91–100 of 102 posts
Dark matter is just a theoretical concept - for now or forever.
Interesting, I always thought of dark matter as just a lot of extra "dust", the dust that clumps to make the stars that make up the universe. The asteroid belt, the extra mass in our kuiper or oort clouds, etc. The dust that blocks parts of our view of the Milky way. This article (and others I'm now skimming) point out that dark matter needs other magical properties however. Why is that the case? Why does simple "dar…
The name isn't great. It sounds like matter that doesn't produce light, when it's really "matter" that's invisible. But not matter you can touch. Which makes it not really matter in normal English. You probably can't see it either. So "Invisible Untouchable Gravitation Sources" would be a more descriptive name. I don't think it'll catch on.
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"it must make new predictions that can be experimentally or observationally tested, and confirmed or refuted, that are unique to this new theory"
("MOND fails spectacularly, either offering no predictions...")
I fail to understand the necessity for new predictions. This simply may or may not come out of new theories as a paradigm shift consequence and it is therefore just optional, not a must. In fact, I fail to fully understand even the first requirement (about reproducing all the successes of previous leading theory) - the current leading theory's explanation may happen to explain things somehow, but that may not be necessarily correct. I wouldn't dismiss a competing theory even with holes in it if there is a slightest chance that further work on it or on something closely related to it may come to cover those shortcomings in time.
Earlier quoted context omitted.
Whereas, since you can adjust the hypothetical distribution of dark matter to be whatever you need it to be to fit the data, you cannot falsify dark matter this way, since proving that no possible distribution of dark matter could fit the evidence is pretty much impossible. Still, to me there seems to be some level of equal implausibility in saying "our theory of gravity is wrong" and in saying "our theory of matter…
From my limited understanding, what's interesting about the dark matter approach is that if you pick the distribution of dark matter to fit the rotational velocity profiles of galaxies that also just happens to be the distribution that has a good fit to various other unrelated data sets (cosmic microwave background fluctuations, say). Now maybe there's a deep underlying reason we don't know about that makes those unr…
"your theory has three burdens to meet:" ... "it must make new predictions that can be experimentally or observationally tested, and confirmed or refuted, that are unique to this new theory" ( "MOND fails spectacularly, either offering no predictions..." ) I fail to understand the necessity for new predictions. This simply may or may not come out of new theories as a paradigm shift consequence and it is therefore jus…
I think the point is that, for a new theory to become more favored than the current leading theory, the new theory must be consistent with at least as much scientific evidence as the leading theory. From there, the value of predictions is that they give a path for strengthening the theory further.
I think you're right in saying that these are not hard-and-fast rules.
Earlier quoted context omitted.
Ditto. Out of curiosity, is dark matter spread unevenly throughout the universe, or is it directly inverse to matter? Like, when we expect dark matter causes an effect, is it because we expect there to be a massive dark-matter "object" acting upon matter, or can we attribute it to denser dark matter as space between matter increases? Edit: would viewing dark matter provide a negative image of the universe? I'm asking…
No, dark matter is definitely not the inverse of regular matter. Dark matter is spread unevenly through the universe, and it's spread in a pretty similar (but still notably different) way to the spread of regular matter. For example, where you have galaxies with lots of regular matter there is also lots of dark matter, but it has a slightly different distribution. You seem to be imagining something cool, but not some…
Something has orbits around galaxies failing to follow the law of gravity from ordinary matter. The orbits are as if there there is some more mass with gravity, mass that doesn't interact with light. Something is in/near galaxies is bending light as if there were more mass there than there is from just ordinary matter. So, for that extra mass, call it dark matter . Seems simple enough. "Flaw in the theory of gravity?…
Exactly. Dark matter and dark energy is just a symptom of the standard model of physics being incorrect. >Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level. According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.[2][3]…
'Dark Energy/Dark Mass: The Slient Truth' https://tienzengong.wordpress.com/2015/04/22/dark-energydark...
"That is, all that we are certain about [is] the dark mass, not dark matter, let alone to say about the dark 'particle'."
Particles of matter move through and displace the dark mass, including 'particles' as large as galaxies and galaxy clusters.
The Milky Way moves through and displaces the dark mass.
The Milky Way's halo is the state of displacement of the dark mass.
The Milky Way moves through and curves spacetime.
The Milky Way's halo is curved spacetime.
The state of displacement of the dark mass is curved spacetime.
'Dark Energy/Dark Mass: The Slient Truth' https://tienzengong.wordpress.com/2015/04/22/dark-energydark...
"That is, all that we are certain about [is] the dark mass, not dark matter, let alone to say about the dark 'particle'."
Particles of matter move through and displace the dark mass, including 'particles' as large as galaxies and galaxy clusters.
The Milky Way moves through and displaces the dark mass.
The Milky Way's halo is the state of displacement of the dark mass.
The Milky Way moves through and curves spacetime.
The Milky Way's halo is curved spacetime.
The state of displacement of the dark mass is curved spacetime.
Interesting, I always thought of dark matter as just a lot of extra "dust", the dust that clumps to make the stars that make up the universe. The asteroid belt, the extra mass in our kuiper or oort clouds, etc. The dust that blocks parts of our view of the Milky way. This article (and others I'm now skimming) point out that dark matter needs other magical properties however. Why is that the case? Why does simple "dar…
This means that dark matter is not like the "physical matter" that you're used to seeing. Dark matter doesn't absorb or emit light, so it doesn't block our view of some parts of the Milky Way. The stuff that blocks our view is basically "space dust", and that "space dust" is made of atoms, not dark matter.
According to the theories of dark matter, it can affect our view of other places in the universe, but only via "gravitational lensing". "Gravitational lensing" is where there are enough particles with lots of mass all together (like a galaxy) that they noticeably distort light as it goes by. There is compelling evidence for dark matter from observations of gravitational lensing effects near galaxies that do not have enough mass from their observable stars to account for the degree to which light is distorted as it goes past the galaxy--in other words, to produce that effect, some galaxies must have significant amounts of mass from particles which are not visible.
Why couldn't that extra mass be from "space dust"? Because there is an enormous amount of mass that we can detect via gravitational lensing, but which is not emitting or absorbing light. "Space dust" does not make up much mass for each galaxy compared to the stars and black holes. It's nowhere near the quantity required to produce the observed gravitational lensing effects.
Related: Space dust: https://en.m.wikipedia.org/wiki/Cosmic_dust
Dark matter & gravitational lensing: http://m.phys.org/news/2014-07-large-dark-peaks-gravitationa... - This article notes that dark matter is estimated to comprise about 80% of the mass of the universe. If dark matter was made of visible particles, that would be like having four times as much visible material floating around in galaxies as the stars and black holes which comprise the galaxies, and somehow we don't see any of it.
Of course dark matter doesn't exist. Hello, people. Dark matter is the eflourescent ether theory of the 21st century. There are things that we don't know how to explain right now. We have some ideas about how they can be explained. But they are really really bad. We will be laughing at dark matter theory in a few years.