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Originally posted by intergalactic fire
Another question i wanted to ask,
If the magnetic poles change, is it possible the earth's rotation direction change also?
Anyone knows the theory why the earth spins counterclockwise?
Originally posted by Phage
While the magnetosphere does protect the atmosphere from the solar wind, it would take millions of years (in the event of a total collapse) for the atmosphere to be stripped away. Even with no magnetic field we would not be toasted but over a long time we may not have enough air to breathe.
edit on 10/7/2011 by Phage because: (no reason given)
Originally posted by MoparDanno
All speculation on my part admittedly, and I have no evidence to back it up, but I firmly believe that everything in the solar system interacts not only gravitically, but magnetically and electrically too.
And how do we know this?
A possible weak link in the condensation theory is sometimes known as the angular momentum problem. Although our Sun contains about 1000 times more mass than all the planets combined, it possesses a mere 0.3 percent of the total angular momentum of the solar system. Jupiter, for example, has a lot more angular momentum than does our Sun—in fact, about 60 percent of the solar system's angular momentum. All told, the four jovian planets account for well over 99 percent of the total angular momentum of the solar system. By comparison, the lighter (and closer) terrestrial planets have negligible angular momentum.
Originally posted by TMJ1972
snip
Then a whole lot of more dust was assimilated in millions and millions of years, and ..similar to an ice-skater pulling its arm to the body...this mass aquisition speeds up the pebble to the rotation it still has today.
And since we have no sort of drag anymore today the earth will spin forever this way.
Originally posted by JustMike
reply to post by Doodle19815
snip
Oh, just one thing I wanted to mention as it came to me while reading Jaded's post about the currently-unaccepted concept of an expanding Earth versus the currently-accepted theory of plate tectonics. I feel that seeing as plate tectonics is only a theory and frankly doesn't answer all the questions anyway, there could be room for them to consider some aspects of the expansion concept within it.
I put that poorly, I know, but for example, I wonder about this fact: our planet's rotational period is not constant. The general trend is that the rotation rate is slowing. I recall reading somewhere that back in the Devonian, the day was around 22 hours, by the Jurassic it had lengthened to 23 hours, because the Earth's rotation had slowed. (Note: the year was around the same, but it just had more days in it then than it does now.)
Now, it makes sense that as our planet is not a closed system (as we're travelling through space), forces acting on it will affect its rate of spin, and one could argue that these external factors are enough to slow down the spin. In fact it seems that generally, that's the argument -- along with energy loss from the planet. (Not sure if that works out but I recall reading it.)
Overall though, this external forces thing sounds fine, but on the other hand, have any detailed analyses been done to demonstrate that the rate of the Earth's slow down is totally accounted for by these factors? Because if the Earth is expanding -- even at an incredibly slow rate -- then the law of conservation of angular momentum has to be considered.
It states that a given mass moving around an axis at a certain rate will move more slowly if some of the mass is positioned further from the axis of rotation. (eg an ice skater doing a spin can slow down the spin quite rapidly by moving her arms out and speed up by moving them in close.)
Ergo, if the Earth is expanding even at a very slow rate, then with more mass further from the axis, it will slow down.
So, putting it simply: does the Earth's reducing rate of spin (over millions of years) correspond exactly to the known external forces acting on that could reduce its spin, when taken along with its energy loss? If not, then it's expanding.
I have no idea if it is or it isn't. My concern is that if it is, then it is something we'd have to consider in quake research.
And with that I really need to sign off. Good night
and stay safe...
Mikeedit on 18/9/11 by JustMike because: typ-o
It is suggested that star formation is organized following the same principles as we have applied in a recent explanation of galaxy and massive black hole formation. In this scenario angular momentum is randomly distributed by tidal torquing among condensations, Lyman-[alpha] clouds or cores for star formation during the initial non-linear phase of collapse.
This parameter is calculated in very many simulations of structure formation of the universe as well as core formation and appears to be universal and independent of any scale.
emphasis mine
Furthermore the NFW distribution of dark matter has not yet formed, but the angular momentum of both the dark and baryonic matter has been set by previous tidal torquing events. (This implies that despite the usual calculations tha t determine X using dark matter, the result should be same for baryonic matter in core formation.)
In the black hole case the single unifiying principle of the RVI predicts not only this mass ratio, but the extraordinary correlation of BH mass with the velocity dispersion of stars surrounding the BH. The same principle can be applied to the stellar case with the prediction of the formation of a solar mass on average, and also the mass of a surrounding disk as well as a flat rotation velocity correlated with the mass of the collapsed star. Before deriving these relations, a discussion of the transport of angular momentum by the RVI and other possible mechanisms is considered.
There are a number of ways that have been suggested to transport the angular momentum: primarily by magnetic fields and the turbulence that is presumed to be generated by the magneto rotational instability, MRI. There are two problems with this explanation: no turbulent viscosity can work for the case of galactic BH formation because of the excessive mass of the disk, >> than the BH mass, necessary t o transport the angular momentum at near the Eddinton limit. In the case of a proto stellar disk, the low electrical conductivity of the near neutral gas a t low temperature, N 100 K , and with N mass fraction of dust. (The dust attaches and immobilizes the free ions from cosmic ray ionization.) The RVI circumvents both these problems and further predicts the masses and velocity dispersion
Among various initial equilibria that we have examined, we generally find t h a t there are three stages of the disk evolution: (1) The exponential growth of the initial small amplitude perturbations are in excellent agreement with the linear theory. ( 2 ) The production of large scale vortices and their interactions with the background flow, including shocks. Significant accretion is observed due to these vortices. (3) The coupling of Rossby waves/vortices with global spiral waves, which facilitate further accretion throughout the whole disk. Even after more than 20 revolutions at the radius of the vortices, we find that the disk maintains a state that is populated with vortices, shocks, and spiral waves/shocks, all of which transport angular momentum outwards. We have shown that there is an efficient outward angular momentum transport in stages (2) and (3) ,over most parts of the disk, with an equivalent Shakura-Sunyaev angular momentum transport parameter a in the range from 10 [super-2] to 10 [super-4]. By carefully analyzing the flow structure around a vortex, we have shown how such vortices prove to be almost ideal “units” in transporting angular momentum outwards, namely by positively correlating the radial and azimuthal velocity component
source
The mission of the Energy Department is to ensure America’s security and prosperity by addressing its energy, environmental and nuclear challenges through transformative science and technology solutions.
We revisit the Riemann-Cartan geometry in the context of recent higher-dimensional theories of spacetime. After introducing the concept of torsion in a modern geometrical language we present some results that represent extensions of Riemannian theorems. We consider the theory of local embeddings and submanifolds in the context of Riemann-Cartan geometries and show how a Riemannian spacetime may be locally and isometrically embedded in a bulk with torsion. As an application of this result, we discuss the problem of classical confinement and the stability of motion of particles and photons in the neighbourhood of branes for the case when the bulk has torsion. We illustrate our ideas considering the particular case when the embedding space has the geometry of a warped product space . We show how the confinement and stability properties of geodesics near the brane may be affected by the torsion of the embedding manifold. In this way we construct a classical analogue of quantum confinement inspired in theoretical-field models by replacing a scalar field with a torsion field.
The idea that our spacetime may have more than four dimensions seems to be a recurrent theme in contemporary theoretical physics research. Such idea was ﬁrst conjectured by G. Nordstrom [1], in 1914 (before the completion of general relativity), whose aim was to achieve uniﬁcation of gravity with electromagnetism. Although Nordstrom’s interesting work, done in the context of a scalar gravity theory, was ignored for a long time, the same basic idea was taken up again, a few years later, by the mathematician T. Kaluza [2]
In almost all theories mentioned above it has been generally assumed that the underlying higher-dimensional space (often referred to as the bulk [7]) has a Riemannian character. Surely this is the more natural assumption to be made since the Riemannian theory is the geometrical setting of the well-established theory of general relativity. With very few exceptions, there has not been much discussion on whether the bulk could admit more general geometries.
In spite of the limited interest it has arisen among theoretical physicists since its conception (perhaps due to the fact that it diﬀers very little from general relativity), some authors believe that the Einstein-Cartan theory can have an important role in a future quantum theory of gravitation [16]. Moreover, torsion cosmology has been investigated recently in connection with the acceleration of the Universe [17]
One of the motivations for studying the geodesic motion in the presence of torsion is the following. As is well known, in the brane-world scenario the stability of the conﬁnement of matter ﬁelds at the quantum level is made possible by assuming an interaction of matter with a scalar ﬁeld. An example of how this mechanism works is nicely illustrated by a ﬁeld-theoretical model devised by Rubakov, in which fermions may be trapped to a brane by interacting with a scalar ﬁeld that depends only on the extra dimension [13]. On the other hand, the kind of conﬁnement we are concerned with is purely geometrical, and that means the only force acting on the particles is the gravitational force. In a purely classical (non-quantum) picture, one would like to have eﬀective mechanisms, other than the presence of a quantum scalar ﬁeld, to constrain massive particles to move on hypersurfaces in a stable way
Two possibilities of implement such a program have already been studied. One is to assume a direct interaction between the particles and a physical scalar ﬁeld [25]. Following this approach it has been shown that stable conﬁnement in a thick brane is possible by means of a direct interaction of the particles with a scalar ﬁeld through a modiﬁcation of the Lagrangian of the particle. A second approach would appeal to pure geometry: for instance, modelling the bulk with a Weyl geometrical structure. In this case it is the Weyl ﬁeld that provides the mechanism necessary for conﬁnement and stabilization of the motion of particles in the brane [14]. At this stage, we would like to know whether classical conﬁnement of particles and photons could also be obtained by using a torsion ﬁeld, that is, by allowing for the bulk to have a Riemann-Cartan geometry.
We have shown that for a class of torsion ﬁelds, the geometry induced on four-dimensional spacetime has a Riemannian structure. This means that it is possible to embed isometrically a Riemannian spacetime into a Riemann-Cartan ﬁve-dimensional bulk with non-vanishing torsion. We also have shown that conﬁnement and stability properties of geodesics near the brane may be aﬀected by the torsion.
Transposing these ideas to the Einstein-Cartan theory of gravity, one would naturally wonder whether spin could also be generated, or induced, in the same manner, from a higher-dimensional space. The results obtained in Sec. 3, allow us to draw some conclusions in this respect. One is that if the bulk M is a torsionless space ( hence not sourced by matter with spin), then it is not possible to generate spin geometrically (through dimensional reduction) in the four-dimensional spacetime M. A second conclusion is that, in general, spin in four dimensions may be generated from ﬁve dimensions, but in some particular cases the bulk does not transfer spin to four-dimension.
Does that paper really say "scalar field?"
You mean like non-existent scalar weapons?
We use data on the local 3-dimensional galaxy distribution for studying the statistics of the detection rates of gravitational waves (GW) coming from supernova explosions. We consider both tensor and scalar gravitational waves which are possible in a wide range of relativistic and quantum gravity theories. We show that statistics of GW events as a function of sidereal time can be used for distinction between scalar and tensor gravitational waves because of the anisotropy of spatial galaxy distribution. For calculation of the expected amplitudes of GW signals we use the values of the released GW energy, frequency and duration of GW pulse which are consistent with existing scenarios of SN core collapse. The amplitudes of the signals produced by Virgo and the Great Attractor clusters of galaxies is expressed as a function of the sidereal time for resonant bar detectors operating now (IGEC) and for forthcoming laser interferometric detectors (VIRGO).Then, we calculate the expected number of GW events as a function of sidereal time produced by all the galaxies within 100 Mpc. In the case of axisymmetric rotational core collapse which radiates a GW energy of $10^[-9]M_[\odot]c^2$, only the closest explosions can be detected. However, in the case of nonaxisymmetric supernova explosion, due to such phenomena as centrifugal hangup, bar and lump formation, the GW radiation could be as strong as that from a coalescing neutron-star binary. For radiated GW energy higher than $10^[-6]M_[\odot]c^2$ and sensitivity of detectors at the level $h \approx 10^[-23]$ it is possible to detect Virgo cluster and Great Attractor, and hence to use the statistics of GW events for testing gravity theories.
This monograph is an excellent introduction to the mathematical techniques used to describe the scattering and propagation of scalar waves, in particular sound waves.