Question regarding M-Theory and Dark Matter

[TobiasTheViking]

Note: i asked this on the BAUT forum, but i didn't feel anyone told me why i was wrong. So i'm trying here now


Second Note: I'll admit as my first line that i am extremely ignorant of these subjects(on a math level), so i'm not trying to make a theory, or even a hypothesis here. Just want something explained.


As far as i understand Dark Matter is, for now, an artifact we use because galaxy rotation doesn't work without more matter around the galaxy. That is, not in the center. Some Dark Matter have been found, but the majority of the matter needed is still not verified.

So, studying some M-Theory(just for haha's) i got an idea. It is most likely wrong(on par with the, go out one side of the universe and come in the other, ideas you get as a 12 year old). But still.

The graviton would be a looped string, not fixed on our brane(in contrast to the other forces). Which means gravity can leave our brane, and influence other branes. So if M-Theory is actually reality, and not just a phillosophy(have there been made a test or observation that updates it to theory yet?), could it be that matter in other branes next to us, could be (some of) the Dark Matter we still haven't found.

If we have a lot of branes next to each other. And look through them(for a 2d image, place them on top of each other and look down through them) have a somewhat uniform attraction across the sum of the branes. So gravity in the center of the galaxies isn't that much more than at the edges of the galaxy.

Of course it could also end up as galaxies having about the same position in all the branes, simply because they are being attracted to each other.


As i stated, i don't know that much on the subject, and this idea is most likely completely wrong, and build on the fact that there is certain information on how M-Theory works that i don't comprehend(or have never been explained to me).

But i would very much like to know why this could NOT be the case.

Sincerely
Tobias.

 

[Xeriar]

The main problem for this (I don't doubt that a good part of "Dark Matter" could well be the shadows of nearby galaxies in other branes... but anyway) is that gravity follows the inverse square law.

Of course, gravity also does not interfere with itself or get obstructed by other 'gravity generators' the way light does. To put simply, it's not obeying the inverse square law in a fashion that makes sense.

The main support for your hypothesis, in my opinion, has more to do with the fact that dark matter gets mapped into a halo, and not a disc. If this model proves to be true, it would seem unlikely that dark matter could be within our universe - dark matter particles ought to form the same disc that the galaxy does, whereas the 'gravitational shadows' of neighboring galaxies in other dimensions has no such limit.

Granted I don't have much of a physics background, but as far as I know (having talked about it with a physicist before) it's not out of the realm of possibility.

 

[TobiasTheViking]

Nor do i.

This isn't really a theory, it is just an idea i formed from the very limited knowledge i have of the subject.
And i'm not trying to prove a "See my new theory that proves [famous scientist] is wrong". I have no illusions like that, and i have too much respect for proper scientists to do anything like that.

I believe that my idea is wrong, but i want to know why.

As for inverse square law, yes, that might prove a boundary, but as far as i know, there may be an unlimited amount of branes, with a distance between them of as little as a milimeter. And even if the distance between them were just a kilometer, the inverse square law would still not pose much of a problem.

There is one thing that can falsify my idea(not a theory, not by a longshot). Which would be that all the galaxies in the different branes would slowly float to the same place. The galaxies would attract eacher other accross the branes, and pull together, so in the end we could have an infinate amount of branes where all(most) of the galaxies would have about the same position in the branes. Which would reenforce the gravitational attraction we see in the galaxies, and thus be the exact oposite of Dark Matter.

I'm sure that there is some mathematics that can be applied to show which of the two would happen, if any of them. But i don't know what they are.

I'm just very interested in figuring out WHY i'm wrong.

Sincerely
Tobias.

 

[SpaceFluffer]

As far as i understand Dark Matter is, for now, an artifact we use because galaxy rotation doesn't work without more matter around the galaxy. That is, not in the center. Some Dark Matter have been found, but the majority of the matter needed is still not verified.

This isn't quite correct. There are several lines of evidence that point to indirect observation of dark matter; the galactic rotation curves is just one of them.

The Cosmic Microwave Background (CMB) points to total baryonic matter being ~4% of the critical density, yet also says that the universe's total energy density is very close to the critical density. Most of this deficit is in dark energy, but observations of galactic cluster dynamics and gravitational lensing surveys have shown that there is a great deal of mass out there in non-luminous material. We also know that the present amount of galactic-scale structure that we observe could not have formed given the age of the universe with only the dark energy and baryonic matter present.

These all point to the existence of some non-luminous non-baryonic mass component to the universe comprised of subatomic particles (WIMPs). These have not been observed directly in the laboratory, however, there are experiments looking for their signature, and should they exist it's only a matter of time (and money).

I don't really understand your suggested theory, to be honest. There have certainly been suggestions in the literature that extend gravity out to other branes, but so far as making currently testable predictions they all come up short.

If the dark matter is what we think it is (and there are several candidates), there's no reason to postulate a solution involving higher dimensions. Most people are betting that the WIMP comes from supersymmetry, though we will see.

So if M-Theory is actually reality, and not just a phillosophy(have there been made a test or observation that updates it to theory yet?)

I think it's a little unfair to call a rigorous mathematical theory that stems from an extension of well understood and well-tested theories, a 'philosophy'. Having said that, there are no results from M-theory that I'm aware of, that give experimental predictions that we could test any time soon.

 

[TobiasTheViking]

This isn't quite correct. There are several lines of evidence that point to indirect observation of dark matter; the galactic rotation curves is just one of them.

Yes, indeed, and after looking a bit at M-Theory i wondered if those galactic rotation curves, and the other symptoms of Dark Matter couldn't just be because of gravitational attraction from matter in other branes.

We haven't been able to find the cause for most of the Dark Matter we should see, and some of it could be from other branes, or so i postulate.

But as i state a few times, i doubt what i'm saying is correct, i just wanna know why it is wrong. But i do agree, Dark Matter, as it is defined now, is part of the universe. But Dark Matter is just a place holder till we get it divided into other more specific and descriptive areas. like WIMP's as you point out. Some of it could be gravitational effects from other p-branes.

I think it's a little unfair to call a rigorous mathematical theory that stems from an extension of well understood and well-tested theories, a 'philosophy'. Having said that, there are no results from M-theory that I'm aware of, that give experimental predictions that we could test any time soon.

Actually, i didn't say that, i think it was a professor from CERN who said it.

If we have some nice beautifull mathematics, and it has nothing to do with the world we live in, but is just pretty. Then it is just a philosophy.
If we have some nice beautifull mathematics, and is consistent with the the world we live in, it is both pretty, and it is consistent with reality.

As far as i know, M-Theory is beautifull mathematics, but can't yet be said to be a real theory, since it can't be falsified.

That being said, i really like M-Theory, and i believe it DOES represent reality. That is just a belief. And untill someone can show me a test or prediction, i will think my belief in M-Theory is no better than someone elses belief in God.

Thanks for your reply, and i don't disagree with you as such, just on degrees.

Sincerely
Tobias.

 

[SpaceFluffer]

Yes, indeed, and after looking a bit at M-Theory i wondered if those galactic rotation curves, and the other symptoms of Dark Matter couldn't just be because of gravitational attraction from matter in other branes.

And my point was that, if dark matter exists, it must consist of a collection of subatomic particles, that we call WIMPs (Weakly Interacting Massive Particles). There are no 'symptoms' of dark matter - just a buttload of evidence from differing areas of observation all pointing to some non-baryonic matter component in the form of subatomic particles.

We haven't been able to find the cause for most of the Dark Matter we should see, and some of it could be from other branes, or so i postulate.

Most?? Read my first post again. You're essentially saying that one could construct a suitable candidate for the WIMP from M-Theory, and so far as I know, there's nothing much wrong with that. But it's almost definitely going to be unneccesary since so many other candidates arise naturally from other theories (like supersymmetry).

But i do agree, Dark Matter, as it is defined now, is part of the universe. But Dark Matter is just a place holder till we get it divided into other more specific and descriptive areas. like WIMP's as you point out. Some of it could be gravitational effects from other p-branes.

So you keep saying. And we really don't know for sure if dark matter is actually part of the universe. But at the moment pretty much everything is pointing to it.

Actually, i didn't say that, i think it was a professor from CERN who said it.

Well, whatever. You did quote it above without a reference, so how am I to distinguish your opinions from someone else's?

As far as i know, M-Theory is beautifull mathematics, but can't yet be said to be a real theory, since it can't be falsified.

Sure, it can. It might be Mathematics, but are you suggesting that theorems in Mathematics cannot be falsified?

That being said, i really like M-Theory, and i believe it DOES represent reality. That is just a belief. And untill someone can show me a test or prediction, i will think my belief in M-Theory is no better than someone elses belief in God.

I really like the theory that everything in the universe is made of jello, but what does that have to do with anything?

You seem to think that M-Theory was just pulled out of someone's ass one day. It doesn't have testable predictions yet, but it is based on some very clever theory, just as QED was before it, for example. That doesn't mean that believing in it is equatable to believing in God, and nor should you have any belief in it ability to represent reality until you see some convincing evidence and/or understand all of the Math behind it.

 

[TobiasTheViking]

And my point was that, if dark matter exists, it must consist of a collection of subatomic particles, that we call WIMPs (Weakly Interacting Massive Particles). There are no 'symptoms' of dark matter - just a buttload of evidence from differing areas of observation all pointing to some non-baryonic matter component in the form of subatomic particles.

WIMPs are only one possibility, and i don't know how much of the Dark Matter they would account for. And just because WIMPs may be a possible explanation for Dark Matter, that doesn't make it enough to disprove my idea.

As for symptoms, i simply meant the effect we see from Dark Matter, where we don't know what kind of Dark Matter it is yet.


Can you provide references to observations that state that ALL Dark Matter must be "non-baryonic matter component in the form of subatomic particles." Because if you can, then i feel my idea has been disproven, and i'm happy, if you can't. well, i'll have to keep looking for something to disprove my idea.

Most?? Read my first post again. You're essentially saying that one could construct a suitable candidate for the WIMP from M-Theory, and so far as I know, there's nothing much wrong with that. But it's almost definitely going to be unneccesary since so many other candidates arise naturally from other theories (like supersymmetry).

I didn't mean that M-Theory had anything to do with WIMPs at all. Besides for the fact that WIMPs might be build from strings, of course. But what i'm postulating, gravity from other p-branes, would NOT have anything to do with WIMPs.

Btw, i must have missed something, supersymmetry would acount for Dark Matter... Would the other particles be much heavier? Please verbose on that.

So you keep saying. And we really don't know for sure if dark matter is actually part of the universe. But at the moment pretty much everything is pointing to it.

Ehm, again, i'm not contesting that Dark Matter i sa part of our universe. What i'm saying is that we don't know what most of the Dark Matter is. Some of it might be WIMPs. All of it might be WIMPs. And some of it might be what i'm postulating, that is, gravitational attraction from other branes. One does not discount the other.

Well, whatever. You did quote it above without a reference, so how am I to distinguish your opinions from someone else's?

Sorry. But it is also my opinion. If you really care, i can dig up who it is.

Sure, it can. It might be Mathematics, but are you suggesting that theorems in Mathematics cannot be falsified?

I'm suggesting that if somethign can't be falsified, it isn't a theory, it is at best a hypothosis(spelling?)

I really like the theory that everything in the universe is made of jello, but what does that have to do with anything?

That you make it sound like i have something against M-Theory, i don't. I support it, i like it. And when i say i don't feel it is a theory yet, that is solely because it can't be falsified yet. That doesn't mean that i can't have the belief that it is concurrent with reality.

You seem to think that M-Theory was just pulled out of someone's ass one day. It doesn't have testable predictions yet, but it is based on some very clever theory, just as QED was before it, for example. That doesn't mean that believing in it is equatable to believing in God, and nor should you have any belief in it ability to represent reality until you see some convincing evidence and/or understand all of the Math behind it.

When have i ever shown contempt for M-Theory that would insinuate that i think it was "pulled out of someone's ass". Actually, when have i shown ANY contempt for M-Theory. The only negative thing that i think i have said, is that for now, it is not a theory, because it can't be falsified. For now, i think it is more a philosophy, because it may or may not be a description of the world we live in.
If it it is not a description of the world we live in, it is just philosophy, or pretty math.

The fact that it is based on clever theory doesn't make it any more of a theory, or any less of a philosophy, if the clever theory doesn't relate to the real world.

You write "nor should you have any belief in it ability to represent reality until you see some convincing evidence", and that is EXACTLY why i say it is a belief, in a philosophy, and not a theory. Because no prediction, observation or test have been performed that can count as evidence for it.


And what is with the hostility, that makes me a saad panda.

Sincerely
Tobias.

 

[Schneibster]

Interestingly, it has been suggested (how seriously I don't know, but I do know that Brian Greene mentioned it in passing) that the reason that gravity is so weak is because it "leaks" out into other branes than ours. This doesn't affect the way it falls off with distance, because that's a property of our spacetime- but it does affect how strong it is compared to, say, the electric force. So maybe your idea isn't so wild after all.

 

[Xeriar]

Nor do i.

This isn't really a theory, it is just an idea i formed from the very limited knowledge i have of the subject.
And i'm not trying to prove a "See my new theory that proves [famous scientist] is wrong". I have no illusions like that, and i have too much respect for proper scientists to do anything like that.

I believe that my idea is wrong, but i want to know why.

Personally, I find the claim that 'all dark matter is composed of particles within our Universe' to be more specious than the idea of several or several trillion branes gravitationally interacting as you describe.

For one, we've only observed neutrinos so far, and they move too fast, have too little mass, and are not in great enough quantity. These WIMPS ought to be hanging around stars like our sun.

For two, dark matter halos around galaxies get modelled spherically, and not to the galactic disc. Slow particles within our Universe -should- ultimately conform to the disc, whereas these are certainly something else.

For three, we're talking about gravity here. They should concentrate in the center just like ordinary matter does.

If we don't find them within the Solar System, unless they are actively repulsed by all electromagnetic force or something weird like that, then I'd have to conclude that dark matter is something else.

As for inverse square law, yes, that might prove a boundary, but as far as i know, there may be an unlimited amount of branes, with a distance between them of as little as a milimeter. And even if the distance between them were just a kilometer, the inverse square law would still not pose much of a problem.

That wasn't my point. Rather, that the inverse square law suggests a 3D Universe.

However, if matter and the warping of space are the same thing, or something similar, then it may be that the inverse square law is just a result of the nature of this curvature, and it would behave the same across any number of dimensions. This seems to require at least two gravitational dimensions and would suggest all sorts of gravitational anomolies at both extremely large and extremely short distances.

There is one thing that can falsify my idea(not a theory, not by a longshot). Which would be that all the galaxies in the different branes would slowly float to the same place. The galaxies would attract eacher other accross the branes, and pull together, so in the end we could have an infinate amount of branes where all(most) of the galaxies would have about the same position in the branes. Which would reenforce the gravitational attraction we see in the galaxies, and thus be the exact oposite of Dark Matter.

On the contrary, I think the math for this requires that the closest branes be tens of thousands of light-years away, at least.

I'm just very interested in figuring out WHY i'm wrong.

In the case of the ekpyrotic model, it would also suggest that these branes are moving at a significant rate over astronomical time. Thus the non-baryonic mass in our Universe would appear to fluctuate over time. To my knowledge, this may be a possibility but seems rather unlikely.

 

[TobiasTheViking]

Interestingly, it has been suggested (how seriously I don't know, but I do know that Brian Greene mentioned it in passing) that the reason that gravity is so weak is because it "leaks" out into other branes than ours. This doesn't affect the way it falls off with distance, because that's a property of our spacetime- but it does affect how strong it is compared to, say, the electric force. So maybe your idea isn't so wild after all.

Which is the basis i'm working on with gravitational attraction from other branes. I believe it is pretty much required of M-Theory.

Sincerely
Tobias

Damn, i overslept.

 

[TobiasTheViking]

Personally, I find the claim that 'all dark matter is composed of particles within our Universe' to be more specious than the idea of several or several trillion branes gravitationally interacting as you describe.

But then again, if we find something similar to a neutrino that has a very big mass, that might change things around a lot.

For one, we've only observed neutrinos so far, and they move too fast, have too little mass, and are not in great enough quantity. These WIMPS ought to be hanging around stars like our sun.

And i would asume that galaxies in other branes would condence so they in the end would all be at about the same place, and then reinforce gravity, and remove the effect of Dark Matter. If it is indeed a cause for Dark Matter.

For two, dark matter halos around galaxies get modelled spherically, and not to the galactic disc. Slow particles within our Universe -should- ultimately conform to the disc, whereas these are certainly something else.

Wouldn't the galaxies accross the branes do the same with time?

For three, we're talking about gravity here. They should concentrate in the center just like ordinary matter does.

Wouldn't the galaxies accross the branes do the same with time?

If we don't find them within the Solar System, unless they are actively repulsed by all electromagnetic force or something weird like that, then I'd have to conclude that dark matter is something else.

Agreed.

However, if matter and the warping of space are the same thing, or something similar, then it may be that the inverse square law is just a result of the nature of this curvature, and it would behave the same across any number of dimensions. This seems to require at least two gravitational dimensions and would suggest all sorts of gravitational anomolies at both extremely large and extremely short distances.

As far as i understand it the inverse square law is a product of the area the Graviton(and other particles) expand in. If we only have two dimensions it can only expand from the light bulb, or sun, in left-right and up-down. And then we just have inverse. Whereas in a 3d universe it can also go back-forward, and have a lot more area to expand in, thus inverse square law.

I'm pretty sure the inverse square law is just a product of the number of (big) dimensions in our universe, and have nothing, as such, to do with the curvature of space.

On the contrary, I think the math for this requires that the closest branes be tens of thousands of light-years away, at least.

That isn't what i have heard, i have specificly heard "could be as little as 1 mm away from us". I think Brain Greene said that.

In the case of the ekpyrotic model, it would also suggest that these branes are moving at a significant rate over astronomical time. Thus the non-baryonic mass in our Universe would appear to fluctuate over time. To my knowledge, this may be a possibility but seems rather unlikely.

ekpyrotic?

And agreed, since the branes would move, and also the gravitational effect from the matter within those branes would move, we would see fluctuations over time. But how can we measure it?

Sincerely
Tobias

Rushing to school.

 

[Xeriar]

But then again, if we find something similar to a neutrino that has a very big mass, that might change things around a lot.

One part that gets me is that our Sun should be trapping these. Since, the Milky Way is now believed to have nearly 2 trillion solar masses, and that visible matter only makes up for a third of that, and that the general velocities of these particles cannot exceed the escape velocity of our Sun, there should be an observed discrepancy between the mass of our Sun and the amount of fusion energy it appears to be generating, given theory. This does not appear to be the case to any large degree, as far as I know.

As far as i understand it the inverse square law is a product of the area the Graviton(and other particles) expand in. If we only have two dimensions it can only expand from the light bulb, or sun, in left-right and up-down. And then we just have inverse. Whereas in a 3d universe it can also go back-forward, and have a lot more area to expand in, thus inverse square law.

I'm pretty sure the inverse square law is just a product of the number of (big) dimensions in our universe, and have nothing, as such, to do with the curvature of space.

In the case of light, it clearly is. The surface area of a sphere is 4 pi r^2. Light locally interferes with itself, is stopped by objects, and actually passes, however. Gravity, on the other hand, is a continuous effect, is not interfered with in any known manner, and has at least three known anomolies associated with it - galactic rotation, the pioneer anomoly, and the Alais Effect.

No matter what, there's something about gravity that we don't understand just yet.

And i would asume that galaxies in other branes would condence so they in the end would all be at about the same place, and then reinforce gravity, and remove the effect of Dark Matter. If it is indeed a cause for Dark Matter.


Wouldn't the galaxies accross the branes do the same with time?


Wouldn't the galaxies accross the branes do the same with time?

That isn't what i have heard, i have specificly heard "could be as little as 1 mm away from us". I think Brain Greene said that.

Only if gravity exerts a different amount of influence over different dimensions. I don't really buy that, myself.

If the neighboring branes were really that close, and they interacted gravitationally, then galaxies would either not have this rotation problem, just obviously missing mass, or would not take the shape of circular discs - we would see 'galactic collisions with nothing'.

ekpyrotic?

A model of the Big Bang that suggests these branes eventually collide, as opposed to the Singularity theory. It solves a number of problems with the Big Bang, and, IMO, could also solve the problem of matter-antimatter imbalance if branes could strike eachother at an angle.

And agreed, since the branes would move, and also the gravitational effect from the matter within those branes would move, we would see fluctuations over time. But how can we measure it?

You might argue that we already have, with the recent discovery of dark energy. To put in a nutshell, a basic observation that we would see the apparent average amount of dark matter in galaxies being slightly related to distance.

 

[SpaceFluffer]

One part that gets me is that our Sun should be trapping these. Since, the Milky Way is now believed to have nearly 2 trillion solar masses, and that visible matter only makes up for a third of that, and that the general velocities of these particles cannot exceed the escape velocity of our Sun, there should be an observed discrepancy between the mass of our Sun and the amount of fusion energy it appears to be generating, given theory. This does not appear to be the case to any large degree, as far as I know.

Our galaxy contains around 100 billion stars. Luminous matter comprises around 4-6% of the total mass in the universe, with non-baryonic dark matter coming in at ~85%. The escape velocity of WIMPs in our galaxy has nothing to do with the escape velocity of the Sun, but with how gravitationally bound a WIMP is within the halo. I don't see how the Sun should be doing anything to the WIMPs, since the WIMP's mass density is around 1e-8 g/cm^3, which is peanuts for gravity to have any effect on them except on large scales on long timescales.

In the case of light, it clearly is. The surface area of a sphere is 4 pi r^2. Light locally interferes with itself, is stopped by objects, and actually passes, however. Gravity, on the other hand, is a continuous effect, is not interfered with in any known manner, and has at least three known anomolies associated with it - galactic rotation, the pioneer anomoly, and the Alais Effect.

1) Galactic rotation curves are explained by the presence of a dark matter halo. 2) The pioneer anomoly is almost certainly not due to new physics, and even if it is the inadvertant 'experiment' is so fraught with difficulties that it will impossible to prove it so. 3) The 'Allais Effect' (for those who don't know - that a pendulum will behave anomolously during a total solar eclipse) seems to go away when suitable controls are in place and is highly likely to be bunk.

Oh, and what exactly do you mean by 'light interferes with itself'. Gravity certainly is "interfered with", by it's self-interaction. I'm not sure what you're talking about here.

No matter what, there's something about gravity that we don't understand just yet.

Well, we don't know how to quantize it, but I don't think that's what you're referring to. To be sure, the MOND proponents (MOdified Newtonian Dynamics) have made great progress, yet their theory lags sufficiently behind Cold Dark Matter as to make CDM the only game in town, at least for now.

 

[Xeriar]

Our galaxy contains around 100 billion stars. Luminous matter comprises around 4-6% of the total mass in the universe, with non-baryonic dark matter coming in at ~85%.

600 billion visible baryonic solar masses worth of matter. That's a lot more than 100 billion stars. Due to its age, and lack of collisions, our galaxy is extremely dim. That will change when it hits Andromeda.

Baryonic matter is 4% of the mass/energy, dark matter 23% and 'dark energy' 73%.

Just correcting

The escape velocity of WIMPs in our galaxy has nothing to do with the escape velocity of the Sun, but with how gravitationally bound a WIMP is within the halo. I don't see how the Sun should be doing anything to the WIMPs, since the WIMP's mass density is around 1e-8 g/cm^3, which is peanuts for gravity to have any effect on them except on large scales on long timescales.

You say that and ignore that the very reason for the discussion of dark matter is that baryonic matter is so much less dense.

The escape velocity of the Milky Way at the sun's position is ~640 kilometers a second. The escape velocity of the Sun from the top of its photosphere (which has 1% the molecular density of Earth's atmosphere) is ~620 kilometers a second. The escape velocity of the Solar System at Earth's orbit is only 45 kilometers a second.

If galactic gravity traps them, so will the sun's gravity.

I mean, think about it - unless these WIMPS have a far greater tendancy to repel eachother than normal matter does (implying a 5th force), then they should coelesce into the same disc that the rest of the Milky Way or other spiral/lenticular galaxies have formed into. They will be attracted to masses like those of our sun, black holes, and the like. We should detect inexplicably dark stellar masses and if they do not have any repulsive force between them, we should see them form black holes.

1) Galactic rotation curves are explained by the presence of a dark matter halo. 2) The pioneer anomoly is almost certainly not due to new physics, and even if it is the inadvertant 'experiment' is so fraught with difficulties that it will impossible to prove it so. 3) The 'Allais Effect' (for those who don't know - that a pendulum will behave anomolously during a total solar eclipse) seems to go away when suitable controls are in place and is highly likely to be bunk.

Halo, not a disc, but I've mentioned problems with that above. It requires a spheroid. Unless these particles have an insane repulsive force and/or are mind-bogglingly huge, anyway.

No satisfactory explanation has yet been put forth for the pioneer anomoly. If it's something that's known, no one has volunteered a proper explanation. Regardless, it's not the last probe humanity will be sending into deep space.

The Allais effect has been observed with such controls, it just hasn't been observed regularly.

Oh, and what exactly do you mean by 'light interferes with itself'. Gravity certainly is "interfered with", by it's self-interaction. I'm not sure what you're talking about here.

Light waves interfering with eachother create new waveforms, such that two light sources may cancel eachother out. The presence of one gravitational body cannot obscure another, however (beyond making it insignificant).

Well, we don't know how to quantize it, but I don't think that's what you're referring to. To be sure, the MOND proponents (MOdified Newtonian Dynamics) have made great progress, yet their theory lags sufficiently behind Cold Dark Matter as to make CDM the only game in town, at least for now.

Last I heard MOND ended up predicting things the wrong way around anyway.

 

[SpaceFluffer]

Baryonic matter is 4% of the mass/energy, dark matter 23% and 'dark energy' 73%.

Just correcting

No, you're not. I was breaking down the total mass, not the energy density. Of the 4% baryonic energy density, only about 1% of that is luminous, so I was referring to the 1/27 of luminous baryonic matter, and the 23/27 as dark matter.

You say that and ignore that the very reason for the discussion of dark matter is that baryonic matter is so much less dense.

The individual mass of a WIMP compared to an atom of Hydrogen, say, doesn't matter given our current mass distribution. The galaxies baryonic matter is heavily clumped, and is sitting in a WIMP gas with characteristic velocity of about 220km/s. If the dark matter was just sitting around, then I'd agree that the Sun would pull it in, as would other stars. The only location where you'd expect an uncharacteristically large clumping of dark matter is in the galactic center, where a 3 million solar mass black hole is thought to reside.

If galactic gravity traps them, so will the sun's gravity.

Escape velocity is calculated for a body that starts AT REST. When you're talking about WIMPs zipping by at 220km/s getting sucked into the Sun, you're talking about a scattering problem, and the Sun's gravitational pull needs to be much greater than it is to do that. Escape velocity of the Sun doesn't come into it.

No satisfactory explanation has yet been put forth for the pioneer anomoly. If it's something that's known, no one has volunteered a proper explanation. Regardless, it's not the last probe humanity will be sending into deep space.

You're correct that we have no conclusive explanation. I don't see why that implies that we don't understand gravity.

The Allais effect has been observed with such controls, it just hasn't been observed regularly.

Again, until it's reliably shown to be a real effect with good controls in place, it's bunk.

Last I heard MOND ended up predicting things the wrong way around anyway.

Perhaps you should catch up - MOND has made some interesting new findings in the last couple of years.

 

[Xeriar]

No, you're not. I was breaking down the total mass, not the energy density. Of the 4% baryonic energy density, only about 1% of that is luminous, so I was referring to the 1/27 of luminous baryonic matter, and the 23/27 as dark matter.

2%... And if you're going to refer only to matter, state such and don't confuse it with dark energy.

The individual mass of a WIMP compared to an atom of Hydrogen, say, doesn't matter given our current mass distribution. The galaxies baryonic matter is heavily clumped, and is sitting in a WIMP gas with characteristic velocity of about 220km/s. If the dark matter was just sitting around, then I'd agree that the Sun would pull it in, as would other stars. The only location where you'd expect an uncharacteristically large clumping of dark matter is in the galactic center, where a 3 million solar mass black hole is thought to reside.

If it's just sitting 'still', it will fall towards the center of the galaxy. It needs to rotate, and will clump and discify just as every other mass over ~10-50 billion solar masses does. The sun is moving at 220 km/s in order to avoid falling towards the center.

Again, this is if dark matter doesn't repel itself. That could imply that 'dark energy' is the repulsive force, and is weaker than gravity at short distances and stronger at long ones, but even that's not a perfect explanation, since it would still have to clump. And it doesn't even seem to clump at the black hole in our galactic center!

Escape velocity is calculated for a body that starts AT REST. When you're talking about WIMPs zipping by at 220km/s getting sucked into the Sun, you're talking about a scattering problem, and the Sun's gravitational pull needs to be much greater than it is to do that. Escape velocity of the Sun doesn't come into it.

Which is all well and good, but the sun is only moving about 20 km/s around the solar neighborhood. These WIMPS can't be sitting still.

You're correct that we have no conclusive explanation. I don't see why that implies that we don't understand gravity.

To my knowledge, the only workable suggestions so far have been:
1: Dark matter somehow having an effect at these scales
2: Gravity is finding a shortcut to the Pioneer through another dimension
3: Our equations for gravity are subtly wrong.

Any of those results change our views on gravity.

Again, until it's reliably shown to be a real effect with good controls in place, it's bunk.

Speaking of that, does anyone have any information on when NASA is going to release the data on its own study?

Perhaps you should catch up - MOND has made some interesting new findings in the last couple of years.

Ahh, it seems that some of the disputed galaxies do fit MOND's equations, but some still don't, at least as far as we can determine. I'm rather skeptical of the theory myself.

However, the Sun's hill sphere extends out past a full light-year. If we begin detecting objects in that neighborhood, then further analysis can be done.