/sci/ - Science & Math

>>7431574
That's the observer effect and it's not strictly quantum mechanical.

>>7431580
What other fields of science use it?

It is also true in classical physics

>You have a table.
>You see its length is between 0.8m and 1.4m.
>Now you take a ruler and measure that the length is between 1.19m and 1.21m.
>Just by measuring it your information about the table changed.
>Fucking magic!!!

>>7431584
Okay I kinda get what you are saying but what about the whole idea of entanglement?

>>7431584
This is obviously different.

In QM, states can be in a superposition of eigenstates. When measured, it collapses to a single eigenstate.

If you had an ensemble of tables and measuring them yields exactly 0.8m for 50% and 1.4m for 50% then you would have an analogy.

>>7431582
Literally all of them. Temperature of a gas is just average velocity, when you measure temperature you'll decrease the average velocity (by a tiny amount) thereby changing the temperature.

>>7431593
So we understand the mechanism behind it in most sciences but what about QM?

>>7431596
No.

>>7431606
Any popular ideas other than "Our eyes are made out of the same particles" and metaphysical sounding bullshit like that?

Let's say you have a system with 3 doors and one door has a car behind it while the other doors have goats then your state at first is
<div class="math">\frac{1}{\sqrt{3}} |Car,Goat,Goat \rangle + \frac{1}{\sqrt{3}} |Goat,Car,Goat \rangle + \frac{1}{\sqrt{3}} |Goat,Goat,Car \rangle</div>
Now you pick a door let's say door 1 and the host opens door 2 which he knows has a goat behind it. By observing this phenomenon the state changed to
<div class="math">\frac{1}{\sqrt{3}} |Car,Goat,Goat \rangle + \sqrt{\frac{2}{3}} |Goat,Goat,Car \rangle</div>

>>7431616
But how can two particles be entangled when they aren't even touching? Also, something they emphasise is that the result isn't even determined until you obverse it.

>>7431619
Nothing is really "touching". Besides, all entanglement means is that two particles are created with opposite spin. That is their only property. No matter how far away you move one particle, when you measure that particle's spin you know that the other particle's spin is the opposite. What is so hard to understand about that?

>>7431625
>Nothing is really "touching"
actually, everything is 'touching' i

>>7431625
Oh, so they are created with opposite spins.. So why do people say their spin is in both directions until they are observed? Is it just media hype?

>>7431631
It's true. There are ways to show that a state is in a superposition or not.

When two particles are entangled, you know the result of one by measuring the other. Measuring one spin collapses both. Even nonlocally.

As an aside, you can entangle spin, polarisation, momentum, etc. Also you can have entanglement that is the same (eg both same polarisation) or opposite.

>>7431642
And we don't know how it works? Or is it just too complex to explain to laymen?

>>7431629
depends on your definition of touching.

>>7431642
There is a very accurate description of what can happen. The predicted results match with the experimental values extremely well.

As far as I know, there is no description in the theory for what wavefunction collapse is. It just happens.

Entangled states are well known and studied. The Bell inequality is the essential experiment that demonstrates this phenomenon.

>>7431574
>a jump
I'd say it's more of a quantum leap.

>>7431690
kek
obviously we don't know what we are looking at yet

>>7431574
>I know jackshit about a certain field of science, therefore it must be wrong

>>7431702
No, what I'm saying is "it's just that way because it is" isn't a sufficient answer no matter how knowledgeable you are. Hence >>7431654

I always wondered about one thing. Say you have an entangled pair of electrons and you force one spin to be up with some kind of device. Will the other particle's spin be always down or did you influence the result already by forcing one electron to have an up spin?

>>7431704
Again, you don't know jackshit about quantum mechanics.

>>7431730
I listened to what the experts say and instead of saying they don't know they just act like it is that way just because.

>>7431822
Tell me what you know about quantum mechanics.

>>7431822
I can see how it would seem that way to someone who doesn't know shit about the subject.

>>7431832
>>7431833
https://www.youtube.com/watch?v=IxRfDtaot5U

>>7431718
never mind, after thinking about it for a while, I see that it can't work like this.

>>7431593
This is the best analogy so far, although in QM the particle is in a state of superposition before measurement.
Hate to say it but schrodingers cat.

>>7431718
>>7431855
Quantum entanglement can be thought of as observing the same particle from different locations if that helps your mental image?

>>7431669
i was a naysayer believing some pilot wave bs before i really understood bell inequalities. that tipping point of being convinced is so weird.

>>7431891
no, I didn't take into consideration that if you could "imprint" the spin before looking at the electron you would be able to transfer information faster than c which is impossible.

>>7431574
>It's a jump to believe that observing a phenomenon changes the result.
bait.jpg

why do people fall for these shit bait threads?

Does observation cause the wave function collapse because it has to use light, and photons are 'uncertain' things themselves? Is it even a valid question to wonder if we could measure things without involving light?

>>7431574
>observing a phenomenon changes the result.

Oh god, not this again. Look, quantum mechanics doesn't actually work that way. You just think it does because popsci people love to say that.

There are many completely valid interpretations of quantum mechanics where collapse is either purely illusory or happens completely independent of "observation"

>>7431574
In order to get information out of a system, you have to interact with that system in some way. That interaction can change the system.

>>7431574
>"hydrogen wave function"
>a bunch of gibberish
All that stuff, huh? Has modern physics really descended so far down the mathematical rabbithole that none of the concepts can be explained in plain English anymore.

>>7431588

eigenstates need not be discrete

>>7431585
You have two tables, one of which is in the Andromeda Galaxy, and one of which is right behind you. You know that one of them is short and one of them is long.

You look at the table behind you. It's short. Instantly, you know - despite the fact that this information must instantly reach you from the other table 2.5 million light-years away - that the other table is long.

(Of course, this is slightly wrong, because this is fundamentally describing a "local hidden variables" interpretation of quantum mechanics, and that would fail the experiments done on the Bell Inequality.)

>>7431588
That's what happens when you try to discretely sample an analog phenomena

>>7432819
>none of the concepts can be explained in plain English anymore
>implying it could at any time be explained to a pleb
What do you mean by "anymore", Peasant?

The idea is that identical particles in a state tend to mix with each other, since they're identical and can't be distinguished.

States with such mixing tend to be in linear superposition and this is how measurement causes superposition to collapse.

>>7431619
>result isn't even determined until you obverse it
A statement that isn't completely wrong is that the state doesn't start to behave primarily like one or the other until it interacts with a macroscopic system. That system can be your eye or measuring apparatus or whatever, or it can be a floppy pink dildo. Nature doesn't give a fuck about you as a person.

>>7431664
I believe that this was Bill Clinton's defense.

>>7431664
at all times, the universe is touching deez nutz.

>>7433411
>nature discriminates between macro and micro objects


>>7432643
>There are many completely valid interpretations of quantum mechanics

such as ?

>>7431596
It's called decoherence, this occurs when the system interacts with the environment in a thermodynamically irreversible way. So what happens is we have some quantum system in a superposition of states when something interacts with it we have a loss in coherence between phase angles of the different states, this leads to the system transitioning from a superposition to a mixture of states that corresponds to what we observe.

>>7432885

Where does the wrongness come from? In this analogy, we know that it's a property of pairs of tables that one is short and one is long. It's THAT information (combined with looking at the one table) that allows a deduction about the other. The transmission of information about the distant table is all within your brain.
This is from someone who's previously tried and failed to understand what local hidden variables is about - though there was something about 'speed of deduction', or something similar, in that, too.

What did Jesus say about quantum mechanics?

Oh yeah, nothing, since it's all bullshit.

tldr all these comments.

When a measurement is done, it excites the atom, we use this information from the excited state to infer things about the ground state. This is why we don't know for sure...

>>7431574
Fucking quantum mechanic bullshit. You've honestly got to be retarded to believe the retarded conclusions it comes up with. The science of coming up with the most retarded explanation for everyday phenomena. That is all it is. Ever seen K-PAX? Quantum mechanics is basically when Kevin Spacey "teleported". Also it the word is used in scams nowadays to make something seem like something scientific proven stuff that you're not meant to understand.

I have long been posting on the internet the problems with QM. Now it looks like it is finally becoming mainstream. It won't be long until it is ravamped in the public domain.