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> Unified Theory Of Everything
kellys_eye
Posted: March 05, 2012 02:06 am
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This is WELL above my comprehension but it got me wondering......

I read somewhere that the laws of physics work perfectly well in the 'real' world but the same laws peter-out (fail) as you approach the macro and mega ends of the cosmic scale.

As such, they haven't (yet) got a unified theory to explain 'everything'.

Why can't they map how 'wrong' the current laws are as they go towards each end of this scale? If there is a relationship between the rate of error of the existing laws, as they taper-off at each end of the scale, then wouldn't the formula for this 'error' be the missing link?



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Geek
Posted: March 05, 2012 02:39 am
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Discover magazine has had three issues on this in the past 12 months (this month is the latest one).

It actually has scientists rethinking everything and coming up with completely new theories using Relativity for the "time standard" for the visible universe at least.

I love the articles on alternative theories biggrin.gif

Cheers!


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Sch3mat1c
Posted: March 05, 2012 06:52 am
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I think it's not so much a difference in scaling, as a way of representing things. Quantum mechanics works with abstract state numbers, particles and waves; relativity does things in four dimensions with curvature and fields. There are a lot of common aspects -- physicists love solving any problem with energy; wave mechanics (whether of matter or energy, photons or gravity) are ubiquitous, and very powerful. But where things get really important, like the mechanism of gravity, the approaches differ.

Relativity says gravity is not so much a force (though it can be derived as the Newtonian quantity) as a curvature of space; it's not that there's a force holding your butt into your chair, it's that your butt is being pressed into the chair because it's on the inside of the curvature of space. There's less "space" inside the curve, so everything comes tighter together there.

In contrast, QM is classically about the distribution of a 'particle' over space, and the energy levels of those distributions. A particle is described, not geometrically as we would intuitively describe a physical object, but by the nature of its interactions. After all, it's impossible to "see" an electron (as if a single electron had a geometrical form), what we actually call "an electron" is a description -- if it quacks like an electron, then you must have an electron. You put a description into Schrodinger's equation -- an energy function (the Hamiltonian), chug away at some math, and out comes a probability distribution.

Now, relativity is no stranger to QM -- it's simple to incorporate special relativity. By changing E = m*p to E = m*c^2 + p^2*c^4 (the relativistic rest mass + kinetic energy formula), you find that, for low momenta, electrons have a 'size' inversely proportional to momentum, but when they're up near the speed of light, the size drops sharply, because relativity gives distance and time contraction. If you envision an experiment where electrons are forced into a small space while giving them increasingly greater energy, eventually the size kind of goes to zero:
http://en.wikipedia.org/wiki/File:WhiteDwarf_mass-radius.jpg
Well, this was done relatively early in the history of QM (1930s, by an Indian scientist no less), and the surprising result was derived from first principles, in terms of fundamental constants, and solutions of mathematical equations -- in short, it turns out that stars will collapse to neutron stars or black holes when they're only a little more massive than our own star (assuming no fusion heat propping it up). No small prediction from such a small field!

That said, why the problem today? As I understand it, when you combine QM with Maxwell's equations, you get QED (electrodynamics) -- which allows you to describe everything about the history of an electron while it's moving -- Maxwell's equations work for all time, so by incorporating QM, you can solve for a system that evolves through time, rather than sitting there with rotating phase shift, which doesn't really help in and of itself. Unfortunately, infinities crop up, which have to be 'ignored' to finish the solution. The solutions still work, so reality at least doesn't seem to mind. It's my understanding that these infinities are roughly equal and cancel, but the magnitude of the energy they represent is immense -- the "quantum foam" allows for particles popping in and out of existence, and permeates all space. But being a statistical effect, it's more noticable on very small scales, and averages out over the universe.

In astrophysics, the big problem they're wrestling with is dark energy. Dark matter isn't so horrible because it's probably just cold regular matter, so it's transparent and not glowing, or maybe it really is something weird and different. Fundamentally, what they mean by "matter" is "something with mass", i.e., it generates gravity, pulling things together. But dark energy isn't so easy to explain. Dark energy is the opposite, an anomalous "push" that seems to repel. What's more, observations of very distant galaxies and clusters seem to suggest that this repulsion has changed through history. It would be elegant and convenient if the quantum physicists' zero point energy could be used to explain dark energy, however the orders of magnitude are completely wrong.

The biggest obstacle to unifying quantum mechanics today (i.e., from the bottom up, working with the smallest of particles) is generating experimental evidence. If gravitons exist, they will behave identically to photons, except the energy levels are astronomically lower -- the Earth going around the Sun makes a displacement of mass, which radiates gravitational radiation, just as an electron orbiting a proton (in a similarly high orbit -- the equivalent is a Rydberg atom) displaces electric field and emits radiation at the orbital rate. Trouble is, the atom emits infrared, which is easily detectable (energy levels of ~meV), while the Earth radiates 1.3 x 10^-22 eV gravitons. Needless to say, detecting gravity waves, let alone observing quantum effects, when liquid helium at 4.2K still has a thermal energy of 0.36meV, is a considerable challenge.

Tim


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kellys_eye
Posted: March 05, 2012 10:24 am
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I really appreciate the effort you put into that reply Tim and your knowledge is peerless .... but you completely missed the first part of my question...

QUOTE
This is WELL above my comprehension....


FAIL

(me, that is) laugh.gif


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Sch3mat1c
Posted: March 05, 2012 05:47 pm
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Well, for whatever reason... you asked... smile.gif

Why ask about something that's beyond your comprehension? To expand your mind... the universe is out there wink.gif

Tim


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kellys_eye
Posted: March 05, 2012 08:42 pm
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Yeah I was a bit tongue-in-cheek in my reply.... I did comprehend most of what you said but at my age I tend to take things in BBC sized (and dumbed down) proportions.
The universe is now for the 'kids' - us oldies have enough trouble understanding day-to-day stuff laugh.gif


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tekwiz
Posted: March 05, 2012 09:57 pm
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"Dark matter" is again in the news, because of the recent discovery of a blob of dark matter apparently left behind by the collision of two galaxies.
This implies that dark matter can indeed interact with the real universe other than just through gravity. Something previously thought impossible.

It wouldn't surprise me at all if there's yet another layer of reality under the quantum waiting to be discovered...possibly an infinity of them.


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Geek
Posted: March 06, 2012 12:23 am
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I wonder if "dark matter" is just a bunch of bloody Buckey-balls stuck together >_>


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