
First real evidence of a strange quantum distortion in empty space - mmastrac
http://www.sciencealert.com/we-just-got-the-first-real-evidence-of-a-strange-quantum-distortion-in-empty-space?
======
joantune
"In the classical physics of Newton and Einstein, the vacuum of space is
entirely empty, but the theory of quantum mechanics assumes something very
different.

According to quantum electrodynamics (QED) - a quantum theory that describes
how light and matter interact - it’s predicted that space is actually full of
'virtual particles' that pop in and out of existence and mess with the
activity of light particles (photons) as they zip around the Universe."

So, does this mean that this explanation for Quantum mechanics
[https://www.youtube.com/watch?v=WIyTZDHuarQ](https://www.youtube.com/watch?v=WIyTZDHuarQ)
has been vindicated?

i.e. the double slit with the fields being the cause of the oddity instead
of... something that is hard to explain.. including the observer effect

~~~
evanb
No. Vacuum birefringence is understandable from a perfectly conventional
understanding of quantum field theory, and does not remotely require anything
about the pilot wave idea to be true. Every quantum field theory, including
QED, has a roiling vacuum of virtual particles, whether you hold an orthodox
view or not.

Source: am physicist ;P

~~~
randomguy1254
Can you give me some hints on what virtual particles actually are if its not
too complicated? I keep reading that they are not actually real particles,
only useful for calculations/as a simple way to understand what is going on.
How does something like Hawking radiation work if they are not real particles?

~~~
Florin_Andrei
The main challenge in understanding QM is the fact that we are all intelligent
animals whose brains developed in what is for all practical purposes a classic
newtonian universe. When you were one year old, crawling on the floor at your
parents' house, your brain was learning to operate within the realm of classic
physics.

In such a universe, things are very clear-cut. An object must be either here,
or there. Something must be either in this state, or the other. Particles
behave like billiard balls, and waves behave like, well, waves. Things either
exist, or they do not. Space and time have perfect accuracy, there's no
"smearing" of coordinates either in space or in time.

The problem is, that is not _at all_ the case at microscopic levels. You've
learned what a marble is as a kid, and you think of electrons as little
marbles racing around the nucleus - but that's utterly wrong. You've watched
water waves on a pond and you think that's how a beam of light behaves, but
that's ridiculously simplistic.

The fundamental reality at the quantum level is the awkwardly named wave
function (awkward because there's no wave proper there). That's what
electrons, and photons, and neutrons, etc, are. It's a function that describes
a probability amplitude as a complex number. That's it. They're not little
marbles - although sometimes they kind of behave like that. They're not little
waves - although they kinda-sorta look like that. They are bundles of
probability amplitudes smeared out over space and time intervals. This is not
a metaphor. This is stark reality.

The familiar classic universe with crawling floors and marbles and water waves
is just an epiphenomenon. It's a collateral that emerges on top of the quantum
world if you zoom out a trillion-fold and ignore all the little details.

The "smearing out" of space, time, momentum and energy parameters at the
quantum level simply means these are not the truly fundamental things you
think they are on that level. Take energy and time; in a quantum system, you
could measure energy with infinite precision, but then you can't say anything
about the time intervals. Or you could measure time very precisely, but then
you don't know anything about energy. That's not a limitation of your
equipment. It simply means neither energy nor time are the precious snowflakes
you thought they are - _but their combination is_.

A particle that does not exist has exactly zero energy and exists for exactly
zero seconds. But wait, this is the quantum world. That means a deviation from
zero energy is permissible, as long as it does not take place longer than a
correspondingly short interval. The higher the energy deviation, the shorter
the duration of the blip. That means, in completely empty space, you will be
able to measure that particles seem to appear out of nowhere, exist a very
short time (the more massive the particle, the shorter the time), then vanish.

But do those particles actually exist? In QM, that's meaningless. Remember,
there's no such thing as a particle? Only bundles of probability density?
Remember that? And those bundles obey the basic relations about energy/time
and momentum/location. As long as you're talking about fluctuations the size
of an electron, then yes, pure vacuum would seem to produce electrons
continuously, but they only blip in and out of measurement for a very short
time.

But are they "real"? If you can measure it, it's real. Full stop. But classic
categories such as "it exists" or "it does not exist" get blurred at the
quantum level. Anything could potentially, and does actually, exist - provided
it does not violate basic QM relations.

\---

So that "quantum fog" exists in a vacuum all the time. Usually it's completely
chaotic. But magnetars have such strong magnetic fields, they impose a
structure over those short-lived virtual particles. And then when light passes
through, it interacts with that structure and gets polarized.

So do those virtual particles exist? Well, they changed the light, didn't
they? But realistically - "exists", "does not exist", that's newtonian
bullshit. At the quantum level, which is the basis of reality as far as we can
tell nowadays, it's all about probability functions.

\---

If you feel compelled to visualize this stuff, think of quantum particles as
little "clouds" of probability. More dense in the middle regions, getting
thinner and thinner towards the periphery - but basically it keeps going on an
on, it's just a stupendously small value far from the thickness. Of course,
this is just a poor visualization, but for some folks it's better than
nothing.

~~~
halpiamaquark
>That's what electrons, and photons, and neutrons, etc, are. [...] They are
bundles of probability amplitudes smeared out over space and time intervals.
This is not a metaphor. This is stark reality.

Aren't you describing a representation of atomic particles, not the particles
themselves?

Edit: I'm not looking to get into a discussion about what constitutes
"existence". I am just wondering if you are conflating a scientific-
mathematical model for a thing with the thing itself.

~~~
Florin_Andrei
> _you are conflating a scientific-mathematical model for a thing with the
> thing itself_

Bohm would say yes. Others would say no.

------
fspeech
I see by "first" they meant the first evidence of vacuum birefringence.
Quantum vacuum fluctuation is by itself well established. E.g., Casimir
effect.

~~~
tfgg
The Casimir effect, contrary to popular understanding, doesn't require
reference to vacuum zero point energy, it's a relativistic quantum effect:
[http://journals.aps.org/prd/abstract/10.1103/PhysRevD.72.021...](http://journals.aps.org/prd/abstract/10.1103/PhysRevD.72.021301)

~~~
fspeech
Thanks for the reference. Just to be clear, his point is made with regard to
the reality of vacuum zero point energy, esp. whether it should affect the
cosmological constant. However quantum vacuum fluctuation (which I read as
meaning the virtual particles) is essential to QED whether zero point energy
is real or not. As far as I can tell, quantum birefringence also does not
refer to the zero point energy.

------
civilian
Another write-up that's maybe more straightforward: [http://www.sci-
news.com/astronomy/vacuum-birefringence-04410...](http://www.sci-
news.com/astronomy/vacuum-birefringence-04410.html)

prepublish link:
[https://arxiv.org/abs/1610.08323](https://arxiv.org/abs/1610.08323) pdf:
[https://arxiv.org/pdf/1610.08323v2.pdf](https://arxiv.org/pdf/1610.08323v2.pdf)

// Edit: And maybe someone can explain this to me, but the "polarization in ->
polarization out" artist's rendering isn't in their paper. Where did it come
from? Is it showing the example of what would be happening if the effect was
happening at 100% ?

[http://cdn.sci-
news.com/images/enlarge3/image_4410_2e-Vacuum...](http://cdn.sci-
news.com/images/enlarge3/image_4410_2e-Vacuum-Birefringence.jpg)

------
jayajay
Misleading article. Einstein is responsible for a lot of quantum statistics
and quantum mechanics.

Also, this isn't really anything new from some new theory.

It's all contained within QFT and the uncertainty principle.

More or less, this happens at the LHC when protons are smashed together,
forcing momentum energy to be converted into rest energy, leading to the
creation of short-lived particles from the vacuum (provided that quantum
numbers, energy, momentum, and angular momentum are conserved).

------
rsp1984
I'm not a physicist but I wonder how is it possible to disambiguate this
effect from classical "Einsteinian" gravitational deflection? Neutron stars
must have strong gravitational effects on light as well.

~~~
sidlls
We can predict the effects of gravitational lensing and note a difference (if
applicable and there are any) which must then be explained by some other
mechanism. That could be anything from a misestimation of the metric in the
region of the body to quantum effects as this observation posits.

