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originally posted by: Erno86
Most stars in our universe don't turn into black holes...though some have they're plasma or photons sucked into them; buy a star that has turned into a black hole. Since some black holes eject lighted photons or mass at there magnetic poles, proves that their is not an event horizon surrounding a black hole --- but what Hawking describes as an "apparent horizon" --- whereas a percentage of photons do not get sucked into a black hole, but are slipped into a apparent horizon and ejected at the magnetic poles of the black hole at near the speed of light.
That Phage...suggests that my hypothesis on interstellar capable starship propulsion --- might indeed be possible --- if it is equipped onboard with a micro-mini black hole propulsion unit.
... the existence of a locally definable apparent horizon is quite sufficient for obtaining the Hawking effect ...
One particularly important result, due to Hajicek [8], is that the existence of a strict event horizon is not nec- essary, and that a long-lived apparent horizon is quite sufficient to generate the Hawking flux (see also [9–11]). More recently, the present authors have developed some “analogue spacetimes” [18–20] for which a Hawking flux is generated even in the absence of a trapping/apparent horizon [21, 22]
...
We have demonstrated that any collapsing
compact object (regardless of whether or not any type
of horizon ever forms) will, provided the exponential ap-
proximation and adiabatic condition hold, emit a slowly
evolving Planckian flux of quanta.
originally posted by: moebius
a reply to: Korg Trinity
Could you please provide a paper or your own derivation that shows that Hawking radiation is only possible when there is a event horizon? Because I can find plenty examples stating that Hawking radiation is a more general effect, not constrained to event horizons.
The paper here arxiv.org... :
... the existence of a locally definable apparent horizon is quite sufficient for obtaining the Hawking effect ...
And more arxiv.org... :
One particularly important result, due to Hajicek [8], is that the existence of a strict event horizon is not nec- essary, and that a long-lived apparent horizon is quite sufficient to generate the Hawking flux (see also [9–11]). More recently, the present authors have developed some “analogue spacetimes” [18–20] for which a Hawking flux is generated even in the absence of a trapping/apparent horizon [21, 22]
...
We have demonstrated that any collapsing
compact object (regardless of whether or not any type
of horizon ever forms) will, provided the exponential ap-
proximation and adiabatic condition hold, emit a slowly
evolving Planckian flux of quanta.
And more here arxiv.org...
Also here I can read that the Unruh effect is a variation of Hawking radiation or vice versa, as the accelerating observer will perceive an apparent event horizon.
arxiv.org...
Are they wrong? Can you show why?
We find that, in any realistic collapse scenario, the backreaction effects do not prevent the formation of the event horizon. The time at which the event horizon is formed is, of course, delayeddue to the radiated flux — which decreases the mass of the shell — but this effect is not sufficient to prevent horizon formation.
The Hawking radiation derived from quantum field theory shows a spectrum that is precisely thermal.
In this thesis, the Hawking radiation is derived as a tunneling process through the event horizon of a black hole. The tunneling rate is related to the imaginary part of the action of the tunneling particle.
Since energy conservation is respected in the calculation, the obtained tunneling rate correponds to a spectrum which is not precisely thermal but has an additional correction term
5 Hawking radiation 16
5.1 Particle creation in the Sandwich spacetime . . . . . . . . . . 16
5.2 Particle creation in the Schwarzschild spacetime . . . . . . . . 19
“The [paper] is nonsense,” Unruh said in an email to IFLS. “Attempts like this to show that black holes never form have a very long history, and this is only the latest. They all misunderstand Hawking radiation, and assume that matter behaves in ways that are completely implausible.”
According to Unruh, black holes don’t emit enough Hawking radiation to shrink the mass of the black hole down to where Mersini-Houghton claims in a timely manner. Instead, “it would take 10^53 (1 followed by 53 zeros) times the age of the universe to evaporate,” he explains.
“The standard behaviour by such people [who don’t understand Hawking radiation] is to project that outgoing energy back closer and closer to the horizon of the black hole, where its energy density gets larger and larger,” he continued. “Unfortunately explicit calculations of the energy density near the horizon show it is really, really small instead of being large-- Those calculations were already done in the 1970s. To call bad speculation "has been proven mathematically" is, shall we say, and overstatement.
In summary, the recent papers by Mersini-Houghton and Pfeiffer contribute to a discussion that is decades old, and it is good to see the topic being taken up by the numerical power of today. I am skeptic that their treatment of the negative energy flux is consistent with the expected emission rate during collapse. Their results are surprising and in contradiction with many previously found results. It is thus too early to claim that is has been shown black holes don’t exist.
originally posted by: moebius
a reply to: Korg Trinity
Could you please provide a paper or your own derivation that shows that Hawking radiation is only possible when there is a event horizon? Because I can find plenty examples stating that Hawking radiation is a more general effect, not constrained to event horizons.
The paper here arxiv.org... :
... the existence of a locally definable apparent horizon is quite sufficient for obtaining the Hawking effect ...
And more arxiv.org... :
One particularly important result, due to Hajicek [8], is that the existence of a strict event horizon is not nec- essary, and that a long-lived apparent horizon is quite sufficient to generate the Hawking flux (see also [9–11]). More recently, the present authors have developed some “analogue spacetimes” [18–20] for which a Hawking flux is generated even in the absence of a trapping/apparent horizon [21, 22]
...
We have demonstrated that any collapsing
compact object (regardless of whether or not any type
of horizon ever forms) will, provided the exponential ap-
proximation and adiabatic condition hold, emit a slowly
evolving Planckian flux of quanta.
And more here arxiv.org...
Also here I can read that the Unruh effect is a variation of Hawking radiation or vice versa, as the accelerating observer will perceive an apparent event horizon.
arxiv.org...
Are they wrong? Can you show why?
According to Unruh, black holes don’t emit enough Hawking radiation to shrink the mass of the black hole down to where Mersini-Houghton claims in a timely manner. Instead, “it would take 10^53 (1 followed by 53 zeros) times the age of the universe to evaporate,” he explains.
In summary, the recent papers by Mersini-Houghton and Pfeiffer contribute to a discussion that is decades old, and it is good to see the topic being taken up by the numerical power of today. I am skeptic that their treatment of the negative energy flux is consistent with the expected emission rate during collapse. Their results are surprising and in contradiction with many previously found results. It is thus too early to claim that is has been shown black holes don’t exist.
originally posted by: neoholographic
a reply to: Korg Trinity
You can't teach this stuff because you don't even know what an event horizon is. When you claim an even horizon rips apart virtual particles it's just asinine. An 11 grader interested in science wouldn't make this silly mistake.
"The smaller the black hole the greater its radiated power and the less its mass, but the shorter its lifetime until it completely evaporates. As a black hole absorbs new matter, it will radiate it."
"An event horizon has been defined as an invisible cloak covering a black hole that allows nothing --- not even light --- to escape. The option proposed by Hawking's paper is that black holes simply don't have an event horizon and the notion of an event horizon, from which nothing can escape, is imcompatable with quantum theory.
According to Nature, this claim is based on the idea that quantum effects around the black hole cause space-time to fluctuate too inconsistently to maintain any kind of sharp border.
Hawking's proposed alternative to the event horizon is an "apparent horizon," which temporarily holds matter hostage and mangles it before releasing it."
originally posted by: Erno86
a reply to: Korg Trinity
Korg --- May I suggest that you google: black hole apparent horizon an black hole starships
www.abc13.com/archive/9407566
"The smaller the black hole the greater its radiated power and the less its mass, but the shorter its lifetime until it completely evaporates. As a black hole absorbs new matter, it will radiate it."
"An event horizon has been defined as an invisible cloak covering a black hole that allows nothing --- not even light --- to escape. The option proposed by Hawking's paper is that black holes simply don't have an event horizon and the notion of an event horizon, from which nothing can escape, is imcompatable with quantum theory.
According to Nature, this claim is based on the idea that quantum effects around the black hole cause space-time to fluctuate too inconsistently to maintain any kind of sharp border.
Hawking's proposed alternative to the event horizon is an "apparent horizon," which temporarily holds matter hostage and mangles it before releasing it."
You have been going on and on about how a collapsing star can't emit Hawking Radiation and how the event horizon rips apart virtual particles.
originally posted by: Erno86
a reply to: Korg Trinity
Any thoughts or suggestions on my hypothesis, about the feasibility of an onboard micro-mini black hole propulsion unit, that is installed on a saucer starship? Whereas the starship funnels photons toward the propulsion unit, and the micro-mini black hole expels the photons at it's magnetic poles, which are funneled towards outlet thrusters --- increasing speed --- exponentially squared, easily up to the speed of light and beyond into the superluminal realm.
Thanks
originally posted by: dragonridr
a reply to: Korg Trinity
I agree a black hole isnt a viable energy source for any kind of space travel. The energy requirements as you said would make it impractical. Not to mention dangerous to the ship and crew do to radiation.
Author George Dyson spins the story of Project Orion, a massive, nuclear-powered spacecraft that could have taken us to Saturn in five years. His insider’s perspective and a secret cache of documents bring an Atomic Age dream to life.
Text "Although the process of generating a black hole is extremely massive, it does not require any new physics. Also if a black hole, once created, absorbs new matter, it will radiate it, thus acting as a new energy source.
The evaporation time of a black hole is proportional to the cube of its mass. For a black hole of 10" kg the evaporation time is 2.667 billion years.
The power in the Hawking radiation from a solar mass black hole turns out to be a minuscule 9x10-29 watts.
As the photons are absorbed into the ergosphere of the rotating black hole causes contiguous spacetime to rotate as well, making a whirlpool --- thusly making a location where the rotation speed is the speed of light --- with the rotational energy would be extracted outward along the magnetic field lines by something called a torsional Alfen wave.
originally posted by: dragonridr
a reply to: Korg Trinity
I agree a black hole isnt a viable energy source for any kind of space travel. The energy requirements as you said would make it impractical. Not to mention dangerous to the ship and crew do to radiation.