Wtf is dark matter?

[surreptitious57]

Matter is composed of atoms which are the building blocks of everything physical with dimension or property which exists at the classical level. Every
thing known to exist is either physical or contingent upon the physical. Nothing observable can be non physical by definition since its existence could
not be verified. Although all matter is composed of atoms the space inside one is virtually empty. This means the physical Universe and everything in
it is also virtually empty. We tend not to notice this however for we experience everything at the classical level. But if we experienced everything at
the quantum level most of space would be empty as such. Though that depends on how one defines empty. Most of space at the classical level is also
empty yet gravity is universal. It may not be physical by the standard definition but it is actually a force and so is physical by that description. In the
same way while most of an atom is empty it has electromagnetic charge that enables electrons to orbit the nucleus and so like gravity is also a force
Although it should be pointed out that electrons do not orbit a nucleus the same way that a planet orbits a star for example because their position or
speed cannot be determined simultaneously due to the different rules which the quantum world operates under. And that is basically what matter is

[hackenslash]

Matter is composed of atoms

Backwards. Atoms are composed of matter.

[Xamonas Chegwé]

if we experienced everything at
the quantum level most of space would be empty as such.

Only if we consider the matter as particles. If, as is equally valid, we consider it as waves, then all of space is full of overlapping waves!

Every point in space has a non-zero potential to hold every particle in space. Or some shit.

[pErvinalia]

I quote Feynman: "If you think you understand quantum mechanics, you are a libertarian and a poopy-head".

[jamest]

Dark matter has to have mass (according to the model). In fact, I think I heard that it constitutes well over 80% of the total mass in the universe. Therefore, given that the models are using the same gravitational equations applicable to 'normal' matter, we must assume that dark matter has an immense gravitational effect upon the universe as a whole.

But this is what puzzles me, since we only need the notion of dark matter to explain the motion of stars on the outer edges of galaxies. For every other event, we can completely ignore dark matter and accurately calculate what's going on as if it had no influence upon events whatsoever. This doesn't make sense [to me], for if there is dark matter out there constituting 80+% of universal mass then any and all visible events would/should be affected by its gravitational affects and our everyday calculations (which ignore dark matter) should not be anywhere close to being accurate.

For me, this is a serious problem. You can't just shoe-horn invisible mass into the universe which only affects the stars on the edges of galaxies. Wtf sort of physics is that?

[Xamonas Chegwé]

Dark matter has to have mass (according to the model). In fact, I think I heard that it constitutes well over 80% of the total mass in the universe. Therefore, given that the models are using the same gravitational equations applicable to 'normal' matter, we must assume that dark matter has an immense gravitational effect upon the universe as a whole.

But this is what puzzles me, since we only need the notion of dark matter to explain the motion of stars on the outer edges of galaxies. For every other event, we can completely ignore dark matter and accurately calculate what's going on as if it had no influence upon events whatsoever. This doesn't make sense [to me], for if there is dark matter out there constituting 80+% of universal mass then any and all visible events would/should be affected by its gravitational affects and our everyday calculations (which ignore dark matter) should not be anywhere close to being accurate.

For me, this is a serious problem. You can't just shoe-horn invisible mass into the universe which only affects the stars on the edges of galaxies. Wtf sort of physics is that?

If there is tons and tons of invisible, heavy dark matter, more-or-less evenly distributed in every direction, then its gravitational effects cancel out. If you could stand in the centre of the Earth, you would feel no gravity for exactly the same reason. So, while the universal effects of dark matter are immense, its local effects are negligible and go unnoticed.

[jamest]

If there is tons and tons of invisible, heavy dark matter, more-or-less evenly distributed in every direction, then its gravitational effects cancel out. If you could stand in the centre of the Earth, you would feel no gravity for exactly the same reason. So, while the universal effects of dark matter are immense, its local effects are negligible and go unnoticed.

Given the gravitational nature of dark matter, it should not have a homogenous distribution across the universe. Just like visible matter, it should clump together as something akin to 'dark galaxies', full of large dark bodies structurally similar to visible stars and planets.

As such, dark matter wouldn't have the same/universal gravitational effect upon all visible bodies. That effect would vary with the proximity of a visible body to a dark body of matter. For that reason, I would expect the velocities/speeds of visible stars within their galaxy to be variable and changeable (and not just those stars on the outer edges of galaxies).

Also, unless there's some sort of unknown force (far greater than gravity - which would effectively nullify gravity in certain regions... so we'd be aware of it) preventing dark matter from clumping with visible matter, then the mass of all visible bodies should be comprised of 80+% of dark matter. Since our calculations of the mass of visible bodies ignores the presence of dark matter therein, and since our calculations using the mass of these visible bodies is extremely accurate, this in itself suffices to refute the existence of dark matter (as presently conceived).

[PsychoSerenity]

You must have learned an awful lot about dark matter in the last 24 hours if you're able to go from asking "wtf is it" to thinking you've come up with a simple idea to refute its existence.

Or perhaps you've still missed a few things about how it's presently conceived. For example that weakly interacting massive particles might be weakly interacting.

[hackenslash]

Dark matter has to have mass (according to the model). In fact, I think I heard that it constitutes well over 80% of the total mass in the universe.

No. Ordinary matter comprises about 4-6%, dark matter 24-26% and dark energy about 70%.

Therefore, given that the models are using the same gravitational equations applicable to 'normal' matter, we must assume that dark matter has an immense gravitational effect upon the universe as a whole.

As does the rest of the mass of the universe. However, unless there are differentials, the net effect is nil.

But this is what puzzles me, since we only need the notion of dark matter to explain the motion of stars on the outer edges of galaxies. For every other event, we can completely ignore dark matter and accurately calculate what's going on as if it had no influence upon events whatsoever. This doesn't make sense [to me], for if there is dark matter out there constituting 80+% of universal mass then any and all visible events would/should be affected by its gravitational affects and our everyday calculations (which ignore dark matter) should not be anywhere close to being accurate.

Confusion between DM and DE aside, this is still wrong, because we also need dark matter (and dark energy) to explain the energy density of the cosmos.

For me, this is a serious problem.

That's because you haven't understood it.

You can't just shoe-horn invisible mass into the universe which only affects the stars on the edges of galaxies. Wtf sort of physics is that?

Speaking of shoe-horning, you've managed to shoehorn a fair portion of misunderstanding in there.

[Xamonas Chegwé]

If there is tons and tons of invisible, heavy dark matter, more-or-less evenly distributed in every direction, then its gravitational effects cancel out. If you could stand in the centre of the Earth, you would feel no gravity for exactly the same reason. So, while the universal effects of dark matter are immense, its local effects are negligible and go unnoticed.

Given the gravitational nature of dark matter, it should not have a homogenous distribution across the universe. Just like visible matter, it should clump together as something akin to 'dark galaxies', full of large dark bodies structurally similar to visible stars and planets.

OK. First off, we don't know the precise distribution of dark matter but that doesn't really matter in this case. All that matters is that it is locally homogenous. Since the strength of a gravitational field depends on the square of distance, the effects of local matter (dark matter included) have a far greater influence than anything further away. So, if the dark matter close to us is evenly distributed throughout our local region of space, it would have no noticeable effect on local gravitational processes.

As such, dark matter wouldn't have the same/universal gravitational effect upon all visible bodies. That effect would vary with the proximity of a visible body to a dark body of matter. For that reason, I would expect the velocities/speeds of visible stars within their galaxy to be variable and changeable (and not just those stars on the outer edges of galaxies).

Again, provided that the dark matter was fairly evenly distributed locally, its local effect would be invisible.

Also, unless there's some sort of unknown force (far greater than gravity - which would effectively nullify gravity in certain regions... so we'd be aware of it) preventing dark matter from clumping with visible matter, then the mass of all visible bodies should be comprised of 80+% of dark matter. Since our calculations of the mass of visible bodies ignores the presence of dark matter therein, and since our calculations using the mass of these visible bodies is extremely accurate, this in itself suffices to refute the existence of dark matter (as presently conceived).

There are several forces greater than gravity. In fact, ALL known forces are greater than gravity.

Seeing as nobody has anything but hypotheses regarding the nature of dark matter, it is a little early to start predicting wether or not it will "clump" with regular matter. One would assume that it doesn't, or else its effects would be dramatically noticed. But as to why it doesn't, that is a question to be answered once we have an idea what it is!

[hackenslash]

Given the gravitational nature of dark matter, it should not have a homogenous distribution across the universe. Just like visible matter, it should clump together as something akin to 'dark galaxies', full of large dark bodies structurally similar to visible stars and planets.

That depends entirely on the nature of dark matter, though I do so love the transition between total ignorance and complete authority within the space of a post or two on a topic that's taken me more than 20 years to get a minimal grasp on. You keep forgetting that the universe isn't actually required to pander to our puny intuitions, let alone intuitions as horribly puny as yours.

As such, dark matter wouldn't have the same/universal gravitational effect upon all visible bodies. That effect would vary with the proximity of a visible body to a dark body of matter.

The inverse of the square of the distance, in fact, approximately, because that's gravity (and all other things that propagate uniformly in a 3-dimensional universe).

For that reason, I would expect the velocities/speeds of visible stars within their galaxy to be variable and changeable (and not just those stars on the outer edges of galaxies).

You'd expect? You, who thinks that the fact that Einstein supplanted Newton demonstrates that the world doesn't exist? The universe doesn't give a flying fuck about your expectations, and I, knowing you considerably better, care even less.

Also, unless there's some sort of unknown force (far greater than gravity - which would effectively nullify gravity in certain regions... so we'd be aware of it) preventing dark matter from clumping with visible matter, then the mass of all visible bodies should be comprised of 80+% of dark matter. Since our calculations of the mass of visible bodies ignores the presence of dark matter therein, and since our calculations using the mass of these visible bodies is extremely accurate, this in itself suffices to refute the existence of dark matter (as presently conceived).

Except that you've gotten the figures all wrong, and you've completely nixed the uniform distribution.
In any event, there most certainly is a force greater than gravity, though it isn't unknown. And yes, it certainly does nullify the effects of gravity in certain regions, because it's considerably stronger and, where it operates, it so totally dominates the environment as to render gravity largely irrelevant, which is why you can pick up a paperclip with an ordinary household magnet, despite the fact that the gravitational attraction of an entire planet is fighting you.

BTW, the electromagnetic force isn't the only one that outstrips gravity in terms of effect.

If dark matter doesn't interact with any of those forces (hint; it definitely doesn't interact with the electromagnetic force, which is why we can't see it), then we would expect to see it dominate where those forces are minimal.

Guess what we observe?

[jamest]

Dark matter has to have mass (according to the model). In fact, I think I heard that it constitutes well over 80% of the total mass in the universe.

No. Ordinary matter comprises about 4-6%, dark matter 24-26% and dark energy about 70%.

Yes, I think I've confused mass with 'total matter' (dark matter constitutes 80+% of all matter).

Therefore, given that the models are using the same gravitational equations applicable to 'normal' matter, we must assume that dark matter has an immense gravitational effect upon the universe as a whole.

As does the rest of the mass of the universe. However, unless there are differentials, the net effect is nil.

There should be differentials (mass clumps together via gravity), which should have noticeable effects at the local scale.

But this is what puzzles me, since we only need the notion of dark matter to explain the motion of stars on the outer edges of galaxies. For every other event, we can completely ignore dark matter and accurately calculate what's going on as if it had no influence upon events whatsoever. This doesn't make sense [to me], for if there is dark matter out there constituting 80+% of universal mass then any and all visible events would/should be affected by its gravitational affects and our everyday calculations (which ignore dark matter) should not be anywhere close to being accurate.

Confusion between DM and DE aside, this is still wrong, because we also need dark matter (and dark energy) to explain the energy density of the cosmos.

Confusion between DM and DE aside, what I've said is still applicable. I'm especially keen to see a response to my previous post, since if DM exists then it should constitute 80+% of the mass of visible bodies.

[hackenslash]

Confusion between DM and DE aside, what I've said is still applicable.

Only if you completely ignore everything I said that you just quoted. In short, no it fucking isn't.

I'm especially keen to see a response to my previous post, since if DM exists then it should constitute 80+% of the mass of visible bodies.

How do you arrive at this bollocks? Not that it matters how you arrived at it, because it definitely is bollocks, and I've already explained why (though I'm not totally convinced you have the equipment to grasp it), but it will be interesting to see your 'working out', if it even deserves such an appellation.

[jamest]

You must have learned an awful lot about dark matter in the last 24 hours if you're able to go from asking "wtf is it" to thinking you've come up with a simple idea to refute its existence.

You should at least be commending me for giving the question considerable thought in that time. Nobody knows much about dark matter. Primarily, according to the model, we know that it has mass and therefore impacts gravitationally upon the universe. With that in mind, one can begin to ask questions and come to a few basic realisations. For instance, matter clumps together, so we cannot have a model whereby dark matter is homogeneously distributed throughout the universe without adding that dark matter itself is not affected by gravity. The shoe fits, but is absurd.

Or perhaps you've still missed a few things about how it's presently conceived. For example that weakly interacting massive particles might be weakly interacting.

I'm not sure what your point is, sorry.

[jamest]

I'm especially keen to see a response to my previous post, since if DM exists then it should constitute 80+% of the mass of visible bodies.

How do you arrive at this bollocks? Not that it matters how you arrived at it, because it definitely is bollocks, and I've already explained why (though I'm not totally convinced you have the equipment to grasp it), but it will be interesting to see your 'working out', if it even deserves such an appellation.

Unless dark matter itself is unaffected by gravity (an absurd suggestion), and given that it constitutes 80+% of all matter, then why should we not expect bodies of matter to be comprised of 80+% dark matter and 20-% of visible matter?