Hi rpenner. Thankyou for your reply. That is precisely it: Is there something “postulated to tend to cause it”? The observational construct is not the reality itself, so I do not have to postulate anything except the gravitational field effects on the neutrino’s increasing “rapidity” from emitter to black hole horizon. GR acceleration is what it is irrespective of which observational convenience one uses for abstractions of that reality. No more. No less. Again, that is the point. You earlier said the “neutrino increases in rapidity”...so you must have some “co-ordinate system” within which that “rapidity” is the real effect irrespective of abtractions about “relative to itself” etc which you now use to negate your earlier statement of the reality to which we have both agreed. No matter what you call it, the reality is what it is, as agreed already. The emitter is at a certain location far from the event horizon and a neutrino is emitted radially towards the black hole at a speed which you have in the past said cannot be reliably distinguished from speed of a photon. So let’s use a ‘co-emitted’ photon as a “control” against which the reality for the neutrino can be compared all the way to the horizon. We know the speed of the photon does not change even as its energy increases; but what is happening to the neutrino by comparison? Being a non-zero-rest-massed particle, it accelerates (in its time-like way, as you prefer). It accelerates due to real gravity effects, not some ‘postulated’ unknown effect. The question was and still is therefore: Will the neutrino (whose speed at emission is ALREADY "virtually indistinguishable from that of lightspeed") ever increase to match the photon speed (NOT overtake the photon itself) before the neutrino hits the event horizon? If not, what is to prevent it being accelerated by gravity in the usual way as non-zero-rest-massed particles are in reality?.....irrespective of whatever co-ordinate system is abstractly used to ‘see’ it one way or another ‘theoretically’; ie, there is nothing ‘theoretical’ about something (like a feather) being dropped from far up in space in the direction of the Moon’s surface, accelerating due to gravity and hitting the Moon surface with greater inward-radial “rapidity” than it had when it was dropped. You are already on record as stating that co-ordinate systems are “UN-real”. I agree with you. Given that agreement, it is therefore irrelevant to the reality I am asking about, as it is, and not with respect to any “UN-real” theoretical overlay or other. I already pointed out that the “Electron’s point of view” (or for that matter, the “Neutrino’s point of view”) is merely just “co-ordinate views” which we have already agreed are “UN-real” things. That is why we must follow the reality effect irrespective of whichever “UN-real view” you may theoretically “prefer”. That reality effect is that, under gravitational acceleration effects between the emitter and the horizon locations: the non-zero-rest-massed Neutrino’s “rapidity” is increased by gravity towards the event horizon; while the “rapidity” of the zero-rest-mass photon is NOT increased. The question was and still is: What stops that increase in neutrino “rapidity” (which was initially ALREADY "virtually indistinguishable from lightspeed" at emission) from accumulating to equal lightspeed (and what happens at that stage, as I also asked earlier)? I realize you are mathematically gifted, but reality is not the maths. That exercise is full of assumptions and theoretical “UN-real viewpoints”. Beware of the law of “garbage in, garbage out”. All that hyperbolic rotation ‘theoretical view’ is not an answer to what actually must happen in reality given the rest-massed Neutrino (as compared to what must happen in reality given the non-rest-massed photon) as affected by gravity acceleration between the same emitter to the same horizon. That reality answer has yet to be provided by you in other than the “un-real’ theoretical terms which you have ‘prefered’ to ‘frame’ it so far. Unlike other acceleration forces, gravity is “always on”. So a rest-massed particle is accelerated, and increasingly so the closer it approaches the horizon. There is no ‘exhaustion’ of acceleration between the emitter and horizon. So any mathematical/geometrical “treatment” like that is self-referential and based on more theoretical “un-real” overlays which does not actually treat the reality that gravity makes rest-massed particles accelerate EVER MORE STRONGLY as it closes on the horizon; so the reality is not a “static” one. And this IS predicated on the fact that mainstream physics treats the neutrino as a non-zero-rest-massed particle. Are you implying that this is not the case? The reality being discussed in context of comparison between what happens to a photon emitted along with the neutrino, just so that we do not lose sight of the gravity acceleration effect being ‘different’ for rest-massed and non-rest-massed entities when it comes to what you termed “rapidity”. Hence the questions I asked. And, given the quantum-scale uncertainties, at what point would a ‘very-near lightspeed’ particle JUMP temporarily into the ‘lightspeed’ range; and what is there to prevent that from happening; and if nothing, what happens to the neutrino ‘particle/energy’ entity at that point? These are all valid questions given the considerations raised here. And I much appreciate your ‘theoretical view’ efforts in reply to date, even though they are not the ‘reality view’ I am seeking to get answers in. Thanks.