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A Physicist Who Denies That Dark Matter Exists

cosmos.nautil.us

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Re: A Physicist Who Denies That Dark Matter Exists

#111

Post by pharrington »

fader wrote: post #106
pharrington wrote: post #87

Earlier quoted context omitted.

This isn't right. Dark matter is a shorthand of saying "our current theory is at least incomplete, there is probably an entirely new class of thing (as in, dark matter is known to be a misnomer), and maybe (with a ridiculously high degree of uncertainty) a separate theory is craftable that precisely explains both what we're currently calling "dark matter" and all other other observed gravitational phenomena. The prob…

The article does mention this: > In 2004, Bekenstein proposed his TeVeS, or Relativistic Gravitational Theory for MOND. Since then, several different relativistic MOND formulations have been put forth, including one by me, called Bimetric MOND, or BIMOND. > So, no, incorporating MOND into Einsteinian physics is no longer a challenge. I hear this statement still made, but only from people who parrot others, who themse…

Just to clarify, that was specifically what that part of my comment was about. The fact that ctrl+f'ing "reference" finds nothing in that article is rather telling.

addendum: If you're going to throw away relativity, step up, stop being a coward: straight up throw away relativity and say Einstein was wrong. Again, you need to come up with some very compelling evidence and a seriously strong theory, but don't weasel around the fact that you're saying that just as Newtonian mechanics accurately models a subset of relativity's domain, relativity accurately models a subset of your theory. Present that new theory or acknowledge you're a mad man that accepts variable physics; don't do neither.

Re: A Physicist Who Denies That Dark Matter Exists

#112

Post by tehwalrus »

benibela wrote: post #99

> 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?

Universal constants changing slowly over the lifetime of the universe is one of the things I remember quite well from undergrad physics. Not as anything that has been proven, but as a meachanism to try and fix some of the astrophysics measurements.

Of course, the radius of the universe has clearly changed with time- this could mean that a0 did or that c did.

Re: A Physicist Who Denies That Dark Matter Exists

#113

Post by pharrington »

XorNot wrote: post #98
dogma1138 wrote: post #75

Earlier quoted context omitted.

We've seen instances already where gravitational lensing was explained through other means (very dim clusters, dust, and even camera issues), we also don't know if the space time on those scales is "smooth", if it isn't then light will not travel in a straight line which would account for the lensing effects. The spacetime curvature, mass/energy, and gravity have quite a few interesting interactions as in gravity as…

Except we have good evidence that the universe is very close to flat, space-time wise. A hypothesis that there's local unexplained curvature...Well that's really what dark matter is all about. What's curving it?

edit: Just ignore my comment, it's wrong.

(for posterity) My understanding is that spacetime being flat is akin to it being the surface of the universe's curves. Explain, expand, or correct me if that's wrong; I'm certainly no physicist.

Re: A Physicist Who Denies That Dark Matter Exists

#114

Post by jack9 »

zeven7 wrote: post #104
roryisok wrote: post #3

> "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 w…

Part of the problem is that fixing Newton is more than just adjusting the equation; it requires making up a whole new constant , which to some is worse than making up a whole new class of matter. Constants don't have explanations; they're just like saying, "I don't know why it works out this way, it just does." It's better to have a reason that explains why something happens than to throw up your hands and say "let's…

A constant is a lot more constrained (existing in a specific context) than a class of matter that can't be observed, which is used as a hand wave to any measurement that is unexpected because not only is it not observed, it's not fully understood/constrained.

Re: A Physicist Who Denies That Dark Matter Exists

#115

Post by xioxox »

Confusion wrote: post #109
jerf wrote: post #13

Earlier quoted context omitted.

One of the mental problems that I think people get in this area is that you can't help but mentally imagine that there's just these few points of data that we need to hit, and so we have a lot of freedom in how to construct formulae that match the observation, so why are scientists being so obstinate about the possibility that MOND may be true? But that's not the case. We have petabytes of data from space (if not mor…

The Bullet Cluster isn’t the incontrovertible evidence for particle dark matter that you have been told it is http://backreaction.blogspot.nl/2017/01/the-bullet-cluster-a...

I wouldn't agree with that post - the probabilities and number of clusters imply we'd expect a bullet cluster. In fact, we observe other similar lower-mass systems.

As an astronomer in the field of clusters, I don't know anyone who takes MOND-like theories seriously. Any non dark matter explanation for the bullet cluster would have to be extremely contrived.

Re: A Physicist Who Denies That Dark Matter Exists

#116

Post by jack9 »

mitchty wrote: post #19
m1el wrote: post #14

Earlier quoted context omitted.

You don't comprehend the magnitude of "just fixing the equations". As other commenters said, physics has a history of "adding unobservable objects", and then finding a way to observe them.

We already observe it via its gravitational effects on galaxies. Additionally, good luck getting "fixed equations" to agree with the reams of data.

Isn't that what MOND is doing, to some degree?

Re: A Physicist Who Denies That Dark Matter Exists

#117

Post by Y_Y »

EGreg wrote: post #88
mikeash wrote: post #28

Earlier quoted context omitted.

It obviously doesn't interact with ordinary matter very much, or else it would have been observed non-gravitationally by now. It could interact a little bit, though. Consider neutrinos: they almost don't interact with ordinary matter at all, but they can be observed with enough patience and care, and they are definitely real. Neutrinos were actually an early candidate for dark matter. The numbers didn't work out, but…

How do we know dark matter isn't just really transparent matter? Like, we can't see it in space but it's there, not reflecting or deflecting enough light for us to detect it.

It could be[0]. It's just not very likely, since you'd have to have very special circumstances, but it's not logically impossible, at least in cosmology.

[0] http://abyss.uoregon.edu/~js/cosmo/lectures/lec17.html

Re: A Physicist Who Denies That Dark Matter Exists

#118

Post by mcguire »

nscalf wrote: post #97
roryisok wrote: post #3

> "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 w…

I'll never forget my banking and financial markets class while getting an economics undergrad degree. The teacher said something close to "I know when you're reading the Wall Street Journal, it seems like just about everything we're teaching now doesn't work, but I promise it's real. The world is just weird right now." This was during the early days of Quantitative Easing, the Federal Reserve and many other nations (…

Debunking Economics by Steve Keen. The book is pretty horrible, but his arguments seem reasonable and interesting.

Re: A Physicist Who Denies That Dark Matter Exists

#119

Post by lngnmn »

MikkoFinell wrote: post #100
lngnmn wrote: post #33

Nothing exist unless experimentally proven and replicated. The way they proved the fact that DNA is the genetic molecule.

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

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.)

Re: A Physicist Who Denies That Dark Matter Exists

#120

Post by dnautics »

zeven7 wrote: post #104
roryisok wrote: post #3

> "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 w…

Part of the problem is that fixing Newton is more than just adjusting the equation; it requires making up a whole new constant , which to some is worse than making up a whole new class of matter. Constants don't have explanations; they're just like saying, "I don't know why it works out this way, it just does." It's better to have a reason that explains why something happens than to throw up your hands and say "let's…

That's not terribly convincing argument. Effectively MOND means adding a single free parameter to the model and dark matter means adding a entire continuous distribution to the model.
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