/sci/ - Science & Math

[Anonymous No.3852546]

What does /Sci/ know about Retrocausality?
My Brother in law believes that he can perform an experiment to prove it's theory true.
I myself, am a chemist and have no clue what he's talking about.
Anyone here want to fill me in?

[Anonymous No.3852562]

that nigga high

[Anonymous No.3852603]

What's retrocausality?
Is it some physics shit?

[Anonymous No.3852623]

What would a guy in law know about time travel?
Ask him to record the experiment on video if possible.
Inb4 some "Primer" shit.

[Anonymous No.3852625]

I assume it means something in the present changing something in the past.

[Anonymous No.3852635]

Everything is some physics shit.
Retrocausality is exactly what it sounds like. Cause and effect reversed. Implying the present or future can effect the past. Please ask him to post experiment on youtube and shit. I'm interested as fuck. Even if he is just a lawyer.

[Anonymous No.3852666]

There are interpretations of quantum mechanics that try to address the measurement problem by replacing the series of collapses by one collapse in the far future, and combining forward- and backward- evolving state vectors using e.g. weak values to characterize what happened in between. However, these don't allow you to send messages into the past unless you deviate from quantum mechanics by violating Born's rule.

I personally think "retrocausality" is a bad name; what we're really talking about is the absence of a fundamental principle of causality.

There are some good reasons to think it might be true. Given Bell's theorem, we know that any theory that offers a complete description of reality and agrees with the predictions of quantum mechanics, and in which reasoning about certain what-if questions are valid, must allow causes to have effects outside their future light cone. If special relativity is to be upheld, it's only natural that causes will affect the past, too.

But until we find the limits of applicability of quantum mechanics (probably a long way off, but who knows?), it all remains speculation and metaphysics.

[Anonymous No.3852676]

>>3852546

tell your brother there's no need, it's already been done.
researchers demonstrated that at the quantum mechanical level, a particle's state can effect it's past state

search it

[Anonymous No.3852704]

>>3852676
You're probably thinking of one of those quantum eraser experiments. You'll find that they can be explained equally well by pilot-wave, many-worlds, and objective-collapse models.

[Anonymous No.3852713]

You obviously knew this had something to do with time travel.
And if he's saying he can prove retrocausality to be a real phenomenon, you better post some details.

[Anonymous No.3852724]

>>3852676
Yes but a guy in law probably isn't talking about sub-atomic particles.
You think he has the kind of equipment to even set up an experiment?

[Anonymous No.3852738]

It's very simple to build the machine, but due to its nature, most people, for one unlikely reason or another, never succeed in doing it. Only a few exist worldwide, in the hands of some very self-disciplined people. Their locations are closely guarded secrets. If you never see one, count yourself lucky.

The completed device is a box with a single button. Its operation is simple: Any circumstance which would lead to the button being pressed is made 50% less likely, relative to other outcomes. That is, if outcome i leads to <span class="math">N_i[/spoiler] button presses and would have probability <span class="math">P_i[/spoiler] without the action of the machine, it occurs with probability <span class="math">P_i 2^{-N_i} / \sum_k P_k 2^{-N_k}[/spoiler].

You can use the button as a sort of time machine. To receive a bit, randomly generate a 0 or 1. In the future, compare the received bit to the bit you wanted to send. If they disagree, press the button several times. The more times you press it in case of a discrepancy, the more accurate the message.

More generally, you can press the button whenever you fail at something. This increases your odds of success.

But the machine is dangerous. What users all too often forget is that their repeated success isn't the only outcome without any button presses, nor is it generally the most likely. If you only intend to use the machine once or twice in your whole life, you might be safe. But for a sufficiently greedy person -- and people are more greedy than they imagine themselves to be -- even the most fantastic gruesome accident can be more probable than the fulfillment of their desires.

[Anonymous No.3852760]

Lol, how retarded. What sense does it make to use time reference from the classical world to quantum level? I mean, really it's not like an electron is getting old or changing into something else than it was. It's the same particles in different states. There's no actual "time".