A Physicist Who Denies Dark Matter • Hacker News Board

Re: A Physicist Who Denies Dark Matter

#11

Post by RockyMcNuts » Sat, May 20, 2017, 2:56 PM UTC

How do you explaining gravitational lensing with no visible mass, without dark matter?

In other words situations where we see twin images of a very distant galaxy because light curves around intervening mass, without sufficient mass observable to explain the deflection?

I was under the impression that we could map dark matter localized to a precision that tended to rule out measurement error or a general divergence from Einstein's laws, unless it had a peculiar non-uniform distribution.

Edit: maybe somebody can explain these maps - http://www.sciencemag.org/news/2017/03/scientists-unveil-mos...

Re: A Physicist Who Denies Dark Matter

#12

Post by wayn3 » Sat, May 20, 2017, 2:58 PM UTC

douche wrote: post #9

Dark matter appears, to a layman with some historical knowledge, as nothing more than modern day epicycles. When we can't explain something with the models we have, and have to invent magic terms to balance the equations, that indicates that we really don't know what the fuck is going on.

And that's exactly what dark matter is.

Journalism misleads people very hard about physics research. Physicists dont run around claiming they've observed dark matter. That's the wrong direction. Physics has a problem with gravity because some things don't behave in such a way that makes theory agree with observation. Since we are talking about gravity here, we call the thing we are observing "matter". Simply because things that interact with gravity have historically been called matter. Because its "dark" in the sense that we can't see (observe) it, its called dark matter. As a placeholder for something that has not yet been explained.

Then journalists come around and spin this tale about how physicists have found this super magical stuff called "dark" "matter" and its so exotic if you dropped it onto des moines it'd turn the place into honolulu.

Dark Matter is just the placeholder name for an observation that disagrees with conventional theory.

Re: A Physicist Who Denies Dark Matter

#13

Post by Koshkin » Sat, May 20, 2017, 3:00 PM UTC

shakna wrote: post #2

The title is irritating. This is an interview with Milgrom, covering the man more than MOND. But, dark matter isn't something to be denied. Because it isn't understood yet, to the point where we can doubt its existence. We don't have all the answers yet, where denial rejects something as patently false. But, "The man who has an alternative to Dark Matter", is a far less attractive title for those clicks.

It appears to be a very common trend. Modern mass culture creates more interest in people's personalities than in anything else. I feel it every day myself, when I can't help noticing how easy it is for any serious discussion to quickly decay into talking about someone's personal traits, habits or preferences.

Re: A Physicist Who Denies Dark Matter

#14

Post by wayn3 » Sat, May 20, 2017, 3:00 PM UTC

matt123 wrote: post #10

solotronics wrote: post #6

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

Clouds of gas and dust don't emit light, yet we know they exist and can estimate their mass. Couldn't we apply the same methods to Dyson spheres if this was the case?

Everything that has temperature emits electromagnetic radiation. Including clouds of dust.

Re: A Physicist Who Denies Dark Matter

#15

Post by hwillis » Sat, May 20, 2017, 3:04 PM UTC

douche wrote: post #9

Dark matter appears, to a layman with some historical knowledge, as nothing more than modern day epicycles. When we can't explain something with the models we have, and have to invent magic terms to balance the equations, that indicates that we really don't know what the fuck is going on.

You have a misunderstanding of the problems and evidence of dark matter: https://www.reddit.com/r/space/comments/6488wb/i_dont_want_t...

Re: A Physicist Who Denies Dark Matter

#16

Post by Maken » Sat, May 20, 2017, 3:04 PM UTC

_0w8t wrote: post #4

What is puzzling about MOND and to lesser extent about Dark Matter is that both uses violation of Newton mechanics to justify themselves when we know that Newtonian mechanics is wrong. The problem is that we cannot yet model behavior of galaxies using just General Relativity. Typically models assumes Newtonian physics with minimal accounting for relativity. However there is no sound proof that it is a valid approxima…

There is something that always puzzles me and I would like if something could illuminate me. How are those kind of massive scale astrophysical calculations made? Do they take into account every visible mass aggregate in the galaxy and simulate them, or just apply cinematic at scale assuming the galaxy centre is a point of certain mass?

I have played a little with N body simulations and I can't but be amazed about how numerically unstable physical simulations are, and how much the result can change depending on trivial simplifications.

Re: A Physicist Who Denies Dark Matter

#17

Post by laretluval » Sat, May 20, 2017, 3:06 PM UTC

douche wrote: post #9

Dark matter appears, to a layman with some historical knowledge, as nothing more than modern day epicycles. When we can't explain something with the models we have, and have to invent magic terms to balance the equations, that indicates that we really don't know what the fuck is going on.

https://xkcd.com/1758/

Re: A Physicist Who Denies Dark Matter

#18

Post by hwillis » Sat, May 20, 2017, 3:06 PM UTC

solotronics wrote: post #6

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

Dark matter isn't just dark, it doesn't interact with normal matter. When galaxies collide when can verify via gravitational lensing that the normal matter smashes together while the dark matter continues unimpeded in straight lines through each other.

Re: A Physicist Who Denies Dark Matter

#19

Post by douche » Sat, May 20, 2017, 3:07 PM UTC

hwillis wrote: post #15

douche wrote: post #9

Dark matter appears, to a layman with some historical knowledge, as nothing more than modern day epicycles. When we can't explain something with the models we have, and have to invent magic terms to balance the equations, that indicates that we really don't know what the fuck is going on.

You have a misunderstanding of the problems and evidence of dark matter: https://www.reddit.com/r/space/comments/6488wb/i_dont_want_t...

I'm not seeing anything there that isn't a handwavey explanation for "reality doesn't match the models, so DARK MATTER!"

Re: A Physicist Who Denies Dark Matter

#20

Post by roywiggins » Sat, May 20, 2017, 3:12 PM UTC

wayn3 wrote: post #12

douche wrote: post #9

Dark matter appears, to a layman with some historical knowledge, as nothing more than modern day epicycles. When we can't explain something with the models we have, and have to invent magic terms to balance the equations, that indicates that we really don't know what the fuck is going on.

And that's exactly what dark matter is. Journalism misleads people very hard about physics research. Physicists dont run around claiming they've observed dark matter. That's the wrong direction. Physics has a problem with gravity because some things don't behave in such a way that makes theory agree with observation. Since we are talking about gravity here, we call the thing we are observing "matter". Simply because…

But dark matter is theorized to he a particle that we haven't observed yet, which sounds like "matter" to me. The specific idea to fix up the discrepancies is, there are huge clouds of invisible particles. There are competing theories on what sort of particle they might be, but dark matter theories predict that these particles are out there.