I’ve read several times some scientific author suggest that to an external observer, someone (or something) that’s on a bullseye path toward an astronomical Black Hole, well someone will not only be travelling at a time rate slower and slower by the external observer’s clock as they (let’s call that person a pilot) approach the Event Horizon (or just the Horizon), but in fact at contact with the Horizon, the pilot’s time, again as recorded by the external observer, will have stopped. In other words, Black Travel the external observer will never witness the pilot’s crossover from outside the Black Hole’s Horizon to inside the Black Hole’s Horizon. The pilot will appear to be frozen in time at the Horizon, as witnessed by the external observer for all eternity, yet as far as the pilot is concerned, everything is normal in terms of time flowing at one second per second. The pilot, from the pilot’s perspective, crosses the Horizon as easily as driving to the local supermarket.
Now that’s a major paradox. The pilot can’t be crossing the Event Horizon at one second per second, while at the same time being frozen in time while crossing, which is the case according to our external observer. Of course the paradox is bullshit. To an external observer, time only comes to a screeching halt from their point of view for someone external to them if they witness that someone travelling at the speed of light. Firstly, that’s a physical impossibility. There’s no reason to believe that our cosmically Black Hole bound pilot is crossing the Horizon at light speed. There’s no absolute requirement that our pilot is crossing the Horizon at the speed of light. The pilot in fact might have fired retro-rockets to slow down just prior to crossing the Horizon in order to better savour the moment (just like crossing the equator for the first time)! So, in actual reality, our external observer will see the pilot cross the Horizon, albeit at a way slower rate than the pilot will because the pilot is travelling, hence doing the Horizon cross-over, though at less than the speed of light but still at some subluminal velocity relative to the external observer. Any velocity incurs some slowing of time when viewed by an external observer; the faster the velocity, the greater the slowdown. IMHO, some ‘experts’ need to go back and redo Physics 101.
Only here’s the expert’s explanation which explains why there is no paradox.
Space is a thing and mass (hence gravity) can warp space, twist space around its little finger. The most extreme form or amount of gravity is contained within a cosmic Black Hole from which not even light can escape – hence the blackness of the Black Hole. Because space is a thing, the Black Hole or the super ultra intense gravity of a Black Hole can suck in space (as well as matter). Okay, so a Black Hole can gobble up space.
Issues arising #1: IMHO, space is not a thing but a concept. Gravity therefore cannot interact with space. Gravity is a thing; matter is a thing; light is a thing, so interactions between gravity and matter and light (representing energy which is just matter in another form) are not an issue.
Issues arising #2: presumably that means that anything that has gravity (like you) will suck in some amount of space since even the tiniest amount of gravity will warp space to some degree.
Meantime, back to the expert: Space (as a thing), gets sucked towards a cosmic Black Hole at less that the speed of light, but speeds up as space gets closer and closer to the point of no return (the Event Horizon). When space crosses the Horizon, it is travelling at the speed of light. Once inside the Horizon, space falls down the gravity gurgler at a speed greater than that of light, which is okay since space, albeit a thing doesn’t have any mass. Anything with mass cannot travel at superluminal velocities since anything with mass can’t cross the speed of light boundary from subluminal to become superluminal.
Any physical object crossing the Event Horizon will be giving off and/or reflecting light (or any other form of electromagnetic energy) at the speed of light. But the Horizon is that exact boundary between space being sucked in at less than light speed and being sucked in at greater than light speed so light being given off at the Horizon is escaping at the same velocity that it is being sucked in. It’s like you running on a treadmill at the exact same velocity but opposite direction to that of the treadmill. To an external observer you are running yet standing still, and would appear so for all eternity.
We have to assume that the material object itself can’t be crossing the Event Horizon at the speed of light (that’s not allowed), nor will it travel at or beyond the speed of light once inside the cosmic Black Hole and dropping down it’s gravity gurgler. Though the material object crosses the Horizon at less than light speed, the visual image of that object will travel at light speed, but light at the Horizon is like the runner on the treadmill. It’s a balancing act in that the image from the object is escaping from the Black Hole’s Horizon outward bound at the exact same rate as it is being sucked into and past the Horizon by space itself.
Issues arising #3: IMHO, the Event Horizon must be extremely thin, since the Horizon by definition is that boundary where a velocity just a tiny, tiny, tiny (add some more ‘tiny’ here) fraction under the speed of light becomes just a tiny, tiny, tiny (add some more ‘tiny’ here) fraction above the speed of light. Or, the Horizon is that boundary that marks the speed of light exactly (and any tiny, tiny, tiny deviation either side is no longer the speed of light). The Horizon must in fact be the shortest allowable thickness that’s allowed by quantum physics, which is the Planck Length (which is so small in length, or thickness, not even the most powerful of microscopes could resolve it).
The implications revolve around the fact that any image, like that of our pilot in their spacecraft, is going to be massively larger than the thickness of the Event Horizon. In actual practice our outside observer will more decidedly not see the image frozen at the Horizon for all eternity. Part of the image will have to be above the Horizon and thus be able to escape away from the Black Hole. Part of the image will be below the Horizon and sucked into the cosmic Black Hole never to be seen again. Any remaining image is one Planck Length thick – invisible to the human eye and the most powerful of microscopes. Even that tiny remnant won’t last long due to ever present quantum fluctuations. The Horizon has the tiniest of jitters but it’s enough to disrupt the remaining bit of image from remaining for very long. The upshot is that the frozen image of the pilot and the craft as witnessed by the external observer will be fleeting at best.
Issues arising #4: When it comes to those astronomical Black Holes, we are all external observers. If our expert is correct, and images are frozen for all time at the Event Horizon by objects consisting of matter and energy that cross the Horizon, then absolutely anything and everything that has crossed over the Horizon since the creation of any specific cosmic Black Hole – since the year dot probably – well their images collectively should still be, well, visible. Each individual image would be piled on top of the next one top of the next on top of the next and so on. Somehow I very much doubt that’s the case. It should be bleeding obvious through our astronomical telescopes. And so, I repeat that IMHO, some ‘experts’ need to go back and redo Physics 101.