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Comment by cowboysauce | Hacker News Reader

Well, then you encounter problems with things like the triangulum Galaxy. Which has dark matter, but no supermassive black hole.

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According to my [limited] reading of MOND, it revolves around an unknown function μ(x). That means it could be adjusted to account for this. Which is a handwavium thesis, but that's what I like about it: how long have we been doing science for? Are we so arrogant that we can claim to know nearly everything? What if we simply started from the beginning? That is the essence that MOND captures.

The fact that galaxies form and light is being bent is not evidence: it is the problem. We don't actually have any classical scientific evidence of the stuff. Dark matter is handwavium. It may be real, but it not being is just as plausible. When the Earth was flat and the universe revolved around it, we solved problems with our theories by adding escape clauses to them: epicycles. An effect was explained with an effect, and dark matter fits that's profile perfectly.

MOND could be incorrect, but it is valuable as an alternative line of thought. There needs to be more like it. Science needs to get into the routine of failure once again, we are making no progress without it.

Cosmologists would agree with you. They are looking to define the hand waving they have to do in order to explain the universe we can see. Whatever that explanation is, it must be “shaped” like dark matter, though. This is different than epicycles, which were a specific “solution” to the problem of Keplerian motion. Dark matter is not an explanation, it is an observation in search of an explanation.

Here’s a not-so-bold prediction: sometime this century some team will detect something new that explains some but not all of the effects we currently attribute to dark matter. We will call it the explanation to the problem and the remainder will be given a new catchy name and people on the HN of the future will complain that this thing is simple hand waving.

Thoughtful comment, thanks.

> people on the HN of the future will complain that this thing is simple hand waving.

So long as we don't fall into a local minimum in the theory space forever, I'd be happy. Progress is progress, no matter how slow.

Copernicus also used epicycles - since he assumed orbits to be circular instead of elliptical (as Kepler deduced).

Does not appear to have one:

https://en.wikipedia.org/wiki/Triangulum_Galaxy

Nice shot!

In fact that article states that the upper limit for the size of a central black hole in the Triangulum galaxy is estimated at 3000 solar masses, so it simply wouldn't be "supermassive" - but there is not a claim that no black hole exists there.

noetic_techy:

> what if the key to dark matter is some unknown property of the central black hole [...] ?

cowboysauce:

> Well, then you encounter problems with things like the triangulum Galaxy. Which has dark matter, but no supermassive black hole.

The initial comment was about a "central" black hole (which may indeed exist), not a "supermassive" black hole.

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