The Nature of Gravity

Gravity has been pretty well shown that its force "moves" at the speed of light (C) everywhere. We are looking for direct confirmation of gravity waves now, but experiments have indirectly shown that its effect travels at C.

As to what gravity actually is, that is another matter that is under deep scrutiny.

The crux is trying to unify what is observed in the macro world (Relativity) with what is understood at the quantum level (quantum physics).

Theory has it that the force of gravity is transferred by a hypothetical particle called the graviton. The Large Hadron Collider has, as part of one of its missions, to look for evidence that would support the graviton.

Further out the branch of theoretical physics is String Theory (or M-Theory), which postulates that gravity is a weak force that moves between branes in the bulk. Both branes and bulk are elements of string theory. Branes are like a 3D+Time universe we experience now. In string theory it is possible to have multiple branes and they can coexist in a "space" known as the bulk.

There are two types of strings; open ended (like a piece of string) and closed (like a circle). Open ended strings are confined to the brane they dwell in. Ordinary matter are proposed to be made of open ended strings.

Closed strings may migrate between branes freely. Gravity is proposed to be a closed string. This behavior of being able to migrate between branes would explain why gravity is a weak force, but has infinite distance in its effect. If the force of gravity is distributed among many different branes it would explain its weak interaction. So the theory goes.

There are other theories of interest such a Loop Quantum Gravity, which are gaining more interest among physicists.

Personally, I find both theories (string and loop) tantalizing and look forward to new evidence that might be uncovered in future experiments as we peel back the layers of the onion trying to unravel the mystery of the universe.

I appreciate your effort here...I am familiar with these theories you mention,

but you did not speculate on any of the questions..

" but experiments have indirectly shown that its effect travels at C."

Could you be more specific here please?

I would have to do a search. Perhaps someone knows a link, but I remember some set of experiments or collection of cosmological data that supported that basis of gravity working at the speed of C.

Another clue is that Einstein's equations utilize C as that velocity and those calculations for gravity and its effects have stunning accuracy.

This Link may give you a primer on it, but there are more detailed papers out there.

I found this Link, too.

I've often wondered, if string theory is correct and the force of gravity can move between branes, whether dark matter might be ordinary matter on a brane parallel to ours.

Remember, ordinary matter is made up of open strings, which can not interact with neighboring branes - at least according to the theory.

However, string theory predicts addition dimensions beyond the four (length, width, height, and time) we are familiar with. It is possible that the actual dark matter could be locked up inside some of or one of those extra dimensions, thus keeping the nuclear weak, strong, and the electromagnetic forces of nature from interacting with our 4 dimensions. However, gravitation (gravitons) are thought to be closed loop strings, which (according to string theory) can interact between other dimensions as well as branes.

Of course there is no reason to discount the possibility of additional branes that lie coincident with ours that contain large amounts of baryonic matter that could interact between branes. Such additional branes could be stacked together like slices of bread.

Pretty speculative stuff.

Mass blocks gravitrons from pushing us onto 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 is 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.

***********

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.

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 surface.

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 good 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! :)

Going further into some of your questions, dark matter is another mystery. One theory is that it is the transitory particles that pop into and out of existence in a vacuum. These particles pop into existence as pairs (matter - anti-matter) an promptly annihilate each other in a tiny fraction of time.

Black holes produce a curious energy known as Hawking radiation. Hawking radiation is believed to be when one of these particle pairs pop into existence at the boundary of the black hole's event horizon. When the pair manifests one of the partners is pulled into the event horizon and the other manages to escape, thus avoiding annihilation. The resulting escaped particle is measured as Hawking radiation.

This is the only known radiation that actually escapes a black hole and even at that it isn't exactly an escape, but ultimately the black hole is thought to evaporate over a long time due to this process.

It gets trickier, but I will try to outline the reason. The split of the particle pair can be thought as positive energy and a negative energy particles. When the negative particle is captured by the black hole the black hole entropy actually decreases. This is the opposite that you would expect from a black hole, which, by it nature, should have an increase of entropy over time and the temperature of the black hole reaching absolute zero. Hawking radiation is a slow reversal of that process. Eventually, over time, the black hole "evaporates" as it loses mass at its accretion disk at the event horizon.

As far as how gravity behaves in a black hole, it is believed that gravity behaves the same inside of the event horizon as it does outside, at least up to the point of the singularity itself. At the point of the singularity the physics becomes undetermined.

In other words, gravity near a black hole increases exponentially as you get closer to the singularity and the gradient of gravity increases toward infinity at the point of singularity.

The point on that ride downward where the escape velocity of the black hole reaches the speed of light is called the event horizon.

As matter is drawn into the event horizon the size of the event horizon is directly equal to the amount of "information" contained or captured in the black hole. More specifically, the surface area of the black hole's event horizon is exactly equal to the volume of information contained or ingested by the black hole. All information ingested by a black hole is contained in the event horizon and not within the black hole itself.

Heady subject and I may have done more to confuse than to actually answer questions, but it is hard to sum up such subjects in a few paragraphs when there are volumes of books that cover the subject in more detail. It is like trying to describe world economics in a few sentences.

AH maybe this is a question for Jorrie but you seem well versed.

Why does a black hole have to have a singularity? Can there not be a transition from a mass so large that it acts like a black hole and a singularity? For all practical purposes, Jupiter is a black hole once you are 50,000 miles from it's center. When a black hole is forming is it not eating nearby material? Would then there not be a transitional period where mass is beyond light escape and a singularity has not yet occurred.

Just driveling.

A black hole is more than a cosmic drainpipe.

To qualify as a black hole the object must be massive enough so as to capture all matter and energy that approaches close enough to it. To do that the escape velocity must be equal or greater than C.

There are equations to calculate the "Schwarzschild Radius" for the event horizon.

A true black hole would have no temperature. That is, no radiating energy whatsoever. Apart from the Hawing radiation I described, this is the case for a black hole. Jupiter obviously radiates energy in a broad spectrum, so would fail the test as a black hole.

I have even "listened" to some of Jupiter's emissions on shortwave radio. If you have a shortwave radio that can defeat the AGC circuit you can do the same.

Here is a page where you can learn how to do it if you want..

anonymous-

Any comments on the MOND model?

I have never heard of MOND. When I first read this I thought that Dark Matter was thought to be responsible for the behavior cited. Reading further the Wiki states this.

I guess MOND has kind of fallen out of favor because there is very strong evidence for dark matter. NASA provided this web link from an observation in 2006, which provide strong evidence for dark matter's existence.

My gut is that dark matter is indeed responsible for the observations for the rotational effect of gasses in galaxies and not some new of inconsistent forces of physics.

As with just about everything in cosmology, I guess we will have to wait and see what other new data uncovers and how it supports or perhaps breaks down current theories.

"... the action of gravity is similar to the action of matter entering a black hole, in that there is force towards the center of an object, and that force increases with the size of the object, but velocity remains constant."

You have not really defined velocity relative to what, or in which reference frame. In the usual Schwarzschild reference frame, the observable velocity of light and objects actually becomes undetermined at the event horizon. Inside the horizon, no velocity is observable by the distant observer.

If general relativity (gr) is expressed in free-fall coordinates, as measured by an observer falling into the hole from a large distance, light remains at c all the way to just short of the central singularity. In this frame, massive objects don't fall faster and faster. You, the observer sits statically at the origin of the coordinate system, there is no gravity in your vicinity, so if you drop an object it just floats near you and stays there, i.e. weightlessness.

You will not notice when you pass the event horizon, but you will notice the central singularity for its tidal gravity (vertical stretching and horizontal squeezing). As AH wrote, gr breaks down when you get too too close to the central singularity and we do not know what happens right there. Quantum gravity of some flavor will hopefully shed some light on it later.

There is certainly no theory that predicts that planets and stars have "weak black holes" at their centers. Theory has it that if enough mass density is present in a small enough volume, the whole body collapses into a black hole and blows a good portion of its outer regions away in explosions called supernovae.

"Possibly this is dark matter...If this is the case, there could be some flow of energy from the poles as exhibited from black holes..."

Remember that the matter/radiation jets that we observe coming from candidate black holes come from outside their event horizons. It is matter in the process of being dragged in by the hole that is blown away by strong electromagnetic reaction at the rotational poles. This happens before it crosses the event horizon.

Part of the polar jet material could perhaps be dark matter, but remember it is thought that not even a magnetic field interacts with dark matter. It also does not really fall into black holes like regular matter - it does not suffer the interactions of a gas, which is heated by compression and friction and then radiate away energy until it falls through the horizon. Dark matter radiates nothing that we know of, except perhaps gravitons, because it gravitates.

-J

"There is certainly no theory that predicts that planets and stars have "weak black holes" at their centers. Theory has it that if enough mass density is present in a small enough volume, the whole body collapses into a black hole..."

Gravity doesn't just pop into existence at the point of collapse. The force of the gravity is constant, the only thing that changes is the amount and type of mass being effected, when the force of gravity exceeds the strength of the atomic bonds, then the collapse occurs...The amount and type of mass determines the outcome from this point be it supernova or neutron star or some other exotic remains...If you ask me, the black hole phenomena only illuminates what is happening with gravity all the time on a lesser scale with all celestial bodies...

SE wrote: ...If you ask me, the black hole phenomena only illuminates what is happening with gravity all the time on a lesser scale with all celestial bodies...

With all? Doubt that. I think stars are pretty well understood in terms of the nuclear reactions in their cores, but that heat-energy is getting out of the star. If there were black holes there, how would the energy get out?

It is true that when the nuclear fuel of a star runs out, the prediction is that the core collapses faster than the rest of the star and some sort of short term vacuum is created between the core and the rest. But the rest of the star must also fall in and create anything from a dwarf star to a supernova, depending on original mass.

So maybe there could be a very brief period of a star with a black hole at its core, but that cannot persist, if stellar theory is correct.

The axial jets from black holes or collapsars are paradoxical: how can any matter be accelerated away from the hole when matter is so strongly attracted? Maybe the assumption of isotropic collapse needs some rethinking.

Maybe there is some structure in the collapse such that there are area-preserving fractal networks in a shear layer between counter-rotating accretion disks. Area-preserving fractal networks, like the root system of trees, are Nature's way of low-pressure-drop advection -- the path of least resistance into the black hole.

A related topic is self-gravitational strain in the Earth: an outward strain results from the sides squeezing in on a wedge being attracted to the center. So the crust is uplifted locally, e.g. the Colorado Plateau.

It depends on which side of the event horizon you are. Anything at or inside the event horizon will not return.

However, this side of the horizon is another matter. Material follows the same laws of orbital mechanics that objects in our solar system.

Now the twist. Black holes severely distort time and space and therefore distort their magnetic fields into a spiral at the black hole's poles. Essentially, a black hole becomes a powerful particle accelerator and produces two jets of particles that can reach speeds of nearly that of light.

This theory is supported by evidence gathered from a black hole nearly a billion LY away with one pole or jet aligned toward us. Material ejected from that black hole does spiral just as the theory predicted.

Restated...

Planets seem to have some sort of weak black hole at the center, drawing a force we perceive as gravity..That force could be dark matter on a lesser scale, reacting as observable matter does entering a traditional black hole...These phenomena are similar...The dark matter could be reacting the same as visible matter..If gravity is traveling at ~c, it's creating a focal point at the center of this and other planets....If this is so, there could be a plume of some sort of energy escaping at the polar or magnetic poles...Then what is holding us on this planet is not the curvature of space, but dark matter wind collapsing to the center of the planet...and gravitons could in fact, be dark matter...

I have some issues with that theory (black holes at the center of a body).

1. If a miniature black hole existed at the center of a planet it would consume the planet's core, followed swiftly by the rest of the planet.

2. There is a minimum mass required to create a black hole - unless some external force of sufficient magnitude crushes a mass to the point of collapse. There are theories that the big bang could have created mini black holes, but none have been detected.

3. Even if a mini black hole was the seed for a solar system it would simply consume all surrounding matter over the course of time and grow larger in the process. There is no way for the black hole to turn off so that mater can accrete around a black hole without falling in. Essentially, the condition set in #1 would not be possible for the reason I stated in #3.

I don't believe you need anything exotic to seed the formation of a planet. Even a dust grain has gravity and if two grains are within close enough proximity and are not perturbed by an outside force, the two grains will attract each other and form a larger body. This process will continue as long as there is free material to drag into its sphere of gravitational influence.

Many people have trouble wrapping their brains around this idea, but the universe has had 13 billion years to do just this. The long time it takes to build a solar system is something that people can not digest easily. Hell, the traffic light in front of you seems to take an eternity to turn green, how do you comprehend a million years or even a billion years?

Your lifetime may span 100 years. However, this world has been here 4.5 * 10^8 times that.

As to what role dark matter may have in planetary formation, who knows. Dark matter is pretty much a mystery and it's hard to determine what it can and can't do. So, it is very much a speculative subject.

Gravitons are thought to be the particle that carries the force of gravity. They are hypothetical at this point. I don't know if dark matter is/are gravitons, but if you put any faith in string theory, closed loop strings are thought to be able to leak across branes and could be the vehicle that transmits the force of gravity.

"1. If a miniature black hole existed at the center of a planet it would consume the planet's core, followed swiftly by the rest of the planet."

Undoubtedly this is true. But what if there was such a thing as dark energy black holes, that formed the framework of all celestial bodies, which did not become what we now call black holes until their mass reached sufficient quantity to facilitate an atomic collapse...

"Even a dust grain has gravity and if two grains are within close enough proximity and are not perturbed by an outside force, the two grains will attract each other and form a larger body."

This phenomena holds true in either scenario. Do you believe then that a single grain of dust can bend space/time?

You wrote, "Undoubtedly this is true. But what if there was such a thing as dark energy black holes..."

I would like to see your underlying theory for that, if you have one. Otherwise it is pure conjecture with nothing to stand on.

You wrote, "...which did not become what we now call black holes until their mass reached sufficient quantity to facilitate an atomic collapse..."

Well that is the way gravity works now in the universe. Keep piling on the mass until it collapses in on itself. Large stars (i.e., >8 or so solar masses) prevent this by the nature of their nuclear engines.

It all boils down to if there is a sufficient kernel of truth to theories like D-Brane theory and string theory that predict the possibility of gravity leaking in from other branes or dimensions. Lovely stuff, but the jury is way out on that right now.

You wrote, "Do you believe then that a single grain of dust can bend space/time?"

That is exactly what Relativity predicts and there is mighty strong evidence that Relativity is correct.

"I would like to see your underlying theory for that, if you have one. Otherwise it is pure conjecture with nothing to stand on."

Oh it's pure conjecture, I'm just exploring...

"You wrote, "Do you believe then that a single grain of dust can bend space/time?"That is exactly what Relativity predicts and there is mighty strong evidence that Relativity is correct."

It just seems odd that this phenomena is so common and space time so easily altered, yet I know of nothing that has been created to exploit it...Do you?

I am not sure what you mean by your question. Do you mean exploitation of warping of space?

If so, we do that every time we employ gravity for our own means. It could be sending probes to distant planets or the gentle pull gravity provides for a game of pinball.

Well I was thinking more of the time aspect...But if we know what causes gravity, it would seem that we should be able to counteract it, we can overcome it, but we can't seem to neutralize or reverse it...

Knowing what causes something does not insure you can do something about it. We may understand the many reasons that causes death, but nobody has cheated it yet.

In the case of gravity, we are really clueless about it. We understand its effects, but we don't understand how it works at a quantum level... Yet.

As for time, dilation of time requires either a lot of mass or a lot of velocity. We really haven't a good handle on either of those as far as cosmic engineering goes.

So the problem is a little bigger than we are right now.

"Knowing what causes something does not insure you can do something about it. We may understand the many reasons that causes death, but nobody has cheated it yet."

Well in some cases we have been able to postpone it..We are making strides, we are effecting it...In the case of gravity we have nothing...It's been my experience that if I know what's causing something, I can effect it..The fact that we have not been able to effect gravity tells me we don't know what is causing it, we have an explanation in curved spacetime, but nobody seems to really understand this well enough to effect it...and this leads me to believe that it doesn't really make sense, and that's why no one can understand it...of course, I could be wrong...but I'm a hands on type of guy and I have to go with what has always worked, and that's a logical approach...

Let me ask you this, If, what ever gravity is composed of, is unaffected by electromagnetic fields, what other type of field or force, might effect it?

I am not sure, but it sounds like you are trying to take this down the plasma cosmology road and we already beat that dead horse in two other posts. I won't bother repeating all those posts here.

It is true that we understand little about gravity, It is clearly one of the mysteries we have yet to unravel.

Gravity is one of the four fundamental forces of nature. It is called the weak force, but its range is infinite. There some interesting theories about gravity in the string theory, M-theory, supersymmetry theories, and a new contender Loop Quantum Gravity. All are very interesting, but we have not reached a stage where we can really test any of those theories even indirectly. I suspect that will change in time.

So, gravity is still a work in progress for now.

Perhaps a bit OT, but I'm curious to your opinion. Have you read through Erik Verlinde's "On the Origin of Gravity and the Laws of Newton"?

I was drawn to it by an article in the NY Times. Verlinde's position was essentially gravity doesn't exist, but is essentially formed from thermodynamics and electromagnetism.

It's an interesting paper. Any thoughts? (I'd have provided a link, but can't locate it anymore. I still have the pdf saved on my computer and would be happy to send it if you need a copy.)

"On the Origin of Gravity and the Laws of Newton"

I have only scanned through it and I do not quite understand it, but it looks like a good, solid scientific paper. The Verlinde paper sits on arXiv:

http://arxiv.org/abs/1001.0785, or can be downloaded directly here:

http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.0785v1.pdf

I have not, but it looks very intriguing and if I can block off some time I will read it.

I did a quick read, but the only part that I fully comprehended was the 2nd last paragraph:

"It is well known that Newton was criticized by his contemporaries, especially by Hooke, that his law of gravity acts at a distance and has no direct mechanical causelike the elastic force. Ironically, this is precisely the reason why Hooke's elastic force is nowadays not seen as fundamental, while Newton's gravitational force has maintained that status for more than three centuries. What Newton did not know, and certainly Hooke didn't, is that the universe is holographic. Holography is also an hypothesis, of course, and may appear just as absurd as an action at a distance."

Well, I just started reading Brian Greene's discourse on the holographic universe, so after I get through that I should be in a better position to read this paper.

Anonymous Hero-

One of the major issues I have with accepting the current Standard Cosmological Model is the fact that it suggests the Universe is only 13.8 billion years old. That seems far too young for me. Sail out into the ocean on a clear night, away from all the light pollution, and look up. All that was created in only 13.8 billion years? Furthermore, it suggests that life as we currently define it has apparently existed on Earth for 25% of the total history of the Universe...

What about starting with naked black holes drifting through space and sucking up anything in their path? Actually, material not directly in the path would tend to follow a separate circular path as it fell into the black hole...You wind up with galaxies, because as the material falls under the influence of the black hole, it accretes into bigger objects such as stars and such. This sort of gives gravity the role of primal force, but builds the universe inside out...

Just tossing some ideas out there- nothing I am prepared to defend theoretically. But I am bothered by the constant tweaking of the Standard Model each time we look a little further into the distance (and the fact that the last image I saw of "the most distant objects yet viewed from earth"- one of the satellite telescope images of what was supposed to be the early universe some few hundred thousand years after the big bang, looked suspiciously like a de-focused image of the visible sky we see today...).

I really believe we are measuring the wrong things, and that we will ultimately need some other marker than c to define things. There are some interesting ideas coming from those exploring "phase space", although I am not sure they are defining phase space the same as I understand it...

I think the timescale for the known universe is pretty close down to one or two billion years.

The fact that the standard model keeps getting adjusted is simply a side effect of learning new things. It would be disappointing if we just knew everything right out of the box. What would we have to reach for.

There are many theories on the creation of the universe. The standard model simply has the most evidence to back it up - right now, so it is the leading candidate until something in the way of new information comes along that either reinforces it or pokes a serious hole in it.

Do a search on Quantum Loop Cosmology if you would like a new theory. It looks interesting, but like anything we need to do a lot more research to determine if this is a viable direction or not.

Here is a starting point.

Learn Whence-Whither The Universe (And Life):

On The Essence And Matrix Of The Universe-Life

The following three sentences are the shortest data-based TOE…seriously. Very seriously.

The clearer the shorter

Natural Selection to Self Replication is Gravity
- Self-replication is the ultimate mode of natural selection is the essence and drive and purpose of the universe. Period.
- The pre-Big-Bang singularity is the ultimate self-replication (SR) of the cycling mass-energy universe. Period. (mother of universal SR mode…)
- Earth's RNA nucleotides life is just one of the myriad modes of self-replication.
Dov Henis (comments from 22^nd century)

http://universe-life.com/

-The 20yrs development, and comprehensive data-based scientism worldview, in a succinct format.

-The Genome is a base organism evolved, and continuously modified, by the genes of its higher organism as their functional template.

- Everything in the universe derives from mass-energy duality, from the universe cycle between its two poles all-mass/all-energy.

- The Origin Of Gravitons is the ONLY thing unknown-unexplained in the Scientism Universe.

PS: Spoon feeding
The universe is a (circa 20 hillion yrs?) cyclic affair between all-mass and all-energy poles. NATURAL SELECTION of a mass format mandates energy intake because since the big-bang the resolved mass is reconverting at a constant rate from inert mass to energy, to moving mass. The mass that reconverts to energy SELF-REPLICATES to mass, in black holes, for the eventual re-singularity. The energy-to-mass SELF-REPLICATION process is GRAVITY. All this is enabled and goes on and mandated by/due to the small size and shape and inter-attraction of the gravitons that enable zero distance between them to re-form singularity.
I hope that now you understand what gravity is and why it is the monotheism of the universe…DH