
Barium-144 Nucleus Is Surprisingly Pear Shaped - rwmj
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.116.112503
======
mrfusion
Anyone know why people are saying this makes time travel impossible?

[http://www.sciencealert.com/physicists-just-discovered-a-
new...](http://www.sciencealert.com/physicists-just-discovered-a-new-nucleus-
shape-and-it-could-ruin-our-hopes-of-time-travel)

~~~
milkmiruku
[https://www.reddit.com/r/Physics/comments/4pt3g6/barium144_n...](https://www.reddit.com/r/Physics/comments/4pt3g6/barium144_nucleus_is_pearshaped_octupole/d4nnwtq?context=3)

~~~
andrewflnr
Ok, but how does that affect, say, closed timelike curves? No need to run
physics backwards for those, which it seems is really what's affected here.

~~~
mirimir
Right. It starts with:

> True time-reversal symmetry would prevent certain static multipole moments
> from existing in nuclei.

Not "Time travel ..."

~~~
imglorp
Why doesn't the entropy portion of thermodynamics have anything to say about
time reversal symmetry? Or does it say that but we're not smart enough to see
it yet?

------
rwmj
Can someone explain how a nucleus can be anything other than a sphere? How do
the protons and neutrons at one end of the nucleus "know" to be pointed, while
the same collection of particles at the other end "know" to be rounded?

~~~
ars
Barium-144 has an excess of Neutrons.

The Protons and Neurons that are properly paired up make a "sphere" that is
nicely distributed, and the leftover neutrons are pushed to one side and make
the tip of the pear.

Now you might think that mixing the extra neutrons evenly would makes things
even more nicely distributed (which in an atom means: lower energy), but
consider the Helium nucleus.

The nucleon binding energy of helium is very different from its neighbors:
[https://en.wikipedia.org/wiki/File:Binding_energy_curve_-
_co...](https://en.wikipedia.org/wiki/File:Binding_energy_curve_-
_common_isotopes.svg)

That is because pairing up the way Helium does is just so favorable. It's the
same with the Barium-144 - the nucleons that can pair up do so, at very low
energy, and then you have some leftovers.

I suspect that lots and lots of unstable nuclei will be found to be
asymmetrical this way.

By studying exactly how asymmetrical they are we can finally find out exactly
how neucleons pair up, so we can actually model the energy levels.

Once we do that we'll be able to figure where the
[https://en.wikipedia.org/wiki/Island_of_stability](https://en.wikipedia.org/wiki/Island_of_stability)
is. Figuring that out might lead to some amazing new materials.

Even better, we'll actually start to understand neutron stars (understand what
actually happens to those neutrons at those pressures), and maybe calculate
the Quark degeneracy pressure - it could be that pressure is so high that
black holes can not exist.

~~~
kobeya
> and maybe calculate the Quark degeneracy pressure - it could be that
> pressure is so high that black holes can not exist

Black holes would exist, but not as point-like singularities, right? There'd
still be an event horizon.

~~~
ars
No, if they exist (if there is an event horizon) then still a point like
singularity. Very high Quark degeneracy pressure would not change that.

But it's not really known though, what the inside of a black hole looks like.

------
powera
The article seems incredibly over-dramatic of a genuinely interesting study.
Saying that this is evidence of it being "more distorted than theorists
expected" is irresponsible from a scientific point of view.

My less-dramatic summary: Barium-144 is a short-lived isotope that was
predicted to have an unusual "pear" shape. A new study suggests that it does
have the shape that was predicted.

------
Cyph0n
Looks more like an egg to me.

~~~
rocky1138
Same, but it's a poor representation of the shape.

A better example is [http://www.sciencealert.com/physicists-just-discovered-a-
new...](http://www.sciencealert.com/physicists-just-discovered-a-new-nucleus-
shape-and-it-could-ruin-our-hopes-of-time-travel)

~~~
B1FF_PSUVM
Also, saying that "things went pear shaped" has a lot more patina than saying
"things went egg shaped".

(This is the crowd that brought us 'quarks' \- notorious lack of 'gravitas'
there ...)

------
Eduard
"Now, researchers have confirmed that barium-144 ([Math Processing Error]) is
a member of this exclusive club."

... that math processing error was really confusing until I understood its
real meaning.

------
poelzi
surprisingly not

[http://vixra.org/pdf/1107.0031v1.pdf](http://vixra.org/pdf/1107.0031v1.pdf)

But yes I know, a crackpots physical model... how bad it fits so well.

------
imafish
I'm sorry but that is not a football.

