It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
She claims that as a star dies, it releases a type of radiation known as Hawking radiation... it also sheds mass, so much so that it no longer has the density to become a black hole.
Before the black hole can form, she said, the dying star swells and explodes.
The singularity, as predicted, never forms, and neither does the event horizon - the boundary of the black hole where not even light can escape.
She claims that as some stars die, they release a type of radiation known as Hawking radiation... they also shed some mass, and in some cases so much so that they no longer have the density to become black holes.
Before a black hole can form, she said, the dying stars swell and explode.
The singularity, as predicted, wouldn't form, and neither would the event horizon - the boundary of the black hole where not even light can escape.
Yes, I know that. What changes is the gravity gradient. But you said this earlier:
Why can you do this? Because the gravitational field of a black hole is the same gravitational field of the collapsing star.
The gravity field changes and gets stronger as the star collapses.
No. Hawking radiation occurs once the horizon forms and continues for long afterward.
What produces these quantum effects near the event horizon? It's the stronger gravitational field that occurs as a star collapses.
rationalwiki.org...
The vacuum of space (or, more correctly any "space") has an energy level. Nothingness is in fact something[2]. Due to the uncertainty principle, virtual particles will always appear from the energy of a vacuum and always appear in pairs. These particles "borrow" energy from the vacuum and immediately collide and annihilate themselves, repaying the energy back into the vacuum so as not to violate the laws of thermodynamics.
Without the separation of particles which occurs because of the event horizon, there is no Hawking radiation.
Again, the event horizon doesn't produce Hawking Radiation. QUANTUM EFFECTS NEAR THE EVENT HORIZON PRODUCES HAWKING RADIATION.
No. The idea is that one member of a pair of virtual particles which forms near the event horizon produces Hawking radiation.
The matter falling into the black hole from the collapsing star produces these quantum effects and gives you Hawking Radiation not the event horizon.
You're the only one who is throwing that word around.
It's amazing that people are trying to act like Mersini Haughton is an idiot for even asking these questions.
No, he did not say that black holes do not exist. That's what the headlines about it said. Your source:
Didn’t Hawking recently claim that black holes as we’ve come to understand them may not exist?
phys.org...
In reality, the headlines should not be "black holes don't exist" but "black holes are more complicated than we thought, but we are not going to really know how complicated until gravity and quantum mechanics try to get along".
originally posted by: Phage
a reply to: netbound
No, he did not say that black holes do not exist. That's what the headlines about it said. Your source:
Didn’t Hawking recently claim that black holes as we’ve come to understand them may not exist?
phys.org...
In reality, the headlines should not be "black holes don't exist" but "black holes are more complicated than we thought, but we are not going to really know how complicated until gravity and quantum mechanics try to get along".
Lol. No wonder then that, einsteins GR is still going strong.
originally posted by: Klassified
I have no idea whether the lady is correct, but if she is, and the past is any indicator, we won't know for anywhere from 25-100 years. That's usually about how long it takes for academia to accept anything that goes against the present standard.
But if she's wrong(even if she's right), we'll know that immediately.
My word. Couldn't have said it better myself
originally posted by: pot8er
a reply to: neoholographic
Buckmeister Fuller said and I paraphrase slightly I suspect. ' If I'm working on a problem and the answer is not both simple and beautiful, then I know it's wrong.'
originally posted by: Korg Trinity
"... more than likely ruin her career.
...What do you think would happen to my career..
...it's hard enough achieving a research grant"
?
Note that Hawking radiation would still be present, even in the absence of an event horizon [15, 16]. More- over, the present authors have noticed that, kinemati- cally, a collapsing body could still emit a Hawking-like Planckian flux even if no horizon (of any kind) is ever formed at any finite time [17];
The paper, which was recently submitted to ArXiv, an online repository of physics papers that is not peer-reviewed, offers exact numerical solutions to this problem and was done in collaboration with Harald Peiffer, an expert on numerical relativity at the University of Toronto. An earlier paper, by Mersini-Houghton, originally submitted to ArXiv in June, was published in the journal Physics Letters B, and offers approximate solutions to the problem.
Particles and anti-particles are constantly appearing and vanishing in the physical vacuum. This can be indirectly observed in numerous lab experiments here on Earth. Near a black hole, the gravitational field changes in strength due to its tidal component, and when this tidal scale equals the scale of a virtual particle pair, the pair can be tidally ripped apart. This causes one of the particles to escape to infinity and the other to fall through the horizon and be lost. The gravitational field, meanwhile, has lost energy in doing the work to separate the particles and to confer 'positive energy' to the particles that escape to infinity as the Hawking Radiation. The net effect is that the black hole has lost mass equal to the mass of the escaping particle.
Hawking radiation starts out as two virtual particles on the horizon of a black hole, one particle and one antiparticle. Usually, the virtual particles are a pair of photons. A photon is its own antiparticle, so this doesn't contradict the fact that a particle-antiparticle pair are produced. However, one particle falls into the black hole, the other comes out. Once the particles separate due to the black hole's gravitational field, they are no longer virtual particles, but real particles.
The best way to think of why indeed the black hole is losing energy in the matter/antimatter scenario is that particles are actually created at the expense of gravitational energy (which is then related to the properties of space-time). Consider the following example. Say there's a particle moving toward a large mass --the particle feels the gravitational pull of the mass. The gravitational field exerts a potential energy on the particle which in turn is converted to kinetic energy of the moving particle. To conserve total energy the potential energy of the mass gets more negative. Indeed, the mass experiences a loss of potential energy as the particle experiences a gain in kinetic energy. So in the same way, at the black hole event horizon, two virtual particles --say photons --separate due to the gravitational force of the black hole; one adds negative energy as it falls into the black hole, the other (now a real particle) escapes.
First Observation of Hawking Radiation?
Physicists claim to have observed Hawking radiation for the first time from a “white hole” in their lab
originally posted by: moebius
a reply to: Korg Trinity
and Phage
I am curious. What is your position regarding the statement that "particles can be created by time independent gravitational fields that have a horizon AND time dependent gravitational fields".?
What I can tell you is that a virtual pair of particles can only be separated by a Horizon.
Particle creation is a generic feature of curved space-time quantum field theory [9]. The time-changing gravitational field of imploding stars gives rise to quantum gravitational particle creation. For the case of stars collapsing to Black Holes, this process is known as Hawking radiation. The whole flux of particles is created from the time the collapse starts, up to the point when the horizon forms, with the very last photon becoming the horizon. From the moment of horizon formation onward, the surface gravity κ of the black hole is nearly a constant and no radiation can escape from the Black Hole to future infinity, since by the definition of the horizon, photons are trapped by the horizon.
Particle creation can be thought of as arising from the ’tidal’ forces of the changing gravitational field near the surface of the collapsing star that ’rip apart’ vacuum pairs of particles antiparticles [2, 3, 13, 15, 18]. The positive energy particles escape and travel to future infinity becoming part of Hawking radiation, while the negative energy particles fall inward in the star [13], [15, 18]. If Σ0 and Σf denote the 3-surfaces at the onset of collapse time and the end of collapse respectively, then the time lapse between the two surfaces is the time interval during which all of the Hawking radiation is produced, with the final photon γf being aligned to the horizon. Any other photon produced after γf has to be trapped by the horizon and can not escape the black hole.
The crucial point to be emphasized here is: Hawking radiation is produced by the changing gravitational field of the collapsing star, i.e. prior to the black hole formation, [18], [9]. Otherwise the surface gravity of the black hole κ, and the temperature of Hawking radiation would increase with time, leading to a nonthermal distribution of radiation. The event horizon of the black hole traps consequent photons of radiation produced near the event horizon. The photons produced after γf can not travel outwards, rather their geodesics focus inside the black hole. More explicitly, the surface gravity of the Black Hole is defined in terms of the 4-acceleration of an external observer. If κ were increasing with time, so would the acceleration of inertial relative to freely falling observers. For these reasons, quantum gravitational particle creation occurs during the collapse phase of the star,(see a seminal paper by Davies [18] for the details).
originally posted by: neoholographic
Virtual particles are not separated by the event horizon. That's just utter nonsense. They're separated by a changing gravitational field as the star is collapsing.
Although the event horizon is an imaginary line that's impossible to observe, astronomers have imaged the region around a giant black hole at the center of a distant galaxy, and measured, for the first time, the closest stable orbit in which matter can circle the black hole. The findings were reported today in the journal Science.
Based on new calculations of particle on the edge of a black hole, Hawking said in the PBS documentary "Hawking", "Some particles could escape the black hole, which seemed to make a mockery of the known laws of physics."
At the heart of this new theory, Orosz said, is an imaginary boundary called the event horizon.
"It's the boundary beyond which you cannot escape," Orosz said. "If you're outside the event horizon, in principle you can escape if you go fast enough and once you cross the event horizon you're stuck."
16. Because an object approaching Event Horizon will not even observe anything strange, it will not even know that it is actually approaching an Event Horizon because this boundary is nothing physical. It is only an imaginary boundary based on mathematical calculations.