Gravity

I'm sorry I spaced out right in the middle of that it took so much time to absorb it...bear with me while I catch up.

I think what you are describing is very similar to a theory that was prominent in the 19th century. It might have been associated with or part of Aether theory.

The rubber-sheet analogy only goes so far. It is an analogy and only applies when you divorce space from time.

In space (and on the rubber sheet) planets orbit in ellipses whereas in spacetime they follow straight lines called geodesics. In General Relativity gravity is not a force, but an intrinsic property of spacetime related to its curvature. It is the natural codification of the stress-energy metric tensor - Einstein's application Gauss' invention of tensor mathematics (tensors are generalised vectors, and vectors and scalars are simple tensors). You can, moreover, have curved spacetime in the where there is no mass - the Lagrangian points of of the Earth/Moon/Sun system for instance. There are in fact spacecraft 'orbiting' these points. Several.

Unlike bonafide forces, such as electrostatic forces whose magnitude depends on the amount of charge present, gravity does not work this way. It affects masses equally as Galileo demonstrated at Pisa. Two different masses fall at the same rate whereas two different quantities of charge accelerate differently, depending on how much charge is present.

You only 'feel' gravity when something - the ground, for instance - interferes with your natural trajectory through spacetime. When nothing blocks your progress, being in orbit for example, you feel no acceleration whatsoever.

Then we have frame-dragging, where spacetime itself is dragged around a rotating mass. It is most pronounced around, say, spinning black holes and neutron stars, but it happens whenever a mass rotates. Gravity Probe B measured this effect around Earth in complete agreement with GR's predictions within the experimental margin-of-error.

What this all says is that spacetime and mass-energy (distinct only in form, not substance) are inextricably intertwined. Energy curves spacetime too. Think of mass as simply a high concentration of energy in one place. That is what E = mc^2 means. Mass and equivalent - and interchangeable - and in GR, indistinguishable.

I like your comment, but there is one part that seems problematic:

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"...Unlike bonafide forces, such as electrostatic forces whose magnitude depends on the amount of charge present, gravity does not work this way. It affects masses equally as Galileo demonstrated at Pisa. Two different masses fall at the same rate whereas two different quantities of charge accelerate differently, depending on how much charge is present....."

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While I agree that there are fundamental differences in the ways electrostatic forces and gravity behave, suggesting that the magnitude of the force of gravity is not not dependent on the amount of mass present (and so differing from electrostatic forces whose magnitude depends on the amount of charge present) presents some significant problems:

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1. For different masses to accelerate at the same speed, the force must depend on the amount of mass present, much as the electrostatic charge depends on the amount of charge present. F=MA if A is constant, F must be proportional to M.

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2. It seems that you are ignoring other effects when considering electrostatic charges but not when considering gravity. So far as I am aware, we don't have mass-less charged particles, so even while gravity appears inextricably tied to mass, it is not really even handed to neglect mention of mass or other factors affecting acceleration in your comparison. To provide good information about force based on observations of acceleration, mass should be considered. A more even handed comparison might be comparing at the level where mass and charge can be proportional, which occurs for both protons and electrons.

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3. Both cases, that considering electrostatic forces and that considering gravitational forces, the picture is only half complete. The other half needed for the electrostatic and gravitational force is not mentioned and of course a mass or a charge in relation to nothing doesn't do a whole lot.

It isn't surprising that two different masses fall with roughly the same acceleration when dropped from the same distance to a third mass that is much much greater than the two being tested. That phenomena fails to hold once you begin looking at systems where the first object is of similar mass to the object it is being acted on and acting on.

When comparing different two mass systems comprised of object that do not differ in mass by more than an order or two of magnitude , since gravitational force is proportional to the product of the two masses, and acceleration is inversely proportional to the mass (not something multiplied by the mass), acceleration is highly dependent on mass.

Choosing the surface of one mass as a convenient reference, given the same starting distance between centers, the system with the great total mass will experience greater acceleration than the system with less mass.

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On a less serious note, I have some suspicions about Galileo's work. He came up with a valid answer, but is it possible he was fudging the numbers on a hunch? How did he account for aerodynamic forces? I have my doubts that his instrumentation have been that well calibrated....I mean have you looked at that tower? I can just eyeball it and tell you it isn't square.

Yes, I am aware of these shortcomings in my post, but the detailed explanation of it all would fill pages and probably would be even less illuminating than my actual post. I debated whether to even post at all for fear that it would not illuminate matters. In this respect I have succeeded.

Ummmm....in 1. You are confusing the acceleration of a mass by something other than gravity with acceleration of a mass by gravity.

Gravity doesn't care about mass, horsepower does.

That is the enigma of gravity...

That seems valid in surroundings where the effects of gravity large enough for us to easily perceive first hand are in relation to a large object (the earth) with a mass much much greater than the other objects we consider to be falling toward it. But, if you step away from the perspective of everything being in the same gravitational field as we are, and remember that that gravitational field itself is a necessary characteristic of the mass, then it should become clear that gravity doesn't just care about mass, it is a slave to it.

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As an example, compare two different two mass systems. The first has two spherical masses weighing 1,000 tons each with a distance between centers of 100 yards. The second has two identical spheres weighing 1,000,000 tons each with the same distance between centers of 100 yards. The gravitational force in the second scenario is 1,000,000 times larger in the first scenario, while the mass in the second scenario is only 1,000 time larger. The end result is that the acceleration will be 1000 times greater in the second scenario......it appear that gravity cared very much about mass.

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If everything you experienced as falling wasn't miniscule to the one thing you always see it falling towards, you would notice that increases in the produce of the two masses leads to increases in the force of gravity.

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There is no enigma.

How about Bismuth falling at a different rate than other matter?

And spinning Bismuth creating an altered gravitational field?

Anyone read about this?

I have not, but bismuth is one of the more diamagnetic materials at room temperature, perhaps any noticed changes in rates of acceleration have to do with magnetic fields in the vicinity.

Check out this link:

Read entire article please.

http://www.gravitywarpdrive.com/NGFT_Documents/Nuclear_Gravitation_Field_Theory.pdf

Your thoughts on this?

Thanks to everyone for trying to illuminate my island of ignorance.

But wait!

What about the recent revelation that the universe is expanding at an accelerated rate.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/univacc.html

Would that not support the suggestion that the Strong Nuclear Force is possibly the same thing as gravity?

No.

Both the strong and weak nuclear forces are very limited in range as I cited earlier and have no effect on the universe on a macro scale.

The strong force is very powerful, but very limited in range. Gravity is very weak, but unlimited in range. They are two completely different fundamental forces.

However, the Standard Model tells us that the four fundamental forces were unified at a point very early in the universe's evolution (10^-50 seconds).

As things began to "cool" the four forces began to unravel as shown in the linked diagram.

Another hole in Ken's theory is that he presumes that gravity travels instantaneously, but both Einstein's General Relativity predicts gravity waves propagate at C and recent experimentation shows that it travels or propagates at C.

Unlike AGW (Al Gore Warming) the science is not quite settled because actually measuring gravitational waves is yet to be done, but indirect evidence seems to support predictions made by General Relativity.

I know this is silly, but the first thing that makes me suspicious is the website design...

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I did read what is presented there and also tried to dig into some of the basis for what was written, all while reminding myself not to allow the ancillary things skew my opinion on the ideas.

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After reviewing the website and the two patents referenced in the website, I cannot tell you definitively that there is something fundamentally wrong with the idea. I will say that there are several factors that in total provide strong indication that this idea lacks merit.

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First, I think it is important to note that the person authoring the website may not have a good grasp on what is being described in the patent. For example, the website claims that the patent talks about spinning 'odd atomic nuclide metals' and goes on to define those as 'those in which the sum of the protons is not equal to the number of neutrons, i.e. more neutrons'. I can't find reference to that in the patents so I strongly suspect it is a misunderstanding since all stable elements with nuclei larger than ⁴⁰Ca have more neutrons than protons, so the restriction is a rather loose one and oddly stated.

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What is described in one of the patents, although convoluted in description (as some patents are want to be), is a device that doesn't present obvious major barriers to being constructed. That, coupled with the patents complete lack of references, and exceeding sparse referenced by other patents, along with the absence of any academic papers on what would be a very significant discovery, suggests either there is something fundamentally wrong with the idea, or that the magnitude of the effects is so small that measuring the changes is not within the sensitivity of modern equipment (which would probably be too small to be useful).

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Why else would patents filed in 1968 describing an attainable device that could produce results that might provide insight into the possible unification of two fundamental forces result in no reference to academic papers on the subject almost half a century later? Things do get overlooked, and people do make mistakes. It seem, given the importance of such a fundamental discovery and the time elapsed since information was publicly available, that there is less to this idea than the original inventor or the website author imagine.

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....If you want to be certain, why not construct the thing and see if you can measure changes in the gravitational field?

That only proves that gravity works at the molecular level which is why planets of similar size like Earth and Venus have different gravitational (averaged) pulls, Venus being 90% as dense as Earth has 90% the gravitational pull of Earth.

Same with the our Moon and Mercury.

I'm not trying to prove anything novel here, just trying to point out the problem with saying that that 'gravity doesn't care about mass'.

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Along similar lines, it is not the density that dictates the gravitational force, but instead the total mass. If the sun were to be replaced with a black hole of equivalent mass, there would be no change in the gravitational frce of attraction felt by the earth...even though the black hole would be be far more dense than the sun.

If you are considering mass in the system, it makes sense to consider all the mass in the system. Noting the proportionality of the force to the smaller mass is only meaningful if you hold an arbitrary portion of the total system mass (the larger mass) as constant and of a much much greater magnitude than the other mass. That is an odd condition to base a relation of gravity and mass upon.

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Let's assume that the ball in question is 1 kg, and that the Earth has a mass off 6 x 10²⁴ kg and that an identical earth would come in at 6 x 10²⁴ kg.

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You did ask for a reference. Everything needed is contained in here, I have merely run the numbers. I hope you find this reference trustworthy.

Now for the 1 kg ball scenario, from an inertial frame off reference between the ball and Earth, the acceleration of the ball in the direction of the Earth will be the same as the Earth towards the new Earth in the second scenario, because the masses cancel out, as you noted....

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....but, that isn't the end of the story....

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For each action, there is an equal and opposite....blah blah blah. In the first scenario, the acceleration of the Earth toward the ball is effectively negligible. In the second scenario however, the old Earth accelerates in the direction of the new Earth at the same magnitude as the new Earth accelerates toward the old, which is an acceleration 6 x 10²⁴ greater than that of the Earth to the ball in the first scenario.

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In the reference of the surface of the Earth, the duplicate Earth would accelerate pretty close to twice as quickly in free fall as the ball would , when dropped from the same height as measured by distance from centers.

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You did request a reference. The formula needed can be found here, it just requires running the numbers. I hope you find this a trustworthy source.

Now you are making the two 'earths' into magnets. Magnetism isn't the same as gravity.

Your answer brings another question to my mind:Are all magnetic objects attracted at the same rate by a magnet?Same physical size,just different densities?

up to a point...

http://www.allaboutcircuits.com/vol_1/chpt_14/4.html

Depends on the purity too

Allow me to rephase the magnetic attraction question:

Imagine two objects, in space.One is solid,the other is hollow; (different masses)The objects are made of the same magnetic material,and they are the same size and shape(Spherical).

Ignoring gravity,for these are relatively small objects,say 10 kilos and 2 kilos.

If an anchored magnet is placed a meter away,equidistant from each object,will the objects be attracted to the magnet at the same rate of accelleration,as in gravitational attraction?

If two objects are in space, then one is not anchored. They will attract each other with a force dependent on their magnetic strength, and the acceleration will depend on it too. Objects with gravity have different accelerations depending on their masses. Note that charged objects are routinely accelerated to near the speed of light in particle accelerators.

With no imagination there can't be any hypothetical situations.

Hypothetically speaking, of course.

Are you suggesting that the force on the new Earth sized mass from Earth will be different than the force on the Earth from the new Earth sized mass?

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or

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Are you suggesting that a force of the same magnitude on the same size mass will somehow yield a different magnitude of acceleration?

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I'm not suggesting anything novel. I'm not using any novel formulas. In fact, I'm not using any formulas that you yourself haven't typed suggesting what should be considered.

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You are right, magnetism is not the same as gravity, but I did not make such a suggestion. The fact remains, that gravity 'cares' very much about mass in a system.

I get your point completely that gravity works harder to accelerate an object of higher mass at the same rate as an object of smaller mass. Pretty simple observation.

Point I was trying to make is that in order to do this, gravity gravity must work at the molecular level to make the math work out.

Earth's gravity distribution is not static:

http://cires.colorado.edu/science/divisions/ses/foci/gravityFromSpace.html

It changes with the changing density distribution.

129CBRider wrote: "Point I was trying to make is that in order to do this, gravity gravity must work at the molecular level to make the math work out."

I think it would be more correct to say that gravity results from a conglomeration of atoms (or molecules, or nuclei), not creating the impression that an atom or a molecule is held together by gravity, where gravity is negligible. I agree that the density distribution of the 'conglomeration' does influence the gravitational strength around it.

Also: "A black hole may by virtue of it's ability to pull in matter from many directions and accelerate it past the speed of light by virtue of it's high gravitational pull around the perimeter of the 'hole' (simple conservation of angular momentum), thereby stripping the matter of it's normal spin and turning all the matter into a concentrated beam of light" does not quite pass muster, as AH has already alluded to in #49.

The jets that you pictured in post #40 are rather charged particles that are beamed as "relativistic jets" from the accretion disk material by the twisted magnetic field lines of a spinning black hole/accretion disk combination. Because the particles are heavily accelerated, they emit photons, which are sometimes observable from Earth.

I think you had pulsar radiation from neutron stars in mind, where there are not necessarily particles involved.

-J

As Jim Watson used to say, "Nature is beautiful in the simplicity of it's complexities". (I may be paraphrasing, it was 43 years ago!) He was talking about the fact that the DNA double helix only uses 4 base pairs to create a seemingly infinite number of genetic variations.

What can be a simpler model than E=MC². (I have long felt something was missing in the form of a modulation component in this formula tho.)

Neutrinos may be capable of traveling faster than the speed of light without any change to their normal characteristics.

http://www.scientificamerican.com/article/particles-found-to-travel/

Perhaps gravity is little more than a change from a circular orbit of the different parts of the atoms of the body of a planet into an egg shaped one with a resulting in a cumulative biased pull towards the center of rotation of the planet.

Even the planets in our own solar system have elliptical shaped orbits.

"Neutrinos may be capable of traveling faster than the speed of light without any change to their normal characteristics.

http://www.scientificamerican.com/article/particles-found-to-travel/"

CERN confirmed in June 2012 that the measurement was in error due to a cable fault. We have good reason to believe that nothing, with or without rest mass, can exceed speed c, as measured locally.

-J

That also seems to include gravity waves.

I realize the gravitation is not uniform, I've even had the opportunity to check out installed equipment for precise navigation based on changes in the gravitational field.

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Since mass is dependent on the number and type (mass) of molecules, I have no problem with the suggestion molecules play a critical role in gravity. Then again molecules play a critical role in a lot of things.

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The thing that I disagreed with at the beginning of this line of the discussion was your statement that:

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"...Gravity doesn't care about mass, horsepower does...."

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Even at the reduced level that seems to be present when the claim is that all objects fall with the same acceleration, I think it is fairly simple to show otherwise, especially if the frame of reference for falling is the surface of one of the masses.

OK, try this concept.

What if gravity is gravitrons pushing on the mass density of an object instead of pulling it?

Mass blocks gravitrons from pushing us off the surface of the planet!

The more dense the mass the larger the quantity of gravitrons that are blocked allowing the ones coming from outer space to hold us onto the surface.

Gravity could be little more than the LACK of equalized forces coming from all directions which would normally hold us in a weightless state.

I used to think it had to do with things spinning and orbiting but not after reading that whole paper and sleeping on it for a couple of days. Our moon was the one puzzle because it doesn't spin in relation to the Earth.

Suppose there actually exists a 'gravitron' particle, devoid of a resting mass, whose only characteristic is spin.

Normal particles without resting mass have spin, vibration and orbit themselves creating a 'center'. Or if they have only two of those characteristics, one of them is ~twice as much as the other one.

Probably why quarks can replicate themselves when you seperate them into two parts.

Pertubation comes when the longitudinal axis of the vibration moment spins out to the circumference of the orbit and for a very brief moment the vibration vector lines up parallel to the orbit and causes a wobble.

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Now about 'gravitrons', suppose they are massless 'particles' that only have spin which would make them hard to detect since they would not respond to magnetic fields or each other.

If objects in space, away from the blocking effects of a planet, were bombarded by gravitrons from every direction, billions of times per second they would become weightless, which they are.

If the mass of a planet were dense enough to absorb these gravitrons there would be an imbalance in impact of the gravitrons on an object sitting on the surface coming from the opposite direction from the planets mass density center.

The object would in effect be pushed to the surface of the planet, not pulled to it.

This would explain why the centrifigal force needed to keep something in orbit is necessary and works all the way around the planet but is affected when planets/moons/suns line up.

This would also account for the fact that gravity APPEARS to act spontaenously (minus the 20C time lag for 'gravitron's to clear out of the space between the an affected object and the heretofore assumed source of the gravity).

This would also account for the seemingly continuous 'fabric' of gravity. It really isn't a fabric, it is a multi-dimensioned medium, the fabric concept takes into consideration only one plane of the 3 dimensional space.

A weak analogy would be something with neutral buoyancy floating in fish tank equipped with a tube with a trap door centered beneath it coming from the bottom of the tank. When you opened the trap door on the tank, the supporting water would drain out eliminating the buoyancy effect and the object would drop down the tube.

So YES!, Star Trek warp drive could be achieved to about 20C if you could line up a dense source of gravitrons to the rear of your space ship and have a cone shaped force field out the front of the ship that would create a void of gravitrons directly in front of the ship, the same way super-cavitating torpedoes work like the VA-111 Shkval.

If you need to name this concept of gravity you have my permission to name it after me! :)

Actually, the big heavy ball beat the smaller ball to the ground by two inches but he blew it off because of air resistance and gloried in the fact that he dis-proved Aristotle's theory by 99.9%!

On a less serious note, I have some suspicions about Galileo's work. He came up with a valid answer, but is it possible he was fudging the numbers on a hunch? How did he account for aerodynamic forces?

I believe that he used inclined planes. This slows everything down (minimizing aerodynamic forces) so it is easier to see what is going on.

...but that introduces all kinds of other problems....moment of inertia, rolling resistance, etc.

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Anyway, I thought he dropped them off the tower in Pisa....

My recollection from a Scientific American article I read a long time ago is that he is believed to have set up a series of ramps or inclined planes which had a series of notches that were spaced at square distances, i.e., 1,4,9,16,25, etc. He observed (by ear, probably) that a ball rolling down the incline hit the notches at an even rate.

The force of gravity, of course, not only accelerates the mass of the balls in a linear fashion but imparts a torque causing them to start rolling. The linear force and the torque would each be constant causing a constant increase in velocity and a constant increase in rotation, so moment of inertia would not affect the time ~ distance squared result.

What is the warping of time and space, I have given the subject some thought, and here are some of my out of the box concepts.

Starting with space being an electro magnetic force in a state of equilibrium, meaning there is no reference points (attraction and repulsion) as space is infinite with no edge or centre.

So starting with a photon, an energy source out of equilibrium, and having two energy sources or reference points, one point of attraction and one point of repulsion, this configuration drives the photon, and there position determines the direction in which it will travel, which it will do indefinitely.

Next matter; equal to a collective combination of a number sources of energy out of equilibrium, this gives three combinations, a group of with an equal number of reference points (neutral), a group with an extra attractive reference point (positive), and a group with an extra repulsion point (negative). These groups inter act with each other and with the surrounding space, creating a reference point in space (gravity), and this reference point acts on the attraction and repulsion points of matter, and biasing them such that they are driven towards that point in space depending on how much gravity has moved the points of references out of balance, same as a photon, but depending on the percentage of out of balance.

Like I said just some ideas? Regards JD.

"If space time is considered as a moving stream of energy…"

I don't think that you could consider space that way. The way that is worded suggests that space is energy and that is not the case.

Space can and does contain energy in at least two ways.

One, matter or subatomic particles transversing space.

two, vacuum energy (sometimes called zero-point energy), which is the the spontaneous creation of particles and their anti-particles creating a quantum fluctuation, but the net sum of that energy is always zero.

Einstein's field equations work fine for describing gravity on a macro scale, but on a quantum scale there are serious issues of renormalization and this has lead to many other theories such as quantum loop gravity and the old favorite string or M-theory.

Essentially, Einsteins field equations work great for gravity at lower energy levels, however, gravity turns out to be much more problematic at higher energies where pesky mathematical infinities break down that theory (renormalization).

Your approach seems to have some holes with the analogy and really doesn't describe how gravity works, at least to my understanding. Even so, you still need to go that last mile and demonstrate how gravity works closer to the Plank scale to reconcile quantum field theory with Einstein's field equations.

That last mile is really where all the work lies.

You are correct that we do not understand why mass and energy warp space-time, but they do. Well, we might actually understand if you are a believer of string theory or M-theory or quantum loop gravity. The problem, as always, is testing those theories.

And on top of that, we've all that gloomy Dark Energy driving things apart at cosmic scales. Gravity's antithesis as it were.

Speaking of which, we've got the mass-energy equivalance principle where ordinary mass-energy is concerned, it/both causing spacetime curvature which tends to pull things together but, whereas Dark Matter seems to behave like ordinary matter in this respect, Dark Energy does not. Its effect is to drive things apart, so is there a corresponding dark-matter/energy equivalence or are they two different beasts entirely?

Well, I think that the discrepancy is that everyone is thinking in terms that the conservation of energy is valid, but it is not in some cases and Einstein demonstrated that whenever the space through which particles move is changing, the total energy of those particles is not conserved.

This allows for the concept that the vacuum energy of 10^-10 joules/meter^3 is constant, even when space is expanding. That would mean that as space expands the sum total of energy in the universe is also increasing because the energy density of space is constant…

Is matter(as a form of concentrated energy) to be considered as energy in the sum total?

Yes. I think it does.

Matter and energy are interchangeable, both in theory and in 'practice.' Several examples:

Atomic nuclei, when fused together, have less mass in aggregate than they do separately. This 'mass defect,' as it is called, is the result of that difference in mass becoming the binding energy of the composite nucleus. When you split a nucleus - fission - you get that energy back.

As another example, when you collide a particle with its antiparticle, you get energy back in the form of gamma rays, neutrinos and lower-mass particle/antiparticle pairs.

Photons have no mass at all, yet have momentum in direct proportion to their energy.

As yet another example, at the event horizons of black holes (as elsewhere), you have pairs of virtual particles flickering in and out of existence, except that, where one of the pair remains inside the EH and the other does not but zips off somewhere else, the mass-energy of the black hole diminishes somewhat in exchange for the production of that errant particle's mass. This is called Hawking radiation, except that now, Steven is having a wee bit harder time explaining it after declaring that event horizons do not exist. My guess is that they'll have to call this radiation by someone else's name. :)

Once again I find myself liking your comment, but in a very similar way to my reply to comment #3 above, I find one part of what you wrote problematic:

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"...This 'mass defect,' as it is called, is the result of that difference in mass becoming the binding energy of the composite nucleus. When you split a nucleus - fission - you get that energy back...."

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Binding energy isn't retained in the nucleus and then given back upon fission. A bound state is at a lower energy level than a state of all individual protons and neutrons. Upon binding that energy would be released into the environment.

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Splitting an atom into individual protons and neutrons would require energy from the outside to overcome the binding energy.

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Binding energy per nucleon increases at a diminishing rate with number of nucleons fairly smoothly with exceptions in the common isotopes related to high binding energy per nucleon for ⁴He (so severe that binding energy per nucleon in isotopes of beryllium and boron are still lower than ⁴He), ¹²C and ¹⁶O; until it reaches a maximum in the area of isotopes of Nickel and Iron. Above that point binding energy per nucleon decreases, but it doesn't fall below the binding energy per nucleon of ⁴He for any common isotopes.

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Energy released from fission is only due to the lower binding energy per nucleon in some larger nucleus than in the products after the split, so it generally only occurs with very large nuclei far above iron/nickel. There are some exceptions in the lower range due to the very high binding energy of ⁴He compared to its slightly larger neighbors. Always though, for a fission reaction, any energy you get is not from a return of binding energy, but a move to greater binding energy.

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Likewise any fusion reaction that releases energy would be from a move to greater binding energy per nucleon.

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Hi europium. Sorry for the late entry...

You wrote: "... at the event horizons of black holes (as elsewhere), you have pairs of virtual particles flickering in and out of existence, except that, where one of the pair remains inside the EH and the other does not but zips off somewhere else, the mass-energy of the black hole diminishes somewhat in exchange for the production of that errant particle's mass. This is called Hawking radiation, except that now, Steven is having a wee bit harder time explaining it after declaring that event horizons do not exist. My guess is that they'll have to call this radiation by someone else's name. :)"

I think physicists have only renamed the horizon and Hawking radiation stays intact. It is now called the "trapping horizon", because it is not necessarily a permanent one-way membrane.

This came about by the theoretical discovery of the "Planck stars" of quantum gravity, where a bounce at Planckian energy levels prevents a central singularity to form during black hole formation. This bounce can theoretically throw the energy back to "outside" of the normal event horizon.

The Hawking radiation at the trapping horizon still shrinks that horizon, while the inner Planck horizon grows after the bounce. When the two meet, the black hole (BH) explodes, but it may take a very long time on our clocks to reach this state, simply due to the intense gravitational time dilation inside the BH. In most cases, this time will be longer than the present "age" of the universe, unless the BH is tiny; such mini- or micro BHs may have formed very soon after the BB.

A few days ago, a paper by Aurelien Barrau & Carlo Rovelli titled Planck star phenomenology appeared, where they suggest that such events may already have been observed in the short gamma ray burst (sGRB) data. The jury is however still out on the theory and the analysis.

http://arxiv.org/abs/1404.5821

"It is possible that black holes hide a core of Planckian density, sustained by quantum-gravitational pressure. As a black hole evaporates, the core remembers the initial mass and the final explosion occurs at macroscopic scale. We investigate possible phenomenological consequences of this idea. Under several rough assumptions, we estimate that up to several short gamma-ray bursts per day, around 10 MeV, with isotropic distribution, can be expected coming from a region of a few hundred light years around us."

-J

GK, don't worry, good old GR still works, until we get to the "hyper-dense" states, that is. GR never professed to predict what happens at or near the centers of BHs. Also, the "old" event horizon still has the same characteristics as before, until some quantum effect eventually takes over.

Remember how bizarre it sounded when Stephen Hawking first said that black holes can evaporate? And that just before they evaporate completely, the last (microscopic) bit will explode? He used a combination of GR and quantum physics for that insight.

This still (almost) holds, but the quantum gravity guys have now shown that instead of a singularity that waits for the black hole to evaporate away, the hyper-dense energy might preempt the issue - it should bounce and meet the shrinking (old) event horizon some distance up and violate it. In other words, the BH can explode at a macroscopic size.

The names "trapping horizon" and "Planck horizon" are a bit arbitrary, I think, but they may just stick. The Planck horizon is loosely speaking the smallest a given quantity of matter can become without exceeding the Planck energy density, which is thought to be maximum possible density.

The "trapping horizon" has the same characteristics as the "old" (gravitational) event horizon, until the time the bounce destroys it. It 'traps' the energy (information) inside for some time, but cannot hold onto it indefinitely. I do not really understand how the energy inside escapes through the trapping horizon in a bang, but I guess it is somewhat like Hawking radiation, but not quite the same. Perhaps some form of quantum tunneling, under the right energy conditions...

Hope this helps to ease the frustration somewhat. :)

-J

Thanks for your reply, Jorrie... So, I think that the whole BH issue is still 'open'... ...

Yes, like in most complex sciences, knowledge is evolving. IMO, quantum gravity (QG) is presently one of the fastest areas of theoretical development. We surely have not heard the last of the characteristics of BHs.

My own understanding of QG is sketchy, but I have learned a few titbits since my prior post. At the Planck horizon (Planck density), a form of ant-gravity balances normal GR gravity exactly - well, at least according to present best-buy theory. This does not create a bounce per se, unless more external energy is falling into the BH, which would make both the external (trapping) horizon and the Planck grow.

Now, the smaller a BH, the hotter it becomes in terms of Hawking radiation. If there are no more objects to "swallow" in the immediate vicinity of a mini-BH's, and it is hotter than the background radiation, it will start to Hawking-radiate away its own mass. However, somewhat surprisingly (to me at least), the 'Hawking-particle' that falls into the BH will add to the size of the Planck volume (since Planck density is max possible). This is the "bounce", i.e. growth of the Planck horizon, while the trapping horizon shrinks.

When the two horizons meet, the QG "anti-gravity" overwhelms the trapping horizon and all that energy is radiated away in a "flash", resulting in an energetic very short GRB. This seems to be the present theory, awaiting observational confirmation. Or awaiting an update of the theory...

-J

Thanks again, Jorrie... very interesting... ...

Perhaps neutrinos are spinning photons or more likely, photons are quarks without spin.

All bodies with gravity, including the nuclei of atoms, seem to have spin, orbit and a wave length relative to the time space continuum.

A black hole may by virtue of it's ability to pull in matter from many directions and accelerate it past the speed of light by virtue of it's high gravitational pull around the perimeter of the 'hole' (simple conservation of angular momentum), thereby stripping the matter of it's normal spin and turning all the matter into a concentrated beam of light.

Matter does not accelerate faster than C, even in a black hole.

Matter without a resting mass can move past the speed of light.

Matter with a resting mass that is accelerated to the speed of light will outrun it's parts, so to speak, and come apart as it goes past the speed of light.

It's parts without mass will continue accelerating.

Yep.

Allow me to turn that around a bit.If the amount of energy in the universe increases,then the universe must expand as well to maintain a constant energy density.

Does mattter,being a concentrated form of energy,require less "space time" to occupy than an equivilent amount of energy?

If so, then the conversion of matter to energy could explain the expansion of space time and black holes could be the driving force?

Has the feeding rate of black holes increased over the long term, and how would one tell if it has?

You are correct sir, SpaceTime is a 4 dimensional map of what has transpired and based on that, what is likely to transpire.

http://einstein.stanford.edu/content/relativity/q411.html

the theory of relativity was so revolutionary when first proposed decades ago but has taken pot shots for decades because it fits "big things, like space but the smaller things in our known universe don't always fit the theory so neatly." I don't have all the answers. personally one of the many versions of string theory make sense but to date remain unproven

John Archibald Wheeler said "Spacetime tells matter how to move; matter tells spacetime how to curve." The first part is not so hard to understand. Bodies take the shortest path between points A and B. A gravitational field makes this path a curve and this is what we observe when a body moves within a gravitational field.

The last part is a mystery. I don't know that anyone really understands why matter curves spacetime.

I do not claim to understand it,but it behaves "as if" it were a liquid or gas moving around an obstruction in it's path.Any molecules suspended in the gas or liquid would take a curved path around the obstruction.But this is happening in 3 dimensions,which is hard to grasp visually in the mind.But of course space time penetrates matter to varying degrees,depending on the density of the matter.The less dense, the less the obstruction,the less the curvature of space time.Time should slow down in the influence of this curve,because time itself takes a longer path .At extreme curvature, as in a black hole, it could almost stop.

I think time itself is merely the rate at which spacetime is flowing around us,and as our velocity increases and approaches the "speed of time" which is "C", the speed of light,time would stop at speed=C.

Hi HiTekRedNek.

<If space time is considered as a moving stream of energy...> What do you mean? Is that the 'vacuum energy' you are refering to? And why this energy is moving? (Is that because the space is expanding? And what about a static space?)

<So the deformation of space time is really caused by a concentration of energy that repels or interferes with the space time energy field.> What does 'repel' or 'interfer' mean? The energy inside a mass body -i.e. between its atoms and molecules- is electrical while the vacuum energy is not. How these two (different type of) energies interact to each other?

<This puts it out of phase with the surrounding space time...> What does 'out of phase' mean?

The gravity phenomenon has nothing to do with the electric fields inside a mass body. It doesn't need a concentration of atoms in order the gravity to emerge. Just a stand-alone subatomic particle -even with no electric field, like a neutron- creates a gravity field (or interacts with a gravity field if you like) and creates its own tiny "dent" in the space-time continuum.