Physicists demonstrate how time can seem to run backwards | Hacker News Reader

Physicists demonstrate how time can seem to run backwards

dailymail.co.uk

13 pointsjonbaer11 comments

A) there are much better sources for science news than the daily fail - like the paper - http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys...

B) this isn't necessarily retrocausality. Could equally be evidence in favour of the pilot wave formulation of QM. No spooky time travel, just a standing wave that guides the particles.

Unfortunately, the letter published by Nature is paywalled after the first page. Science Daily has a write-up at [1] which is also probably more accessible to non-specialists.

Agree with you on the daily mail. A really terrible source, and I have it null routed on my machine. Any chance of the mods changing the link and title?

[1] http://www.sciencedaily.com/releases/2015/05/150527103110.ht...

One of the many "benefits" of reading daily mail articles is you can go to the comments section and be utterly confused.

>Time travels like a tube returning inside itself. It can do this as many times as the space between the tube wall allows. Like when you take a rubber glove off.

What?

http://timecube.com/

I know this article is a bad source, but why do scientists and the press continue to use the provocative explanation of QM: "things don't exist unless you look at them at the quantum level."

According to QM, things don't exist until they are measured which is quite different (unless you are tied to an anthropomorphic interpretation of 'observer').

Since there is no formal definition of observer that in any way limits such to humans, an observer/measurer can in essence be any interacting particle in physics-- measurement is an interaction.

This specialist notion is so far removed from the lay-person's interpretation of an anthropomorphic observer creating reality wherever they look as to be nonsense. Especially since the intuition is likely to be applied at the non-quantum scale.

Systems of interacting particles are the norm, not the exception as our careful laboratory experiments are crafted to be.

> things don't exist unless you look at them at the quantum level

But looking IS measuring.

Sure. But either term is usually passive in classical contexts and always destructive in QM contexts. You can't uncollapse a wave function!

Consider a twist on Schrödinger's cat experiment: there are two scientists, A and B. The box can only be opened by one scientist at a time... the other scientist must wait outside the room. Scientist A looks in the box and collapses the wave function and sees that the cat is dead.

What is the probability that scientist B will see a dead cat when she opens the box afterwards? 50%? 100%?

Or, more simply: by the time you've 'looked' and understood what you are looking at, billions of other particles have already interacted with the experiment output, collapsing the wave function... so no, by the time you actually look at anything, it's classical, not QM.

Ah, the Daily Hate, well-respected bastion of the truth...

Thank you for that very helpful comment.

These results only imply time travel if you insist that something must either be a wave or a particle in the first place, and that 'therefore' the particle must be communicating with itself back through time somehow. Funny that a thought experiment originally designed to challenge the notion of wave-particle duality would instead be used to suggest time travel.

(Note that I don't think the researchers are doing this, but the Daily Mail certainly is.)

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