Quantum entanglement can create causal effects much “faster” than c, but you cannot use such effects to transmit information still.
(Maybe a stupid question, I’ve only a passing interest in this stuff)
For example, if you go on a trip and bring your suitcase with you. You discover on opening it that you packed only one blue sock. You then gain the information that your other blue sock must be at home. You didn't "cause" your sock to appear at home at that moment, you simply gained that information from a correlation that you know must be true. The cause occurred when you were packing. In this case the correlation is entirely local though: you always had that information with you in your suitcase, you just didn't look at it until now.
In quantum entanglement the cause and effect were the entanglement itself. When one of the particles is later observed, you're using correlation to decide what the other end is. The difference is that in quantum theory this correlation can be demonstrated to be non-local -- the information wasn't with you the whole time and was only determined at the moment of observation. But you can't take any action based on it and the other side can't either as you have no way to know who caused the collapse. You can't cause any meaningful effect on the other end with the information you get from your observation or the act of your observation.
If we are using "cause" in the colloquial sense then yes I see what you're saying, it "causes" it. But it's important to be specific with domain terms here because entanglement does not violate causality, which has a specific definition.
Thanks for taking the time to comment. How could I go about learning more about the specific definition of causality you’re referring to here?
As the wikipedia article touches on, there's not an agreed global definition and it can be used differently in multiple contexts (hence why it's important to be specific).
This stack exchange answer gives a good list of terminology: https://physics.stackexchange.com/a/34675
And this article puts a far more technical description on terms: https://www.mprl-series.mpg.de/media/proceedings/3/9/Proc3ch...
Anyway, chrisfosterelli already elaborated on why thinking of the collapse at A "causing" the collapse at B is not a good idea from the perspective of quantum mechanics, either.
There’s no need for FTL if you accept MWI.
And yes, the speed of light is defined by the speed of causality, but c is still, among other things, the speed of light.
The speed of causality varies depending on the speed of the causal particles and waves which propagate from an event. I was just reading an article on surviving nuclear detonations, and from those you have a few causal events propagating at different rates: the radiation, the shockwaves, the fallout.
And if a tree falls in a forest with no one around, it does still make a sound.
I don't think you'll like the reason why. It was Bishop Berkeley[1], who gave his name to Berkeley CA, that originally posited and answered this question, and his answer was that God is always around and, thus, among other things, hears everything, so the falling tree makes a sound.
[1] https://en.wikipedia.org/wiki/George_Berkeley#Contributions_...
The first person to ask a question doesn't have a monopoly on the answer.
For this particular instance, since the event is about 26,000 light years away, we could as easily say that it happened in 50,000 B.C., since that was the time on Earth when our light traveled to meet it.
All but a 3D place so we could avoid time dilation and experience other planets in real-time.
The whole philosophical debate is the most idiotic thing I have ever heard. Of course things happen even if a human doesn’t observe it. Then they have to make up something about a magical religious figure hearing the tree. All I can think of is the Monty Python skit “..pray that there's intelligent life somewhere up in space, 'cause there's bugger all down here on Earth”
Short of a lazier universe than we're willing to accept, it almost certainly did cause an effect, including harmonic vibrations, ones that are replicated around like echos, etc. It's just unclear if it's sound if there's nobody there to interpret it.
Not saying I buy it one way or the other, just that it's the reason I never thought it was as stupid as you do.
Extending this take back to thread root and then the objection, I always understood "speed of sound" to be more or less "speed of causalty filtered through a substrate", i.e. if you bump into this side, how long does it take that side to be affected by it? "Sound" is just one potential type of bump to be traveling, if we subjectively interpret the vibrations that eventually make it through to the other side that way.
It is probably wrong to assume that God interfaces with the physical universe in the same way as us (and other living beings who perceive sound).
They (God) may perceive vibrations of air particles in a way that we wouldn’t call “sound”.
In fact, I’m pretty sure they have to otherwise they would be overwhelmed by all the noise they hear from everywhere all the time.
[1] https://www.merriam-webster.com/dictionary/sound
[2] https://en.m.wikipedia.org/wiki/Sound
[3] https://dictionary.cambridge.org/dictionary/english/sound (note that "can be heard" != "is heard")
But I agree with that those debates are quite uninteresting, so let's not do that.
A 'fact' that is relative to the frame of reference of the observer.
When you say "there’s nothing less interesting and more irritating than", are you speaking universally, or of your own personal experience?
> Nobody cares about some blowhard’s attempt to generate pointless “debate” over hypotheticals and semantics.
How do you people have knowledge of each others thoughts? Serious question.
https://www.lesswrong.com/posts/a7n8GdKiAZRX86T5A/making-bel...
Not sure about calling this "real time". If you actually wanted to do something about it (like saving the poor, mysterious object), then any help you send will face a completely different situation from what we see now.
In the distance, there was another civilization that didn't have the technology to see us, or any other way to communicate with us. We also didn't have lasers or any other tech to send messages to them, other than travelling there (which would take some years), but we could see what was going there in almost real time.
Wouldn't the same still apply, even without the limitations of the speed of light?
And when should the family back home celebrate?
Defining the actual timing of events based on the presently available methods to perceive or communicate them seems odd if not also a bit impractical.
The family back home should celebrate when it's relevant. If there's a wormhole, then the kid can probably make a call through it, so they can call on their (self-perceived) birthday. If the wormhole is a one-way trip, then the people back home should wait an additional 4.3 years to celebrate, because they won't have any idea until then.
If your friend tells you today about how they did X yesterday, would you also argue X happened today from your frame of reference?
They're both valid interpretations.
If that friend was 671 million miles away, I was say it happened yesterday. If it was a much smaller distance, I can intervene in the event because the relative effects do not prevent me from interacting.
> They're both valid interpretations.
That's true if you want to accept interpretation without restraint. I prefer consistent interpretations that are compatible with known physics. YMMV
The photon you're seeing that came from 671 million miles travelled to your eye instantly, from its "perspective."
Of course there are. You're confusing the "relativity" part in "General Relativity" with "anything goes" or "anyone can interpret things however they want, without any rules". I have elaborated on this in my other comment to you[0]:
> GR is concerned with objective, well-defined statements. Sometimes a statement might depend on the observer (this is relativity after all) but other observers will still be able to predict what that observer will say because there are clear rules to translate observer-dependent statements between observers. So subjective observer-dependent statements can still be objectively true in this sense.
And no, you wouldn't deny it happened yesterday. If you were watching a live event in front of you you'd have the ability to interact with it, such as by asking your friend to stop. If you're viewing something that already happened, you don't have that ability to interact.
Quantum theory and relativity aren't tools to decrease our specificity and understanding of the universe so they shouldn't be used to justify "all interpretations are valid" type statements.
I'm not trying to do some new-agey "everything is valid" thing here. If I, like the photons, travelled from the source 671 million miles away to Earth at the speed of light, time would not have advanced for me at all. I would be telling you that what you are seeing is happening right this instant. And I would be right!
And of course time on Earth has advanced considerably while I was traveling, from Earth's perspective. This is also true.
It is a remote viewing device because we're discussing using it to view remote events. And you're trying to say "just the same" despite that there are obviously some differences so it cannot be just the same. Try "somewhat analogously".
> If I, like the photons, travelled from the source 671 million miles away to Earth at the speed of light, time would not have advanced for me at all. I would be telling you that what you are seeing is happening right this instant. And I would be right!
No, because it took you 1 hour to get here, and if you went back you wouldn't be there at the time you left, so in no way are the events simultaneous.
You're only describing subjective experience - and someone who travelled much more slowly in stasis would have the same subjective experience despite their report of objective simultaneity being even more obviously incorrect.
If he is right in front of me, it won't take a day for the light to reach me. So, no, I wouldn't.
> They're both valid interpretations.
I wasn't talking about subjective interpretations. I was saying that General Relativity clearly distinguishes between the event X of something happening and the event Y of information about that event reaching an observer. X and Y will necessarily be at a timelike or lightlike distance. Therefore, unless this distance is zero, time will necessarily pass between those two events from the perspective of the observer and, in fact, from the perspective of any other observer you could possibly ask, where "observer" is more or less defined by a coordinate system (whose time axis will be the observer's worldline).
This is not up for debate.
No, this is where I disagree. From the perspective of the observer, they are seeing what they are seeing exactly when they see it. They don't perceive any time having passed at all, because we can't perceive an event's age.
What's not up for debate is how long it would take to do round-trip communication between the two places.
What's also not up for debate is that is impossible to show that these far away events are not happening at the time we see them.
How you interpret this is absolutely up for debate, because it's not some intrinsic physical fact.
You are twisting my words and once again interpreting the words "observer" and "event" in a way that deviates from their standard definition in General Relativity.
Yes, of course we (as beings with pairs of eyes) will perceive something happening in the sky when we actually see it happening or, more generally, when we first hear about it. This is trivial. That's not a good way to define when something happened, though, because it is highly subjective – depending on whether you received the information through light, gravitational waves, sound, or carrier pigeon, your notion of when something happens will differ greatly. In fact, given that information from the event will typically reach you in multiple ways at the same time (think of lightning & thunder) and sometimes you might focus on one, sometimes on the other, and your brain might process things at different speeds, even if we're just talking about you, this is not a great and consistent definition.
Moreover, other people could not predict what times you would ascribe to certain events.
This is why General Relativity does not define it that way. GR is concerned with objective, well-defined statements. Sometimes a statement might depend on the observer (this is relativity after all) but other observers will still be able to predict what that observer will say because there are clear rules to translate observer-dependent statements between observers. So subjective observer-dependent statements can still be objectively true in this sense.
> What's also not up for debate is that is impossible to show that these far away events are not happening at the time we see them.
This is simply not true. How do you think we know that they are actually not happening at the time we see them? Would you also say that it's impossible to prove that the events which cause thunder don't happen at the time you hear the thunder, but earlier, i.e. shortly before you see the lightning?
> How you interpret this is absolutely up for debate, because it's not some intrinsic physical fact.
You are of course free to interpret all the things you see in the sky or on Earth however you like. The problem is: Given the aforementioned issues with such subjective interpretations, they are essentially useless. We won't be able to agree on anything and won't be able to make reliable predictions.
In any case, I was responding to OP who was saying[0]
> For all intents and purposes this is happening in real time from our local frame of reference.
"Frame of reference" has a precise mathematical meaning: It's a coordinate frame with coordinates that an observer would use to map out their local region of the universe, with some precise rules as to what "mapping out" means. Now this coordinate frame assigns different times to the event X of something happening and the event Y of you receiving light that was emitted at X (again, provided that the distance between the thing that's happening and you is not zero but that's essentially always the case). So from the perspective of our local frame of reference, whatever we see in the sky is not happening in real time.
In hindsight, I should have maybe omitted the second half of my comment
> If your friend tells you today about how they did X yesterday, would you also argue X happened today from your frame of reference?
I was merely trying to hint at the fact that the definition "It happens when I perceive it" is, as discussed above, completely and utterly useless, let alone ill-defined.
> This is simply not true. How do you think we know that they are actually not happening at the time we see them? Would you also say that it's impossible to prove that the events which cause thunder don't happen at the time you hear the thunder, but earlier, i.e. shortly before you see the lightning?
No, and this is exactly where the analogy between the speed of sound and speed of light breaks down, because they are fundamentally different. The speed of sound is not subject to (significant) relativistic effects.
You can easily prove the speed of sound by measuring the time between the lightning flash and when you hear the thunder. There is no analog with the speed of light.
I agree that this is the crux of the argument:
> For all intents and purposes this is happening in real time from our local frame of reference.
But you have not shown this to be false.
> But you have not shown this to be false.
Once again you have ignored how General Relativity defines "local frame of reference" – which I have elaborated on extensively –, replaced it with your very own and, as discussed, inconsistent definition, and assert that I am wrong based on this made up definition of yours.
Take gravitational lensing. Light from one event will reach you in multiple (in fact, an infinite number of) ways, at different times. What now? How do you define the time at which an event occured?
Take the fact light often propagates at speeds v < c, where c is "the" speed of light, an effect that all light rays you see in the sky are subject to to some degree because they are passing through interstellar medium et cetera. (For an extreme example see slow light[0].) How do you reconcile your definition with the fact that the speed of (such) light will no longer be the speed that bounds whether two events are causally connected?
Things happen at the earliest possible moment I could know about them.
I was able to get that information about my friend yesterday, I just didn’t.
I couldn’t have learned about this 26,000 years ago.
> Things happen at the earliest possible moment I could know about them.
You're of course free to define the word "happen" this way but among physicists you'd be the only one in doing so.
The speed of light is not always c. That’s why refraction happens. Because light slows down in certain mediums below c. It’s kid of a coincidence that the speed of light happens to be c in a vacuum (actually I’m not sure about this…maybe there’s an organic reason why electromagnetic waves will be c in a vacuum that is fundamental).
I do think it’s interesting that as humans our primary sense is to light which does happen to travel at c. I wonder how different our species would be if we couldn’t sense waves traveling at c, and for example, were only capable of detecting sound.
Alternatively it may be that a species which could not sense waves traveling at c would not be capable of becoming as sophisticated as humans.
More seriously, I don't think speed-of-light has much biological relevance. It has consequences for microchips, though.
For all intents and purposes this is happening in real time from our local frame of reference.
https://youtu.be/msVuCEs8Ydo