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Reality doesn’t exist until it is measured, quantum experiment finds

227 points| lermontov | 10 years ago |anu.edu.au | reply

239 comments

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[+] Strilanc|10 years ago|reply
The linked article is titled "Experiment confirms quantum theory weirdness". Please don't exaggerate the title. These experiments do not show that "reality doesn't exist until it's measured".

First, "realism" [1] is not the same thing as "reality". "Realism" basically means "physical quantities have a definite value". "Reality" is that thing that determines your experimental outcomes. Don't mix them up.

Second, interpretations of quantum mechanics disagree wildly about what kind of weird you use to explain things. Some interpretations have "realism", some don't. Some interpretations have retrocausality, some don't. Some interpretations have FTL effects, some don't. Since all the interpretations give (mostly) the same experimental predictions, it's misleading to single one out and say just that particular brand of weirdness was confirmed.

We confirmed that there's weird there. We didn't distinguish what brand of weird it is. Physicists widely disagree about which brand of weird to use, with no position achieving even a majority [2]. The original title was better.

1: https://en.wikipedia.org/wiki/Na%C3%AFve_realism#Realism_and...

2: http://www.preposterousuniverse.com/blog/2013/01/17/the-most...

[+] cristianpascu|10 years ago|reply
A standard case of mixing (or actually confusing) epistemology with ontology. That is to say that something doesn't exist until we get to know something about it. Or, by all means, knowing something about something is posterior to us being here AND that something being there. Here lies the danger of dismissing philosophy as a bag of words when compared with the Holy Science that works, bitches.
[+] yummyfajitas|10 years ago|reply
I don't think the title is a misrepresentation of the article, just the physics:

From the article: "It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it..."

The article does appear to be (incorrectly) arguing that this experiment proves one interpretation of QM correct. It's definitely incorrect - some years back myself and others used non-experimentalist interpretations of QM to get the same result - but it's not a misrepresentation of the article.

[+] jdmichal|10 years ago|reply
To be fair, the submitted title is directly culled from the first sentence of the article:

> The bizarre nature of reality as laid out by quantum theory has survived another test, with scientists performing a famous experiment and proving that reality does not exist until it is measured.

[+] zw123456|10 years ago|reply
And perhaps someday we'll get to meet the great programmer in the sky the developed the simulation we are living in and we will ask him why he designed it that way and he will say something like "oh I just wanted to optimize the code so I simply excluded reality subroutines when there were no beings looking. I just never thought you guys would notice. As soon as I saw that you guys noticed the flaw, I was going to load a patch but then the confusion it was causing with the simulated beings became interesting and so I just left it in as an accidental feature of the game." Meh, but probably not.
[+] antimagic|10 years ago|reply
I always find it fascinating at just how much of our fundamental physics ends up being constraints on information movement. The laws of thermodynamics are about entropy, general relativity puts constraints on the movement of information (for example, Spooky Action as a Distance(tm) is faster than light, but you can't transmit information with it), the Uncertainty Principle puts limits on how much information you can have on a given system.

Information information everywhere you look in fundamental physics. It does make me wonder why.

[+] stingraycharles|10 years ago|reply
In other words, reality is lazily evaluated and is written in Haskell ?
[+] Strilanc|10 years ago|reply
That would quite possibly be the worst optimization ever.

"Yeah, I could have tracked and updated n values pretty cheaply, but instead I decided to exponentiate an exponentially huge matrix and use that to update a vector containing 2^n complex numbers associated with the possible assignments of the original n bits. Also, you should use bogosort. It's the best."

[+] violentvinyl|10 years ago|reply
Off to be the Wizard by Scott Meyer is a very funny fiction book that is based on the concept of reality being a computer program that hackers can manually manipulate to do cool stuff. It mostly occurs in King Arthur's Court, which happens to be the chosen time and place all these hackers wind up.
[+] yummybear|10 years ago|reply
Reality frustrum culling?
[+] caf|10 years ago|reply
Surely, "As soon as I saw that you guys noticed the flaw, it became part of the ABI and had to be maintained."
[+] madaxe_again|10 years ago|reply
Well, if you want to prove the simulation argument, all you have to do is simulate a reality for an individual at any time-dilation you like. With the parallel compute capabilities we are increasingly growing, simulating a small section of the universe at a large time-dilation should be within our grasp sooner than we think.
[+] amelius|10 years ago|reply
> developed the simulation we are living

Well, the way I understand this, is that this result proves that we do NOT live in a simulation. Because if reality does not exist until measured, then we apparently cannot compute reality ahead of time. And if we cannot compute reality ahead of time, it does not exist yet.

[+] andy_ppp|10 years ago|reply
The equivalent of a memory leak being spooky action at a distance?
[+] EC1|10 years ago|reply
But probably though.
[+] hasenj|10 years ago|reply
I'm not familiar with this particular experiment, but all my pondering on the subject - as a layman - leads me to a simple conclusion.

The properties these experiments are measuring are simply bogus. They are not well defined. The answer that comes out is not some intrinsic property of the "particle", but the result of the environment in which the particle interacted with the "measurement" system, so to speak.

The particle has some other properties, but what's being "measured" is not one of those properties.

How can I explain?

Imagine someone who has never tried any Korean food, and you try to ask him/her: what's your favorite Korean food? There's no answer. So you try to "measure" it by feeding him some Korean items and recording his facial expressions. He will like some items more than others, but it has nothing to do with "his favorite Korean food", and has more to do with how the items were prepared and his mood at the time.

A "point" location for a photon is never defined; it's not a property of a photon that it exists in a point in space. When you fire a photon at a "wall" and see a "blip", you're not seeing the position of the photon at some point in time. You're seeing the rough position of the atom that had an electron that absorbed the photon's energy, and I'm not even sure the atom has a well defined point position either. The whole thing is an artifact (a side effect) of some interaction between several systems and doesn't really tell you anything fundamental about the photon (or the quantum object).

At least that's how I understand it.

[+] Kequc|10 years ago|reply
The topic outlined in the OP's article has been raised before, multiple times, once every couple of years. It was even the focus of a cult indoctrination propaganda piece called "what the bleep do we know".

http://skeptico.blogs.com/skeptico/2005/04/what_the_bleep_.h...

Essentially, yes, it's bogus science. Quantum physics are much more complex than these articles ever bring on. But by explaining it simply, it sounds awe inspiring and so it propagates across social media. Over and over again.

It isn't that particles exist in multiple states until they are measured. It is that the mechanism by which you measure very small things affects the outcome.

[+] FranOntanaya|10 years ago|reply
Intuition tells me this is like saying a droplet of water can both be a sphere and a single point because it'll pass through several holes on a net, but capillary action makes it collapse into a needle.
[+] westoncb|10 years ago|reply
This is of course extremely interesting and probably important for understanding our universe—but how is it helping anyone to say something like, "...with scientists performing a famous experiment and proving that reality does not exist until it is measured." The statement is like a distraction at a magic show, drawing the reader to the glittery 'reality' and 'exist,' which are totally undefined so the reader's imagination can rove without limit.

Maybe this is really just a fundamental challenge to our assumptions about motion of particles or information transfer in the universe. Isn't that interesting enough without these vague, human aggrandizing assertions about creating reality?

[+] chakademus|10 years ago|reply
The thing is, this isn't even a challenge to any assumptions physicists have, or even a surprising result. Every prediction of quantum theory for these kinds of atomic systems has been borne out.

All this "weirdness" is the same old story of "Is it a particle or a wave?!," when in reality, we know its neither. Quantum objects are represented by wavefunctions, or vectors in a Hilbert space, to which "particle" and "wave" are intuitive approximations in certain regimes, that makes it easier for humans to talk about in natural, non-mathematical language.

All this experiment has shown is that a object that we expect to be described by quantum mechanics turns out to, indeed, be described by quantum mechanics.

[+] epitomix|10 years ago|reply
"Maybe this is really just a fundamental challenge to our assumptions about motion of particles or information transfer in the universe."

Check out this TED talk on just that subject. http://www.ted.com/talks/donald_hoffman_do_we_see_reality_as...

Here's the punch line, space, time and matter are components of a user interface produced through evolution. We don't take the desktop and icons of our computer UI literally and we shouldn't take our evolved UI literally either.

[+] deckar01|10 years ago|reply
I think it is the most digestible title. "The Causality of Atomic Particles is Symmetric with Respect to Time" doesn't have quite the same ring to it.
[+] deciplex|10 years ago|reply
John Wheeler's delayed choice thought experiment was already confirmed in the lab over ten years ago. It's neat that they were able to get results with baryonic matter, and it was definitely worthwhile to try to do that, but this article seems to be implying that the results could have been anything else than what they were, or that there is new physics here, and is wrong on both counts.

Also the deference to the Copenhagen interpretation is annoying - it's wrong. What they've observed is a consequence of how decoherence works, and 'observation' has nothing to do with it. Not faulting the researchers on this but seriously, it's time to stop talking about mythical 'observation' as though it's some integral part of quantum theory.

[+] ghosthamlet|10 years ago|reply
http://www.simulation-argument.com/simulation.html says: at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a “posthuman” stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation. It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living in a simulation. A number of other consequences of this result are also discussed.

COMPUTER SIMULATION vs HOLOGRAPHIC UNIVERSE

http://www.crystalinks.com/holographic.html http://thelaymansanswerstoeverything.com/2013/01/scientific-...

[+] exch|10 years ago|reply
What does 'post human' mean? Unless we go extinct, we will always be humans, regardless of what species we evolve into. Our current species is "Homo Sapiens Sapiens", not "Human". Ergo, if we evolve into amorphous blobs of space goo, we will still be Human but not "Homo Sapiens Sapiens". Which means it is physically impossible for us to ever reach a "post-human" stage.
[+] eli_gottlieb|10 years ago|reply
Proposition (2) is just flagrantly, blatantly bullshit. The amount of computational power needed to simulate even just the bits of the universe we conscious humans happen to be observing at any one time is so stupendously humongous that you'd get more utility out of repurposing your cosmic-scale computers to play video games.
[+] z5h|10 years ago|reply
What does it mean to exist? A thing exists specifically when it affects something else. What is measurement? It's a reciprocal affecting.

So does a thing which is not affecting anything else and not being measured exist? No! QED

[+] themgt|10 years ago|reply
Right. This way of describing it is much closer to "zero-worlds" or relational quantum mechanics, and to my mind is a far simpler, deeper way of understanding what's really going on - reality is simply all entanglement.

What really still gets me is the way it's not simply that the atom wasn't interacted with, but that if the information about the interaction never leaks to the outside world - if it's "erased" after the interaction takes place - then the system still behaves as if the interaction never took place.

It undermines not just the concept that matter really exists, but time as well.

[+] wtbob|10 years ago|reply
> What does it mean to exist? A thing exists specifically when it affects something else. What is measurement? It's a reciprocal affecting.

All that's starting to sound an awful lot like Orthodox Christian theology about the essence of God…

[+] anti-shill|10 years ago|reply
depends on what the meaning of "is" is....
[+] davidrusu|10 years ago|reply
Clever optimization by our simulators, Big up
[+] marwatk|10 years ago|reply
I've always wanted to read (or write?) a book about us determining we are in a simulation, but we find subtle flaws like this we're able to exploit in weird ways. Kind of like breaking out of a VM through register flaws or something. Anyone know of a story along those lines?
[+] CamperBob2|10 years ago|reply
Once you read Teller and Hanrahan's SIGGRAPH paper on potentially-visible set computation, you instantly grok what quantum mechanics is for. At least in an "I want to believe" sense.
[+] has2k1|10 years ago|reply
How do we go about determining if we are in a lossless compression or not?

I wonder if there is some ordering of "conservation of ---" laws that is strictly enveloping/hierarchical, such that you could choose a level at which to simulate/design a universe.

[+] icanhackit|10 years ago|reply
Had to find a way to keep the framerate from dropping below Planck time levels.
[+] davej|10 years ago|reply
I find it fascinating how the speed of light, quantum indeterminacy and Planck's length could all be seen as allegories for computational optimisations in a simulated universe.

This is something that I've thought about for some time, I posted a question about this a number of years ago on Reddit: http://www.reddit.com/r/Physics/comments/g287k/quantum_indet...

[+] A_COMPUTER|10 years ago|reply
If I'm standing here, all the stuff that the atoms in my body could conceivably interact with have to be backfilled for me to interact with them according to this experiment, but since I'm not special to the universe, atoms three billion light years over, they are still interacting with each other, just not with me. So am I decohered to them? Is this like a divergent timelines theory such that coherence is defined as when different possibilities converge while following possibilities, reducing them and then so must necessarily collapse as other possibilities drop off? So what's the difference between cohered and decohered reality then? It sounds then like it would just be one of those paths, the one that we happen to be on that we only notice because we're conscious so that's our arbitrary (to the universe) observation point. That's the only way I can make sense out of this without attaching significance to human observation.
[+] mjfl|10 years ago|reply
The philosophical interpretation of Quantum Mechanics is a very hard, unsolved problem. There are many reasons why quantum mechanics is theoretically good and philosophically terrible, and not just in a subtle, esoteric way. The reason is that in Quantum Mechanics there are 2 main types of entities: particles, "things" that evolve according to the Schrodinger equation, and "observers". Observers are what deliver to us the results of randomly sampling from the probability distribution defined by the squared amplitude of the wave function by "collapsing" it, according to the Copenhagen interpretation. However, there is no particle that acts as an observer, they all just follow the Schrodinger equation, but nothing that exists isn't a particle. How could "observers" exist and interact with particles then? The Copenhagen interpretation is philosophically terrible. And it really pisses me off that this article title seems to hint that they've really confirmed it. In a lab, an experimenter can just point to his apparatus and say, "that's the observer". Or, being more formal, they can say a thermodynamically irreversible process plays the role of an observer. But this is not really a satisfying explanation because how could it be possible to generate these large, discontinuous motions we call "collapse" on the macroscale if it is impossible on the microscale? There are the multiverse theories that you seem to describe, but they have their own problems. Rae's Quantum Physics: http://www.amazon.com/Quantum-Physics-Illusion-Reality-Class...

goes over a lot of them without getting to messy in the math. Other interpretations of QM are in the book as well. There are many:

https://en.wikipedia.org/wiki/Interpretations_of_quantum_mec...

[+] hackinthebochs|10 years ago|reply
Let us not forget about Pilot-Wave theory, where it has both particle and wave-like properties simultaneously. In fact, I don't quite get why people are so enamored by these fanciful interpretations when Pilot-Wave is so much more down-to-earth.
[+] db48x|10 years ago|reply
Just remember that in quantum physics, any interaction between two particles is a measurement.
[+] nosuchthing|10 years ago|reply
Observation does not exist until observed, experiment finds.
[+] graycat|10 years ago|reply
We know that light bends near a gravitational field with a big gradient before it is "measured".

Sounds like that light existed and generated and responded to a gravitational field after it was emitted and before it was detected or measured.

[+] vectorpush|10 years ago|reply
armchair musings of a layperson physicist/philosopher follow:

the non-interference pattern is the optimized result of a deterministic universe that requires the observation to occur. The measurement didn't reach back in time, the results were specifically determined by the same causal chain that determined an experiment would be performed.

[+] jondubois|10 years ago|reply
I always found the notion that "If you measure it, it behaves differently" to be really confusing. When considering the double slit experiment - In both cases (whether we are observing the particle going through a single slit or otherwise observing the interference pattern left afterwards), we are in fact simply measuring 'observable effects' in both cases - It's just that we are measuring them in different ways.

If you didn't measure both cases, you wouldn't be able to compare their outcomes. It seems that it is not about whether or not the event was measured/observed but about HOW and WHEN it was measured.

In neither case do we actually 'witness it happen' - In both cases, we are just observing effects of those events.

The light which allowed us to 'directly observe it' is as much a byproduct of the actual event as the interference pattern left behind on the surface.

[+] agd|10 years ago|reply
> "At the quantum level, reality does not exist if you are not looking at it"

So much physics reporting mistakes science for philosophy. It leads to so much confusion among laypeople.

[+] hkailahi|10 years ago|reply
In the time of Empiricism, the philosophers George Berkeley and John Locke proposed something similar. I believe it was called it immaterialism, or the idea that nothing exists without being perceived. Berkeley went further saying that objects only exist in the mind, or something like that.
[+] facepalm|10 years ago|reply
"If one chooses to believe that the atom really did take a particular path or paths then one has to accept that a future measurement is affecting the atom's past, said Truscott."

Is that equivalent to "reality doesn't exist until it is measured"? Because I don't see the latter claim (which is the headline on HN) anywhere in the text?

Also, didn't Feynman explain in q.e.d. that it's not either a wave or a particle, it's always a particle and the probabilities for the path the particle takes behave like waves? (Something like that, I am foggy on the details).