
One-electron universe - _pius
http://en.wikipedia.org/wiki/One-electron_universe
======
chriswarbo
There's a related idea called the "transactional interpretation" of quantum
mechanics:
[http://en.wikipedia.org/wiki/Transactional_interpretation](http://en.wikipedia.org/wiki/Transactional_interpretation)

The idea is that every event (eg. a particle collision) sends waves forwards
and backwards in time, eg. if * is an event and </> are waves moving
backwards/forwards in time:

    
    
        <- past   future ->
        <<<<<<<<<*>>>>>>>>>
    

The waves from multiple events can overlap and interfere, eg.

    
    
        <<<<<<<<<<<<*>>>>>
        <<<*>>>>>>>>>>>>>>
    

The interference depends on the phase of the waves, but let's simplify and say
that similar arrows are destructive (represented as a space) and opposite
arrows are constructive (represented as a dash). In which case, the
interference pattern of the example above would be:

    
    
           *--------*
    

It _looks like_ there is something which is created at the first event,
travels through time to the second event, and is then destroyed. That "thing"
is what we'd call a particle. This idea is called "transactional" because it
treats the existence of a particle as not just depending on the event which
_creates_ it, but also on the event which eventually _destroys_ it, and the
interference of these "waves through time" is like a 'negotiation' between the
two events.

~~~
drostie
It'd be interesting to know how they deal with the phase requirements--
normally you have boundary conditions which set up these sorts of standing
waves but it sounds like these "events" would not have that and thus would
have to conspire their phases so that you wouldn't get something more like:

    
    
        ---*        *---
    

Probably it's something like, "each event must exist on at least two different
fields; if you look at the other (~) field too then this event looks like

    
    
        ---*~~~~~~~~*---
    

so that, for example, this electron clearly collided with a high-energy photon
to become a muon for a time and then relaxed back to being an electron,
emitting the photon back."

------
tempestn
I'm with Feynman. One electron sounds like nonsense. (Where exactly does the
"looping around" happen, where it changes directions? Outside of time?)
However, the idea of positrons as electrons moving backward in time is cool,
and does seem like a convenient sort of an explanation for their creation and
annihilation.

~~~
one-more-minute
The idea is that any time an electron-positron pair is created or destroyed is
a change in direction.

Say a pair is created in space, they move around for five seconds, and
annihilate each other. You could also explain that as a single electron in a
loop – electron moves forwards in time for five seconds, changes direction
(becomes a positron), moves back in time for five seconds, changes direction,
the cycle repeats.

You can extend that to a set of two of electrons/positron pairs. Assuming each
electron is created and destroyed with different positrons, you can again
explain the system in terms of a single electron that changes direction four
times. Add a few more in and you have a whole universe with one electron.

(That assumption may be a big one, which is where things fall down, but it's
not nonsense. Also, bear in mind that the while idea of "moving" back in time
is a helpful analogy, it's not very precise and shouldn't be taken too
literally)

~~~
tempestn
Of course, yes. Thank you. For some reason my mental picture was limited to
creation and annihilation events being the exception, with most particles
existing 'throughout time', but that's what's nonsense.

In fact, if you consider that a lot of particles would have presumably been
created in the big bang, at which point they would conveniently be in the same
location in our other three dimensions as well, it's certainly conceivable
that you could have a single particle pinballing back and forth as you (and I
guess Wheeler) describe.

Of course, still far from a certainty, but a neat idea.

------
skywhopper
I love the direct quote: "I did not take the idea that all the electrons were
the same one from [Wheeler] as seriously as I took the observation that
positrons could simply be represented as electrons going from the future to
the past in a back section of their world lines. That, I stole!"

I can absolutely hear it in Feynman's rapid, wry, dramatic voice.

~~~
drostie
You can read his whole Nobel speech online and it's well worth a read. My
favorite part is:

"There was a gentleman, newly arrived from Europe (Herbert Jehle) who came and
sat next to me. Europeans are much more serious than we are in America because
they think that a good place to discuss intellectual matters is a beer party.
So, he sat by me and asked, "what are you doing?" and I said, "I'm drinking
beer!" Then I realized that he wanted to know what _work_ I was doing..."

link:
[http://www.nobelprize.org/nobel_prizes/physics/laureates/196...](http://www.nobelprize.org/nobel_prizes/physics/laureates/1965/feynman-
lecture.html)

------
quarterto
One-electron seems very problematic in light of the observed antimatter
asymmetry. Why/how could the electron travel forwards in time more often than
backwards?

~~~
yk
Well, assume that time loops back onto itself. Then the electron goes forward
most of the time and you see multiple copies. ( This is of course ridiculous,
everybody knows that all electrons are just pointers to one _const particle_
structure. )

~~~
V-2
Obtaining multiple electrons by forcing a single one to bounce back and forth
all the way across the time line a zillion times seems like a major design
smell. That would be the worst hack ever, or at least the worst one before
Facebook devs hacked Dalvik just to get their app to run on Android:
[http://jaxenter.com/facebooks-completely-insane-dalvik-
hack-...](http://jaxenter.com/facebooks-completely-insane-dalvik-
hack-105776.html) ;)

Perhaps our universe is one created by a junior, or an intern, and this
"creative" workaround got mocked on TheDailyWTF somewhere.

~~~
jdrols
It's only a "major design smell" to "bounce back and forth" if it's
computationally expensive. This theory makes it sound like electrons aren't
firmly rooted in space and time to begin with.

Maybe it's computationally cheaper to define something as existing in all
places and all times.

~~~
one-more-minute
You can make it cheaper, but you have to accept a certain amount of
uncertainty in your position and momentum data.

~~~
wlesieutre
Don't forget the maximum speed, it'd be tough to simulate a universe where
things could affect arbitrarily distant objects instantly!

[http://www.smbc-comics.com/?id=2535#comic](http://www.smbc-
comics.com/?id=2535#comic)

------
V-2
Let's hope nothing bad happens to that electron, then.

~~~
stesch
Are you blackmailing the universe?

------
nilkn
> Any given moment in time is represented by a slice across spacetime

Is this actually true when we take into account special relativity? I've
always struggled with this.

I was taught that this sort of thing is not nearly so simple. For instance, if
you fix a point in spacetime and have a timelike vector, representing the
motion of an observer, then the set of events which that observer will
perceive as simultaneous to the fixed point all lie in the plane orthogonal to
that timelike vector. Even more bizarrely, because this is a non-Euclidean
notion of orthogonal, this orthogonal complement rotates _towards_ the vector
as it deviates from the centerline of the future line cone at that point.

Given all this, I don't see how one can just say that a slice across spacetime
somehow represents a particular moment in time. I thought the whole point of
relativity is that there are no absolute time slices in spacetime.

~~~
drostie
Yes, it's still true when we take special relativity into account. One good
perspective on special relativity is that it sort of says, "everybody's
right." That is, you abstract _your_ "present" moment to distant positions as
a 3d plane in the 4d space; someone else at the same position with a different
velocity will have _their_ present too, and those will not be 100%
commensurate, but that's OK -- both of you have valid coordinate systems for
any calculations you want to accomplish.

The family of all the "presents" of a point in spacetime is the set of all
points which are spacelike-separated from that point -- i.e. if that point is
at the origin of some coordinate system, the complete "relativistic present"
is all of those points such that

    
    
        c² t² − x² − y² − z² < 0
    

Every observer passing through a point agrees upon these points exactly; the
only difference is that my t=0 will not correspond to t' = 0 under a Lorentz
transform, so that my "simultaneous" at space-separated points is not someone
else's "simultaneous" at those points.

(Light bubble picture: imagine that the light which shines upon an event in
spacetime expands outwards with speed c, forming an expanding bubble of light.
Consider two events. They are both "simultaneous" in the sense that there is
an observer who thinks that they are simultaneous, if their light bubbles
start out topologically disconnected and overlap eventually. They are both
"time-ordered" in the other case, if one bubble is inside the other. If two
things are objectively time-ordered then they are not objectively space-
separated, because the points in the larger bubble correspond to valid
inertial trajectories of a spaceship going less than the speed of light --
there are some spaceships which visited both events inertially. Similarly if
two things are objectively space-separated then they are not objectively time-
ordered; consider someone on the intersection of the two light bubbles seeing
both events happen "right now"; there is always a velocity vector such that
they will trace the distances back to the origins of the events as equal --
and hence that observer thinks that both happened simultaneously at their
different locations.)

~~~
saganus
Wow... that made my mind bend or something. This sounds pretty dense (or maybe
the dense one is me...)

------
krylon
Not being a physicist (not even close), I find it amazing how within just ~100
years, "our" model of the universe has changed so drastically.

I once read that sometime in the late 1800s, people assumed that they had
basically understood how the universe works, and that all that was left was to
fill in some of the blanks.

And now look what an increasingly strange (and wonderful!) place we find
ourselves in.

------
pmontra
I remember I already heard that, but is there a way to proof it? Annihilating
electrons with positions obviously isn't enough.

~~~
foobar2020
Well I suppose there is a way to disprove this: create an electron-positron
pair, then annihilate the pair. This way we would get a closed loop, which
would obviously not be a part of a giant knot spanning through the universe.

~~~
raldi
Measure their mass first, too. If they don't match the mass of the ones that
are part of the knot, then you know you've stumbled onto something _big_.

------
theon144
>"the eventual creation and annihilation of pairs that may occur now and then
is no creation or annihilation, but only a change of direction of moving
particles, from past to future, or from future to past."

Forgive my ignorance, but how does the fact that annihilation "produces"
energy out of the two particles fit into this?

~~~
one-more-minute
Since a photon is its own antiparticle, you might imagine that a photon and an
electron "bounce" off of each other in time, and both reverse their
directions. From our point of view it looks like two photons created and two
electrons annihilated, or vice versa.

Interesting idea at any rate.

~~~
sukilot
One electron and one positron, not two electrons.

------
scotty79
It's really neat that electrons and positrons traveling in time just bounce of
photons, that are timeless (because of the speed they have).

I wonder what cool observation might make by similarly rotating they intuition
90 degrees so that time becomes axis something can move on.

------
fibo
I also arrived at the same conclusion during meditation

~~~
icebraining
groovy, man!

------
gesman
Different sources are saying the same:

[http://www.youaretrulyloved.com/bashar-explains-how-
everythi...](http://www.youaretrulyloved.com/bashar-explains-how-everything-
is-the-one-same-thing/)

------
olla
Every time some limit is reached in a physics equation, dilation, contraction
or even moving in time is taken as a measure to rescue. It all sounds like a
convenient method for explaining something we can not explain. It all comes
from the fact that time is defined through speed and speed depends on space,
thus time cannot describe dimensions not dependant of space.

~~~
one-more-minute
In what sense is time defined by speed? Surely it's the other way around?

Currently the second is defined by a number of oscillations of a known
wavelength of radiation, which explicitly avoids any dependence on space /
measurement of spatial speed.

~~~
olla
Isn't wavelength as such dependant on space? It all seems to come together as
A is defined by B and B is defined by A.

~~~
one-more-minute
Yes, but the standard second doesn't depend on wavelength (maybe I should have
said "known energy"). You take a Caesium-133 atom, look at it's emission
spectrum, isolate the ground state radiation and time a number of
oscillations. Of course, the radiation _has_ a specific wavelength/energy, but
the calculation doesn't depend on it.

Once you know about time, you can start talking about distance – a meter is
defined as the distance light travels in a given time. Given that the meter is
defined this way, defining time in terms of speed would be a bit circular.

~~~
olla
Ok, the time dilation makes actually sense now. So like chemical reactions
depend on temperature and pressure, physical reactions (if they can be called
this way) are dependant on gravity and velocity (dependance on the last I can
not quite get still). By physical reactions I mean the transitions between the
ground states that time is defined by.

~~~
one-more-minute
Sure, local velocity at any rate. If someone goes past you in a rocket, you'll
notice that their Caesium radiation is oscillating slower than yours, so their
second will appear to take longer than yours.

------
resyum
I received a telephone call one day at the graduate college at Princeton from
Professor Wheeler, in which he said, "Feynman, I know why all electrons have
the same charge and the same mass" "Why?" "Because, they are all the same
electron!"

