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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

#91

Post by snowwrestler »

richardw wrote: post #20
snowwrestler wrote: post #5

Earlier quoted context omitted.

Ok, but physics has had a long and fruitful history of inventing invisible stuff when theory and results disagree. I mean, have you ever seen an atom? A proton? A neutrino? Scientific theories are generally not just amalgamations of tweaks. General relativity is internally consistent, explains so much , and just got a huge boost last year with the first detection of gravity waves... which BTW are invisible stuff that…

> Ok, but physics has had a long and fruitful history of inventing invisible stuff when theory and results disagree Inventing and then testing , though. As you said, GR got a huge boost last year, still being tested a century after being proposed. That's how science should be! We know the darkX behaviour and we have some ideas as to explanation, but far from being proved in the way GR has been. Dark energy, dark matt…

We have a lot of the same type of evidence for dark matter that we have for black holes: strange movement of distant luminous bodies. We've never directly observed either. (With light, anyway. I suppose the gravity wave observatory could be said to have directly observed black holes.)

And like dark matter, black holes point out shortcomings in our theories--they are ground zero for the incompatibility between general relativity and quantum mechanics.

And yet, even though we don't fully understand them, there is not much public doubt that black holes really exist. To the contrary: they are quite popular!

I'm not arguing that just because we think black holes exist, therefore dark matter must also exist. That's bad logic. I'm just pointing out that a lot of the popular concerns with dark matter are not unique to dark matter.

Re: A Physicist Who Denies That Dark Matter Exists

#92

Post by snowwrestler »

arenaninja wrote: post #12
snowwrestler wrote: post #5

Earlier quoted context omitted.

Ok, but physics has had a long and fruitful history of inventing invisible stuff when theory and results disagree. I mean, have you ever seen an atom? A proton? A neutrino? Scientific theories are generally not just amalgamations of tweaks. General relativity is internally consistent, explains so much , and just got a huge boost last year with the first detection of gravity waves... which BTW are invisible stuff that…

Evidence for atoms and protons was already there before they were "invented". I think neutrinos and the Higgs boson were theorized before their discovery. Physics also has an unfruitful history of invisible stuff: ether, strings (string theory), etc. Personally I'm glad something other than dark matter is being considered. I was only told that the rotational velocities of galaxies did not match the predictions. IME s…

> Evidence for atoms and protons was already there before they were "invented".

Right, and there is also evidence for dark matter.

Re: A Physicist Who Denies That Dark Matter Exists

#93

Post by saboot »

danielweber wrote: post #73
dogma1138 wrote: post #71

Earlier quoted context omitted.

Actually dark matter and dark energy are "fudge factors" that are being inserted in order to explain observations. There are multiple "contenders" for dark matter, none of them actually explain observations and measurements. Dark Energy is also in that same category especially in it's purest form as a "universal constant" that was added then removed then added back again to GR when we were sure if the universe is sta…

Shouldn't there be a big lump of dark matter at the center of every planet, moon, and star? If we were to hollow out an asteroid, would there still be a blob of intangible dark matter inside of it?

In fact, the answer for planets is Yes!

http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20176

Re: A Physicist Who Denies That Dark Matter Exists

#94

Post by TheHegemon »

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.

Like some kind of dark matter?

Re: A Physicist Who Denies That Dark Matter Exists

#95

Post by XorNot »

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.

Because it would collide with itself. Dark matter isn't just "not visible" - it's non-electromagnetic. As observed it didn't aggregate when colliding with itself, so there aren't big dark matter made black holes around, nor gravity anomalies from dark matter nebula or the like.

Two dark matter particles headed directly at each other would pass through each other and be only slightly deflected by their gravitational interaction.

Re: A Physicist Who Denies That Dark Matter Exists

#96

Post by scatters »

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.

Yes, that's what cosmologists mean by "dark": not interacting with light of any observable wavelength, to any detectable degree.

Re: A Physicist Who Denies That Dark Matter Exists

#97

Post by nscalf »

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 (notably from the lesson I'm thinking of, Japan's National Bank) were flooding money into the market, so QE wasn't working properly.

There is a serious problem with economics on the larger scales, and I've yet to hear anyone talk about it.

Re: A Physicist Who Denies That Dark Matter Exists

#98

Post by XorNot »

dogma1138 wrote: post #75
thechao wrote: post #31

Earlier quoted context omitted.

You can observe it via gravitational lensing. For instance: http://scienceblogs.com/startswithabang/2011/04/20/how-gravi... .

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?

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