# This lecture on entanglement seems awesome but are the words correct?

https://youtu.be/wZzHnZzm_58?t=5m50s

His words seem contradictory when explaining entanglement.

When the two entangled particles ( red and white ) are taken apart. He describe them as pink.

Then he states, if you measure one particle as red.

that the other "particle becomes white"

What he really means is if you were to measure it it will be white.

I mean if you had to measure one particle to determine it was red, you would need to measure the other particle to know it was white.

I completely understand that only one will be red and one will be right due tot he conversation of "color" in the universe. Where color is an analogy for something else.

The nuance is that, we can not infer if this is causal or not.

Is this correct?

• This is a highly informal and surface-level description of entanglement, and should not be analyzed in any depth because it wasn't designed for that. Commented Nov 22, 2017 at 18:31
• I'm not analyzing it in depth, I'm pointing out an inconsistency on a superficial level that requires no knowledge of physics ... if you must measure one particle to know it's color, shouldn't you need to measure the other particle to know it's color? It's a cool concept but I think he's trying to make it sound more cool for the sake of being informal and appealing to a larger audience. I'm not 100% sure of this, and that is why I posted. Is this the case? Commented Nov 22, 2017 at 18:53
• This is horrible. This has nothing to do with quantum mechanics. Commented Nov 22, 2017 at 21:39

## 1 Answer

You are very roughly correct, although the analogy is a bad one, raising more questions than it answers.

Entangled pairs of particles (let us call them A and B) have certain sets of properties such that we know that if particle A has property F1, particle B will have property F2; likewise, if particle A has property F2, particle B will have property F1.

The behavior around these properties is strange, however. If you measure G, a different property, after measuring F, then measure F again, it might have a different value. More, you can set up experiments which "measure" G but don't record it anywhere or show it to anyone, and F won't change, which rules out the measurement itself as causing the issue.

Even stranger, under circumstances in which a particle's behavior is determined by the property F but F isn't directly measured or observed, the particle will behave as if it is both F1 and F2.

Which, along with some other experiments, adds up to the idea that a particle's value for F is determined at the time of measurement, which means measuring particle A's F property "causes" particle B to take on a value as well.

There are a few explanations for this behavior, but they aren't really verifiable.

• I stopped reading after the 3rd paragraph as this was mind boggling. Are you sure about the 3rd paragraph. That would imply the particle "knows" if a human looked at the measurement show it to anyone. I think your words might be a bit off ...? If not can you provide a reference. Commented Nov 22, 2017 at 19:16
• The language is imprecise, but yes, that is how things appear to work. en.m.wikipedia.org/wiki/Elitzur–Vaidman_bomb_tester is the most dramatic demonstration of this behavior I am aware of, although I don't think it necessarily involves entanglement (although the specific experiments may). Commented Nov 22, 2017 at 19:27
• So are you implying or saying that the particles are aware of the human mind? Commented Nov 22, 2017 at 20:33
• There are a number of interpretations. The short version is "probably not", but the specifics get no less weird. It is hard to talk definitively past this point, as the interpretations are opinion-based rather than scientific. Commented Nov 23, 2017 at 1:13