Evidence Points to the Detection of Dark Matter

[trish]

I like you too scroller, and all the contributions you make to the forum. But my aim here isn’t to antagonize but try to answer reasonable objections. Hippiefried objects that we merely changed our minds about what to call a straight line and so of course the interior angles theorem is going to fail. But he seems also to claim real triangles made with real lines still behave as common sense would have them behave, with angles adding up to 180 degrees. My reply is that the curves that are most appropriately called lines for the purposes of dynamics (i.e. those curves which are shortest distance routes and those followed by photons and objects not acted upon by outside forces) do not behave in accordance with Euclidean geometry. Moreover, there are no curves that one can easily describe within the framework of the natural world that do behave in accordance with Euclidean geometry. My claim is that if you insist on using the modifier real in any reasonable way, then real triangles don’t generally obey the Euclidean interior angles formula. This is because in order for the laws of dynamics to remain the same in all frames of reference, the geometry of space-time suggested by the first law of inertia must exhibit a curvature which reflects the amount of mass/energy within; i.e. real lines aren’t generally straight and indeed there is no such thing as a real line that’s straight in the proximity of a star because the space that houses it isn’t flat. Can I know this? Not in the skeptical sense of the word, “know.” I can only say that at the moment there simply is no better understanding of gravity with regard to making accurate predictions. Are there problems with the theory and experimental anomalies to be explained? You betcha.

[El Nino]

Trish.. any thoughts on what may have caused or triggered the proverbial "Big-Bang"? It is undoubtedly a phenomenon which can 'boggle the mind'...

[trish]

Trish.. any thoghts on what may have caused or triggered the proverbial "Big-Bang"?

The Big Bang Theory was named by its detractors. It’s really a theory of the expansion of the universe. Evidence that the universe was expanding was first discovered by Hubble and later the expansion was “predicted” by GR. According to GR a homogeneous, isotropic universe could be expanding, contracting or in steady-state. These three types of universes are called the Friedman-Robertson-Walker universes (FRW for short). However, if GR is correct the steady-state universe is very unstable; i.e. a steady-state universe wouldn’t stay steady-state for long; the smallest perturbation would cause it to either collapse or expand. In this sense GR plus the assumptions of homogeneity and isotropy anticipate a dynamic universe …one that expands or collapses. The FRW universes have finite ages, but no first moment, just like an interval (0,1] can be open on the left and yet have a finite length…such intervals have no smallest member. If our universe is a FRW universe there was no time before the expansion, and there was no moment when it started to expand. The universe was always expanding, even though it has a finite age. Since Friedman, Robertson and Walker things have gotten a lot more complicated. Guth added a scalar field to the mix that causes the early universe to expand exponentially. Others, like the string theorist Gasperini hypothesize a pre-expansion history. Gott invented models of universes that perpetually create themselves in a time loop. Vilenkin proposes multiple universes. All three of these guys have popular books for the “layman” by the way…just google them if you’re interested. There’s no end to speculation, but sometimes there’s no profit either. If a theory promises no measurable consequences (say in the structure of the anisotropies of the cosmic background radiation), then I can’t really don’t know how to evaluate it or use it.

My personal favorites for the moment are those models like the FRW and Guth models which have no moment of creation and no history prior to expansion. The universe didn’t have a start, it just was always expanding and yet it’s only 13-14 giga-years old. The expansion periods of most of the other models are consistent with the Guth-FRW models but add very little more in the way of testable predictions.

[hippifried]

My reply is that the curves that are most appropriately called lines for the purposes of dynamics (i.e. those curves which are shortest distance routes and those followed by photons and objects not acted upon by outside forces) do not behave in accordance with Euclidean geometry.

Well, you can call me all wet if you like. I haven't studied, & therefore am not bound by, the differing mathematical disciplines. (Wow! Managed to get a smidgen of sexual innuendo in there.) It just seems to me that forces such as mass or curvature don't actually change the geometry. They merely add more variables for y'all to calculate. Regardless of what routes photons or objects are forced to take, or what's in the way, the shortest distance between 2 points is still a straight line. The basic rules don't change just because you add complexity. Do they?

I have just a couple of problems with the "dark matter" assumptions.
First: It would have to be totally light absorbant. Wouldn't that require density, which in itself would be detectable? We can't see the entire spectrum by a long shot, but we can detect a lot more than what's visible with the eye. Stars emit all kinds of radiations, at nearly all frequencies. One would think that something would be reflected or affected in a detectable way. Or maybe it's totally transparant. But that would mean no density, & therefore no gravitational effect.
Second: The assumption that something is necessary to stabilize the "fabric of space", that started the search for the elusive "dark matter" in the first place. Why would anybody entertain the idea that the universe is stable or should be. Personally, I don't buy into the idea that there's an ether, or that the various stars & galaxies are behaving erratically. Again, relative to what? We certainly haven't discovered all the rules yet, as evidenced by invention of new math disciplines. We don't have the foggiest idea what kind of forces are at work outside of our sphere of detection.

I don't really buy the ever-expanding universe theory either. In fact, I'm not really convinced that it's not contracting. We look at red shifts & say that things are moving away from us. But then again, we don't really know where we are, how fast we're moving, or in what direction. Or even what kind of direction to compare to. We don't know how big the universe is, or if there's any limit to it at all that would make it measureable. We assume everything is finite. Why? Because we're finite? We keep looking for origins, but who says there has to be one? In order for the universe to be expanding, there has to be non-universe for it to expand into. I'm not willing to make that assumption.

Maybe this really is all just Brahma's dream, & we all go poof if/when he/she/it wakes up.

We don't know jack shit. So... I'm inclined to declare myself the center of the universe & let it go at that.

[trish]

Hi hippiefried. Again you raise interesting questions. I'm in a bit of a rush this weekend & hope to get back to this discussion on Monday. See ya then.

[scroller]

Regardless of what routes photons or objects are forced to take, or what's in the way, the shortest distance between 2 points is still a straight line. The basic rules don't change just because you add complexity.

Did you see the picture?

http://en.wikipedia.org/wiki/File:Triangles_(spherical_geometry).jpg

What you call "basic rules" is just an assumption, a totally an unprovable personal bias. This fact was proven hundreds of years ago.

[evilernie]

http://en.wikipedia.org/wiki/File:Triangles_(spherical_geometry).jpg

If I may interject, we are discussing two different objects: a 2D and a 3D. 3 dimensional objects have depth. If you where to "flatten" that 3D object, you will find that it's not even a triangle anymore. That's not because of personal bias or geometric "tricks".

I'm supposed to be snowed in, so I'm planning to participate in every topic in HA.

[scroller]

If I may interject, we are discussing two different objects: a 2D and a 3D. 3 dimensional objects have depth. If you where to "flatten" that 3D object, you will find that it's not even a triangle anymore. That's not because of personal bias or geometric "tricks".

No, the whole premise if this discussion is: if space is curved, then triangles don't add up to 180 degrees. That's the whole point of what we've been saying all along. Demanding that it be "flattened out" is indeed completely personal bias.

If luminous matter (i.e. the stuff bright enough to see) were the only matter there is, the universe would have negative curvature; (i.e. the interior angles of triangles would sum to less than 180 degrees).

[hippifried]

Regardless of what routes photons or objects are forced to take, or what's in the way, the shortest distance between 2 points is still a straight line. The basic rules don't change just because you add complexity.

Did you see the picture?

http://en.wikipedia.org/wiki/File:Triangles_(spherical_geometry).jpg

What you call "basic rules" is just an assumption, a totally an unprovable personal bias. This fact was proven hundreds of years ago.

Yeah, pretty pictures. But the shortest distance from the equator to the axis is through the sphere. Those lines are just surface measurement, a necessity to us because we live on the surfice. The inset is incorrect by these surface measurement standards. That area of Akita may be small, but it's still on the surface of the earth & therefore is affected by the curvature, as is all cartography. That changes the length of the hypotenuse. Not by enough to make a difference in what we're trying to do, probably, but now we're just talking degrees of how much we should care. There's physical objects in the way too. Should we take those into consideration? Do we need to go around, or can we agree to take the imaginary line through the building or hill like the line on the global picture that goes through the Himalayas.

Look, I understand there's calculus for measuring curvature. Not being an engineer, there's no reason for me to learn how to do it. But this is a conversation about "dark matter", & the reasons for its theoretical existence. The reason I object is because I don't by into the idea of curved space. I've seen no evidence that space is anything but just that. Space. The currently accepted likelyhood is that everything is in motion. Since, as far as we know, all objects affect all others in any kind of gravitational proximity, & maybe beyond, I see no necessity for an intermidiate mass. There's all kinds of junk passing through space, from the most minute subatomic particles to the largest black holes. But trying to prove the assumption that any of it has the same properties as any of the rest of it just seems like a fool's errand to me. We just don't know what we're looking at yet, & we're trying to measure the motion without knowing what's affecting what & by what degree. I see way too much hubris in the sciences, & I think it gets in the way.

[evilernie]

This again has to do with 2 dimensional and 3 dimensional figure. If you depth dimension is close to zero. This is what essentially happens when you zoomed in. The relative depth compared to a whole sphere is enormous, which become a 2 dimension figure. Since the distortion of depth was minimal, the rule of "2D" works.