Case Western Reserve University

Stacy McGaugh

I travel to Cambridge, MA tomorrow to participate in the
workshop [Rethinking the Dark Matter
Paradigm](http://projects.iq.harvard.edu/rethinking_the_dark_matter_paradigm){target="_blank"} (I
had nothing to do with the choice of title). I went to college at MIT in
the '80s, so is a bit back to the future for me in space as well as
time. There is a lot to rethink, or nothing at all, depending on who you
ask. I'm curious to see if any of us are willing to think beyond *I was
right all along!*

One of the compelling notions that emerged in the '80s was non-baryonic
dark matter. Baryons are the massive particles (protons & neutrons) of
which normal stuff is made. It was well established by that time that
the light elements were produced in the early universe by [Big Bang
Nucleosynthesis](http://www.astro.ucla.edu/~wright/BBNS.html){target="_blank"} (BBN).
It became clear in the '80s that the mass density of normal stuff
produced by BBN did not add up to the mass we needed to explain a whole
host of astronomical observations, in both cosmology and galaxy
dynamics. In short, Einstein's General Relativity plus the baryons we
could see did not suffice to explain the universe.

There were two obvious paths forward. Modify Einstein's theory, or
invoke unseen non-baryonic matter. The latter course seems by far the
more plausible. No one had a compelling reason to challenge Einstein's
highly successful theory. On the other hand, there were plenty of
reasons in particle physics to imagine new particles outside the
standard model, particularly in the hypothesized supersymmetric sector.

It was quickly realized that large scale structure would only grow if
this new stuff were composed of slow moving, non-relativistic particles
-- a condition summarized as dynamically "cold." Hence Cold Dark Matter
(CDM) was born. Weakly Interacting Massive Particles (WIMPs) from
supersymmetry were a good candidate to be the CDM.

Thus began the marriage of astronomy and particle physics, two fields
divided by a common interest in dark matter and cosmology. The heated
embrace of the honeymoon has long since worn off, to the point that some
of us are ready to rethink the whole paradigm.

This is no small step. Though I've come to doubt the existence of CDM, I
still feel very comfortable with it.  First love, and all. More
importantly, it has been the one essential item in cosmology that has
remained unchanged through the turbulent '90s and on to today. But that
is a longer story that will take many posts to tell.

For now, we'll go see how much rethinking we're willing to do.


I travel to Cambridge, MA tomorrow to participate in the workshop Rethinking the Dark Matter Paradigm (I had nothing to do with the choice of title). I went to college at MIT in the ’80s, so is a bit back to the future for me in space as well as time. There is a lot to rethink, or nothing at all, depending on who you ask.

Rethinking the Dark Matter Paradigm

*A beginning is the time for taking the most delicate care that the
balances are correct. ... take care that you first place him in his
time... And take the most special care that you locate \[him\] in his
place...*

-- Princess Irulan (*Dune*)

A human being is complex beyond the knowledge of any other individual.
Identifying oneself is not a simple matter. Professionally, I am a
scientist. But I am also a father, a husband, a son... a host of
identities that are all valid all the time, but in a given context, some
are more relevant than others.  To be brief, I offer the bio commonly
used when I give public talks:

------------------------------------------------------------------------

Stacy McGaugh is an astrophysicist and cosmologist who studies galaxies,
dark matter, and theories of modified gravity. He is an expert on low
surface brightness galaxies, a class of objects in which the stars are
spread thin compared to bright galaxies like our own Milky Way. He
demonstrated that these dim galaxies appear to be dark matter dominated,
providing unique tests of theories of galaxy formation and modified
gravity.

Professor McGaugh is currently the Chair of the Department of Astronomy
at Case Western Reserve University and Director of the Warner and Swasey
Observatory.  For fourteen years previous to joining the faculty at
Case, he was a member of the faculty at the University of Maryland.
Prior to that, he held postdoctoral research fellowships at Rutgers, the
Department of Terrestrial Magnetism of the Carnegie Institution of
Washington, and the Institute of Astronomy at the University of
Cambridge. McGaugh earned his Ph.D. from the University of Michigan
after studying physics at MIT and Princeton.

------------------------------------------------------------------------

Even identifying myself as a scientist is vague. One may [read my
cv](http://astroweb.case.edu/ssm/cv.html){target="_blank"} or [peruse my
scientific
publications](http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PRE&qform=AST&arxiv_sel=astro-ph&arxiv_sel=gr-qc&sim_query=YES&ned_query=YES&adsobj_query=YES&aut_logic=OR&obj_logic=OR&author=mcgaugh%2Cs.&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=&txt_logic=OR&text=&nr_to_return=200&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1),
but these are specialized and will tell the non-specialist little more
than that I've worked in lots of places and written lots of refereed
publications. Even specialists will see different things, depending on
their own specialty. To astronomers, I am probably best known for my
work on [low surface brightness
galaxies](http://astroweb.case.edu/ssm/research.html){target="_blank"}.
Cosmologists are more likely to have heard of me in the context
of [MOND](http://astroweb.case.edu/ssm/mond/){target="_blank"}. I find
the reactions I get are strongly colored by these associations.

One rule of science, and logical reasoning in general: *ad hominem*
attacks are irrelevant. One must analyze and criticize an idea or
hypothesis on its own merits. Whether the person who advocates that
position is a sinner or a saint is irrelevant to evaluating the idea.

At least, that's the ideal. In practice, scientists are people. They
care about their paradigms. If you point out problems, you must be a bad
person.

I started my career in science in the 1980s as a physics student at MIT.
Many compelling ideas emerged at that time. Grand Unified Theories,
Supersymmetry, string theory, dark matter, Inflation, and even MOND were
hypothesized (or matured) in those days. These ideas are with us still.
Some have overstayed their welcome; others were never welcome. Whether
any prove to be correct remains to be seen.

So, to answer the Princess Irulan, my time is now, but I started in the
80s. One's time inevitably colors one's perspective. I am now old enough
to recognize this in my colleagues, whose horizon of expert knowledge
often seems to correspond to the date of their Ph.D. I try to take a
longer view of scientific history when I am able, but first one should
acknowledge the limitation imposed by not being there in person.

As for place, my wave function is not easy to locate. That was already
a [long
story](http://astroweb.case.edu/ssm/ronin.html){target="_blank"} in the
previous millennium.


A beginning is the time for taking the most delicate care that the balances are correct. … take care that you first place him in his time… And take the most special care that you locate [him] in his place…

– Princess Irulan (

 Dune

) A human being is complex beyond the knowledge of any other individual. Identifying oneself is not a simple matter. Professionally, I am a scientist.

Who am I?

*Tell me, O muse, of that ingenious scientist who travelled far and wide
after he had falsified the famous cosmology of Ptolemy. Many paradigms
did he visit, and many were the theories with whose manners and customs
he was acquainted; moreover he suffered much from the two body problem
while trying to save the soul of science and raise his family safely at
home. Tell me about all these things, O daughter of Jove, from
whatsoever source you may know them.*

Those familiar with the Classics will recognize the above text as a
paraphrase of the opening lines of Homer's Odyssey. It seems a fitting
start to this blog, as my career in science has been a long voyage beset
with many storms, complete with monsters worthy of mythology, both great
and petty. I have, by chance of circumstance as much as choice of will,
led an epic life.

This is a bold claim. Whether it is an accurate depiction of the stories
I have to tell, I leave for others to judge. But I do have stories to
tell. Many stories, such that it is impossible that they should all come
out. Yet they clamor to be heard, and I find myself compelled to begin
to tell them, at long last overcoming my discretion and better wisdom.
Though in truth I have been [at it since
1997](http://astroweb.case.edu/ssm/mond/), just not in blog form.

These words may sound odd as the preamble to a science blog. The
reigning stereotype of a scientist is that of a dry arbiter of facts.
This could not be more opposite the truth. We are passionate about the
science we do. We care about the paradigms we develop, often much too
deeply. We want them to be accurate depictions of the Truth, and all too
often convince ourselves that they are.

This blog will cover many topics in science. Primarily it will focus on
my own subjects of cosmology, astronomy, and astrophysics. These words
mean different things to difference people, so the sociology of science
will also be a frequent topic, as will the philosophy and history of
science.

There is a tendency to oversimplify the history of science in order to
satisfy the human need for a compelling story told in a short time. This
serves an essential function: both our patience and our lifespans are
finite. It is impossible to relate all the lessons of the past in their
full detail. Yet sometimes the oversimplification inverts the truth, and
scientists are as susceptible to this human foible as anyone.

I have no plan for how the stories will progress. They boil up, wanting
to be told. I expect they will tumble out piecemeal, unstuck in time and
devoid of linearity. Sometimes I will discuss current events. Sometimes
I will relate what seem to be ancient anecdotes. In no circumstance will
I dumb it down. Indeed, one thing I expect to do is write brief
summaries of refereed science papers, which even scientists rarely
manage read.

I am a practicing scientist. I am not a science journalist. I will
attempt to be clear, but I am not trying to reach a mass audience nor
explain things to the lowest common denominator. I make this distinction
because I am what historians would call an original source.  I am not a
reporter of science: I do it.


Tell me, O muse, of that ingenious scientist who travelled far and wide after he had falsified the famous cosmology of Ptolemy. Many paradigms did he visit, and many were the theories with whose manners and customs he was acquainted; moreover he suffered much from the two body problem while trying to save the soul of science and raise his family safely at home.

Postagens de Rogue Scholar

Rethinking the Dark Matter Paradigm

Who am I?

Hello, World