MigL

To be fair Zap, John usually is not, but Dim is always ambiguous ... 😁😁

IIRC, that happens when a test mass is counter-rotatng wrt the BH, within the ergosphere, and by what is called the Penrose process, that mass can split in two, one half falling through the EH and gaining negative energy, while the other half has more energy than the original. This energy comes from the rotational energy of the BH, and slows its rotation down. Usually, the accretion disk is rotating with the BH ( due to frame dragging effects ) and actually add to its rotational momentum.

If anmyone doesn't want their Astra-Zeneca, send them to Canada. Our only hope for large scale vaccination is if J Biden is right, saying that all Americans who want a vaccine will have it by the end of May; then ( maybe ) Moderna and Pfizer will send us some.

I would think that R-N and Schwarzschild BHs are highly unrealistic. A R-N BH with any charge will be highly 'selective of the ionized plasma in its accretion disk, and quickly rid itself of that excess charge. While any collapsing body, with even the smallest hint of rotation, will see it amplified tremendously by the 'ice-skater drawing in her arms' effect. That makes Kerr BHs the only realistic solution. Hawking radation is only a 'tacked-on' QM effect, due to having assigned entropy to the surface of the EH, and therefore, a 'temperature' to the BH. Glad this conversation is ongoing.

You are one of the people I've learned a lot about GR from, on this Forum, and a previous one. You were always appreciated, and while sad to see you go, you gotta do what makes you happy. Good luck; hope to hear from you again, whenever you can.

Today I learned that a 17 year old girl will marry a 93 year old widower. https://www.yahoo.com/huffpost/civil-war-veteran-widow-helen-jackson-030518406.html Thanks Zap.

No, it was M Grossmann, an expert in differential geometry and tensor calculus, and a former classmate of A Einstein at the ETH, who helped Einstein with the non-Euclidian geometry of GR. Meanwhile N Tesla was feeding birds in the park , and going broke with unworkable schemes. Did I mention he was nuts ?

And why do you keep bringing up N Tesla ? You realize he was half-nuts ? ( its a fine line between genius and madman )

They may be fellow countrymen, but I don't think Studiot is as 'quirky' as P A M Dirac is reputed to have been. What do you think ?

What 'time' are you referring to ? Proper time is necessarily linear, as the clock moves along your wordline. "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 is a Lorentz scalar.[1] The proper time interval between two events on a world line is the change in proper time." Co-ordinate time is not necessarily linear. "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." Quotes from Proper time - Wikipedia

It was also, IIRC, derived from experimental data, not first principles. I could, however, be wrong; it has been a while since I read that. And it was P Dirac, I believe, who showed that E Shrodinger's wavelike differential approach, and W Heisenberg's matrix mechanics were equivalent.

Frankly, I haven't a clue what you're referring to, half the time. I gave an example of a classical wave which demonstrates uncertainty. And you started talking about 'collapse'. What 'collapse' are you talking about here ? Or is it simply nonsense, as usual ?

Didn't have time to read all your post. The first part, which deals with the fact that vision ( used by most predators at long distance ) can be asily fooled by evolved 'countermeasures', is not evidence for your assertions. It is simply that as evolution ( adaptive survival of the species ) has evolved sharper eyesight in predators, it has also evolved camuflage in their prey.

Noahs flood has been proposed as ancient memories of the Zanclean flood, of 5 million years ago, that flooded the Mediterranean basin. I find it hard to believe that our ancestors of 5 million years ago ( Australopythecus, I believe ), could preserve such 'memories' through story-telling, since Homo Sapiens only emerged ( in Africa ) about 300 000 years ago.

I predict that, when AI gains 'imagination', and starts believing it has a 'soul', we'll be close. Of course, by then, it will have ALL human failings, and send Terminators back in time to kill me.

What do you mean by a classical wave 'collapse' ?

I know what you mean ... I was thinking about it overnight, and almost ready to give in to Halc and md65536 PoV, thinking that maybe I had made some incorrect assumption. Then Markus posted, and now I'm not sure either. It seems to be a scale problem, with differing scenarios, and gruesome calculations. But I did enjoy th discussion 🙂 .

The best example I can think of involves classical wave motion, and, apparently, was an example used by R Feynman. To localize a wave packet, and so determine its position to arbitrary precision, it has to be built up of many ( infinite ? ) harmonics, such that wavelength/frequency, and therefore momentum, hv, are increasingly indeterminate. The alternate, where the wave has an exact wavelength/frequency ( and momentum ), sees a wave of infinite length.

I don't understand, JC. The photon has to hit your eyes (radially ) for you to see it. If it moves tangentially, at the speed of light, it will not be there anymore when your eye gets there. As for red shift, the wavelength of radially outgoing light is redshifted to infinity at the EH, as measured at any distance outside the EH. That means it disappears; there is nothing imperceptible about it. ( or should that be perceptible ? ) Except the OP, where he says ... "At some point, the astronaut sends a message basically saying "My feet are now inside the event horizon", and Earth eventually receives that message." IOW, he 'sees' ( gets information from ) his feet, inside the EH, and relays that information arbitrarily far away, to Earth. For simplicity's sake, I recommend considering only radial movement, and Schwarzschild BHs

If it went 900, it wouldn't hit your eyes. ( so you still wouldn't see it )

Even if you could devise an experiment which didn't involve an interaction, you could never measure momentum and position of a quantum particle to arbitrary precision. The uncertainty is inherent to the model, because the model, QM, necessarily treats them as waves. ( the clue is in the name, wave function )

Maybe the confusion stems from the fact that we can't imagine not being able to see our own feet ... Light, like any nformation, cannot travel to the exterior of the EH of a BH. Gravity, or rather, the pre-existing gravitational field, does. When we consider very large BHs, it is the differential gravity which leads to tidal forces, and since the differential gravity is small for very large radius, there is no spaghettification, and things are normal ( GRAVITATIONALLY ) for a laarge BH. For a small BH, however, the differential gravity is very large because of the small radius, and the tidal forces will spaghettify. That does not mean that everything else is also 'normal' on crossing the EH of a large BH. If you had a transmitter attached to your feet, could they transmit a signal to a receiver on your head, after your feet had crossed the EH, but your head was still outside ? And a repeater on your head, which is still outside the EH, could then transmit the signal to infinity ? Could a transmitter that is further inside the EH transmit a signal to your feet, which could then tranxmit it to your head ? Could you have a chain of transmitters, all sending information to the next, all in close proximity, lowered all the way down to the center, and transmit information, in small steps, to your head, and out to distant observers ? If you answer yes to any of the above, I congratulate you. You have just 'discovered' a way to probe the singularity/center of a BH. ( i'm being sarcastic 🙂 ) Addendum: the light cone of your feet is not the same as the light cone of your head. Your feet have their own proper time, and will cross the EH, while your head is still an external observer. Before reaching the EH, the light from your feet ) moving towards your head ) will be red shifted, and seemingly stop ( or rather, fade away ) at the EH. It will be followed by the disappearance/stopping of your knees, thighs, hips , waist chest and shoulders; all fading away to infrared and nothingness before your head ( and eyes ) cross; and you see nothing else ahead of you. I will grant you that, depending on your speed of radial infall, those frozen, red-shifted images will experience some blue-shift because of your infall speed, so you may 'crash' into a sort of frozen image at the EH ( but I would think not, as the images have their wavelength stretched to infinity at the EH, and you cannot be moving fast enough to blue-shift them back ).

His 'package' ? I think Joe is probably much more indebted to Pfizer for Viagra, not the Covid vaccine.

This is no different than the case where the iron particles are suspended in water with no external magnetic field. The iron particles stay in suspension because they are josteled about by the kinetic energy of the water molecules in the weak gravitational potential. When you apply the external magnetic field of much greater potential, the iron particles now have much greater kinetic energy as they move towards the magnet, imparting some of their kinetic energy to the water molecules and heating it up.

Is this a screenplay for a prequel to DieHard, when John Mcclane is in high school ? And is "Yippie-kai-yay, mother f***er" appropriate language for a high-schooler ?