
A Physicist Who Denies That Dark Matter Exists - dnetesn
http://cosmos.nautil.us/short/144/the-physicist-who-denies-that-dark-matter-exists
======
roryisok
> "If Newtonian physics can’t predict the fixed curves, perhaps we should fix
> Newton, instead of making up a whole new class of matter just to fit our
> measurements."

I've always felt this way about dark matter, but as a lay person with no
background in physics, it's an opinion I'm hesitant to express.

if you have a model that predicts something, but the prediction is off by
several orders of magnitude, the model is wrong. no other field would invent
invisible stuff to explain that the model is still right. (well, maybe
finance)

~~~
fuhrysteve
> I've always felt this way about dark matter, but as a lay person with no
> background in physics, it's an opinion I'm hesitant to express.

I have always had the same inclination. It seems like a classic candidate for
using Occam's razor. Would love to hear someone who knows more about physics
weigh in with a more nuanced viewpoint.

~~~
pja
(I have a physics degree, but it’s very rusty at this point)

Particle physics has a _long_ history of noticing gaps in the experimental
data that don’t match up with current theories and positing that maybe a new
particle would solve the problem. This goes right back to things like the
neutrino (which was posited to preserve momentum in certain particle
interactions IIRC) and even the neutron.

Sometimes the suggestion pans out, sometimes it doesn’t. You can see this kind
of thing in action - when there was that anomaly in the CERN data a year or
two ago there were a flurry of papers suggesting possible particles, none of
which panned out because the anomaly turned out to be statistical noise. The
various particulate explanations for the observed discrepancy between the
spiral galaxy rotation curves and the observed distribution of matter are very
similar: Take a gap in the data & speculate about what kind of particle would
fill the hole.

When you combine the fact that, historically, speculating about whether new
particles could explain anomalies in the observed data has been _very_
productive for C20th physics with the reality that physicists are also loath
to toss aside general relativity (which has been spectacularly successful)
just because of one observed anomaly that has yet to be explained, it’s
entirely unsurprising that physicists are keen on new particles as
explanations for the galactic rotation curves.

At the same time, every physicist will happily admit that there’s a great big
hole in the standard model - i.e. that it doesn’t include gravity _at all_ \-
and that any unifying theory might also explain away the galaxy rotation
curves in a way that doesn’t require new particles. Indeed, if a unifying
theory could pull off that trick it would be evidence that the theory has a
good chance of being true. Sadly, to date, no one has managed to come up with
such a unification, and we have no real idea what such a theory would look
like beyond the obvious: that it should explain the observed facts & match QFT
& GR in the regimes where those theories are accurate.

~~~
pka
My impression was that QFT includes gravity and "only" breaks down when things
get extreme, i.e. black holes/big bang/etc.

~~~
pja
No, there is no quantum theory of gravity & QFT doesn’t include gravity at
all. The best you can do is add gravitational effects as an after-thought, but
the things you might analyse with the full QFT are generally far too small &
short lived for gravitational effects to matter anyway.

~~~
raattgift
> No, there is no quantum theory of gravity

Here's a couple of examples of quantum theories of gravity.

[http://www.phys.lsu.edu/faculty/pullin/talks/pire1.pdf](http://www.phys.lsu.edu/faculty/pullin/talks/pire1.pdf)

[http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pd...](http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pdf)

[http://einrichtungen.ph.tum.de/T31/seminars-past/seminar-
tal...](http://einrichtungen.ph.tum.de/T31/seminars-past/seminar-
talks/FrankSaueressig13.pdf)

[http://www.damtp.cam.ac.uk/research/gr/public/qg_ss.html](http://www.damtp.cam.ac.uk/research/gr/public/qg_ss.html)

The extent to which these are complete, consistent, natural (in the fine-
tuning sense), and so forth is debatable but these are certainly existing
examples of quantum theories of gravity, and indeed the first is a perfectly
reasonable Effective Field Theory that people work in regularly.

> QFT doesn’t include gravity at all

I think you mean "The Standard Model of Particle Physics", which is a quantum
field theory (as is e.g. perturbative quantum gravity).

> the things you might analyse with the full QFT

Atoms and molecules have gravitational fields; when you send one through a
double slit, which way does their gravitational field go?

[http://www.nature.com/nnano/journal/v7/n5/abs/nnano.2012.34....](http://www.nature.com/nnano/journal/v7/n5/abs/nnano.2012.34.html)

A quantum theory of gravity is needed to answer that.

Assemble a huge number of particles in superposition with 1/(sqrt 2) (|M @ a>
\+ |M @ b>), with a & b separated. A quantum theory of gravity is needed to
describe the gravitational influence of M on a small test object (General
Relativity's answer is just wrong :( ).

~~~
pja
I’m not sure I believe that a mathematical formalism that is unable to make
useful real world predictions deserves the “theory” moniker. Hence your list
of quantum theories of gravity aren’t.

But perhaps that’s me being picky :)

> I think you mean "The Standard Model of Particle Physics", which is a
> quantum field theory (as is e.g. perturbative quantum gravity).

Sure: I was just quoting the parent comment & using the term informally to
stand in for the mouthful that is TSMoPP.

(I’d love to see an experimental setup that was capable of detecting the
gravitational field of a single molecule: that would be impressive!)

~~~
raattgift
> I’m not sure I believe that a mathematical formalism that is unable to make
> useful real world predictions deserves the “theory” moniker. Hence your list
> of quantum theories of gravity aren’t.

On the contrary, the ones I listed are all _completely_ in accord with General
Relativity up to strong gravity and absent superposed sources, which is found
from studying the renormalization group flow of perturbative quantum gravity
and is four loops of gravitons in a 3+1 dimensional spacetime. Strong gravity
can only be found very close to the singularity of black holes (and well
_inside_ event horizons, except at the final evaporation), or in the very
early universe. So we're good for neutron stars, and have no problems studying
things around the event horizons of astrophysical black holes.

The only new mathematical formalism in perturbative quantum gravity is
renormalization, and that goes back to the 1980s. Perturbative quantum gravity
itself comes from the 1990s.

Sean Carroll has a good explanation of renormalization and effective field
theory here:

[http://www.preposterousuniverse.com/blog/2013/06/20/how-
quan...](http://www.preposterousuniverse.com/blog/2013/06/20/how-quantum-
field-theory-becomes-effective/)

Asymptotically safe gravity posits an ultraviolet fixed point at which one can
take a finite number of measurements, producing a strong gravity completion
that perturbative renormalzation cannot; this is prompted by asymptotic safety
in QCD. Below that limit, ASG completely matches perturbative quantum gravity,
and so in the EFT limit it's the same as General Relativity.

There are five or six of other _viable_ families of quantum theories of
gravity, where viability means they accord exactly with perturbatively
quantized General Relativity in its effective field limit, and thus agree
completely with GR in the classical limit and weak gravity, and additionally
are candidates as fundamental theories because they do not rely on
perturbative renormalization by power counting and thus are expected to be
useful to arbitrarily high energies.

Additionally it is not wildly irresponsible to think that mathematical
research (perhaps not driven by physics!) will produce a tractable
renormalization that does not require nature to select a convenient effect to
suppress the explosion of parameters at high energies.

> I’d love to see an experimental setup that was capable of detecting the
> gravitational field of a single molecule: that would be impressive!

Everyone would. We're down below milligrams and yoctoNewtons:

[https://arxiv.org/abs/1602.07539](https://arxiv.org/abs/1602.07539)

[http://newscenter.lbl.gov/2014/06/26/smallest-force-ever-
mea...](http://newscenter.lbl.gov/2014/06/26/smallest-force-ever-measured/)

I'm not as au fait about how the other side of the tunnel is approaching the
ultimate meeting point, but it's not unreasonable to think of nanogram masses
in superposition. Experiments were only at thousands of atomic mass units a
few years ago, though:
[https://arxiv.org/abs/1310.8343](https://arxiv.org/abs/1310.8343)

Unfortunately General Relativity can only have the whole gravitational
influence of these molecules go through one or the other slits. However all of
the quantum theories in my previous message have the distribution of the
gravitational influence follow distribution of the matter, as one would
expect.

~~~
pja
I _think_ we’re disagreeing over terminology rather than the actual physics?

But I’ll chase up some of the ASG references. Thanks for those.

(yoctoNewtons! We live in amazing times...)

~~~
raattgift
If one can extract practical comparisons between a pair of mathematical
formalisms, and map those to differences in observables, I think that
qualifies both as physical theories. Between ASG and string theory (with some
assumptions about how to get the latter out of the AdS box and ignoring the
landscape problem) there are noteworthy differences that are likely to
manifest in the detailed accounting of accretion disks around astrophysical
black holes. QG phenomenologists (who are sadly rare) are professionally
interested in extracting such comparisons among various theories with a view
to distinguishing them observationally or experimentally.

Annoyingly, experimental evidence can be hard to come by because any viable
mathematical formalism has to reproduce the successes of GR, and it is
shockingly easy to depart from GR in a serious way even in very weak gravity.

ASG's main anti-features are that it's not in itself a fundamental ToE; what
it would accomplish (if it holds up) is getting the gravity part right to
Planck scales and avoiding the incompatibility with QFT. Who knows what
beyond-the-Standard-Model physics outside the gravitational sector will look
like at those scales?

ASG is not alone in this, though.

String theory, on the other hand, would let gravity and matter emerge from
something like a field of strings resembling dark energy, where cooling
increases the apparent volume of the cosmological frame at a given scale
factor. Slow thermalization in turn produces everything else, like dark
matter, baryons, light, and so on.

There are other less popular theories from which matter and spacetime geometry
emerge, too.

And of course it goes the other way around too, where matter theories can
arise from geometry (Cartan torsion is still viable, and Poplawski still tries
to get people to pick up Riemann-Cartan geometry; and quantum geometrodynamics
remains viable too).

> We live in amazing times

The amazing thing is that collaboration, simulation, and publication is
_hugely_ improved upon even a couple of decades ago. If in the early 1900s
people had WWW and message boards, email and message boards, LaTeX, ArXiv, and
so forth, who knows what might have been different given the big brains around
at the time !

In richer countries we have relative peace, antibiotics and sanitation.
Feynman's wife died of TB while he was working on the Manhattan project;
that's the trifecta there, just once removed from a theoretical physicist.
Henry Moseley was shot through the head on the battlefield at Gallipoli. Many
other scientists had their work seriously disrupted during both world wars and
during cold war repressions (Sakharov on the one hand, Condon on the other;
the former got it much worse of course).

~~~
pja
> If one can extract practical comparisons between a pair of mathematical
> formalisms, and map those to differences in observables, I think that
> qualifies both as physical theories.

That’s fair. I wasn’t aware that anyone had managed to make any potentially
observable predictions at this point, so thanks for updating me on that.

(As an observer from the sidelines of physics I’ve always had a fondness for
Loop Quantum Gravity / Spin Foams over String Theory(ies) personally, but not
for any particularly deep reason that I can point to as justification.)

------
cwmma
So this doesn't actually get into the actual big issue with MOND which is that
observational results [1] tend to imply some sort of dark matter so current
MOND theories actually include some dark matter, just less of it.

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

~~~
simonh
> actually include some dark matter

They include some non-luminous matter, but only require 1/5th to 1/10th as
much as would be required by Dark Matter theories. So I think saying they
require 'Dark Matter' is confusing. They don't really require a new class of
matter and could easily be explained by the presence of some amount of non-
luminous baryonic matter in some cases which hardly seems outrageous.

~~~
cwmma
non-luminous baryonic matter has long been a contender for dark matter, I
think the technical term is Massive compact halo object aka MACHO (as opposed
to WIMPS or Weakly interacting massive particles) so saying it still requires
dark matter is accurate we could rewrite it to 'actually include some possibly
non-exotic dark matter'.

Because even though it reduces the amount of dark matter required it still has
missing matter.

------
Mendenhall
Good read about a contrasting scientific view of dark matter.

I also found this quote very relative to this age.

"Why not? What’s the big deal? If something doesn't work, fix it. I wasn't
trying to be bold. I was very naïve at the time. I didn't understand that
scientists are just as swayed as other people by conventions and interests."

------
chopin
Afaik there is strong support for dark matter via gravitational lensing
effects of galaxies. Unfortunately it is not mentioned in the article whether
MOND can cope with these observations. At least I would expect that there
might be some integration of MOND into ART which explains that.

~~~
M_Grey
Increasingly, observations like the ones you mention, along with galaxy
rotation curves and more, have really narrowed down the space that DM can
occupy. MOND in particular has only very narrow ranges with which it can
remain sound, and increasingly it requires modifying the modification to keep
that.

------
benibela
> In fact, MOND’s constant equals the speed of light squared, divided by the
> radius of universe.

That does not sound like a coincidence.

Did the constant change when the universe was smaller? Or does the light speed
depend on the size of the universe?

~~~
_FKS_
There are some theories on variable cosmological constants:
[https://en.wikipedia.org/wiki/Variable_speed_of_light](https://en.wikipedia.org/wiki/Variable_speed_of_light)

------
bartj3
> Perhaps somewhere out there, in one of those galaxies I spent my life
> researching, there already is a known unified theory of physics, with a
> variation of MOND built into it. But then I think: So what? We still had fun
> doing the math.

His life's work: we had fun doing the math :)

~~~
etrevino
While I was getting my PhD(in History), my advisor told me about meeting
Lawrence Stone towards the end of his life (Dr. Stone died in 1999). Lawrence
Stone had spent a great deal of his career investigating early modern and late
medieval marriages. Grossly summed up, he argued that marriages and child
bearing in this era were defined more by convenience than by love and it was
only in the eighteenth century that love became the defining prerequisite for
marriage (I'm being very broad here). My advisor very gently probed Dr. Stone
on how he felt about new research that largely puts the lie to Stone's thesis.
It was a big deal, because Dr. Stone's theories had defined how we think about
marriage and the family for about a generation.

Dr. Stone said that "no quest for the truth is wasted." (that's a quote from
my advisor, not Dr. Stone) And he's right! Even if we've got a far more
nuanced view of marriage and the family now, he turned over new stones and
raised questions that people had to address. His methodology made further
research possible. Even if he was wrong (and he thought that he _had_ gotten
it wrong), he still made it possible for later historians to do great things.

All that's to say: I totally respect the attitude of having fun doing the
math. (as I think parent does as well) This kind of effort is never wasted.

------
benibela
Quantized inertia sounds like a nice theory:
[http://physicsfromtheedge.blogspot.de/2016/09/mihscqi-vs-
new...](http://physicsfromtheedge.blogspot.de/2016/09/mihscqi-vs-new-mcgaugh-
lelli-data.html)

------
misnome
Responding to the title, in case it misleads, such "Denial" isn't rare or
controversial for topics as far into the unknown such as this.

Don't mistake it with scientific topics like e.g. Climate science "Denial".

------
agentgt
The way I see the MOND vs Dark Matter is that there are two philosophies. One
is we need to add something _new_ to explain the behavior and the other is we
need to adjust the existing theories.

This is key because people (IMO particularly engineers like myself) think when
stuff is added it is less likely to be correct which in some cases true but
others not so much.

The thing is MOND actually adds a bunch of stuff and doesn't explain a whole
bunch of other stuff (yet). What sell me on dark matter is the clustering of
galaxies and the universe itself (like how did we get these massive super
black holes in the galaxy with MOND?).

On a rather tangental note... do you remember when maverick scientist were
shunned and if you go back far enough in some cases heretics? Now days it
seems to pay nicely to be contrarian in terms of media coverage (at the cost
of being revolted by your peers. There was a SA article on this a while back
(famous scientist being hated).

------
djkrudy
Can we retag this "Scientist who denies that dark matter exists exists"

~~~
vorg
Story about scientist who denies that dark matter exists exists exists.

------
mirekrusin
Dark matter is probably just practical joke where the rest of civilised
universe is looking at us from behind their see-through shields.

~~~
gadders
I always thought that. I imagine a sci-fi story where someone manages to
finally observe dark matter and when they flip the switch they realise that
the earth is actually on the equivalent of a traffic island.

------
amelius
> when you study textbook material, you’re studying done deals. You still
> don’t see the effort that goes into making breakthrough science, when things
> are unclear and advances are made intuitively and often go wrong. They don’t
> teach you that at school.

Why don't they ever fix that?

~~~
twoodfin
I don't think that's a fair characterization of how the history of science is
taught. There are other examples in these threads, but even in a high school &
EECS-biased undergraduate science education I was exposed to "ether" theories
of light propagation and Lamarckian evolution.

------
andy_ppp
I always wonder if gravity could be a force that runs across infinite quantum
universes, but really, while a fun mental experiment I have no idea how to do
the maths for what that would mean...

------
rurban
Occam's razor surely is with him, and not the Dark Matter/Dark Energy people.

Just would loved more current criticism on his theories.

------
categorygirl
wow what if the electron is like a straw we're looking at through and we're
just rolling around on it instead. ALL OF US...

------
lngnmn
Nothing exist unless experimentally proven and replicated.

The way they proved the fact that DNA is the genetic molecule.

~~~
MikkoFinell
Okay. Your consciousness doesn't exist. Plz go away you scary philosophical
zombie!

~~~
lngnmn
Weak attempt. The mind is what the brain does. The very same way your browser
appears on your screen.

Good philosophers, mostly eastern ones, tried very hard to establish a
distinction between products of imagination and adequate representations of
what is.

The classic example is how the brain conditioned by hundreds of thousands of
years by Mother Nature readily mistakes a rope for a snake. Notice, that there
is nothing arbitrary here - just wrong interpretation of an appearance.

Modern, based on statistics hipster's science could be compared to a bundle of
snakes.)

~~~
MikkoFinell
Don't change the subject. Explain how consciousness arises, and describe an
experiment that replicates it.

~~~
lngnmn
Every single morning one could see how it changes the states. For proper
experimental evidences visit any hospital.

~~~
MikkoFinell
You said

    
    
      Nothing exist unless experimentally proven and replicated.
    

Describe the experiment that proves you are conscious.

~~~
lngnmn
I did.

~~~
MikkoFinell
What you subjectively experience in the morning is not proof of anything.

Since you continue to evade the question, I will only ask once more time:
Describe the experiment that demonstrates the existence of consciousness in a
manner which is "experimentally proven and replicated".

I'm forced to interpret failure to describe the experiment as your admission
that you don't actually require "experimentally proven and replicated" to
believe things, or at least that you cherry pick some propositions to require
that standard.

That's OK too, no one is demanding that you be intellectually honest or self-
consistent. But you should not be surprised if people call you out on it
though.

~~~
lngnmn
Oh, please, cut this cosplay out. In every surgery room of the whole world you
could see how chemical compounds administered to patients would turn them
unconscious and back. This implies that the consciousness is a product of the
brain, not some immaterial substance, divine presence or other kind of
abstract crap. This also implies that it is not mere an abstract idea of so-
called pure reason ("soul", "I" and "god" are such idea, "awareness" isn't),
but a valid linguistic label associated to a real high-level biological
phenomena (a set of coordinated processes).

In every neurology department which deals with brain injures and pathology one
could see the evidences that the states of consciousness and even its pretense
or absence are bound by particular parts of the brain, which, in turn, is an
artifact conditioned by the evolutionary forces and constraints of this
particular universe and its physical laws.

The way medical science went from Phineas Gage to modern maps of the brain
centers, insights into how the vision sub-system works, etc. constitutes the
experimental proofs you are asked for.

The proof could be considered still incomplete (but nevertheless it is valid
because there is not a single contradiction in what is experimentally
confirmed), because there is no way to describe step-by-step the whole
development from a single fertilized egg to you, but there is no doubt that
there is _nothing extra_ to that mere "mechanical" process, and that the mind
is what the brain does and that conscious, which some people would call
primordial awareness, is mere a product of the brain activity, which can be
affected by chemical compounds and even switched on and off, which, BTW,
happens every time you fall asleep (because it is not required) and wake up.

~~~
MikkoFinell
I didn't ask whether consciousness is abstract crap, nor did I ask about
vision subsystems (which aren't even unique to brains), nor did I ask you to
explain the whole process of development from fertilized egg to me. Well,
unless that has something to do with the experiment that would show that
consciousness exists, which it may or may not, at least you drew no apparent
connections in your post.

I asked you to describe the experiment which proves that consciousness exists.

Merely saying that consciousness is a product of the brain is like proving
dark matter by saying it's a product of the universe. I hope you can
understand why that is not a convincing argument.

~~~
lngnmn
> Merely saying that consciousness is a product of the brain is like proving
> dark matter by saying it's a product of the universe.

This statement is nonsense. The presence or absence of consciousness could be
empirically verified and experimentally tested. The presence or absence of
dark matter could not be empirically verified because the concept which is
referenced by this pair of words belongs to the category of abstract ideas.

Notice, that consciousness is not an abstract idea, it belong to the category
of biological processes. You have here a logical error of assuming existence
of an abstract concept, which neither could be empirically verified nor
experimentally tested.

There is a subtle difference between a product of the physical brain and a
product of group-thinking or sectarian beliefs. While the concepts which form
the basis of this or that system of beliefs are certainly exist inside the
consciousness of the individual believers and certainly are presented in their
shared vocabulary, the phenomena which these concepts presumably accurately
and completely capture does not exist anywhere in the universe.

~~~
dragonwriter
> The presence or absence of consciousness could be empirically verified and
> experimentally tested.

No, it can't; there are various behavioral traits that are conjectured to be
indicative of consciousness that can be tested, but consciousness itself can
either be tested nor observed in anyone except the observer.

> Notice, that consciousness is not an abstract idea, it belong to the
> category of biological processes.

No, consciousness is not a biological process, it's a phenomenon which is
assumed to occur as a _product_ of biological processes, though it's often
conjectured that it could also occur as a product of other processes as well.

~~~
lngnmn
Yes, consciousness is a product of various behavioral traits, but its presence
could be empirically tested. There are simple quick medical procedures which
could tell whether a man (or even a dog) is conscious or not, and there is an
ultimate test in a fMRI scanner which could _prove_ that the patient has no
consciousness. Any religious nonsense about validity of the fMRI test is plain
stupidity.

Some limited artificial consciousness is obviously possible, even artificial
self-consciousness, at least in theory. But possibility does not imply
existence.

------
SagelyGuru
There is another possible explanation instead of dark matter and that is
electric charge and currents (plasma flows).

Electric force is many orders of magnitude stronger than gravity. So, if the
objects in the universe are charged, the repelling force between them could
account for the expansion acceleration in a very simple way.

~~~
simonh
Except that electrical/magnetic forces are vastly more powerful than
gravitational forces. Any such force that's noticeable at the cosmic scale
would be powerful enough at the object scale (star, planet, even galaxy) to
tear them apart or cause them to collapse.

Lets suppose the Earth and the Sun were both positively charged sufficiently
that their repulsive force was enough to noticeably affect the orbit of the
Earth. For that to be true, the repulsive forces due to the positive charge on
earth itself would have to be so great that it would blast the planet to
fragments.

~~~
davrosthedalek
I don't think this is true. Let's assume every matter is our solar system is
actually not neutral, but slightly positively charged. For Sun-Earth, let's
say this reduces the effective force by 1%. Since both Coulomb and
gravitational attraction has the same power law, this fixes the change
everywhere, or in other words, you could absorb the change into the
gravitational constant. Same goes for making everything 1% less dense.

~~~
adekok
That's not how physics works.

We've measured the charge of base particles, we know their charge to 8 decimal
places. (e.g. for electrons).

There is simply no way for the force of electromagnetism to be different at
the scale of solar systems.

Even MOND is a _tiny_ modification to Newtons laws, and only a modification in
extreme circumstances.

~~~
davrosthedalek
I think you misunderstood my post. My parent post argued that a mass-
proportional charge imbalance big enough to cause a measurable change in
gravitation would have catastrophic consequences for planets. Indeed, this is
not true, the effects on the planet are of the same scale, i.e. ridiculously
small.

Of course, as I wrote, both laws follow the same power-law, so this can not
solve the dark matter problem. Indeed you can absorb it in the gravitational
constant.

I also did not suggest that electromagnetism should be different at the scale
of solar systems.

A test of the charge equivalence of protons and electrons to 8 digits is by
far not good enough to rule this out. You have to probe the proton charge to
~1E-20 for a 1% change of the gravitational effect. This is beyond the reach
even for atomic level measurements. More interesting are the bounds on charge
conservation.

