Physics of "Ender's Game/Xenocide"

I’ve been reading the Ender’s Game series of books and am now at the third book, Xenocide.

In this fictional future universe, the “Hundred Worlds” communicate via ancible, a device that relies upon quantum entanglement to function. I recall reading some time ago that quantum entanglement cannot be used for communication. Can someone explain why?

Further, the book explains fictional particles called “philotes” that have no mass yet build connections that are the cause of quantum entangelement. Are such connections a viable explanation for the pheonomena? Large networks of philotic connections become sentient, and are the basis for conscious life. Nonsense or not?

I don’t think quantum entanglement is given as an explanation for the philotic connection – it certainly wouldn’t work, for the reasons you alluded to. Card’s invention of philotes is a way around the limitations of known physics, not an extension of it. And I don’t think the way he describes philotes makes them particles, exactly.

However, I’ll have to let wiser heads explain the physics to you – I have a vague sense that it’s a consequence of the Exclusion Principle.

The ancible was invented by Ursula K. LeGuin for her early, mid-60s, books about her Hainish universe. I don’t remember them talking about quantum entanglement, which I’m sure that she had no knowledge of at the time. The ancible was just a device for faster-than-light communication, some variation of which is necessary for any viable interstellar empire or confederacy.

Adding gobbledygook scientific terms to justify their fantasy science is what sf writers do. All of us. All quantum entanglement means is that two particles with complementary properties will display these opposite properties when either one is measured.

Put it this way. If you send out two entangled particles and find out by measuring one of them that it has the property of spin up, then the other one when measured will have the property of spin down. Nobody understands how this works. The first particle should have a perfect 50/50 chance of measuring spin up or spin down, so how can the second particle “know” to do the opposite?

But this is why communication is impossible. Just because the second particle is opposite the first, you haven’t transmitted any information, because the first particle’s result is entirely arbitrary and random. Information could only be sent if there were a way to force to first particle to be up or down in the way you want. Right now, our understanding of the quantum world tells us that there is no way to force this. Maybe in the future we’ll learn how and so that makes for a nice scientific sounding underpinning for what is still fantasy.

But instantaneous communication is just a necessary device, no more how it’s presented. Don’t think too hard about the gobbledygook behind the curtain.

No idea on the physics.

IIRC in Ender’s Game the ansible was presented as an alien technology that was borrowed but not understood. So their was never the pretense of a scientific explanation in the books. Course I read Ender’s game like 10 years ago so someone correct me if I’m wrong.

Great books though.

That is only a paradox if you assume that the “spin” comes into existence at the moment of the measurement, and was not simply “stored” in the particles from the moment they became entangled.

For example, let’s say I put a red ball and a green ball in two identical envelopes. I send the two envelopes several light-years away from each other, and you receive one of them and open it. By looking into your envelope, you can predict with perfect accuracy the color of the ball in the other envelope, even though for each envelope individually the chance of getting a particular ball is 50/50. Nothing magical about any of that. Likewise, the obvious explanation of the quantum entanglement thing would be that the particles are created with opposite spin, and each of them simply keeps its own spin until it is measured.

Now, I understand that it has been pretty well established that such “hidden variables” cannot be the whole explanation. I even more-or-less understood the explanation at one point, long ago – something about how you could use a variation of the double-slit experiment to show that the probability of a given spin depends on how it is measured, and that spin can therefore not be a static property of a particle? I think it had something to do with measuring the spin at different angles (think polarized light) and the different probabilities, depending on the angle, did not add up to 1 like they normally would.

However, it’s a long time ago that I even believed I fully understood the explanation, much less that I would have been able to explain it to someone else. Anybody able and willing to explain it to me again?

Entanglement doesn’t let you choose the spin or either the near particle or the distant one, but can decoherence itself transmit information?

In other words, let’s say we generate two entangled particles. I put one in a box and carry it with me to Alpha Centauri while you keep the other one at home. At some point you decide to measure your particle’s spin. I never directly measure my particle, but could I tell if it suddenly ceased to be in a indeterminate state? I’m pretty sure there have been experiments in which it was demonstrated that you could (indirectly) show that an indeterminate state exists and therefore could presumably know when one has ceased to exist.