/posad/ - Paranormal

dark matter is literally everything we cannot measure, it has mass but different from a dark hole.
How do you even deny its existence? What is the reasoning for denying it in the first place?

I have confidence that in several decades we'll be able to look back and laugh at how ridiculous people were to believe in things like "dark matter" and "dark energy".

My understanding is dark matter exists or conservation of momentum is false. And the second can't really happen since all of physics is based on it.

>>115
Basically if you are going to invalidate the physical science equivalent of the Pythagorean theorem you better have a pretty good reason for it, since the aftermath means rediscovering the entire field after removing it's foundation. It's just easier to assume dark matter is really real.

Also looking and not being successful for fifty years isn't that big of a deal, gravitational waves a theoretical insight of Einstein took one hundred years to discover empirically.

>>107
Dark matter is the margin of error of our current scientific ontology (theory of what is).

It may be true, but the argument is, 'there is a universe shaped hole around this sentence.' Therefore I infer the positive existence of a self hating black trans-female Donald Trump who is currently serving his third term as prime minister of the United States of China in the Southern hemisphere of htraE, the fourth planet in the loS system in the north eastern spiral arm of the Bready Stop Galaxy.

The hole is bigger than the consistent portion. Good computational auxiliary for now, likely to be proven bunk as new data comes in. But it has the unnerving fear inducing the 'others' narrative where absence of evidence counts for evidence of absence which is fundamentally fallacious reasoning and reactionary.

>>115
>My understanding is dark matter exists or conservation of momentum is false.
No, just the theory of gravity is at stake.

>>120
> the theory of gravity
You mean Newtonian Mechanics, there's nothing terribly fancy they are applying kepler's laws of motion to the outside matter and realizing an anomaly. kepler's laws of motion are derived from first principles - ie conservation.

It's been several years since I took a GR class but I remember them not using anything advanced like the Riemann tensor to show the anomaly - it was just rotational energy doesn't match with the expected mass of the galaxy - hence the 'fudge' dark matter factor is added to make it work.

Cosmology is ofc known for this, because looking billions of light years out involves quite a lot of approximation.

>>121
>fudge factor
in the 18 century Newtonian physics failed to accurately describe the procession of Mercury. Urbain Leverrier proposed dark matter in form of a small invisible planet Vulcan between Mercury and the Sun to explain the discrepancy, but then in the 1920s Einstein came along with general relativity that more precisely described laws of gravity, and the invisible planet theory was discarded. Nobody thinks that Newtonian physics is wrong because of this, it's just inaccurate, when a lot of mass warps space time.

If Milgrom turns out to be correct, it would just mean that general relativity is inaccurate for large distances on the scale of galaxies what the falloff of gravity is concerned.

>>123
No you fundamentally don't understand why people use GR. GR is used for very strong gravity (like a black hole) or high precision (like the precession of planets over years, or NASA landing a rover within 1 meter of its landing site). Gravity at the ends of a galaxy is abysmally small, since gravitational force drops off as 1/r. This isn't a GR problem and to add GR to it would explain such a small difference that its worthless. This is why except in cases where Kepler can fundamentally not explain a body (like a black hole) physicists start with Newtonian and then 'add' on GR to get a more accurate number - for instance NASA.

Keplerian mechanics are deadly accurate (seriously using only Keplerian mechanics we could land a rover to 40km accuracy ON FUCKING MARS WHICH IS 245 MILLION MILES AWAY), except in the high precision cases like the above. The spirals of a galaxy rotating at such a discrepancy is something fundamental such as rework conservation, or maybe the gravitational constant isn't actually constant (the article was kinda implying this). It's a fool's errand to navelgaze for us, I mean I have a BS in physics and I have no idea who the fuck Milgrom is - literally two dozen people in the planet can be said to be masters of Milgromian Mechanics. The article like all pop science articles are just spinning a narrative that is impossible for plebians like you or I to have any worthwhile thought about without mastering the material (which neither of us will do).

>>124
So actually I just wikipedia'd Milgrom because I was curious and sure enough he is changing Newton's second law to account for this galaxy thing, so it is a fundamental change - one that other physicists are skeptical of. This is why using worthless terms like 'theory of gravity' are misleading because the 'theory of gravity' in this case is Keplerian motion - ie conservation laws.

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

>>125
This blurb gives a nice tl;dr

This observation necessitates at least one of the following:

(1) There exists in galaxies large quantities of unseen matter which boosts the stars' velocities beyond what would be expected on the basis of the visible mass alone, or
(2) Newton's Laws do not apply to galaxies.

Option (1) leads to the dark matter hypothesis; option (2) leads to MOND.

The basic premise of MOND is that while Newton's laws have been extensively tested in high-acceleration environments (in the Solar System and on Earth), they have not been verified for objects with extremely low acceleration, such as stars in the outer parts of galaxies. This led Milgrom to postulate a new effective gravitational force law (sometimes referred to as "Milgrom's law") that relates the true acceleration of an object to the acceleration that would be predicted for it on the basis of Newtonian mechanics.[1] This law, the keystone of MOND, is chosen to reproduce the Newtonian result at high acceleration but leads to different ("deep-MOND") behavior at low acceleration:

>>124
I thought GR is generally the accepted model, but, it's just easier to use Newtonian mechanics when you are using the reference point of an individual on the earth.

>>128
> reference point of an individual on the earth
I think you are getting some terms mixed up, for an understanding of why GR becomes involved when talking about spacetime between different points in the universe this is a good summary.

https://blog.degruyter.com/the-fall-of-the-apple-and-the-general-theory-of-relativity/

Wait, so, if MOND is true how do you explain other predictions by GR like gravitational lensing and time dilation?

all astrophysics is bullshit

go to skyscholar channel on YT

>>124
>No you fundamentally don't understand why people use GR
nobody uses GR or SR in any real place

>>107
Yeah, stuff like this would make me sceptical of whole heartedly embracing natural sciences, much prefer math & engineering if I had to choose.