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).
Only useful links to Ives and Bridgman are through Amazon if they still carry their books. Internet has fallen down on the job.
‘Debris from the U.S. intercept of a spy satellite in February and from China’s anti-satellite test in Janaury 2007 is still orbiting Earth’
Don’t have time to worry about quantum mechanics right now when space junk refuses to be cooperative.
Is it? There is the theory, traditional, good enough, but if math is a problem try philosophy. In particular Husserl. I would recommend Whitehead but there is nothing in English.
That’s some very interesting rambling. Thanks for sharing your thoughts.
My post was more of a tangent off on the subject of game probabilities, which is a different animal than the probability of one wave form collapsing out of all the possible wave forms an a quantum system.
Shuffling a deck of cards is very deterministic, it’s just impossible for the human eye and mind to follow the cause-effect chains that end up in the “random” shuffle.
Quantum mechanics is different than that.
Nevertheless, game probabilities are a good analogy in some respects, don’t you think?
Just as the chances of getting dealt 13 spades in a bridge hand is very remote (but possible), so outcomes of experiments in particle physics do allow for the occasional occurrence of a highly improbable event.
Or am I wrong to think that the analogy is apt?
I agree. It is far more likely that we simply don't fully understand Cosmology and the background radiation. QM has been going pretty strong for a while. It is interesting though.
Good thing the Bible didn't have alot to say about this stuff, otherwise these posts might turn into pages long flames.
Maybe time is more contiguous than continuous. Not moving, just re-appearing in a neighboring slice of Planck time like the procession of images on a 35mm film strip and the phenomena of after-images creating the illusion of continuous, smooth motion. Does that make sense?
The probability of being dealt all spades is not less than the probability of being dealt any other particular hand.
As an analogy, I don't think it fits Quantum indeterminism, because it does not allow for just anything to happen. The uncertainty is limited. I suppose if you think of all possible hands being the limiting factor (Planck's constant?), it might be. Honestly haven't given as much thought as it deserves.
Hank
Interesting post, good enough place to bookmark this thread.
The probability of being dealt all spades is not less than the probability of being dealt any other particular hand.Yes, that's true. But the probability of being dealt ANY particular hand (in which you name all 13 cards by suit and face-value in advance) is exceedingly low (56!/13!), it's just that "all spades" is an easy way to specify one of those particular hands.
What I should have said is that the probability of being dealt a WINNING hand, in poker, for example, varies inversely with the ranking of that hand. You're going to get more single-pairs dealt to you in your life than you are royal-straight-flushes, even thought the probability of any PARTICULAR single-pair hand (if I specify 2h, 2s, 5c, 9d, ks, for example) is the same as expecting royal-straight-flush in spades.
And even the word "probability" is somewhat suspect. If you play 10,000 hands of poker a year, you will CERTAINLY see more crappy hands than you will great hands (crappy and great as per definitions within the game).
The more I think of it, the more I think this is a good way to explain QM to the lay person, even though cards, of course, are definitely not quantum events but causal on a macro level just like a baseball, if it's hit with enough force in the right direction, will go sailing over the fence.
Thank you for the ping. It is my personal opinion (personal, not calculated) that Physics will not resolve the separation between quantum mechanics and relativity until it accepts the notion that every particle contains a little smidge of time, a small degree of space, and energy. The variable expressions of both dimension Time and dimension Space must be resolved in continua of combinatoric expressions before calculations for ultimate measurement will be possible ... Ol’ Werner will continue his laughing until that is accomplished.
OR as "Spaceman" Bill Lee of the Boston Red Sox said circa 1975, "With Skylab falling you have to pitch faster."
Cheers!
Be still my heart!
(...or is that Holiday Inn Express and Resnick ?)
Cheers!
Interesting.
you lost me. any geometric ratio can be expressed exactly, mathematically. what's an example of a "ratio that cannot be expressed exactly, mathematically"?
The whole point of quantum mechanics is that sometimes the particles can be treated as discrete and sometimes they can't. Regardless of how we treat the "particles", they will behave as the quantum theories predict, sometimes inconsequentially close to the predictions of newtonian physics; sometimes quite different.
I believe that you are exactly correct. The proto-typical example I recall is of a "particle" in a potential well. The particle has a finite amount of kinetic and potential energy.
Classical physics predicts that the particle cannot leave the well, because there is insufficient energy to escape. Quantum physics predicts that there is a small probability that the particle can leave the well, appearing outside the well. I believe this is referred to as "tunneling".
I don't think that radioactivity of many substances is possible without this effect. The particles emitted from radioactive nuclei shouldn't be able to escape the nucleus; but they DO.
Quantum physics is not just classical physics with uncertainty thrown in. It is more complicated than that. Quantum physics predicts events which can't happen given the constraints of classical physics.
It makes sense to me.
If I gave you a length standard and told you it was 1 meter long, but in fact it was 1.01 meters long, you could measure things forever without detecting that the standard was wrong.
Similarly, we are forced to measure durations using whatever we adopt as a measure of "time". It may just be that we can't observe any lack of continuity in time because of the tools we have to measure it.
The ancients believed that there were a few pure substances and that they consisted of "atoms" which, as the name implies, were indivisible. Using the tools they had, they were not going to be able to observe the particles inside atoms. Nor were they ever going to properly explain all the phenomenon that are the result of atoms not being indivisible.
“what’s an example of a ‘ratio that cannot be expressed exactly, mathematically’?”
I gave two examples. When expressed they are called “irrational” numbers, which really means a number which cannot be perfectly expressed as a ratio [it has nothing to do with rationality].
But I’ll give you one detailed example. It is Bertrand Russell’s recasting of Euclid’s explanation of incommensurables arising from the Pythagorean theorem.
“In a right-angled isosceles triangle, the square on the hypotenuse is double the square on either side. Suppose each side is an inch long; then how long is the hypotenuse? Let us suppose its length is m/n inches. Then m²/n²=2. If m and n have a common factor, divide it out, then either m or n must be odd. Now m²=2n², therefore m² is even, therefore m is even, therefore n is odd. Suppose m=2p. Then 4p²=2n², therefore n²=2p² and therefore n is even, contra hyp. Therefore no fraction m/n will measure the hypotenuse. The above proof is substantially that in Euclid, Book X.” (Bertrand Russell, History of Western Philosophy)
The reason I like this is because it illustrates that what are called irrationals and often expressed as incomplete decimals are not just a problem of precision. Irrationals are things which cannot technically be expressed mathematically—there is no number, positive or negative, that represents the ratio between the hypotenuse and either leg of an isosceles right triangle.
Hank
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