External reality exists!

[Mayabird]

...I think. I barely squeaked through Physics 2 (e-mag and optics) so I wouldn't know the difference here. Physicists and mathematicians, is the article generally correct or valid? The next time I run into some imbecile philosophy major who claims that our existence is all in our head, can I retort by citing this? (Or should I stick with the usual method, which is hitting them while saying "Stop hitting yourself!" Note that this has never actually come up.)

I'm not looking, honest!

Mar 5th 2009
From The Economist print edition

The good news is reality exists. The bad is it’s even stranger than people thought

“HOW wonderful that we have met with a paradox. Now we have some hope of making progress.” So said Niels Bohr, one of the founders of quantum mechanics. Since its birth in the 1920s, physicists and philosophers have grappled with the bizarre consequences that his theory has for reality, including the fundamental truth that it is impossible to know everything about the world and, in fact, whether it really exists at all when it is not being observed. Now two groups of physicists, working independently, have demonstrated that nature is indeed real when unobserved. When no one is peeking, however, it acts in a really odd way.

In the 1990s a physicist called Lucien Hardy proposed a thought experiment that makes nonsense of the famous interaction between matter and antimatter—that when a particle meets its antiparticle, the pair always annihilate one another in a burst of energy. Dr Hardy’s scheme left open the possibility that in some cases when their interaction is not observed a particle and an antiparticle could interact with one another and survive. Of course, since the interaction has to remain unseen, no one should ever notice this happening, which is why the result is known as Hardy’s paradox.

This week Kazuhiro Yokota of Osaka University in Japan and his colleagues demonstrated that Hardy’s paradox is, in fact, correct. They report their work in the New Journal of Physics. The experiment represents independent confirmation of a similar demonstration by Jeff Lundeen and Aephraim Steinberg of the University of Toronto, which was published seven weeks ago in Physical Review Letters.

The two teams used the same technique in their experiments. They managed to do what had previously been thought impossible: they probed reality without disturbing it. Not disturbing it is the quantum-mechanical equivalent of not really looking. So they were able to show that the universe does indeed exist when it is not being observed.

The reality in question—admittedly rather a small part of the universe—was the polarisation of pairs of photons, the particles of which light is made. The state of one of these photons was inextricably linked with that of the other through a process known as quantum entanglement.

The polarised photons were able to take the place of the particle and the antiparticle in Dr Hardy’s thought experiment because they obey the same quantum-mechanical rules. Dr Yokota (and also Drs Lundeen and Steinberg) managed to observe them without looking, as it were, by not gathering enough information from any one interaction to draw a conclusion, and then pooling these partial results so that the total became meaningful.

What the several researchers found was that there were more photons in some places than there should have been and fewer in others. The stunning result, though, was that in some places the number of photons was actually less than zero. Fewer than zero particles being present usually means that you have antiparticles instead. But there is no such thing as an antiphoton (photons are their own antiparticles, and are pure energy in any case), so that cannot apply here.

The only mathematically consistent explanation known for this result is therefore Hardy’s. The weird things he predicted are real and they can, indeed, only be seen by people who are not looking. Dr Yokota and his colleagues went so far as to call their results “preposterous”. Niels Bohr, no doubt, would have been delighted.

link

[General Zod]

That sounds almost as confusing as how quantum computers work better when turned off. I kind of sort of get the gist but most of it just makes me go ". . .huh?"

[Vendetta]

It's certainly a moment to consider the Feynman mantra.

But yes, it certainly does seem that it is one more way to tell sophists that they're wrong, whilst making sure that they feel inferior for not understanding really complicated physics.

[Feil]

The article is available in full here. I wish somebody would pass a law requiring popular media to properly cite the works they reference.

http://www.iop.org/EJ/article/-search=6 ... 33011.html

Also, stick with the usual method. The existence of evidence for the world not being all in their head would, naturally, be all in their head. You can't bludgeon through an anti-evidence argument by throwing evidence at it.

[Modax]

But yes, it certainly does seem that it is one more way to tell sophists that they're wrong, whilst making sure that they feel inferior for not understanding really complicated physics.

I actually found this dissapointing, because it seems to be incompatible with a theory of the origin of the universe which made a big impression on me. I guess I must be a sophist

In reality, since I'm not a physicist, I'm not sure if these finding invalidate the 'causal loop' explanation, which I learned about in the books Deep Time by David Darling and Cosmic Jackpot by Paul Davies. Both authors basically assumed that nothing is real unless observed.

I think I should clarify; by origin of the universe I do not mean the Big Bang, since we don't know where the Big Bang came from or why it happened. The causal loop theory attempts to explain this. It posits that the big bang was caused by events in the future of the universe, but that (perhaps paradoxically) all moments in time exist simultaneously with the big bang, hence the universe is a causal loop. Not sure where the observer effect fits in to all of this since its been a while since my last reading.

I probably just slaughtered the theory in trying to explain it, but at least I tried.

[Junghalli]

But yes, it certainly does seem that it is one more way to tell sophists that they're wrong, whilst making sure that they feel inferior for not understanding really complicated physics.

Erm, doesn't this experiment still rely on the information we recieve from our senses being accurate? If we were really in a simulation or something, it could just be feeding us false instrument readings. For that matter, it could just be feeding us a fake article with no actual experiment happening at all, it's not like you or me would know better. So it doesn't really seem to undermine the solipsism or simulation arguments much at all.

Not that they aren't both useless intellectual dead-ends anyway.

[Akkleptos]

I think I should clarify; by origin of the universe I do not mean the Big Bang, since we don't know where the Big Bang came from or why it happened. The causal loop theory attempts to explain this. It posits that the big bang was caused by events in the future of the universe, but that (perhaps paradoxically) all moments in time exist simultaneously with the big bang, hence the universe is a causal loop. Not sure where the observer effect fits in to all of this since its been a while since my last reading.

A paradox in space time would probably be not all that important in a singularity (of which the state of all matter/energy, time and space were in before the big bang, IIRC), but maybe Imaginary time could help, since it'd mean other ways "time" could go, besides the forwards/backwards standard directions we know.

In any case -and pardon my resorting to sci-fi examples- would it be unthinkable to propose a situation like that described in The Gods Themselves, by Isaac Asimov? Human or alien intervention aside, wouldn't it be possible for matter/energy seeping from one universe into another universe, a cosmic egg universe at that (as per the multiverse theory) in some way could make the cosmeg explode into a big bang? (in this part of the story -spoiler alert?- a character says that pouring the excess energy/matter into the cosmeg universe would in time make it so unstable that it'd undergo a big bang -hence the title of the novel)