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A few weeks ago, some very excitable science journalists
were plastering the internet with headlines,
like "Fifth Fundamental Force of Nature Discovered."
What was that all about?
Is there really a new force?
Can I finally get my X-wing out of that swamp?
Let me make it sound a little less hyped.
There was something slightly weird about how
a bunch of beryllium atoms were acting,
that told physicists that for a tiny fraction of a second
an unknown particle may have existed.
Hm.
All right.
Let me make it sound a little more hyped, but also
a lot more specific.
Atomic nuclei have energy levels,
just like their electron shells do.
Protons and neutrons can occupy excited states,
contain excess energy.
And when they settle down again, they
give off that energy as photons, but also sometimes
as a particle or a particle-antiparticle pair.
One thing that comes out of a pile of beryllium-8 atoms
is a lot of electron-positron pairs.
They can pop out at a lot of different energies.
Researchers noticed a slight excess in their energies
at 17 megaelectron volts.
It's as though something with a mass energy
equivalence of 17 MEV was decaying into those particles.
Now, this might sound a little bit familiar.
The same sort of excess in the photons emitted after proton
collisions in the Large Hadron Collider
led to the discovery of the Higgs boson.
Just recently a new very slow excess of the LHC
was originally thought to be a new particle.
But It was discovered to have been a statistical fluke.
But this excess in the beryllium-8 decay
is not slight.
It's now a 6.8 sigma excess, which is statisticease
for it being pretty darn certain that something weird is
going on.
But why do they think that the mysterious 17 MEV
particle is a new type of fundamental force?
Well, in short, it's because the anomaly
was observed for a very particular transition
between the beryllium nuclear states.
That transition meant a difference in energy,
but also a difference in some of the quantum stuff,
spin parity and isospin.
And the easiest way to explain this
is if a spin-1 gauge boson was created.
Such a particle would be a mild extension
of the standard model, not too crazy, but certainly brand new
physics.
Yes, a new spin-1 gauge boson.
No, seriously, this is awesome, if it's true.
See, three of the four fundamental forces,
electromagnetism and the strong and weak nuclear forces,
are all communicated by these gauge bosons things.
A new gauge boson means a new fundamental force.
Why are we only spotting this thing now?
Well, the standard wisdom for finding new particles
is to create higher and higher energies;
hence, the Large Hadron Collider.
Any particle capable of existing at lower energies
should have been spotted.
But that's not true if the particle is a ninja.
By that, I mean dark to electromagnetism
and generally interacting with regular matter very little.
If that's the case, it could be produced at much lower energies
than the gigaelectronvolt energies produced in the LHC,
like the megaelectronvolt transitions
of atomic nuclear energy levels.
If the decay product of such a transition
is very weakly interacting, these particles
could be everywhere and we wouldn't know it, like ninjas
and like dark matter.
In fact, this is a tantalizing possibility.
Not that dark matter is ninjas.
Although, as a scientist, I'd need
to test that before I ruled it out.
No.
I mean that this new particle may have something
to do with dark matter.
It's very weakly interacting.
But the researchers suggest it could mediate interactions
between the so-called dark sector
and the visible universe.
OK, on to the solution to the quantum eraser challenge.
To summarize, I asked you to tell me
why it's impossible to send any real data back
in time using the delayed choice quantum eraser experiment,
and so cheat on the lottery?
Remember, the landing location of each individual photon
passing through to the interference
screen of this experiment does seem
to be influenced by a decision that
is made regarding each of those photon's entangled partners
in the future.
That decision was whether we would
know the path of the original photon,
thus eliminating any interference pattern,
or to erase our knowledge of that path, which brings
the interference pattern back.
That decision is made randomly by a beam splitter
in the original experiment.
But it's conceivable that the experiment
could be adjusted so that a person could make the decision.
So why can't I send winning lottery numbers back to myself?
The reason is that there's absolutely
no way to tell if any given photon at the interference
screen has a known path until you compare
the results of the screen with the results at the detector.
In fact, the distribution of photons at the screen
always looks like a single blurred distribution.
There's no visible interference pattern at all.
It's only when you flag which photons
had twins arriving at detectors A, B, C,
or D that you see patterns arise.
In fact, even if you remove all of the A and B photons,
you still don't see an interference pattern
until you distinguish C versus D.
And this is because those photons have interference bands
that are exactly out of phase.
The peaks of C line up with the troughs of D.
And together, they look like the same sort of blur
you get if you combine A and B.
This is pretty insane.
The photon positions are decided and presumably those patterns
are embedded in the distribution.
Those embedded patterns are set by the eventual destination
of the entangled partners of those photons.
But the distribution may be in place
long before those twins finish their journey.
Yet, we can't extract the patterns
of the photons that landed at the screen
until we get the information of which detectors
their entangled twins hit.
That information can't travel backwards in time or faster
than light.
So unfortunately, this means the information about the winning
lottery numbers remain embedded in the pattern
and lost to us until after the numbers are drawn.
If your name appears below, you got this right
and described your reason well.
You guys should email your names,
addresses, US t-shirt sizes, so small, medium, large, etc.,
to pbsspacetime@gmail.com.
Also, let us know which of these t-shirts you want.
We'll send it right out to you.
For the rest of you, you can still
grab a "SpaceTime" t-shirt of your very own via the link
in the description.
OK, that's the answer.
But there's still time for a mini-rant
about the role of consciousness in quantum mechanics.
The delayed choice in this experiment
is whether or not to know the path of the original photon
or whether to erase that knowledge.
But don't take this too literally.
We don't need to invoke conscious knowledge
to explain the results.
If either detectors A or B are triggered,
then there's an asymmetry in the global wave function,
passing through one slit versus the other.
And this can lead to decoherence.
Admittedly, this decoherence appears
to affect the wave function at times before the apparent cause
of the decoherence.
But this doesn't end up violating causality.
And so it's way less out there than photons
somehow knowing that in the future
some conscious mind will know its path.
Frankly, it's all just so weird and amazing, amazing enough
without inventing mystical interpretations that somehow
give us psychic wave function collapsing powers, as much
as we'd all like to believe we have them.
Nonetheless, there is a clue somewhere
in all this weirdness to the fundamental workings
of spacetime.
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