Space-Time-Gravity and Magnetism

BigDaddyMike wrote to us with a piece from Nature that discusses the latest in gravity and space time magnetism, casting some doubts on the theories of Universe Formation.

Comments

Grand Unified Theory Still Not There Yet?

[4of12]

I stopped studying physics after my sophomore year, so I'm a qualified dilettante in the area.

From what little I recall, however, the holy grail at that time was to discover a Grand Unified Field Theory so that a single equation describes not just electricity and magnetism (Maxwell's contribution), but also gravity and the weak and strong forces, incorporating relativistically correct space time.

Is this still the standing problem, or has the question shifted over the past couple of decades?

Re:Grand Unified Theory Still Not There Yet?

[SIGFPE]

The Salam-Weinberg electroweak unification is ancient history. They've handed out the Nobel prize for that work already.

However the quest is still on to unify the other forces. However we don't even have a working theory of quantum gravity (in 4 dimensions) yet - let alone a unification with the other forces.

The popularity of String Theory is due to the fact that it seems to be able to contain all four known forces - but it has many other problems.

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Preprint

[JPMH]

The full paper is available at http://xxx.lanl.gov/abs/astro-ph/0012345

It's an interesting prospect, if instead of being an effect of the physically rather dubious "dark energy" (vacuum energy density), or the even more dubious "vacuum state tunneling" of inflation, the apparent flatness of space at large scales might be due to plain old magnetic fields.

Re:Preprint

[PB-MX]

What I question aren't the strengths of these effects, but the areas over wich they act. For the most part magnetic fields are very strong but very localized. Gravitational fields however weak are spread over much larger areas. It is also important to keep in mind that all "Field measurements" can only be taken with another interacting body. Any "magnetic anti-gravity" would have no effect on a non-magnetic body...Like dark matter, can you say dead nutron star.

Not exactly "casting doubts"...

[fnordboy]

Speaking as a physics graduate student whose PhD thesis will be in cosmology, I would consider it a strong overstatement to say that this paper "casts doubts" on our theories of galaxy formation. The paper (available here) describes the possible effects that magnetic fields could have on inflation. Basically, the tension in cosmic magnetic field lines (which act like big rubber bands - the more you stretch the field line, the stronger the tension in it) tends to accelerate spatially closed regions and decelerate open regions. What's important about this is that even weak fields can have a very strong impact in an open universe, suppressing the acceleration phase of inflation. The addition of the magnetic terms to the FRW metric (which describes how the universe curves) causes makes the universe tend towards flatness in an effect which is potentially much stronger than the amount of matter and dark energy in the universe, to a degree.

However, it would be rather difficult to have a significant net magnetic field in the inflationary era. The universe was basically an incredibly hot, dense soup of plasma at this era and most importantly, is almost totally homogenous and isotropic (ie there are no preferred directions or places in the universe at this time) which would serve to keep magnetic fields somewhat local and randomized. The net result is that there probably weren't large-scale magnetic fields in the early universe.

All in all, it's a very interesting paper, and makes a very valid point - namely, that magnetic fields have the potential to be very influential in a cosmological model! However, it's important to realize that the author wasn't trying to say that the inflationary theory was wrong, just that in theory things could have turned out much, much differently.

Re:Possible implication

[SIGFPE]

It's nothing new that an electromagnetic field couples to gravity. Everything couples to gravity - including gravity itself (which one of the reasons quantum gravity is so hard). But you need a lot of electromagnetic field for space-time curvature to notice. It's hard to express just how much you need. Suffice it to say that if you could make such a magnet you probably would have invented the anti-grav drive centureis before.
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This comes up every few years.

[K-Man]

Electromagnetic forces are, IIRC, 10^42 times stronger than gravitational ones, so every once in a while someone comes up with a theory that galaxies repel each other due to static buildup, or form giant magnets, etc. Since any effect theorists come up with is 10^42 times more powerful than any similar gravitational effect, it doesn't take much to get these arguments going.

However giant supercluster-moving charge and current distributions have yet to be discovered in any shape or form, to put it bluntly.

Re:This comes up every few years.

[drudd]

Electromagnetic forces have the potential (pun intended!) to be stronger, but they nearly always average away at any significant distance.

Gravitational force is additive... all mass simply adds to the force, and thus it is very easy to build up a large force (think of galaxy superclusters).

Electromagnetic charges cancel each other, however, and since like charges repel, it is nearly impossible to build a significant amount of charge without an opposing charge to nullify the force at some distance.

There's a classic problem in elementary physics which asks how much force would be generated by your body if you had 1% more electrons than protons. It turns out that if you could concentrate that much charge, it would have enough electromagnetic force to lift the earth. The tough part is containing that large a charge without it ripping your body apart ;)

Doug

Only Problem Is, Nothing Can Move in Spacetime

[Louis Savain]

Tsagas says that magnetic fields are woven into space-time itself, becoming "an inseparable part of the space-time fabric".

When are people going to realize that spacetime is a fictitious, abstract math construct? There is something out there that is responsible for gravity. Something material, physical. That something is certainly not spacetime. Why? Because nothing can move in spacetime, by definition. Spacetime is just a math hack. Sorry.

"It is up to us, it is up to the citizens of a free society to either accept the chauvinism of science without contradiction or to overcome it by the counterforce of public action." Paul Feyerabend

Re:Only Problem Is, Nothing Can Move in Spacetime

[Louis Savain]

I've read that website, and I'm just curious about one thing; how can one person be so wrong, and yet have the ability to make a shockingly ugly website, too? Further, how could someone actually be taken in by all of this quackery?

Interesting but where is the argument?

That whole website comes from the naive, Newtonian definition of motion. Asserting that the colloquial meaning of a word influences it's technical definition is a fallacy.

For your information, Newtonian mechanics and Einstein's relativity are both classical physics theories. They both use the same definition of motion.

Re:Only Problem Is, Nothing Can Move in Spacetime

[Louis Savain]

Nobody defines motion as v= dt/dt.

That's the point.

Re:Only Problem Is, Nothing Can Move in Spacetime

[Louis Savain]

Nobody debunks a scientific theory without first understanding the claims it is making. In smaller words, try reading before making an ass out of yourself.

You'd have a little bit more credibility if you showed any hint that you actually read the page you are criticising. I have nothing against relativity. I have something against famous con artists who claim that it does not forbid time travel. Too bad you feel you need to defend them.