interpret the dust particles as galaxies, so that the Gödel solution becomes a cosmological model of a rotating universe. Besides rotating, this model exhibits no Hubble expansion, so it is not a realistic model of the universe in which we live, but can be taken as illustrating an alternative universe which would in principle be allowed by general relativity (if one admits the legitimacy of a nonzero cosmological constant). Less well known solutions of Gödel's exhibit both rotation and Hubble expansion and have other qualities of his first model, but travelling into the past is not possible. According to S. W. Hawking, these models could well be a reasonable description of the universe that we observe, however observational data are compatible only with a very low rate of rotation.[3] The quality of these observations improved continually up until Gödel's death, and he would always ask "is the universe rotating yet?" and be told "no, it isn't."[4]

We have seen that observers lying on the y axis (in the original chart) see the rest of the universe rotating clockwise about that axis. However, the homogeneity of the spacetime shows that the direction but not the position of this "axis" is distinguished.

Some have interpreted the Gödel universe as a counterexample to Einstein's hopes that general relativity should exhibit some kind of Mach principle,[3] citing the fact that the matter is rotating (world lines twisting about each other) in a manner sufficient to pick out a preferred direction, although with no distinguished axis of rotation.

Godel was way, way ahead of his time.

As for why I got out of math - aside from wanting to feed myself - it's this:

Gödel's incompleteness theorems are two theorems of mathematical logic that demonstrate the inherent limitations of every formal axiomatic system containing basic arithmetic.[1] These results, published by Kurt Gödel in 1931, are important both in mathematical logic and in the philosophy of mathematics. The theorems are widely, but not universally, interpreted as showing that Hilbert's program to find a complete and consistent set of axioms for all mathematics is impossible.

The first incompleteness theorem states that no consistent system of axioms whose theorems can be listed by an effective procedure (i.e., an algorithm) is capable of proving all truths about the arithmetic of the natural numbers. For any such formal system, there will always be statements about the natural numbers that are true, but that are unprovable within the system. The second incompleteness theorem, an extension of the first, shows that the system cannot demonstrate its own consistency.

Employing a diagonal argument, Gödel's incompleteness theorems were the first of several closely related theorems on the limitations of formal systems. They were followed by Tarski's undefinability theorem on the formal undefinability of truth, Church's proof that Hilbert's Entscheidungsproblem is unsolvable, and Turing's theorem that there is no algorithm to solve the halting problem.

For a math guy, letting that sink in deep is like disproving Jesus to a Christian.

Highly recommended reading Godel's works, or at least Godel, Escher, Bach.

 

[marduk]

I don’t think that’s a problem – locally time is always moving forward (positive) with all of the approaches to time travel that I’ve seen, so your entropy is always increasing (positive) in that reference frame. And with respect to an external observer, your entropy is decreasing (negative) but your time direction is also negative, so the product is still positive. I think if there were an entropic argument against time travel, physicists would’ve jumped on it – most of them will leap at any opportunity to reject the prospect of backward travel in time.

Here's what I'm getting at:

Life decreases the local entropic state for itself. And that's groovy thermodynamically because it actually increases the entropic state of it's environment by eating and shitting.

If you 'copy' life without the metabolic processes that led to it's existence into the present, you've violated both the local and environmental entropic state.

Plus, you've just manifested mass out of nothing as far as the universe is concerned. Because that mass won't exist all at one time, or doesn't exist yet. It's like a divide by zero error.

I’ve seen an entropic model of gravity, but not of time itself. Entropy defines the direction of time, but I don’t see how it can be time, because it’s a purely statistical concept. If you have a reference I’d like to read up on it; perhaps I’m missing something.

Sure, start here, I have a book on it somewhere. If I find it I'll let you know:

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says, the entropy of an isolated system can increase, but not decrease. Hence, from one perspective, entropy measurement is a way of distinguishing the past from the future. However, in thermodynamic systems that are not closed, entropy can decrease with time: many systems, including living systems, reduce local entropy at the expense of an environmental increase, resulting in a net increase in entropy. Examples of such systems and phenomena include the formation of typical crystals, the workings of a refrigerator and living organisms, used in thermodynamics.

Much like temperature despite being an abstract concept everyone has an intuitive sense of the effects of entropy. For example, it is often very easy to tell the difference between a video being played forwards or backwards. A video may depict a wood fire that melts a nearby ice block, played in reverse it would show that a puddle of water turned a cloud of smoke into unburnt wood and froze itself in the process. Surprisingly, in either case the vast majority of the laws of physics are not broken by these processes, a notable exception is the second law of thermodynamics. When a law of physics applies equally when time is reversed it is said to show T-symmetry, in this case entropy is what allows one to decide if the video described above is playing forwards or in reverse as intuitively we identify that only when played forwards the entropy of the scene is increasing. Because of the second law of thermodynamics entropy prevents macroscopic processes showing T-symmetry.

When studying at a microscopic scale the above judgements can not be made. Watching a single smoke particle buffeted by air it would not be clear if a video was playing forwards or in reverse and in fact it would not be possible as the laws which apply show T-symmetry, as it drifts left or right qualitatively it looks no different. It is only when you study that gas at a macroscopic scale that the effects of entropy become noticeable. On average you would expect the smoke particles around a struck match to drift away from each other, diffusing throughout the available space. It would be an astronomically improbable event for all the particles to cluster together, yet you can not comment on the movement of any one smoke particle.

By contrast, certain subatomic interactions involving the weak nuclear force violate the conservation of parity, but only very rarely,[citation needed] According to the CPT theorem, this means they should also be time irreversible, and so establish an arrow of time. This, however, is neither linked to the thermodynamic arrow of time, nor has anything to do with our daily experience of time irreversibility.[1]

Entropy (arrow of time) - Wikipedia

A coupe off months ago we published a Physics Frontiers episode called “A Gravitational Arrow of Time” about this fascinating paper that identifies a gravitational arrow of time by modeling the evolution of the universe with novel concepts like complexity, information, and structure. It kind of blows my mind to see a paper that completely reframes the way we think about physics, yet is internally consistent, and offers new explanations – that’s very rare to see in academic physics papers.

Same kinda deal with entropy. In an informational universe, time actually makes sense. The problem is, if it's a one way computation (like encryption is), you could never go back in time.

 

[ALPHA ROMEO UNIFORM]

Bill Moore perhaps.

Where's the evidence on Bill Moore ? and" MK ULTRA stuff hmm naive to blame everything on that the CIA and those folks would have to employed thousands . Agree experiments were in action during the Cold War going on the declassified material and book out there. However, to label all the UFO and so encounters on MK ULTRA that is stretching the fabric of time. Reminds me of the throwing mud at a wall sooner or later some will stick.

 

[Randall]

Time travel does seem counterintuitive to us, but we really do have to reckon with it in real-world terms – here’s a mundane example that we absolutely know is real: the twin paradox (it’s not really a paradox, btw – it’s just kinda strange).

I think most people already know the scenario: an astronaut departs from the Earth and travels in space near the speed of light for awhile, leaving his identical twin brother behind on the Earth. The traveling astronaut twin is traveling through space at relativistic speed, which slows his rate of motion through time relative to his initial rest frame at the Earth (this conjoined space and time geometry is the key feature of special relativity). So when he gets back to the Earth, his brother is an old man, but only some smaller interval, perhaps mere days, have passed for the travelling astronaut twin. It seems unrealistic to our human intuition that a pair of identical twins could end up at different physical ages, standing side by side, simply by moving one of them through space at a high rate of speed, but it’s an absolutely proven scientific fact that this actually happens in physical reality. And gravity has the same effect of aging you more slowly, just like high-speed travel does.

Right. I get all that. But relative changes in localized systems involve different frames of reference. It's not really time travel in the sense we're talking about. It's more a time dilation situation. Let me try to illuminate the perspective I'm coming at this from this way: It may take a few steps, and then we can come back to the rest of the points. This is all very interesting, so maybe we'll both have some sort of epiphany ( or end up equally confused ). To make sure we're on the same page, let's start with what we mean by time in the first place. I'll go first:

Time is change, and all measurements of time depend on being able to detect change. So if change can be detected, time necessarily exists. Are we okay with that or do we need to refine that to some extent?

 

[marduk]

Right. I get all that. But relative changes in localized systems involve different frames of reference. It's not really time travel in the sense we're talking about. It's more a time dilation situation. Let me try to illuminate the perspective I'm coming at this from this way: It may take a few steps, and then we can come back to the rest of the points. This is all very interesting, so maybe we'll both have some sort of epiphany ( or end up equally confused ). To make sure we're on the same page, let's start with what we mean by time in the first place. I'll go first:

Time is change, and all measurements of time depend on being able to detect change. So if change can be detected, time necessarily exists. Are we okay with that or do we need to refine that to some extent?

Interestingly, in physics, the definition of time is the following:

It's what a clock says.

I'm not even kidding.

In relativity, proper time along a timelike world line is defined as the time as measured by a clock following that line. It is thus independent of coordinates, and a Lorentz scalar.[1]The proper time interval between two events on a world line is the change in proper time. This interval is the quantity of interest, since proper time itself is fixed only up to an arbitrary additive constant, namely the setting of the clock at some event along the world line. The proper time between two events depends not only on the events but also the world line connecting them, and hence on the motion of the clock between the events. It is expressed as an integral over the world line. An accelerated clock will measure a smaller elapsed time between two events than that measured by a non-accelerated (inertial) clock between the same two events. The twin paradox is an example of this effect.


The dark blue vertical line represents an inertial observer measuring a coordinate time interval t between events E1 and E2. The red curve represents a clock measuring its proper time interval τ between the same two events.
In terms of four-dimensional spacetime, proper time is analogous to arc length in three-dimensional (Euclidean) space. By convention, proper time is usually represented by the Greek letter τ (tau) to distinguish it from coordinate time represented by t.

By contrast, coordinate time is the time between two events as measured by an observer using that observer's own method of assigning a time to an event. In the special case of an inertial observer in special relativity, the time is measured using the observer's clock and the observer's definition of simultaneity.

Which means, it's what a clock says while the clock is moving relative to something else.

Or, in math:

The formal definition of proper time involves describing the path through spacetime that represents a clock, observer, or test particle, and the metric structure of that spacetime. Proper time is the pseudo-Riemannian arc length of world lines in four-dimensional spacetime. From the mathematical point of view, coordinate time is assumed to be predefined and we require an expression for proper time as a function of coordinate time. From the experimental point of view, proper time is what is measured experimentally and then coordinate time is calculated from the proper time of some inertial clocks.

Proper time can only be defined for timelike paths through spacetime which allow for the construction of an accompanying set of physical rulers and clocks. The same formalism for spacelike paths leads to a measurement of proper distance rather than proper time. For lightlike paths, there exists no concept of proper time and it is undefined as the spacetime interval is identically zero. Instead an arbitrary and physically irrelevant affine parameter unrelated to time must be introduced

Which is to say, it's what a clock says depending on what you're doing as measured from the clock.

It gets even goofier from that point forward.

 

[Randall]

Interestingly, in physics, the definition of time is the following: It's what a clock says. I'm not even kidding.

That's like saying heat is what the thermometer says. What I'm getting at is more fundamental. What the clock says is a measure of change. Different clocks use different types of change such as the movement of a gear, the oscillation of a crystal, the decay of an isotope. If those things never changed, the clock's time would never change.

 

[Trajanus]

And yet it was leaked and blown wide open.

I presume that happened because it was no longer deemed worth keeping under wraps. Whatever is behind the phenomenon does care about maintaining secrecy.

 

[Trajanus]

Eh, maybe. I remember seeing a Richard Dolan talk where he showed infrared footage of a TR-3B-looking craft zooming around the upper atmosphere on an odd sort of meandering trajectory, with no observable emissions or turbines – it sure looked like field propulsion of some kind, and if I had to guess, I would guess that it was US military tech. I’d love to really know how much progress we’ve made in those directions. I sort of assume that we’ve made some progress, though perhaps only at the lab level, but I very much doubt that we can produce anything like the dramatic leaps from a dead hover to over the horizon in a second or two, which we seem to hear about often.

Agreed. Progress is limited at best or we'd see more of this.
@blowfish: I just recall an accusation against Bill Moore as the perpetrator of MJ12 hoaxes. IIRC the source was The Randle Report.