The background patterns of space could help us focus on quantum problems.NASA / ESA / Hubble Heritage Team
Posted on 05/18/2008 10:40:38 PM PDT by neverdem
Observations of the cosmic microwave background might deal blow to theory.
The background patterns of space could help us focus on quantum problems.NASA / ESA / Hubble Heritage Team
The question of whether quantum mechanics is correct could soon be settled by observing the sky — and there are already tantalizing hints that the theory could be wrong.
Antony Valentini, a physicist at Imperial College, London, wanted to devise a test that could separate quantum mechanics from one of its closest rivals — a theory called bohmian mechanics. Despite being one of the most successful theories of physics, quantum mechanics creates several paradoxes that still make some physicists uncomfortable, says Valentini.
For instance, quantum theory uses probability to describe the properties of a particle. These properties obtain definitive values only when they are measured, which means that you cannot predict a particle's position or momentum, for instance, with certainty.
These premises troubled Albert Einstein. He believed that particles contain extra properties — or 'hidden variables' — that determine their behaviour completely. If only we knew what these hidden variables were, we could predict the fate of particles and the outcome of measurements with certainty. Bohmian mechanics is one of a suite of 'hidden variables' theories — many now discredited — formulated to tackle this problem.
Neck and neck
So far it’s been impossible to pick apart quantum mechanics from bohmian mechanics — both predict the same outcomes for experiments with quantum particles in the lab.
But Valentini thinks that the stalemate could be broken by analysing the cosmic microwave background — the relic radiation left behind after the Big Bang. The cosmic microwave background contains hot and cold temperature spots that were generated by quantum fluctuations in the early Universe and then amplified when the Universe expanded.
Using the principles of quantum mechanics, cosmologists have calculated how these spots should be distributed.
“It’s far too early to say that this is definite evidence of a breakdown in quantum mechanics – but it is a possibility.”
Antony Valentini
Imperial College, London
However, Valentini’s calculations show that the hidden-variables theory might give a different answer. “Any violation of quantum mechanics in the early Universe would have a knock-on effect that we could see today,” says Valentini.
Almost all measurements of the cosmic microwave background seem to fit well with the predictions of quantum mechanics, says Valentini. But intriguingly, a distortion that fits one of Valentini’s proposed signatures for a failure of quantum mechanics was recently detected by Amit Yadav and Ben Wandelt at the University of Illinois at Urbana-Champaign (see 'Deflating inflation?'). That result has yet to be confirmed by independent analyses, but it is tantalizing, Valentini adds.
“It’s far too early to say that this is definite evidence of a breakdown in quantum mechanics — but it is a possibility,” he says.
Cosmic predictions
Hiranya Peiris, an expert on the cosmic microwave background at the University of Cambridge, UK, is impressed by the new work. “This is a pretty cool new idea,” she says. “Nobody has ever thought of using the cosmic microwave background to look into really fundamental quantum questions — cosmologists just assume that quantum mechanics is correct,” she says.
But Peiris adds that Valentini must now come up with more detailed predictions about the types of distortion that will arise in the cosmic microwave background to convince cosmologists that they are really caused by a breakdown of quantum mechanics. “He has thrown some really exciting ideas out there, but now he needs to do the nitty-gritty calculations,” she says.
Vlatko Vedral, a quantum physicist at the University of Leeds, UK, agrees that the cosmic microwave background will be a useful way to test quantum mechanics. But he adds that even if quantum mechanics is shown to break down in the early Universe, that doesn’t necessarily mean that the hidden-variables theory is correct.
References Valentini, A. preprint at http://arxiv.org/abs/0805.0163 (2008). Yadav, A. P. S. & Wandelt, B. D. Phys. Rev. Lett. 100, 181301 (2008).
A fool who was vastly smarter than you.
I dunno - that cat does look dead and alive.
Quantun mechanics! Hell, I can’t even find a decent mechanic for my Saturn!
You mean if we knew exactly what every atom in a die was going to do, we could predict the behavior of the die?
You seem to be stating that classical physics applies to very large systems without stating that such an outcome is predicted by quantum physics due to the very large number of independent random events.
I certainly hope that Valentini is able to come up with a convincing set of parameters to distinguish this (bohmian mechanics hypothesis) from quantum mechanics using the primeval radiation pattern.
Contrary to some folks who have already chimed in here,:
- I don’t think that Heisenberg was a fool, but instead that he was a brilliant man who was deprived of his best colleagues.
- I believe the Heisenberg uncertainty principle is extremely useful in describing the world as we observe it today - but as Einstein enhanced Newton, so sometime theory will enhance Einstein (which directly yields Heisenberg).
- I agree with Einstein, not Hawkins, that “God does not play dice”. It may not be in my lifetime before we figure that out, but this hypothesis may be a way it could.
- (as an aside, I also don’t believe “dark matter/ dark energy hypotheses, so I hope such an advance will show us the way out of that mess, too)
The microwave background might be a local phenomenon and have nothing to do with quantum mechanics. Also, the only reason quantum mechanics might be relevant to cosmology is the supposed inflationary phase, which answered a tricky problem but it is only a hypothesis as is all the rest. Relativity is inherently bogus as formulated and it is about time to do it right.
Oh yeah, like that explains something scientific, man.
A fool? Who is calling Heisenberg a fool? If there be fools they be those who quote Heisenberg to support their Cartesian worldview.
Classic historical post with details I had never heard before.
I have read that also. Ruled out.
Last I heard quantum theory has not been proven to be valid... it has simply not been proven to be invalid, there is a huge disparity in saying one proves the other.
What is true as I understand it is that what we observe when we expirament with the quantum is what the probabilities of the theory predict, we have never obsevered to date an outcome that was not predicted by the math.. However this does not mean the theory is fact or valid. It may mean that only we have not attempted to uet to obsever the case(s) that do not meet the probabilities predicted in the math.
Of course quantum theory also states that by simply observing we affect the outcome.
I admit I am no quantum physicist, but of what I understand about it, which admittedly isn’t much, I don’t color myself convinced that the theory is wholey correct.
The late Dr. David Bohm presented a new formulation of work he did in the the 1950s. He dropped the original work of the '50s because I believe Einstein didn't think very highly of his ideas. However with the advent of Bell's theorem calling into question Einsteins theory of locality (you know the spooky action at a distance), Bohm renewed his pursuit of his theory of Quantum mechanics. The dislike of Bohm's theory is due to the fact that not that much changes. He in effect moved the goal line by stating the random nature of quantum mechanics is not due to any underlying physical property implied by the theory, instead it's due to our lack of knowledge of the state of the system at the beginning of the experiment. That and the fact that dimensions run wild with even simple calculations of particle experiments.
I believe the proof against hidden variable was due to Von Neuman (?). But Bohm addresses this in his last book and his theory is not affected by the proof.
So what's cool about all this is that if Bohm's theory is correct then it changes Einsteins Theory of Relativity. In Relativity is the concept of locality, that everything is capped by the speed of light. So that an event that happens on one side of the solar system can be detected no sooner than it would take light to travel across and reach a detector (your eye). But if Bohm's theory holds special quantum mechanical events could be transmitted faster than light (I believe near instantaneous).
I apologize in advance for errors in history. It's been a while since I've read about this stuff. But I'm glad Bohm's theory is alive and kicking. Even if he was a Marxist.
Interesting. Bumping for later
Bohm’s hypothesis might be alive if Ives’ and Bridgman’s hypotheses are. Of course they are, but nobody cares for alternatives.
from some reading today, I learned that (probably vastly over-simplifying and being incorrect here) that Bell’s Theorum said that if we want hidden variables then we must also accept instantaneous communication across light year distances.
in other words, maybe hidden-variable explanations can still be valid, but the explanation must somehow take into account nonlocality.
one thing that freaks me out is the (I believe commonly accepted) concept of “advance waves” which are electromagnetic waves that travel backwards in time to exactly “balance out” every normal (goes forward in time) electromagnetic wave.
my head hurts.
If (as Lisa Randall [Goddess-Harvard Physics] has suggested, see her book Warped Passages)--there are extra hidden dimensions;
and those dimensions may be on the order of 10-33 cm, but possibly much larger;
and there may be 'branes' connecting portions of reality with additional dimensions which are closed to us;
How do these extra dimensions relate to the Big Bang and the Higgs boson? How would the other dimensions and the associated branes be affected by inflation?
Well over my current state of reading.
The questions themselves may be meaningless, or indicative of *profound* misunderstandings on my part.
Cheers!
The only Bridgeman's I know is an ice cream shoppe in Minneapolis.
Cheers!
Have a Guinness.
Slainte!
I am so happy to read that Schroedy’s cat’s still kicking, because he was first written up in 1935.
Actually he was alive hundreds of years earlier or maybe not.
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