Cosmology

[BobHegwood]

Personally, I would like to see the results of this. It would be interesting to have this experiment running while a star, perhaps at the distance of the crab nebulae or closer, go supernova. What would really be interesting is to have LISA detect "strong"gravity waves for say a month or so and then bam, a supernova lights up the sky. It would probably detect these waves soon after or at the same time. Or maybe not at all. Who knows.
cartrite

But now that kind of result WOULD muddy the waters for a while,
would it not? I mean - if the gravity waves were detected before the
light from a Super Nova, then the "gravity waves" would have to be
moving faster than light. Yes? That would make for some interesting
debates, I'm sure.

[cartrite]

Yes it would.

[t00fri]

This is now really for another forum ("alternative" physics or whatever these are called)

Selden?

Bye Fridger

I'm afraid I don't understand you. Or rather, I'm afraid you don't understand me.

My purpose here is not to argue for alternative theories as much as it is to argue against the current popular ones. More accurately, I am trying to have a dialog about why current theories are so popular (although that dialog is clearly not happening here). My "crazy theories" as you would probably label them are more presented as arguments. Look at these theories, and explain to me why they are impossible.

I can certainly become clearer: You were speculating about gauge theories, whence it became more than obvious that you had no idea about them. Proposing new interpretations about properties of gauge theories, can only make sense, once you master at least their basic implications.

Similarly, it makes no sense that I try to tell you why your proposals
are entirely nonsensical, since you obviously don't understand how gauge theories work.

I hope you are aware at least that gauge theories represent the current most beautiful and extremely successful framework for ALL fundamental interactions we know (weak, electromagnetic, strong AND gravitational) .

I believe what I'm thinking of is called "guage symmetry".
...
Now lets give this hypothetical type of "charge" some sort of name. How about "mass"? Yeah, mass would be a good name for it.

This is really utter nonsense: Mass is a dimensionful quantity!
You should at least get the dimensions right when writing here

Bye Fridger

[t00fri]

As authority in matter, can I ask to you, Fridger, what do you think about the M.O.N.D. theory and about the Dirac's suggestion concerning the variation in time of the gravitational constant?

MOND is an intelligent attempt to modify gravity such as to understand the outer rotational curves of galaxies without introducing Dark Matter.

Unlike Einsteins original version of gravity, MOND became an increasingly "baroque" construct, the more new evidences for Dark Matter it had to explain without it . One "tough" (but not impossible) case for MOND is the "bullet event" (see above)

Dark Matter is an entirely NATURAL possibility, since e.g. SUPERSYMMETRY that we need for other good reasons, offers suitable DM candidate particles automatically.

It is quite possible that certain "constants" of Nature like the gravitational or the fine structure constant are actually time dependent (on cosmological time scales!). There are known mechanisms that might cause such time dependence.

Bye Fridger

[Fenerit]

Thanks.

[DonAVP]

Fridger listed the four forces.

weak, electromagnetic, strong AND gravitational

What strikes me as interesting is the difference of the first three forces relative to gravity. The weak and strong forces are at the sub-atomic scale and influence small amounts of matter. Electromagnetic force influences certain types of atoms only at the outer electron shells and also has a temperature variable as it interacts with atoms. Gravity is such a different animal compared to these. It only comes into play when very very very very large numbers of atoms come together. And is a function of mass only. Yet gravity appears to be the driver at the macro scale and can over whelm the other forces (black holes). If one were to plot on a log scale with influence to size or number of atoms. I would guess that starting at the weak force through strong to electromagnetic the line would start curving up but when it gets to gravity the line goes straight up.

I am not sure if I explained myself clearly and correct me if I am missing something. The point is we need to keep the different forces in perspective. Not sure were SUPERSYMMETRY or gauge theories fits in all of this. Factoring in dark matter and dark energy does not seem to answer all of the question. The terms seem to be place holders for lack of a better name or understanding. Just guessing maybe there is something about gravity that has not be understood.

I will be quiet now that you all can see how limited my knowledge is. Keep talking, like others have said this is a good thread. Even if we don't come to a conclusion.

Don

[t00fri]

Fridger listed the four forces.

weak, electromagnetic, strong AND gravitational

What strikes me as interesting is the difference of the first three forces relative to gravity. The weak and strong forces are at the sub-atomic scale and influence small amounts of matter. Electromagnetic force influences certain types of atoms only at the outer electron shells and also has a temperature variable as it interacts with atoms. Gravity is such a different animal compared to these. It only comes into play when very very very very large numbers of atoms come together. And is a function of mass only. Yet gravity appears to be the driver at the macro scale and can over whelm the other forces (black holes). If one were to plot on a log scale with influence to size or number of atoms. I would guess that starting at the weak force through strong to electromagnetic the line would start curving up but when it gets to gravity the line goes straight up.

Don,

this is a VERY good question, indeed. Thanks for asking it. Let me try to explain in a non-technical way, why the ranges of the 4 basic forces are so different despite their common nature based on gauge theories.

There are two main ingrediens one has to know.

i) Reminiscent of Heisenberg's uncertainty principle, the range of an elementary force in distance is inversely proportional to the mass of the particle that acts as the carrier of the force, i.e.

range * mass ~ 1

(in particle physicst's units: h-bar = speed_of_light = 1)
In gauge theories, the carrier particles of the force are called "gauge bosons":

Some names should be familiar:

Force:.......................................Carrier particle
===================================
Electromagnetic:........................Photon (massless)
Weak.................................W, Z bosons (very massive)
Strong (QCD)............................Gluons (massless)
Gravitational.............................Graviton (massless)


ii) In any gauge theory, the occurrence of mass and thus a finite range for the force requires a subtle mechanism, since massive carriers of the gauge force are INCOMPATIBLE with the underlying gauge symmetry!

To generate mass in gauge theories in accordance with the gauge principle, there are precisely TWO alternatives:

• The so-called Higgs mechanism as taking place in Weak Interactions.
• Confinement as taking place in Strong Interactions (QCD)

Hence despite gluons being massless, the confinement of quarks and gluons within protons or pions, shortens the basically infinite range of the strong force (massless gluons!!) to the size of the proton, say. I.e. to

1 fermi = 1.0 x 10?€“15 metres = 1 femtometre

You may rephrase this by saying that due to confinement, the range of the strong force is determined by the mass of the lightest boundstate particle of gluons and quarks, the Pion.

The range of the Weak force is becoming VERY short, since the weak gauge bosons W, Z have acquired a heavy mass due to the Higgs mechanism.

NOTE: The latter mechanism requires the existence of yet another special particle, the Higgs boson, that is the last missing link in the famous Standard Model of particle physics. The Higgs boson will hopefully be discovered soon, at the forthcoming LHC collider(CERN)!

In summary: Gauge Theories are basically theories the corresponding forces of which have infinite range, since the gauge particles should be massless unless one of two possible mechanisms took place (Confinement or "spontaneous breakdown of the gauge symmetry" via the Higgs mechanism).

We have seen why --exceptionally-- the ranges of the weak and strong forces are VERY short, acting only within subatomic scales. In contrary, the carriers of the electromagnetic and the gravitational force (Photon and Graviton, respectively) are TRULY massless and thus the corresponding forces act on VERY LARGE distances, despite being weak in nature.

Despite these different manifestations, the structure of the underlying theories is all the same, nevertheless, i.e. we have a most beautiful and highly constrained gauge theory for all known basic forces.

NOTE: It was only noted much later that Einstein's gravity can be recast in form of a gauge theory, thus making all known interactions look similar. Of course, this lends strong weight to the possibility that at very short distances all known forces can be unified into one.


Bye Fridger

[BobHegwood]

Force:.......................................Carrier particle
===================================
Electromagnetic:........................Photon (massless)
Weak.................................W, Z bosons (very massive)
Strong (QCD)............................Gluons (massless)
Gravitational.............................Graviton (massless)

Pardon the interuption again, but can one assume that all the
massless particles (for lack of better terminology) will be found
to travel in the cosmos at the SAME velocity i.e.-the speed of light?

Is there any research here which would enlighten the Brain-Dead?

Thanks, Bob

[Fenerit]

Surely as scientist you'll look with suspect at the philosophical questions inside the scientific work, nevertheless, when through the gauges theories and the so-called "renormalization", the gravity can be "coupled" with the electromagnetism, is easy to think for the unauthorized persons how these two force deal with the same phaenomenon from two point of view, in similar manner to the "wave-particle" analogy. I'm wandering if that analogy can be right or, insted, if it's totally wrong; because as analogy it wouldn't have any sense within the supersymmetry's framework in which the other two forces plays a decisive role (that is, it would be a welded four-fold analogy, if any). Moreover, I knew how, as the proposition itself says, in an unified theory the "split-and-couple" may not be done in order to hold the gauge math's coherence. I'm asking for it because in the "philosophycal pub's discussions" with my friend this point it's no clear; so, as scientist, if you, with courtesy, can cast the shadows away on which side stand the reason, I could sleep more clean.