
The Dark Energy of a Theoretical Physicist - mathgenius
http://www.newyorker.com/culture/persons-of-interest/the-dark-energy-of-a-theoretical-physicist?mbid=social_facebook
======
kitchi
There's a tendency in the popular science world and the physics world to
glorify high energy physics, and string theory and all that goes along with
it.

It's definitely useful - After reading one of those books I was pretty
convinced I wanted to do a PhD in Physics. I'm currently four years into a PhD
in physics, except in something completely removed from what she works on.

There is also a tendency to elevate theorists and denigrate experimentalists.
The experimentalists work is often portrayed as 'dull and technical' and they
only worry about the details, whereas the theorist dreams up these wild
theories in flights of genius. I can't speak for anyone else, but this was
true of school where I was from.

I'm just a little tired of this fairly one dimensional portrayal of physicists
(theoretical or otherwise). There's plenty of interesting stuff out there that
doesn't involve dark matter or strings (or quantum field theory!). Fluid
dynamics is endlessly fascinating to me, or non linear systems ("chaos
theory").

Lisa Randall is a phenomenal physicist and I don't begrudge the author her
admiration - There just need to be more pieces like this about other facets of
the sciences.

~~~
rubidium
"The experimentalists work is often portrayed as 'dull and technical' and they
only worry about the details, whereas the theorist dreams up these wild
theories in flights of genius. I can't speak for anyone else, but this was
true of school where I was from."

Woah woah woah. You trying to start a theory/experiment fight?

I'll just put in my 2 cents. Experiments are where all the cool action is at.

Also, scoreboard:

Nobel prize distribution (as of 2014). Theory: 30.75 prizes (28.7%)
Experiment: 76.25 prizes (71.3%)

~~~
frozenport
There are much fewer theorists compared to experimentalists.

~~~
eanzenberg
That's surprising if true because it doesn't take much resources to become a
theorist vs. an experimentalist. Usually a modern computer will do. An
experimentalist is usually out >$1e6 to setup a novel lab.

~~~
Koshkin
I, too, have a feeling that in the 21st century theoretical physics
(understood as mathematical, or computational, physics) is destined to replace
experimental physics in all areas - except those that do not yet have an
effective mathematical model to work with. (I do not know if String Theory can
qualify as such.)

------
Luc
I don't know. For a writer looking for inspiration for a character, she
doesn't seem to be doing a very good job relating to or understanding Lisa
Randall.

It reminded me a bit of The Big Bang Theory.

------
firethief
> New York _Times_

Is this just a New Yorker-ism? If they're referring to NYT, I've never seen it
formatted that way.

~~~
anatoly
It's a New Yorker-ism, much like "coördinate".

~~~
rudolf0
I've been reading the New Yorker for years (though I feel they've become even
more politically charged than usual within the past year and have since
stopped) and was always irked by those damn diaereses.

It makes "oo" easier to parse as separate syllables, but English has a huge
amount of non-phonetic words. Why does this get an exception?

------
Ygg2
Too bad recent discoveries rule out Dark Energy:
[https://news.ycombinator.com/item?id=12783631](https://news.ycombinator.com/item?id=12783631)

So, this can read - The Phlogiston of a Theoretical Physicist.

~~~
privong
> Too bad recent discoveries rule out Dark Energy:
> [https://news.ycombinator.com/item?id=12783631](https://news.ycombinator.com/item?id=12783631)

The methodology of that paper has been questioned by other researchers in the
field[0]. Among other things, the paper claiming cosmic acceleration was not
significant did not factor in constraints on cosmology from other types of
observations (e.g., cosmic microwave background, baryon acoustic
oscillations).

[0] [https://arxiv.org/abs/1610.08972](https://arxiv.org/abs/1610.08972)

~~~
SomeStupidPoint
That paper's abstract seems to be "We're not systemically wrong so we're not
systemically wrong, ergo, the result shouldn't be interpreted as us being
systemically wrong", without ever actually addressing the possibility that
they're systemically wrong (eg that an unfounded assumption is in all of the
models with the "correct" value), but I feel that the actual thrust is meant
to be something about independent lines of investigation.

Could you elaborate a little more on what they're actually saying, since I
don't seem to understand it?

In particular, where they show that their lines of investigation are actually
decorrelated in terms of assumptions (ie, there can't be a common, systemic
conceptual flaw in all of them), or that those assumptions are all included by
the disagreeing model? Because otherwise, it seems a bald assertion that their
assumptions are correct.

~~~
privong
Regarding being systematically wrong, the rebuttal paper is essentially
arguing that, by ignoring other cosmological measurements, the original study
refuting acceleration is potentially falling prey to systematics. The other
cosmological measurements that are typically used rely on completely different
observing techniques and physical processes.

Baryon acoustic oscillations[0] (BAO) rely on there being a predicted
characteristic length scale based on when the baryons and dark matter de-
couple from each other. By measuring the large-scale distribution of galaxies
you can measure this characteristic length.

The cosmic microwave background[1] (CMB) is looking at the redshifted thermal
emission from the hot plasma which filled the Universe during its youth. The
brightness fluctuations correspond to temperature fluctuations in the early
Universe.

Both the BAO and CMB are sensitive to the energy content of the universe and
the relative balance between baryonic matter, dark matter, and any dark
energy. Examining the BAO signal as a function of time may provide constraints
on the acceleration (if the characteristic length scale grows faster than
expected from a non-accelerating universe, I believe). Additionally, the power
spectrum of the cosmic microwave background is sensitive to the existence of
dark energy[2, e.g., pg 24].

Because these three measurements (BAO, CMB, Type Ia supernovae) are looking at
completely different things (characteristic separation between galaxies,
temperature distribution of hot plasma when the universe was 380,000 years
old, and apparent vs intrinsic brightness for a special class of supernovae)
which can be linked back to cosmological model parameters, it is unlikely that
the systematics of all three would conspire to provide a false signal of dark
energy. So, using all three as simultaneous constraints makes it far less
likely to be mislead by systematics inherent in a single one of those three
datasets.

Another aspect of the rebuttal (which I don't really understand because I
don't work on Type Ia supernovae) is that the N16 authors made an assumption
for the luminosity-corrections of the Type Ia supernovae that could increase
the derived luminosity; this would reduce any signal of acceleration. The
authors of the rebuttal also argue that this is part of what resulted in the
decreased significance found by N16.

So, from my understanding, the rebuttal is essentially arguing that N16
incorrectly computed the dark energy signal by using an incorrect correction
to the Type Ia supernovae and by ignoring additional cosmological datasets.

[0]
[https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations](https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations)

[1]
[https://en.wikipedia.org/wiki/Cosmic_microwave_background](https://en.wikipedia.org/wiki/Cosmic_microwave_background)

[2]
[http://www.quantumfieldtheory.info/cmb.pdf](http://www.quantumfieldtheory.info/cmb.pdf)

