
Could dark matter not exist? - strttn
https://medium.com/starts-with-a-bang/ask-ethan-94-could-dark-matter-not-exist-de5cd810e446
======
lordnacho
It reads like a great example of how theory works.

You have some evidence (old planets), and a model that predicts it well
(Newton/Kepler). Then some new evidence comes in (Uranus), and the theory is
almost right, but not quite. So we modify it a little, or we start searching
for an extra mass to explain the error.

Then some more experimental evidence comes in (galactic radial velocity), and
we are thinking about modifying the theory a bit more (MOND). This is good for
the radial velocity explanation, but not certain other things. We suppose
there's some dark matter, and think about the consequences that would have.
Then we see evidence consistent with that.

Of course this is a boiled down version. Real science is rarely so clean.

~~~
zamalek
> Real science is rarely so clean.

I'm no physicist but I've never liked dark matter and dark energy: they smell
suspiciously similar to hacks (the bad kind) if a hack could be defined as
over-fitting a solution to a problem.

It seems as though, recently, science has become rather bad at the words "I
don't know." Things were staying together more than they should so we invented
dark matter in order to explain that. Now, whenever something stays together
more than it should we claim that dark matter has more evidence[1]: no, there
is simply more evidence of the problem that dark matter seeks to solve. How do
we even know it's a single problem (a.k.a. force)? How do we even know that
dark energy is another problem?

It's like me claiming that little monsters called frombles are responsible for
light and every time I see light I claim "see! There's light, so there are
frombles!"

Not that dark matter is a bad solution, I just feel as though there is a
disproportionate amount of people looking into it given that we've never
_actually_ observed a WIMP. Nor do I think that research into dark matter
should cease, it has so far found a really good definition of the problem and,
yes, WIMPs are a good candidate solution.

If we could have a few more people educated in the field start off at "I don't
know," that would be great. You know, the "dirty" kind of science that used to
be done when nobody really knew what was going on at all - that's when we
learned the most: when we didn't have the "safe bet" research topics. When
people came up with stupid ideas and tested those stupid ideas. Stupid ideas
are the best ideas because it at least means that one person is thinking
outside of the box.

[1]: [http://www.iflscience.com/physics/researchers-claim-have-
fou...](http://www.iflscience.com/physics/researchers-claim-have-found-
evidence-hypothetical-dark-matter-milky-way)

~~~
jpallen
Dark matter isn't a solution, it's a quantification of the unknown. It's more
nuanced than just "I don't know", but it's not far from it. I think you're
wrong that science is bad at those words, it's just that's it all plays out a
little more subtly than that. There are lots of things we DO know about this
unknown phenomenon that we've named dark matter, and we have lots of theories,
but everyone will admit it's still a bit of a mystery.

~~~
zamalek
> Dark matter isn't a solution

Very often it's "played" as _the_ final solution, though - if you look at the
tone of the article I linked or even the original post. Those articles are
very consistent with us laymen get, so you can hardly blame me for thinking
that this is the case :).

------
InclinedPlane
Sigh. Sure, it's possible, but very unlikely.

These "MOND" gravity theories purport to explain observations better than the
theory of dark matter, but they don't. They explain some things and leave
gaping holes elsewhere. On the whole they are hugely inferior theories in
terms of matching observational evidence. Their only advantage is that they
lack the existence of massive, weakly interacting particles, which a lot of
people seem to have strong objections to despite the fact that several types
of such particles are already known to exist.

Throughout the entire history of the development of the theory of dark matter
the bias has always been against the idea of true dark matter, unseen
particles that make up most of the mass of the Universe. But at every single
step all of the other possibilities have been eliminated as realistic
explanations of the evidence. The cold WIMP dark matter theory is the only one
that explains the structure of the cosmic microwave background radiation, the
large scale structure of the Universe, and the structure and behavior of
galaxies and galaxy clusters. At this point the theory of dark matter is
remarkably well hemmed in, it would be absolutely shocking to an extreme
degree if it did not truly exist in the form we think it does.

There's additionally a very elegant mechanism behind the formation of dark
matter. It seems most likely to be composed of super-symmetric particles. Such
particles would only be able to form in extreme, high-energy conditions.
Precisely the sort of conditions that existed in the early era of the Universe
immediately after the Big Bang. So the early Universe would have been creating
huge quantities of such particles, which would then not interact much due to
their weak interactivity. It wouldn't be until the Universe had expanded
enough and cooled down enough to halt their production. This would neatly
explain why so much of the mass of the Universe is in the form of dark matter
rather than conventional matter.

~~~
dkbrk
> These "MOND" gravity theories purport to explain observations better than
> the theory of dark matter, but they don't.

MOND consistently fits the rotational velocity profile of galaxies better than
dark matter. This isn't too surprising as MOND originated as an ad-hoc formula
derived from observations of said rotational profiles, however MOND works very
well over a very wide range of galactic profiles. The mass deficit observed in
tidal dwarf galaxies is also quite strong evidence against _just_ dark matter.
I don't think anybody is seriously claiming that MOND is a complete theory,
though of course there have been attempts by theorists at creating complete
models, but they've failed to explain large-scale structural observation and
the cosmic microwave background. This just means these attempts at creating a
complete theory are probably wrong, not that there isn't something funky going
on with galaxies that isn't completely accounted for by dark matter.

> They explain some things and leave gaping holes elsewhere.

This is a false dichotomy. MOND is not incompatible with dark matter. This "us
vs them" mentality is really quite harmful. A combination of MOND and dark
matter matches most observations very well, far better than dark matter in
isolation.

> Their only advantage is that they lack the existence of massive, weakly
> interacting particles, which a lot of people seem to have strong objections
> to despite the fact that several types of such particles are already known
> to exist.

While I'm sure there are quite a few people for whom this is the case, you
shouldn't dismiss the possiblity there are people who take MOND seriously
because it legitimately fits the data better in some circumstances.

~~~
BlackFly
Well, Newtonian physics can be readily derived from General Relativity as a
sensible approximation. General relativity has a sensible backing in
Hamiltonian mechanics.

The relativistic version of MOND, TEVES, is known to be unstable and its
action is a complete mess. Moreover, since the action is attempting to add a
scalar field and a vector field (which in relativistic theory is just a matter
field) it is exactly proposing the existence of an unexplained matter field:
dark matter.

So in the end most people disregard MOND.

------
cristianpascu
I graduated physics, but I'm almost a layman when it comes to general
relativity. Still, I wonder if another possible explanation for stuff that
don't match theory could be the basic assumption about our current cosmology.
That the space is flat where there's no matter. Since there's a relation
between the geometry of the space and the matter within, would it be
unreasonable to believe that space itself could be curved independently of the
matter we can observed? Maybe for other reasons, yet unknown?

------
graycat
Something has orbits around galaxies failing to follow the law of gravity from
ordinary matter. The orbits are as if there there is some more mass with
gravity, mass that doesn't interact with light.

Something is in/near galaxies is bending light as if there were more mass
there than there is from just ordinary matter.

So, for that extra mass, call it _dark matter_.

Seems simple enough.

"Flaw in the theory of gravity?" Maybe, but that seems to be the hard way to
get an answer.

~~~
smil
Exactly. Dark matter and dark energy is just a symptom of the standard model
of physics being incorrect.

>Dark matter neither emits nor absorbs light or any other electromagnetic
radiation at any significant level. According to the Planck mission team, and
based on the standard model of cosmology, the total mass–energy of the known
universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark
energy.[2][3] Thus, dark matter is estimated to constitute 84.5% of the total
matter in the universe, while dark energy plus dark matter constitute 95.1% of
the total mass–energy content of the universe.[4][5][6]

Science is literally religious faith.

~~~
apalmer
Ummm... this is kind of thing is well in line with the history of science.
Clearly dark matter is a fudge factor to make the current model of physics
work. Obviously there is a flaw here somewhere, so there are multiple
competing theories of which dark matter & dark energy are but one for
explaining this. Some theories are more popular than others...

But pretty much within 5 years of a new falsifiable theory that can explain
the situation which can be experimentally proven dark matter will go the way
of the myriad of disproven theories... whereas religious faith would extend
the belief in dark matter out for possibly thousands of years after it is
shown to be experimentally incorrect.

So not 'literally' religious faith at all...

------
raverbashing
There might not be dark matter, but we need a better explanation than MOND

------
restalis
"your theory has _three_ burdens to meet:"

...

"it must make new predictions that can be experimentally or observationally
tested, and confirmed or refuted, that are unique to this new theory"

( _" MOND fails spectacularly, either offering no predictions..."_)

I fail to understand the necessity for _new_ predictions. This simply may or
may not come out of new theories as a paradigm shift consequence and it is
therefore just optional, not a must. In fact, I fail to fully understand even
the first requirement (about reproducing _all the successes_ of previous
leading theory) - the current leading theory's explanation may happen to
explain things _somehow_ , but that may not be necessarily correct. I wouldn't
dismiss a competing theory even with holes in it if there is a slightest
chance that further work on it or on something closely related to it may come
to cover those shortcomings in time.

~~~
drpre
Disclaimer: far from a physicist.

I think the point is that, for a new theory to become more favored than the
current leading theory, the new theory must be consistent with _at least_ as
much scientific evidence as the leading theory. From there, the value of
predictions is that they give a path for strengthening the theory further.

I think you're right in saying that these are not hard-and-fast rules.

------
mixmastamyk
Interesting, I always thought of dark matter as just a lot of extra "dust",
the dust that clumps to make the stars that make up the universe. The asteroid
belt, the extra mass in our kuiper or oort clouds, etc. The dust that blocks
parts of our view of the Milky way.

This article (and others I'm now skimming) point out that dark matter needs
other magical properties however. Why is that the case? Why does simple "dark
dust" not fit?

~~~
BurningFrog
The name isn't great. It sounds like matter that doesn't produce light, when
it's really "matter" that's invisible.

But not matter you can touch. Which makes it not really matter in normal
English. You probably can't see it either.

So "Invisible Untouchable Gravitation Sources" would be a more descriptive
name. I don't think it'll catch on.

~~~
bdamm
Perhaps it could be some form of friction we don't yet understand? I mean a
form of gravitational friction?

The nice part of being an armchair physicist is spouting off nonsense - I
suppose if I really wanted to find out, I could make up a mathematical model
of my theory and then find out if the evidence fits. Sadly, I really have no
idea how to do that!

~~~
themartorana
Ditto. Out of curiosity, is dark matter spread unevenly throughout the
universe, or is it directly inverse to matter?

Like, when we expect dark matter causes an effect, is it because we expect
there to be a massive dark-matter "object" acting upon matter, or can we
attribute it to denser dark matter as space between matter increases?

Edit: would viewing dark matter provide a negative image of the universe?

I'm asking mostly because I'm curious if there is dark matter, "light" matter,
and empty space, or only one or the other? I love imagining this stuff, as if
two different universes in a multiverse - ours and one we can't see - are
acting upon each other and causing what we strive to explain. As if they were
passing through each other.

~~~
smeyer
No, dark matter is definitely not the inverse of regular matter. Dark matter
is spread unevenly through the universe, and it's spread in a pretty similar
(but still notably different) way to the spread of regular matter. For
example, where you have galaxies with lots of regular matter there is also
lots of dark matter, but it has a slightly different distribution. You seem to
be imagining something cool, but not something that bears much resemblance to
our universe.

~~~
socceroos
That's part of the problem with dark matter theory, isn't it? Theory predicts
even and well distributed dark matter anti-particles, yet there isn't in the
observable universe...

~~~
smeyer
I'm not sure what you're referring to. I don't think the theoretical problems
around antimatter are any worse for dark matter than they are for baryonic
matter.

------
madaxe_again
Almost certainly not. Do epicycles exist? No. They were a handy tool/kludge.
Our understanding of space-time is incomplete.

------
0xe2-0x9a-0x9b
You can distribute dark matter in space to shape it in any pattern you like
and give the dark matter any kind of property just to create a mathematical
model that is consistent with observations.

Dark matter is just a theoretical concept - for now or forever.

------
dschiptsov
Most of concepts we are conditioned to take for granted does not exist outside
our head.)

The essence of scientific method is not in piling up concepts or in building
up a support for a fancy theory. On the contrary, it is in exactly opposite -
it is to refute and remove everything "mental" to see what remains, something
which cannot be shaken by mere speculations or dismissed by any experience.
That, perhaps, has something to do with what we call Truth.

According to the ancients, who practiced this method, there is nothing but
different forms of light.

The question "what is between two Photons" makes no sense, because two Photons
have nothing in common exept an imagination of an observer. Tracing them back
"in time" makes no sense either, because time as a category is irrelevant to
the light. It doesn't change.

------
morsch
I found the most interesting part of the article to be this image of a 1919
newspaper illustrating _" Starlight bent by the sun's attraction": The
Einstein theory._

[https://d262ilb51hltx0.cloudfront.net/max/847/1*LV-
wtp9IclSx...](https://d262ilb51hltx0.cloudfront.net/max/847/1*LV-
wtp9IclSx2-SZuP1FsA.jpeg)

As for the rest of the article, well, Betteridge's law holds, though with the
"as best we know"-suffix implicit to science and science journalism.

------
ianamartin
Of course dark matter doesn't exist.

Hello, people. Dark matter is the eflourescent ether theory of the 21st
century.

There are things that we don't know how to explain right now.

We have some ideas about how they can be explained. But they are really really
bad.

We will be laughing at dark matter theory in a few years.

~~~
Sharlin
You might do well to familiarize yourself with the Dunning-Kruger effect.

------
AdieuToLogic
> Could dark matter not exist?

Sure.

~~~
AdieuToLogic
I guess I need to elaborate on this answer.

Perhaps our observations are a result of existing within two gravitational
space-time distortions, one trivial and one not. The trivial one being the Sun
and the non-trivial being the galaxy which we inhabit.

If curvature of space-time theorized by General Relativity is accepted, then
observing non-local energy will be affected by gravity in which the
observation is being undertaken. Accounting for the Sun's influence has
largely (if not completely) been addressed, but there lies a more difficult
"elephant in the room" problem of determining what effect the gravitational
curvature of the Milky Way has on _any_ observations we can make.

According to the University of Oregon[1], the observable mass of the Milky Way
is 200,000,000,000 Solar masses. The same material indicates that visible
stars account for 30% of that. Throw in a bit for singularities and lets call
it "less than 50%" for the sake of discussion. In any event, there exists
enough mass in this galaxy to plausibly state that the space-time we inhabit
is affected. Yet a non-trivial amount considered "unaccounted for."

Using the canonical 3d inverse-cone visualization of matter's effect on space-
time, imagine our solar system exists on some point within the galaxy's
gravitational cone yet not near its center. Making intra-galactic calculations
may be influenced by compressed space-time instead of the presence of dark
matter. And observations regarding other galaxies colliding (as mentioned in
the article) migth be explained by gravitational phase shifting.

Though all of this likely will be rebuked, it is why I originally said "sure."

1 -
[http://hendrix2.uoregon.edu/~imamura/123cs/lecture-2/mass.ht...](http://hendrix2.uoregon.edu/~imamura/123cs/lecture-2/mass.html)

------
HillOBeans
For those who are interested, physicist John Hartnett has developed a model
that does not require dark matter. His work builds on that of Moshe Carmeli,
who published "Cosmological Special Relativity". Hartnett's book is
"Starlight, Time, and the New Physics" ISBN 978-0-949906-68-7. Disclaimer: I
am not a physicist, and the math is way over my head, so I cannot double-check
it. Hartnett has not made much, if any, headway with mainstream scientific
publications, probably because he is a Biblical Creationist.

~~~
gnufied
Just read one of his articles from his Website. He mixes physics and mythology
with impunity. No wonder, his theories are not taken seriously.

~~~
cristianpascu
So, say, if someone comes to you with a clean demonstration of how and why
something is happening in the world, people verify it and it proves correct,
and (s)he says the idea was revealed while smoking pot in a mystical hotel in
north canada, or france for that matter, you'd say no one should take the
theory seriously? Good job!

~~~
dalke
I believe that gnufied is saying that this isn't a clean demonstration. If one
paragraph of explanation is buried in 1,000 pages of dreck, then is the onus
on the reader to find the nugget, or the author to emphasize the important
part?

If you've ever hung around a physics or astrophysics department you'll find
that a lot of people send in explanations of how modern science is wrong. For
example, [http://www.universetoday.com/108044/why-einstein-will-
never-...](http://www.universetoday.com/108044/why-einstein-will-never-be-
wrong/) comments:

> One of the benefits of being an astrophysicist is your weekly email from
> someone who claims to have “proven Einstein wrong”. These either contain no
> mathematical equations and use phrases such as “it is obvious that..”, or
> they are page after page of complex equations with dozens of scientific
> terms used in non-traditional ways. They all get deleted pretty quickly, not
> because astrophysicists are too indoctrinated in established theories, but
> because none of them acknowledge how theories get replaced.

------
cletus
I'm no physicist but I've asked myself this question. It's a bit like string
theory. String theory is a mathematical answer that solves some (all?) of the
inconsistencies between quantum theory and gravity but has some implications
that have no experimental evidence (eg extra dimensions).

Dark matter always struck me as a kludge to explain the universe fit our
model. There are many theories on it but no observed or experimental effects
of dark matter to date.

We say that there are four fundamental forces in the universe: weak nuclear,
strong nuclear, electromagnetism and gravity. The first three are pretty
adequately explained by quantum mechanics (AFAICT). The last of course isn't
but is described pretty darn well by relativity.

Thing is, what's always struck me as odd is the other forces, I believe, can
both attract and repel. There is no observation or experimental evidence of
"antigravity".

It has always made me wonder if we're not making an error by trying to fit
gravity into the Standard Model. Perhaps it's not a force like the others are
and simply the result of the nature of space-time.

Anyway, like I said: complete layman here. What I'm saying might be completely
nonsensical to anyone with half a clue about physics.

I know the LHC has looked and is looking for any evidence at the edges of the
Standard Model of some violation that will hint at something that might
explain all this. I also know minds far brighter than mine have spent a lot of
time thinking about this.

I'm still left wondering if dark matter/energy isn't simply another "string
theory".

~~~
tjradcliffe
Dark matter is no more a kludge than phlogiston, or the lumineferous aether,
or neutrinos. All of them were introduced as novel entities to explain
experimental phenomena. The first two turn out not to exist, the latter does:
[http://www.tjradcliffe.com/?p=1801](http://www.tjradcliffe.com/?p=1801)

Calling them kludges is to mistake the basic process of science for a hack.

There are any number of confirmatory observations that fit the dark matter
model, just as there were any number of confirmatory observations that fit the
neutrio model. It's just that we haven't observed any dark matter particle
interactions directly, just as we hadn't observed any neutrino interactions
directly before Reines' experiment.

It may be that dark matter turns out not to exist, and then we will know it
was wrong. Until then it is perfectly ordinary science working in perfectly
ordinary ways as it has been for over a century.

