Tiramisu And Gemstones

“Sis, you say there’s dessert?”

“Of course there is, Sy. Teena, please bring in the tray from the fridge.”

“Tiramisu! You did indeed go above and beyond. Thank you, Teena. Your Mom’s question must be a doozey.”

“I’ll let you enjoy a few spoonfulls before I hit you with it.” <minutes with spoon noises and yumming> “Okay. tell me about entanglement.”

“Whoa! What brought that on?”

“I’ve seen the word bandied about in the popular science press—”

“And pseudoscience—”

“Well, yes. I’m writing something where the notion might come in handy if it makes sense.”

“How can you tell what’s pseudoscience?”

“Good question, Teena. I look for gee-whiz sentences, especially ones that include weasely words like ‘might‘ and ‘could.’ Most important, does the article make or quote big claims that can’t be disproven? I’d want to see pointers to evidence strong enough to match the claims. A respectable piece would include comments from other people working in the same field. Things like that.”

“What your Mom said, and also has the author used a technical term like ‘energy‘ or ‘quantum‘ but stretched it far away from its home base? Usually when they do that and you have even an elementary idea what the term really means, it’s pretty clear that the author doesn’t understand what they’re writing about. That goes double for a lot of what you’ll see on YouTube and social media in general. It’s just so easy to put gibberish up there because there’s no‑one to contradict a claim, or if there is, it’s too late because the junk has already spread. ‘Entanglement‘ is just the latest buzzword to join the junk‑science game.”

“So what can you tell us about entanglement that’s non‑junky?”

“First thing is, it’s strictly a microscopic phenomenon, molecule‑tiny and smaller. Anything you read about people or gemstones being entangled, you can stop reading right there unless it’s for fun.”

“Weren’t Rapunzel and the prince entangled?

“They and all the movie’s other characters were tangled up in the story, yes, but that’s not the kind of entanglement your Mom’s asking about. This kind seems to involve something that Einstein called ‘spooky action at a distance‘. He didn’t like it.”

“‘Seems to‘?”

“Caught me, Sis, but it’s an important point. You make a system do something by acting on it, right? We’re used to actions where force is transmitted by direct contact, like hitting a ball with a bat. We’ve known how direct contact works with solids and fluids since Newton. We’ve extended the theory to indirect contact via electric and other fields thanks to Maxwell and Einstein and a host of other physicists. ‘Action at a distance‘ is about making something happen without either direct or indirect contact and that’s weird.”

“Can you give us an example?”

“How about an entanglement story? Suppose there’s a machine that makes coins, nicely packaged up in gift boxes. They’re for sweethearts so it always makes the coins in pairs, one gold and one silver. These are microscopic coins so quantum rules apply — every coin is half gold and half silver until its box is opened, at which point it becomes all one pure metal.”

“Like Schrödinger’s asleep‑awake kitty‑cat!”

“Exactly, Teena. So Bob buys a pair of boxes, keeps one and gives the other to Alice before he flies off in his rocket to the Moon. Quantum says both coins are both metals. When he lands, he opens his box and finds a silver coin. What kind of coin does Alice have?”

“Gold, of course.”

“For sure. Bob’s coin‑checking instantly affected Alice’s coin a quarter‑million miles away. Spooky, huh?”

“But wait a minute. Alice’s coin doesn’t move. It’s not like Bob pushed on it or anything. The only thing that changed was its composition.”

“Sis, you’ve nailed it. That’s why I said ‘seems to‘. Entanglement’s not really action at a distance. No energy or force is exerted, it’s simply an information thing about quantum properties. Which, come to think of it, is why there’s no entanglement of people or gemstones. Even a bacterium has billions and billions of quantum‑level properties. Entanglement‑tweaking one or two or even a thousand atoms won’t affect the object as a whole.”

~~ Rich Olcott

Reflections in Einstein’s bubble

There’s something peculiar in this earlier post where I embroidered on Einstein’s gambit in his epic battle with Bohr.  Here, I’ll self-plagiarize it for you…

Consider some nebula a million light-years away.  A million years ago an electron wobbled in the nebular cloud, generating a spherical electromagnetic wave that expanded at light-speed throughout the Universe.

Last night you got a glimpse of the nebula when that lightwave encountered a retinal cell in your eye.  Instantly, all of the wave’s energy, acting as a photon, energized a single electron in your retina.  That particular lightwave ceased to be active elsewhere in your eye or anywhere else on that million-light-year spherical shell.

Suppose that photon was yellow light, smack in the middle of the optical spectrum.  Its wavelength, about 580nm, says that the single far-away electron gave its spherical wave about 2.1eV (3.4×10-19 joules) of energy.  By the time it hit your eye that energy was spread over an area of a trillion square lightyears.  Your retinal cell’s cross-section is about 3 square micrometers so the cell can intercept only a teeny fraction of the wavefront.  Multiplying the wave’s energy by that fraction, I calculated that the cell should be able to collect only 10-75 joules.  You’d get that amount of energy from a 100W yellow light bulb that flashed for 10-73 seconds.  Like you’d notice.

But that microminiscule blink isn’t what you saw.  You saw one full photon-worth of yellow light, all 2.1eV of it, with no dilution by expansion.  Water waves sure don’t work that way, thank Heavens, or we’d be tsunami’d several times a day by earthquakes occurring near some ocean somewhere.

Feynman diagramHere we have a Feynman diagram, named for the Nobel-winning (1965) physicist who invented it and much else.  The diagram plots out the transaction we just discussed.  Not a conventional x-y plot, it shows Space, Time and particles.  To the left, that far-away electron emits a photon signified by the yellow wiggly line.  The photon has momentum so the electron must recoil away from it.

The photon proceeds on its million-lightyear journey across the diagram.  When it encounters that electron in your eye, the photon is immediately and completely converted to electron energy and momentum.

Here’s the thing.  This megayear Feynman diagram and the numbers behind it are identical to what you’d draw for the same kind of yellow-light electron-photon-electron interaction but across just a one-millimeter gap.

It’s an essential part of the quantum formalism — the amount of energy in a given transition is independent of the mechanical details (what the electrons were doing when the photon was emitted/absorbed, the photon’s route and trip time, which other atoms are in either neighborhood, etc.).  All that matters is the system’s starting and ending states.  (In fact, some complicated but legitimate Feynman diagrams let intermediate particles travel faster than lightspeed if they disappear before the process completes.  Hint.)

Because they don’t share a common history our nebular and retinal electrons are not entangled by the usual definition.  Nonetheless, like entanglement this transaction has Action-At-A-Distance stickers all over it.  First, and this was Einstein’s objection, the entire wave function disappears from everywhere in the Universe the instant its energy is delivered to a specific location.  Second, the Feynman calculation describes a time-independent, distance-independent connection between two permanently isolated particles.  Kinda romantic, maybe, but it’d be a boring movie plot.

As Einstein maintained, quantum mechanics is inherently non-local.  In QM change at one location is instantaneously reflected in change elsewhere as if two remote thingies are parts of one thingy whose left hand always knows what its right hand is doing.

Bohr didn’t care but Einstein did because relativity theory is based on geometry which is all about location. In relativity, change here can influence what happens there only by way of light or gravitational waves that travel at lightspeed.

In his book Spooky Action At A Distance, George Musser describes several non-quantum examples of non-locality.  In each case, there’s no signal transmission but somehow there’s a remote status change anyway.  We don’t (yet) know a good mechanism for making that happen.

It all suggests two speed limits, one for light and matter and the other for Einstein’s “deeper reality” beneath quantum mechanics.

~~ Rich Olcott

Gargh, His Heirs, and the AAAD Problem

Gargh the thinkerGargh, proto-humanity’s foremost physicist 2.5 million years ago, opened a practical investigation into how motion works.  “I throw rock, hit food beast, beast fall down yes.  Beast stay down no.  Need better rock.”  For the next couple million years, we put quite a lot of effort into making better rocks and better ways to throw them.  Less effort went into understanding throwing.

There seemed to be two kinds of motion.  The easier kind to understand was direct contact — “I push rock, rock move yes.  Rock stop move when rock hit thing that move no.”  The harder kind was when there wasn’t direct contact — “I throw rock up, rock hit thing no but come back down.  Why that?

Gargh was the first but hardly the last physicist to puzzle over the Action-At-A-Distance problem (a.k.a. “AAAD”).  Intuition tells us that between pusher and pushee there must be a concrete linkage to convey the push-force.  To some extent, the history of physics can be read as a succession of solutions to the question, “What linkage induces this apparent case of AAAD?”

Most of humanity was perfectly content with AAAD in the form of magic of various sorts.  To make something happen you had to wish really hard and/or depend on the good will of some (generally capricious) elemental being.

aristotle 1Aristotle wasn’t satisfied with anything so unsystematic.  He was just full of theories, many of which got in each other’s way.  One theory was that things want to go where they’re comfortable  because of what they’re made of — stones, for instance, are made of earth so naturally they try to get back home and that’s why we see them fall downwards (no concrete linkage, so it’s still AAAD).

Unfortunately, that theory didn’t account for why a thrown rock doesn’t just fall straight down but instead goes mostly in the direction it’s thrown.  Aristotle (or one of his followers) tied that back to one of his other theories, “Nature hates a vacuum.”  As the rock flies along, it pushes the air aside (direct contact) and leaves a vacuum behind it. More air rushes in to fill the vacuum and pushes the rock ahead (more direct contact).

We got a better (though still AAAD) explanation in the 17th Century when physicists invented the notions of gravity and inertia.Newton 204

Newton made a ground-breaking claim in his Principia.  He proposed that the Solar System is held together by a mysterious AAAD force he called gravity.  When critics asked how gravity worked he shrugged, “I do not form hypotheses” (though he did form hypotheses for light and other phenomena).

Inertia is also AAAD.  Those 17th Century savants showed that inertial forces push mass towards the Equator of a rotating object.  An object that’s completely independent of the rest of the Universe has no way to “know” that it’s rotating so it ought to be a perfect sphere.  In fact, the Sun and each of its planets are wider at the equator than you’d expect from their polar diameters.  That non-sphere-ness says they must have some AAAD interaction with the rest of the Universe.  A similar argument applies to linear motion; the general case is called Mach’s Principle.
JCMaxwell

The ancients knew of the mysterious AAAD agents electricity and its fraternal twin, magnetism.  However, in the 19th Century James Clerk Maxwell devised a work-around.  Just as Newton “invented” gravity, Maxwell “invented” the electromagnetic field.  This invisible field isn’t a material object.  However, waves in the field transmit electromagnetic forces everywhere in the Universe.  Not AAAD, sort of.

It wasn’t long before someone said, “Hey, we can calculate gravity that way, too.”  That’s why we now speak of a planet’s gravitational field and gravitational waves.

But the fields still felt like AAAD because they’re not concrete.  Some modern physicists stand that objection on its head.  Concrete objects, they say, are made of atoms which themselves are nothing more than persistent fluctuations in the electromagnetic and gravitational fields.  By that logic, the fields are what’s fundamental — all motion is by direct contact.einstein-tongue edged

Einstein moved resolutely in both directions.  He negated gravity’s AAAD-ness by identifying mass-contorted space as the missing linkage.  On the other hand, he “invented” quantum entanglement, the ultimate spooky AAAD.

 ~~ Rich Olcott