Are observers really necessary in order for reality to have reality? Is the realm of the quantum really spooky? Is causality doomed? Welcome to the world of the quantum mess!
Continued from yesterday’s blog…
THE QUANTUM MESS – WAVE/PARTICLE DUALITY: It’s well established that elementary particles can behave in experiments like waves, and waves behave like particles. It’s called ‘Wave-Particle Duality’ or just ‘Duality’. That duality isn’t in doubt, but it is one of those aspects of the quantum that is a puzzlement. So, to explore a bit about this, I was interested in whether or not generalized wave behaviour, or generalized particle behaviour, seems to be predominant. If waves (or particles) could account for 90% that’s quite a different kettle of fish than if it’s a 50-50 split.
So, let’s represent particles in motion (particles standing still are rather boring) by machine gun bullets. I’m sure we all agree bullets are particles. Let waves be presented by water waves or sound waves – again, I’m sure we can agree these are true waves or exhibit real wave behaviour. Now, can one or the other (maybe both) account for these particular bits of physics.
Reflection – Well, waves can reflect off of surfaces; so can bullets. No help.
Refraction – Refraction represents a change in velocity and direction when going from one medium to another. Both particles (bullets) and waves (water or sound) refract. Bullets fired in air towards water will alter direction and slow down when hitting the water. A water wave will change speed and direction if the bottom conditions change – say become shallower and more on one side of the wave than the other. No help.
Density – Particles slow down as the density of the medium increases. Bullets go farther and faster in a vacuum than in air; faster in air than in a liquid; and they don’t really travel all that well through solids. Solids really cramp their style. Waves, as represented by sound, don’t travel at all in a vacuum; slowly in air; faster in liquid; faster still in a solid. So what do elementary particles do in experiments? They tend to exhibit pure particle behaviour. Stuff tends to impede their progress. If photons were waves, they couldn’t (seemingly) travel in a vacuum. It’s one vote for particles.
Energy Transfer - Water waves can convey energy; ditto sound waves – thunder can rattle windows. If you get hit with a bullet, well particles too can carry and transfer energy. No help.
Collisions – Fire two machine gun bullet streams at right angles to each other, or head on for that matter. While you’ll get lots of misses, you’re bound to get some impacts and scattering too. Two waves crossing at right angles, or meaning head on, ultimately pass right through one another. Photons (light beams) pass through one another; but electrons or protons or neutrons collide (in particle accelerators). It’s a draw.
Obstacles – Water waves will tend to go around small obstacles, like rocks or boats they encounter, but not large obstacles, like a coastline. Sound waves might find a large obstacle too big to circumnavigate and bounce off instead. But sound waves will go around a chair in middle of your living room where your speakers are. Hiding behind the chair won’t eliminate the sound. But hiding behind a rock or boat or chair though when the bad guys show up firing their bullets just might protect you. Substitute the bullets with a flashlight beam (light photons). Well, you’re protected. Light doesn’t go around corners. Substitute the bullets with radio energy photons. Well, you’re not protected. That suggests waves and obstacle size are both relevant. But electrons, neutrons or protons – well a rock or chair should shield you. It seems to be a draw again.
Escape Routes – A wave (water or sound) can go through an open door or through two (or more) open doors side-by-side at the same time (and cause constructive and destructive interference on the other side). A bullet can go through one door or another door (if there are two side-by-side), but not through both at the same time. It’s an either/or proposition. Even firing lots of bullets will provide an either/or situation for each individual bullet. There will be no interference pattern on the other side. So what do real micro particles do? Well, both. One door (or slit), it’s bullets time. Two doors or slits, its wave time because you get interference patterns. So, overall, it’s a vote for a wave, since a wave won’t be expected to produce an interference pattern going through just one door. BUT it’s here where Mother Nature (mom) goes off the deep end, because if you fire your micro particles at a very slot rate at the two doors, you’d expect that each particle will be faced with an either/or choice, and thus no interference pattern should form. Mom says otherwise, and mom rules, OK?
So, for all this pondering, I’m left with one vote for particles; one vote for waves. It just apparently reaffirms that wave-particle duality is real, and here to stay.
THE QUANTUM MESS - ENTANGLEMENT: Pick and remove a card from a standard deck. Don’t look at it. Bury it in a time capsule. Send the rest of the unobserved deck of 51 cards via rocket ship off to the Andromeda Galaxy. Leave instructions. Generations upon generations later, with the deck of 51 safely in the Great Galaxy of Andromeda, you’re great, great, great (add lots more greats) grand-person can dig up and look at lone card in the time capsule. Say it is the Ace of Diamonds. You do not now need to observe the original deck in Andromeda to know 1) it contains 51 cards, and 2) that it is missing the Ace of Diamonds! That’s entanglement. And entanglement is something that Einstein called ‘spooky action at a distance’ because you can come by information/knowledge instantaneously – faster than the speed of light. Thus, Einstein was not amused!
On the micro level, the example usually given involves electrons (though one can experimentally substitute oppositely polarised photons). No two electrons can be in the exact same atomic ‘orbit’ if they have the exact same quantum configuration – the Pauli Exclusion Principle. One such configuration is called ‘spin’ and there are two mutually exclusive possibilities called ‘spin up’ and ‘spin down’. Any electron is either ‘spin up’ or ‘spin down’ with respect to ‘spin’. So, two electrons can occupy the same atomic ‘orbit’ if one is ‘spin down’ and the other is ‘spin up’. If either electron flips from ‘spin up’ to ‘spin down’, then its orbital partner must instantaneously flip too, but in the opposite manner. [Ignore the fact that even while in their atomic orbit, two electrons couldn’t ‘communicate’ quite instantaneously and thus it would still take some finite time for a spin to flip.] Now, separate the two electrons and send them travelling so that there becomes a vast distance between them. If later on you observe the spin orientation on one, then you instantaneously know the spin of the other – faster than the speed of light! Where ‘spooky’ comes in is that if one of the isolated electrons flips, then the other apparently must flip also in response. Yet the two are out of touch and out of reach, so how do they know each other’s state, and how do they instantaneously communicate same – faster than the speed of light? Something’s rotten somewhere! I can only conclude that since electrons have no free will, no ability to communicate with each other, and can not violate the cosmic speed limit, that once separated and thus isolated they either don’t flip, or it doesn’t matter because observing one will now tell you nothing about the state of the other, and therefore nothing ‘spooky’ happens. It doesn’t matter because once separated, the entanglement is no longer valid – the two electrons are like a divorced couple that have no further interaction with each other.
Further readings in entanglement:
Aczel, Amir D.; Entanglement: The Greatest Mystery in Physics; John Wiley & Sons, N.Y.; 2002:
Clegg, Brian; The God Effect: Quantum Entanglement, Science’s Strangest Phenomenon; St. Martin’s Griffin , N.Y.
To be continued…
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