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A Physicist Who Denies Dark Matter

nautil.us

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Re: A Physicist Who Denies Dark Matter

#131

Post by Eyght »

knodi123 wrote: post #122
amai wrote: post #118

MOND might explain rotation curves of galaxies. But it doesn't explain all the other places in astrophysics, where one needs dark matter. Especially MOND (and any modification to gravity) cannot explain the Bullet Cluster: https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to... The Bullet Cluster is especially significant, because it shows gravitational lensing by dark matter spatially separated from visible…

> Especially MOND (and any modification to gravity) cannot explain the Bullet Cluster The creator of MOND addressed that: http://www.astro.umd.edu/~ssm/mond/moti_bullet.html

Your link made me very grateful for Firefox's Reader View.

Re: A Physicist Who Denies Dark Matter

#132

Post by scythe »

knodi123 wrote: post #122
amai wrote: post #118

MOND might explain rotation curves of galaxies. But it doesn't explain all the other places in astrophysics, where one needs dark matter. Especially MOND (and any modification to gravity) cannot explain the Bullet Cluster: https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to... The Bullet Cluster is especially significant, because it shows gravitational lensing by dark matter spatially separated from visible…

> Especially MOND (and any modification to gravity) cannot explain the Bullet Cluster The creator of MOND addressed that: http://www.astro.umd.edu/~ssm/mond/moti_bullet.html

It seems like the takeaway is not that galactic cluster anomalies support or break MOND, but that MOND is a way to reduce the general astroöbject mass anomaly problem to a modified gravity plus the cluster mass anomaly problem. This makes sense if the cluster anomaly is tractable (?) and there are no other problems created by MOND (the real question IMO).

The problem then is that we want to have enough examples where MOND "works" that we don't think we'll run into another cluster anomaly. However, there aren't too many types of objects in the sky. So we either need very good numerical evidence for MOND in all other systems (unlikely) or a solution to the cluster anomaly which might not be too hard, unless MOND is actually wrong of course, and that's a risk you often face as a scientist.

Re: A Physicist Who Denies Dark Matter

#133

Post by alayne »

gaius wrote: post #66
douche wrote: post #36

Earlier quoted context omitted.

We don't understand how matter acrually works on a large scale. Inventing imaginary terms that we can't observe to satisfy the equations in the models to match the observed reality seems a poor practice.

Right it's like when people say, I don't believe in Creation, that stuff is just nonsense. And you say, so what's your alternative theory then? And they reply, well there was a "big bang" and everything just sort of appeared, for no reason. Really, that's the alternative explanation?

Creationism is nonsense and has no place in a scientific discussion because it's not a falsifiable scientific theory. Thanks for derailing this discussion.

Re: A Physicist Who Denies Dark Matter

#134

Post by krapp »

gaius wrote: post #88
douche wrote: post #74

Earlier quoted context omitted.

When you get down to the bedrock, there's very little difference between theistic and atheistic explanations for creation.

Absolutely. "Big bang" or "let there be light", what's the difference?

>"Big bang" or "let there be light", what's the difference?

There is evidence supporting the existence of the Big Bang. There is no evidence supporting the existence of the Judeo-Christian God.

Re: A Physicist Who Denies Dark Matter

#135

Post by DanBC »

gaius wrote: post #88
douche wrote: post #74

Earlier quoted context omitted.

When you get down to the bedrock, there's very little difference between theistic and atheistic explanations for creation.

Absolutely. "Big bang" or "let there be light", what's the difference?

People are prepared to drop big bang if the evidence changes.

Re: A Physicist Who Denies Dark Matter

#136

Post by scythe »

hwillis wrote: post #99
maratd wrote: post #51

Earlier quoted context omitted.

When we're confronted with something we can't explain using our existing equations and theories, the conclusion is that there must be some mysterious thing there that fixes our current equations and makes them work again? A thing we can't detect or see or have any other evidence of ... other than our equations and theories need that thing there for them to work? > In other words situations where we see twin images of…

Dark matter is predicted at every level of astrophysics. It's not just "hey, galaxies look weird". The amount of visible matter only accounts for 4% of the cosmic microwave background. The CMB is extremely smooth, but visible matter is highly clumped up. This can only be explained by a huge amount of matter that doesn't clump up ie non-baryonic. The ratio of deuterium to hydrogen rises based on the density, since the…

>The CMB is extremely smooth, but visible matter is highly clumped up. This can only be explained by a huge amount of matter that doesn't clump up ie non-baryonic

This is not correct. Datk matter's presence is inferred from the CMB anisotropy not because it doesn't "clump up" but because it does not interact with photons (EM field). Inflation is responsible for excess smoothness. In fact dark matter drives regular matter to "clump". See eg:

https://physics.stackexchange.com/questions/61239/how-the-cm...

>every single one of those discrepancies is solved exactly

This is quite an oversell as far as I know. The margins of error on these calculations are often large.

In particular the version with a slightly modified gravity field and smaller amounts of unobserved regular matter is not too outlandish. What would be needed to exclude this is a proof that the amount of unobserved matter cannot be reduced significantly by modifying G, which has not been written yet.

Re: A Physicist Who Denies Dark Matter

#137

Post by powera »

Between dark matter and the problems with inflation theory (https://www.scientificamerican.com/article/cosmic-inflation-...) I think there's enough evidence to show that the Big Bang model of the universe is flawed.

As soon as somebody invents/discovers a better model, most of current research will prove itself completely useless.

Re: A Physicist Who Denies Dark Matter

#138

Post by boomboomsubban »

kradem wrote: post #115
boomboomsubban wrote: post #112

Earlier quoted context omitted.

No, as the entire concept of "fully understand" is ridiculous. We can't fully understand anything, so if you assume the answer is yes then we could dismiss everything. The actual quote agrees with me here. If we understood it better the best you could do is doubt its existence.

>> could something be dismissed if we don't fully understand it? > No, as the entire concept of "fully understand" is ridiculous. We can't fully understand anything, so if you assume the answer is yes then we could dismiss everything. It's not a concept, it's just my lousy English and awkward abbreviation of "to the point where" with "fully". I'm here just to play a game of logic. Did we dismiss the ether at the poin…

It's not your English, I understand what you are saying, you're game of logic is using an old copy of the rules.

Science doesn't dismiss things. Theories about ether were put aside when we started getting experimental results that it could not support and developed other models that explained it better. The theory still exists, and there is a possibility that someone will use it to better explain things in the future.

Your logic boils down to "if we understand something, it can not be dismissed. If we do not understand something, it can be dismissed..." This doesn't work in science though, the first assumption can not be true, so the second ends up saying you can dismiss everything. Leibniz and other's noticed and addressed this flaw in logic in the 1700's, and expanded logic to deal with it.

I am not great at this logic either, but a laymen's version goes "if `theory` supports experimental evidence better than anything else, you should act as if it were true until a better theory is available."

Re: A Physicist Who Denies Dark Matter

#139

Post by JadeNB »

autokad wrote: post #82
joeberon wrote: post #78

Earlier quoted context omitted.

Yeah there's a huge amount of politics in research IN GENERAL, but not so much in physics. Like there are no big questions covered up because they're inconvenient or anything.

the big bang theory was dismissed for decades. Even Einstein said to someone suggesting it that his physics was "abominable".

> the big bang theory was dismissed for decades.

Dismissing a theory that is (now known to be) right is not necessarily political; it can be just a mistake. There are certainly cliques that are invested in believing the orthodoxy, but there are ways in the hard sciences of absolutely disproving that orthodoxy; and, though they are subject to fierce scrutiny, as they should be, they can be, and have been, accepted after surviving that scrutiny.

Re: A Physicist Who Denies Dark Matter

#140

Post by quickben »

pishpash wrote: post #22
solotronics wrote: post #6

the non light emitting mass could be Dyson spheres of space based computers

I think you got caught up by the misnaming of 'dark matter'. It's better to think of it as 'transparent matter'. It's non-interacting, not like a Dyson sphere which would obviously be interacting e.g. from it blocking what's behind it even if it itself makes no emissions.

So, aether?
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