Evidence Points to the Detection of Dark Matter

[trish]

http://www.guardian.co.uk/science/2009/dec/17/dark-matter-detected

[BrendaQG]

Right now the media is over hyping this.


Dan Bauer, head of the Cryogenic Dark Matter Search (CDMS), said the group had spotted two particles with all the expected characteristics of dark matter. There is a one in four chance that the result is due to some other effect in the underground detectors, Bauer told a seminar at the Fermi National Accelerator Laboratory, near Chicago.

A 1/4 chance that this is some other random effect is as good as not having a discovery at all. At Fermilab the scientist will not say they have detected the particle until they have eliminated all the uncertainty out to 6 standard deviations. In plain language, a lot less than a 1/4 chance of random error. This is as good as no detection at all.

In short I agree with the comments in the comment thread. This is a statistically insignificant measurement.

In terms appropriate for Hung Angels. It's like saying that a tranny who's non-functional 1/4 of the time is 100% guaranteed functional.

[El Nino]

Cool article, Trish. Thanks for posting. If it does turn out a positive result, this is an epic scientific discovery. I wonder what "it" is exactly?? Can it even be explained using current vocabulary? I also am curious as to why the detection experiments were carried out at the bottom of a mine? Is it because there are fewer molecular compounds present in the air? And if Dark Matter is down there, does it also pervade everywhere on this planet? Hmmm, all so very interesting.

[hippifried]

For 80 years, it has eluded the finest minds in science. But tonight it appeared that the hunt may be over for dark matter, the mysterious and invisible substance that accounts for three-quarters of the mass of the universe.
So... If nobody's ever actually found any of this stuff before, how do they know it makes up 3/4 of the mass of the universe? Sounds more like hubris than science.

[BrendaQG]

Cool article, Trish. Thanks for posting. If it does turn out a positive result, this is an epic scientific discovery. I wonder what "it" is exactly?? Can it even be expained using current vocabulary? I also am curious as to why the detection experiments were carried out at the botom of a mine? Is it because there are fewer molecular compounds present in the air? And if Dark Matter is down there, does it also pervade everywhere on this planet? Hmmm, all so very interesting.

We don't really know. The type of search that was being done was looking for so called "weakly interacting massive particles" or WIMPS. These WIMPS were supposed to only interact by gravity, and by the weak atomic force. Essentially the only way they could interact with normal matter is by directly hitting it, dead bang on the nucleus.

The detectors were large tanks filled with fluid and lined with very sensitive light sensors. When a WIMP hits a atom in the fluid it would release a flash of light. Until now these flashes could not be attributed to WIMPS.

Supposedly there is much more dark matter in the universe than there is normal matter. In turn there is more dark energy than either normal matter, or dark matter. It must pervade everywhere and be all around us.

It has taken decades of operating these experiments to get even a marginal signal, if it takes decades to detect two more possible particles; then I think scientist should reconsider how much dark matter there is, if any. This observation needs to be replicated by another group of scientist in order to be validated.

It was originally proposed to balance our observations of the universe with Einstein's theory of general relativity.

[El Nino]

Mathematics, Hippi.

[BrendaQG]

For 80 years, it has eluded the finest minds in science. But tonight it appeared that the hunt may be over for dark matter, the mysterious and invisible substance that accounts for three-quarters of the mass of the universe.
So... If nobody's ever actually found any of this stuff before, how do they know it makes up 3/4 of the mass of the universe? Sounds more like hubris than science.

Exactly!

I said in a colloquium I spoke at a while back that , if there were as much dark matter as they say we could just about flap our arms and fly through it.

The longer the interval between supposed detections is the less of it there must be.

As for the timing of this kind of thing. Follow the money. Cuts mark 'sad day for British science' (http://www.guardian.co.uk/global/2009/dec/16/science-funding-cuts-stfc-physics-studentships) "Researchers criticise government U-turn as major projects are closed down and studentships slashed"

This is the inevitable result of a bad economy. Displaying results which can justify sitting in a hole and collecting a paycheck is good business.

[El Nino]

Thanks for the reply, Brenda. I was aware of the popular theory of D energy and D matter being present in the known universe but have not studied a whole lot about it as I am a cell biologist. Maybe it is kind of like an inter-dimensional entity or energy, it's source of which is undetectable. Anything is possible at this rate...

So you said that this was originally proposed to establish some equillibrium to "holes" Einstein's Theory of Relativity?

[BrendaQG]

So you said that this was originally proposed to establish some equillibrium to "holes" Einstein's Theory of Relativity?

Yep. General Relativity, the modern theory of gravity, by itself predicts the wrong distribution of velocities for stars in a galaxy. If the universe is filled with only normal matter and energy it gets the wrong results for a number of other observed cosmological facts.

The alternatives are much more complex theories of gravity. GR is already so complex that most physicist give up trying to understand it. In a class of 20 students only four finished the course in general relativity I took. There is a real desire to not have to create a more complex theory. If dark matter exist it makes life relatively simple.

The real straight talk on this is in Scientific American. "Dark Matter Researchers Still in the Dark as Underground Search Returns Uncertain Results (http://www.scientificamerican.com/article.cfm?id=dark-matter-cdms)"


Even so, Cooley and her colleagues calculated that the detectors could be expected to pick up approximately 0.5 WIMP-mimicking background events in the course of acquiring the newly unveiled CDMS-2 data set, a run that spanned 2007 and 2008. Even with a more cautious look at background sources, the CDMS team came to an estimated background contribution of 0.8 event.

I am not a particle physicist per se, I specialize in cosmology. But as I understand this a new detector being built will have an 80% chance of detecting a random event that will be indistinguishable from dark matter.

How the heck does such a mess get funded? While I must struggle just to get a student loan. :evil:

[trish]

While I was composing this Brenda already made most of the points I wanted to make. But I'll post it anyway.


So... If nobody's ever actually found any of this stuff before, how do they know it makes up 3/4 of the mass of the universe? Sounds more like hubris than science.
Brenda’s right to say we don’t know. Dark matter was hypothesized as a possible for a problem that arose in attempting to understand how galaxies “spin” around their centers. The velocity of a star’s orbit around galactic center depends on its distance to that center, but not in the way Newtonian gravity or general relativity predict … unless there was a significant amount of undetected matter yet to be found in each galaxy. Dark matter isn’t the only way around the observation/theory discrepancy. Another possibility is that general relativity is wrong on galactic scales. There have been a number of people promoting various “modified theories of gravity” in opposition to the dark matter hypothesis. Fewer scientists were willing to take this route because general relativity seems to be very well tested on the large scale. The dark matter hypothesis gained ground as observations of colliding galaxies seems to exhibit dynamical features that confirmed the DM hypothesis, and also as particle theorists were quick to provide possible candidates for what dark matter could be.

Newspaper articles that state scientific advances as facts (especially advances as speculative as this one) do in fact make the endeavor seem like an act of hubris. Most of my colleagues are in fact quite humble and quite willing to hedge their claims like I did with the title of this post, “Evidence Points to …”

[peggygee]

Fascinating and exciting stuff particularly these two points.


"Dark matter is what created the structure of the universe and is essentially what holds it together. When ordinary matter falls into lumps of dark matter it turns into galaxies, stars, planets and people. Without it, we wouldn't be here," Gilmore said.


Some dark matter particles could explain why ordinary matter is not radioactive, while others may help scientists understand why time – so far as we know – always runs forward.

By the by, did folks get a chance to read some of the comments on the article
at the site, it read like some typical HA responses. :shock:

[trish]

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). Measurements indicate the geometry of the universe is nearly zero, which is further evidence that there’s a lot of matter in the universe that is not seen. Indeed, according to general relativity (if it’s right) for the universe to have its present degree of flatness about 70% would have to be dark and only 30% the normal stuff that observation accounts for. Without this extra 70% there probably would not have been enough gravitational “impetus” to draw the uniformly distributed matter of the expanding universe together into clumps that eventually formed stars, galaxies and the folks who inhabit them. This is what I think the commentator is referring to when she says, “Dark matter is what created the structure of the universe and is essentially what holds it together.”

I don't know what DM has to say about the arrow of time. I always thought time ran backwards, i.e. the future runs toward us and recedes behind us as the past. :)

I only made this thread so that if it turns out to be true, you can say you heard at HungAngels first.

[scroller]

Ummm... stuff like the following always really bothers me about stories like this. Last line of the main article:


Detectors in the mine will be upgraded in the new year before the search for more dark matter continues, Bauer said.

So in other words, they're in need of a bunch of money for refurbishing to continue the project, and they just happened to have a (statistically insignificant) detection right as their current funding/equipment runs out. Fancy that.

Reminds me a of the research facility in Antarctica that announced discovering signs of life on a meteorite from Mars at exactly the time their funding ran out.

[hippifried]

Sorry Trish. More hubris. Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle. We can change that any time we please.

The truth is that we really don't know jack shit. We don't know how big or how old the universe is, or if there's even an age to measure. We don't know what gravity is. Einstein spent his whole life trying to define it & failed. We've never even seen a planet in another star system. There's mathematical evidence, based on the motions of some stars, so we just assume they're there.

I'm not saying that DM doesn't exist, but I don't see why it has to. Stars don't behave like mathematicle models because they're all different sizes & densities, & we can't really measure them accurately. Why can't there be open space? Who says there's a "structure" to the unicerse?

[trish]

You raise many interesting issues, hippiefried. More than can be adequately addressed in a single post. So I’ll just pick on one of two of your points.

I agree that mathematics is a mental construct. That is why mathematics is one of the few subjects in which practitioners actually prove results. In any particular mathematical field, a set of undefined terms (terms formally without meaning) are listed and a list of statements using those terms is also laid out for all to see. The statements in this list are called axioms (or in prior times postulates). The game is to define new terms from the undefined ones and derive other statements (called theorems) from the axioms using only logical inferences. In some modern geometries (Euclidean, Hyperbolic and Elliptic) the terms “point”, “line” and “plane” are entirely undefined. You can formally practice geometry without ever having in your head a notion of what they mean. The term “incident” is also an undefined term in modern geometry. However, a triangle is defined to be three points that are not incident to the same line. The points are called the “vertices” of the triangle. One of the axioms of Euclidean geometry is that given two points, there is one and only one line incident to both those points. If those two points are vertices of a triangle, the line to which they are both incident is called a side of the triangle. And so on (as Vonnegut would say). The entire subject makes no direct reference to points and lines a[s] ordinary language uses the terms and in that way geometry is entirely a mental construct.

In spherical geometry lines are in fact defined. They are the intersections of the sphere with planes that pass through the center of the sphere. We could call these spherical-lines, but in the context of spherical geometry they’re usually just referred to as lines. In spherical geometry the shortest route between two points lies along a spherical-line incident to both. Now just to help visualize things, imagine a sphere is given a reference frame like the one we use on Earth; there’s a north pole and a south pole, and equator and meridians. Imagine the zero degree meridian (through England). It intersects the equator at a ninety degree angle. So does the ninety degree west meridian (through Indiana). Together the two meridians and the equator determine (by definition) a spherical triangle. The sum of the interior angles is two[-hundred] and seventy degrees (not one and eighty). Yet there are still three-hundred and sixty degrees in a circle! All of this is of course still mathematical and therefore mental construction, though it’s all logically consistent even if sometimes surprising or counter-intuitive.

So what does this have to do with things like physics which purport to have something to do with the world beyond mental constructs; i.e. the real world the parlance of our times?

Well of course we use Euclidean geometry all the time in the real world. Instead of taking the term “line” to be meaningless, our everyday language assumes we know what lines are and how they behave. The assumption through the ages was that the things we call lines follow the axioms of Euclidean geometry. This is the geometry Newton ha[d] in mind when he penned the law of inertia. The law of inertia says the world-line (the graph of its position against time) of an object not acted upon by a force is a line. The world-lines of baseballs are [NOT] lines because baseballs are subject to the force gravity. The weird thing about gravity is that it’s universal. It doesn’t just act on particles with special properties or charges, it acts on everything. Einstein hypothesized an explanation. What if gravity isn’t a force but rather a manifestation of a different, more appropriate set of rules for the geometry of space-time; i.e. what if the assumption that the geometry that’s most applicable to “real-world” space and time isn’t Euclidean? Einstein kept the law of inertia, and just redefined a line in space-time to mean the path traced out by particle not acted upon by a force … and oh, gravity doesn’t count as a force. By this slight of hand, he essentially redefined the term line in space-time geometry so that Newton’s first law is automatically true and gravity is by definition a manifestation of geometry. This is the idea of general relativity (GR) in a nutshell. This simple recasting of the terms of physics might seem to be nothing but redefinition of terms. But this redefinition has consequences that differ from predictions of Newtonian physics. GR predicts th[at] clocks slow down as they near massive bodies, Newtonian physics makes no such prediction. Both GR and Newton predict that massive bodies will bend light rays th[at] pass near, but they make different quantitative predictions as to the amount of deflection. Newton predicts planets travel around the Sun in ellipses, though the orbits are perturbed in predictable ways if there’s more than one planet in the system. Einstein predicts the ellipse precesses even if there are no other planets perturbing it. Einstein predicts the gravitational lensing of images of distant galaxies by a massive galaxy between the observer and the objects of observation. What’s interesting is that all the observations we’ve made so far eliminate Newton['s] theory of gravity in favor of Einstein['s]. Does this mean we know GR is true? Of course not. But it is the best description we have so far. When we need or want to make decisions or venture answers to questions about astronomy, remaining consistent with GR is our current best course of action. This doesn’t prevent perfectly good scientist[s] from writing respected articles on modified gravity which contradict GR.

Back to triangles. Even though there are three-hundred and sixty degrees in a circle, GR predicts that near a massive object, like a star, if you form a triangle with three lasers beams the interior angles won’t add up to one-hundred and eighty degrees.

[edits in square brackets]

[BrendaQG]

What she said.

It's Geometry but it's not Euclidian, entry level geometry. The observed flatness of the universe only exist because there is just the right amount of matter-energy present.

Physics goes through phases where fudging becomes popular and acceptable. This last happened in the 1880-1920 time period. 40 years where something call Lumeniferious Aether was thought to fill all of space much the way Dark matter is now. Numerous numerous experiments had to fail to find it before the idea was abandoned. Even after Einstein's wrote about Special Relativity. He spent many more years as an unemployed physicist. Working in the patent office, or lecturing at various schools for very little money.

I predict that relatively soon dark matter will be considered the stupidest thing serious scientist ever considered.

[zlorg]

Sorry Trish. More hubris. Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle. We can change that any time we please.

The truth is that we really don't know jack shit. We don't know how big or how old the universe is, or if there's even an age to measure. We don't know what gravity is. Einstein spent his whole life trying to define it & failed. We've never even seen a planet in another star system. There's mathematical evidence, based on the motions of some stars, so we just assume they're there.

I'm not saying that DM doesn't exist, but I don't see why it has to. Stars don't behave like mathematicle models because they're all different sizes & densities, & we can't really measure them accurately. Why can't there be open space? Who says there's a "structure" to the unicerse?

There're a few point here, most of them already replied by trish, but I miss a few ones.

You said: "We don't know what gravity is. Einstein spent his whole life trying to define it & failed." and well, we also don't know what is time or charge or whatever. Science is usually bad at these questions, but better in other as "how does it behave?". By the way, the very best definition you can give is an operational one. i.e. that "time is this thing measured by clocks and that make one day different uppon another". And so on with charge and the rest, we can try another but is easy to mess up.

This rests at the basement of physics; you supose that exists a world (outside our heads), you supose that there some kind of regularity on it , that we can achieve some knowledge about it applying scientific method and that is useful to write this knowledge using maths.

The last statement sets up the relationship between mathematics and the natural sciences. Sure, mathematics are a mental construct. But when we're saying that a given triangle can, o can not, sum 180 degrees for all three angles we're not talking about mental constructs (at least if you don't want to push a very extreme philosophical POW), we're talking about a thing in the real world (whatever it is) and maths are used here as nothing more than a set of tools or language or similar.

And I cut here, because I'm going offtopic. Soory for this lengthy text.

[hippifried]

Relative to what?

If you bend a line, it becomes an arc. The triangle still has three angles, but you're not using straight lines anymore. We can do that without being next to a large mass. But even if the wind catches your tape measure between stakes, the measurement is still figured as a straight line so that Pythagoras can get you that square corner laid out on the ground.

Look Professor Trish; I'm hot for teacher & all that, but I'm not going to pretend to understand high mathematics. It just seems to me though, that we're merely talking about measurement systems that we've invented to explain what's already there & what's already happening, within our limitations. We do rocket science every day in our heads without using a single number. Think about all the calculus that goes into catching a fly ball: You need to judge triangulation, velosity, trajectory, gravity, mass, wind, your own speed to get to where you need to be & all it takes to get that speed, etc... All done in a split second without a thought to the math. We just grok. Common sense works whether there's any science to muddle the thought process or not.

[trish]

The triangle still has three angles, but you're not using straight lines anymore. We can do that without being next to a large mass.Near a massive object, such as a star, you can pick three points A, B and C. Then find the shortest route from A to B, the shortest route from B to C and the shortest route from C back to A. In ordinary parlance those routes are lines. The interior angles of the triangle just traced out fail to sum to 180 degrees. If to don’t want to call those shortest distance routes lines, that’s fine. The insight of general relativity is that the geometry obtained by thinking of these routes as lines is non-Euclidean and that this is the geometry that applies when one wishes to answer questions about the routes laser beams and material objects take passing near a massive object.


Relative to what?The word “relativity” in Special Relativity merely meant that the laws of physics should be the same regardless of the inertial frame used to express those laws. This implies there are no “preferred” inertial frames and consequently the values of certain measured quantities (such as velocity) are relative to the inertial frame of the observer. In special relativity though one could say that Nature prefers inertial frames and physicists had a problem with this from the very start. For one thing, how does one decide whether your own frame of reference is inertial or not? Einstein pursued general relativity in part because of these problems and in part because he saw in their solution a way toward a new theory of gravity. In general relativity the laws of physics are to be expressed in the same way in all frames of reference. If a law is not invariant under a switch in frame of reference, then it’s not really a law of physics. At least that’s what Einstein was advocating. A shortcut way of saying this: there are no frames of reference which Nature prefers over others.


We just grok. Common sense works whether there's any science to muddle the thought process or not.I have great respect for what we can grok but can’t seem to do with mathematics. But sometimes common sense is wrong in the last decimal place while physics gets that most recent decimal right. In fact that’s when the fun begins. Because then we get to reassess all our common sense notions of world and reformulate. It’s gets to be even more fun when science gets the next decimal wrong.


I'm hot for teacher & all thatAnd your presence on these boards is much appreciated. Whenever you post, if it's not right on the mark, then it's thought provoking.

[scroller]

Sorry Trish. More hubris. Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle. We can change that any time we please.

You don't know what the hell you're talking about, and this is just the first droplet of you demonstrating that. Non-Euclidean geometry has been well-established for over 200 years now. For example, here is a picture of a curved surface creating a non-180 degree triangle:

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

[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. :D

[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.

[scroller]

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.

And it's also a necessity if space is curved. If space is curved, then triangles don't add up to 180 degrees. There's simply no way to deny that, it's a proven mathematical fact.

[evilernie]

The best example I can give you is a beach ball. Think about why you cannot fold it flat neatly along the seams. The depth dimension distort rules that is meant only for a 2D world.

If you really create a 2d triangle, into a spherical earth you have to cross the mantle.

[evilernie]

If space is curved, then triangles don't add up to 180 degrees.
Triangle is a 2D object. By adding another dimension, it is no longer a triangle, hence would not add up to 180 degrees.

[hippifried]

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.

And it's also a necessity if space is curved. If space is curved, then triangles don't add up to 180 degrees. There's simply no way to deny that, it's a proven mathematical fact.
Well that's the point. I don't buy the curvature of space. Modern memetics have the scientific world talking about space as if it has substance in & of itself. Hence the "dark matter" theory. I've seen no evidence of that. Just a bunch of computer models trying to claim that space acts like water. Well, until it doesn't, & then you get a bunch of oh so smart professional students trying to invent new math to make it work. To me, a layman, it just looks like somebody trying to get around trying to explain the fact that they can't define gravity. But so what? We can't define electricity either, but you're reading this on a computer screen.

Mathematics is a measuring tool. If something doesn't add up, there's usually a simple explanation. I'm sure there's forces that we haven't discovered yet, or that we just can't calculate because we're missing something. But that's no reason to make shit up or pull theories out of your ass. The "dark matter' theory has been around for a while now (80 years or something?), & nobody's been able to lend it credence. This article strikes me as suspicious. I keep getting visualizations of an astronomical equivalent to Piltdown Man.

[evilernie]

I don't think they're inventing a different math. They're just doing representation or illustration. It's just a maybe - a what if scenario.

As for dark matter, what if it is true. Then one pound of water may not be one pound of water, i.e. one pound of water may not be y * (mass of H + 2x mass of O). There might be dark matter that we are not accounting for since only matter has mass.

Did their discovery prove it for me? No. But my mind is open to the possibility.

[hippifried]

Huh? A poud of water will still be a pint. There's always something else in it.

[Teydyn]

If I may interject, we are discussing two different objects: a 2D and a 3D.

But the shortest distance from the equator to the axis is through the sphere.
We are not talking about the "ball", we are talking about the surface of the sphere. Thats perfectly 2 dimensional.


To me, a layman
This sums it up quite good. You have no clue (neither do i).


Just a bunch of computer models trying to claim that space acts like water. Well, until it doesn't, & then you get a bunch of oh so smart professional students trying to invent new math to make it work.
Thats the way it works. Formulate a theory that explains what you can see. If it works it will be accepted as "true" till you find evidence it isnt. Thats the way it has always been.
Maybe you have heard of this maniac upstart trying to rewrite the laws of gravity? Crazy fellow, this einstein...


I'm sure there's forces that we haven't discovered yet, or that we just can't calculate because we're missing something. But that's no reason to make shit up or pull theories out of your ass.
So is it a thing we havent discovered yet or is it "made up" bullshit? You have no clue and the professionals neither. Till there is a thing that disproves the theory. As long as there is only evidence that fits into it, it can be considered true.

[hippifried]

The surface of the ball is part of the ball.

I never studied formal logic either, but I know faulty logic when I see it. You can't just keep piling theories on top of other theories without coming up with some kind of evidence to support the original premise. The premise I have trouble with is the one that says there's a texture to space. That's what gives birth to the "dark matter" theory, among others. I'm lobbyable. I can be convinced. I'm not a total cynic. Just show me something. Anything. So far, they're batting zero, & I have have serious doubts about this "discovery" in the mine shaft.

Math is consistent logic. In the end, the numbers still have to add up or there's a problem with the formula. Nobody wants to backtrack or start over, so ya just toss out another theory. If the premise is wrong to start with, none of it works. It's not really possible to prove a negative, but if you can't find evidence to support the premise, sooner or later you just have to abandon the search & admit that you're all wet.


Maybe you have heard of this maniac upstart trying to rewrite the laws of gravity? Crazy fellow, this einstein...Yeah, well... He failed.


So is it a thing we havent discovered yet or is it "made up" bullshit?How the hell should I know? Nobody else does, unless they're makintheshitup, & I wouldn't be in on the hoax. I just like Trish & enjoy yanking her chain. If I can formulate an unanswerable question in the meantime, all the better. That hasn't happened yet, but i'm having fun.

[evilernie]

http://landcover.usgs.gov/images/global_map.jpg

Ever wonder why global maps are drawn this way? Because you cannot flatten a sphere and expect the same dimension coming out of it.

Just because you don't know, you shouldn't call something bullshit. It's just because you don't know. Denying all science, especially basic geometry, by misstating concepts just denies you the possibility of accepting it.

There is NO conspiracy here. Science is very strict. That's why a lot of "theories" that we accept as truth are still considered theories. This includes your 180 degree triangles.

The dark matter concept is difficult to "prove" because they are not easily observable. That's why electrons are discovered before protons then neutrons. Without these discoveries, there wouldn't be electricity or nuclear power.

The article claimed "detection" could just be an attempt to fame, but maybe not. I just want to keep an open mind.

[scroller]

Well that's the point. I don't buy the curvature of space.

Well, no, earlier you were a denier of the logical fact that if space is curved, then triangles don't have 180 degrees. Are you now agreeing with that implication, or are you just "yanking chains"?


Sorry Trish. More hubris. Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle.

[hippifried]

???? What are you talking about? I don't care about spherical geometry at all. It has nothing to do with my argument, & I didn't bring it up. But if you want to get technical, the area of the curved triangle is still measured in squares, & the volume of the sphere that it's taken from is still measured in cubes. But it's all irrelevant. I take exception to the assumptions in this paragraph:
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). Measurements indicate the geometry of the universe is nearly zero, which is further evidence that there’s a lot of matter in the universe that is not seen. Indeed, according to general relativity (if it’s right) for the universe to have its present degree of flatness about 70% would have to be dark and only 30% the normal stuff that observation accounts for. Without this extra 70% there probably would not have been enough gravitational “impetus” to draw the uniformly distributed matter of the expanding universe together into clumps that eventually formed stars, galaxies and the folks who inhabit them. This is what I think the commentator is referring to when she says, “Dark matter is what created the structure of the universe and is essentially what holds it together.”(2nd page of this thread, 2nd post)& it's not just curvature. The biggest assumption of all is that we have any measurements of "the universe". Doesn't the idea that the the universe is 'held together' fly in the face of the idea of the 'expanding universe'? Why would there be a flatness, & where does the 70% figure come from? Etc...

As for "dark matter": There's probably all kinds of particulates speeding through space. I just find the idea that they have anything in common with each other a sort of giant leap of faith. Has it occured to anyone that the reason we can't detect it as "matter" is because the subatomic particles are miles apart? Just a thought.

So far, I haven't seen any actual evidence that the current math structures we have don't work on a galactic scale. Or any reason why scale would affect the math in the first place. What I see is predictive models that don't work because we just don't have enough data to go on, & currently don't have the ability to gather it through our observation techniques. Somebody says; "Oh look. XYZ Galaxy isn't behaving in accordance with my theoretical model. Let's change the rules." But the reality is that the forces at work in XYZ Galaxy are incalculable because we just don't have the ability to measure them.

[yosi]

the BIG BANG theory can also be defined as : A journy to our subconscious..................................

there is a black hole that frightens the shit out of us.
a black hole , that you know.............will be our end.

we also want a beginning , we ourselves were born sometime ago.
(have we been here before our birth? who knows.)

so we have another great theory called : the BIG BANG".

dark matter? what is that matter that keeps our body temprature the same for all humans? it doesn't have any scientific proof :wink:

we get this imformation from lights coming of other galaxies , some of them 7.5 billion years of light ago, it's also obvious that during these 7.5 billion years of light those lights on their way to us ,have been in other galaxies , and were bent alittle because of very strong gravitation stars on the way .
you know , when we look at the stars , we actualy see lights that reached our sights , each light from a different time , quite confusing , isn't it?


all of this come from : our A journy to our subconscious..................................

reach for the stars and see inside yourself............. 8)

[BrendaQG]

@ Hippifried - and any other totally perplexed people.

Trish gave a good explaination of all of this. Allow me to oversimplify by allot.

Think of this physically and non-mathematically. Think of a trampoline. A common way curvature of space is demonstrated is to show such a surface with a bowling ball on it. Now try to envision just the right distribution of mass on the trampoline to cause it to sag without denting the strechy fabric. The trampoline stays flat, but the springs at the edges are displaced. It's hard to imagine how difficult it would be to attain such a state by accident. This is the problem of the flatness of the universe.

To be more precise in General Relativity the curvature of space time is mathematically defined by taking derivatives of the elements of the metric.

The metric is a mathematical function (usually written as a four by four matrix) which determines the distance between two points.

Everyone who got to algebra and geometry in school knows this formula

Distance between points = √(x^2+y^2+z^2). The metric is not explicilty written there. For this three dimensional space.

100
010
001

In a four dimensional space-time which is curved the metric could be like.

-1 0 0 0
0 r^2 0 0
0 0 r^2 0
0 0 0 r

If you write the distance formula in such a space-time you see that where you are in space-time now effects the distance between two points. Which can be shown leads to the distortion of familiar triangles, circles, squares etc.

This is more than a mathematical construct. Space-time really can bend and is curved near large masses. Einstein's General Relativity requires it, and various experimental test prove it. (Such as the observation that light, which only travels on "straight" lines can be bent by the gravity of large masses.

(I just noticed I'm approaching the 2000 post mark. )

[scroller]

???? What are you talking about? I don't care about spherical geometry at all. It has nothing to do with my argument, & I didn't bring it up. Blah blah blah nonsense nonsense...

You said this:


Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle.

This is factually incorrect. Curvature will change how many degrees are in a triangle. There's no point in even reading anything else you write if you can't get fairly simple facts that have been known for hundreds of years correct.

[hippifried]

@ Hippifried - and any other totally perplexed people.

Trish gave a good explaination of all of this. Allow me to oversimplify by allot.

Think of this physically and non-mathematically. Think of a trampoline. A common way curvature of space is demonstrated is to show such a surface with a bowling ball on it. Now try to envision just the right distribution of mass on the trampoline to cause it to sag without denting the strechy fabric. The trampoline stays flat, but the springs at the edges are displaced. It's hard to imagine how difficult it would be to attain such a state by accident. This is the problem of the flatness of the universe.

To be more precise in General Relativity the curvature of space time is mathematically defined by taking derivatives of the elements of the metric.

The metric is a mathematical function (usually written as a four by four matrix) which determines the distance between two points.

Everyone who got to algebra and geometry in school knows this formula

Distance between points = √(x^2+y^2+z^2). The metric is not explicilty written there. For this three dimensional space.

100
010
001

In a four dimensional space-time which is curved the metric could be like.

-1 0 0 0
0 r^2 0 0
0 0 r^2 0
0 0 0 r

If you write the distance formula in such a space-time you see that where you are in space-time now effects the distance between two points. Which can be shown leads to the distortion of familiar triangles, circles, squares etc.

This is more than a mathematical construct. Space-time really can bend and is curved near large masses. Einstein's General Relativity requires it, and various experimental test prove it. (Such as the observation that light, which only travels on "straight" lines can be bent by the gravity of large masses.

(I just noticed I'm approaching the 2000 post mark. )Oh I see... So that's what oversimplification looks like. :lol:

Look! I'm really sorry I focused on the triangle thingie. I was being a smartass, but apparently that didn't work. Mea culpa etc... It really is irrelevant, & I took it out of context. The point that I failed miserably in expressing is that there's really no curvature of space. Space is just that. Space. The only curvature is the motion of the stuff careening through it, including us. I'm really not perplexed by the universe. I'm just perplexed by people who think they aren't, or think they can cipher their way out of perplexity with a bunch of "timeses & gozintas".

Oh & by the way: Time is also an intellectual construct. There's a continuum, & there's our invention of time as a tool to measure speed & distance. We can track the past, & even see it over distance due to the speed limitation of light. We can predict the future, sometimes accurately, due to our knowlege of the past. We only exist in the present. Everything else is in our head.

P.S. 2000 posts, huh? Congratulations on your upcoming knighthood into geekhood. :wink:


You said this:

hippifried wrote:
Mathematics is an intellectual construct, & curvature doesn't change how many degrees are in a triangle as long as we count 360 in a circle.


This is factually incorrect. Curvature will change how many degrees are in a triangle. There's no point in even reading anything else you write if you can't get fairly simple facts that have been known for hundreds of years correct. Yes I did. I'm so sorry that you missed the point with your fixation on 3 dimentional measurements, which of course, cannot include triangles. Of course, being the layman that I am & all, I keep making the distinction between an arc & a line.

Hey. So far, I've tried real hard to keep my part of this conversation light & polite. If you can't do the same, leave me out of your attempts at smugness. I'll respond in kind.

[scroller]

I'm so sorry that you missed the point with your fixation on 3 dimentional measurements, which of course, cannot include triangles. Of course, being the layman that I am & all, I keep making the distinction between an arc & a line.

All of this is factually incorrect. This discussion is about curved 2D space, not 3D space. I'm glad that I saved myself the time from reading anything else of yours, when you're unwilling to get even your first, most simple statements of fact correct.

[trish]

Modern memetics have the scientific world talking about space as if it has substance in & of itself.
This may be true of “memetics” but Einstein’s theory of gravity (GR) maintains the opposite. Einstein eliminated any absolute or metaphysical notion of space from the science of his time. To insist that real lines are straight and real space is Euclidean and the interior angles in real triangles sum to 180 is to maintain that space is a thing that has these properties in and of itself. Since the nineteenth century mathematicians have understood that the postulates of Euclidean geometry (or any geometry) are neither true nor false until one interprets the undefined terms. In my admittedly quick and dirty explication GR on page two of this thread, I put the word “real” in quotes because the interpretation I gave there of the word “line” in a space-time chart was an operational definition, not a metaphysical definition. To repeat that definition, lines in space-time charts are the trajectories of particles which are not acted upon by external forces, under the agreement that, for the purposes of this definition, gravity will not be counted as a force. Einstein defined them the same way. A few more undefined terms from geometry needed to be operationally interpreted before his task was complete; i.e. Einstein defined the metric so that it corresponded in a proportionate way to the matter and energy within the region of space-time under consideration. In this way Einstein overlaid space-time, a completely mere mental construct, with a man-made, operationally defined geometry. There is no need to assume space-time actually exists, or that space actually exists in and of itself … whatever that means. Geometry is used merely as a language. What Einstein expressed in that language may be true or false, but he said nothing about absolute lines or metaphysical space-time but about the operational interpretations of the undefined terms of geometry. That is why his theory is subject to empirical testing and has held up nicely for nearly a century now. It doesn’t explain gravity and it isn’t meant to explain it, except in terms of other things that are left unexplained. But it is an elegant theory and no other has yet equaled in predictive power.


Space is just that. Space. The only curvature is the motion of the stuff careening through it, including us. I'm really not perplexed by the universe.There are solid geometries in which there are no pairs of parallel lines and in which every line has finite length. Pick a point P and a line L through P and start walking along L and eventually you will wind back up a P again. Perhaps curvature is a poor choice of words for it (though I don’t think so) but geometers like say these geometries exhibit curvature. In these examples the curvature (I think, perhaps Brenda can correct me if I misremember) is defined to be inversely proportional to the cube of the line’s length. The inspiration for the definition is that the line is LIKE a circle and it’s length is LIKE a circumference which in Euclidean geometry would be proportional to it’s radius. The curvature of an ordinary circle is 1/R, the curvature of a sphere is 1/R squared and the curvature of a 3-sphere is 1/R cubed.

I’m not going out of my way to defend the theory of dark matter. It’s a hypothesis which can account for the angular velocities of stellar orbits within spiral galaxies. For the hypothesis to be successful at such an accounting it has to have a spherically symmetric distribution around the galactic center, it has to be of a certain density and a certain size. It’s has to be a lot like a neutrino, except more massive. At the moment it’s a nose ahead of the competition, but I haven’t any money on the race.

Unfortunately, I have to leave this conversation again for a few days. Don’t expect to be around till after Christmas sometime. So happy winter solstice everyone.

[hippifried]

You're wrong, scroller. This discussion was never anything about "2D space", because there's no such thing.

[hippifried]

Oh hi Trish. Didn't see you sneak in yesterday.

Actually, I think we're more in agreement on all this insanity than not. I'm never going to learn the math. No need. I have you. I'm not a linguist. I understand the concepts though. Math is an abstract. A tool to measure the reality surrounding us. It's not the reality itself. We measure everything with straight lines. Calculus is just shortcuts. An arc is a radius. A straight line. To distort the arc, we just have to shorten or lenghten the radius. If there's a formula or formulae to avoid constant remeasurement of the straight line, that's a shortcut. 3D just adds more lines & makes for a whole lot more remeasurement, unless there's a shortcut in the form of a calculus. Those calculi are the tools of the scientist.

Why isn't it neutrinos? They change flavor as they pass through matter. With the 4 or 5 quintillion that pass through each one of us daily, & the extrapolation of just that little bit to some kind of google number that's out there, it only makes sense that there's going to be collisions & some will stick to make them bigger & more massive &/or dense. Isn't that the basic hypothesis of how space dust becomes planets etc...? We're just talking scale. Everything has mass, even light. Isn't that the theory behind black holes? Extreme mass & density with gravitational force so intense that visible light can't escape it? Gotta have mass for gravity, right? We have trouble measuring the miniscule amount of mass per neutrino, but when you add it all up, that's a lot of mass. It just lacks density.

I'm pretty good with summaries. It's not necessary to explain all the methodology as long as the conclusion makes sense. I think it's the idiomatic linguistics that cause misunderstandings. Mathematics is a craft, as are all the sciences. Craftsmen (a gender neutral term) tend to slip into their own jargon, where word definitions change from discipline to discipline. It works well within the craft where it's universally understood, but not so well when conversing with laity. I'm thinking a new craft or sub-craft is due that would translate craft specific lingo back to common language without having to backtrack to elementary levels or leave out details. That could avoid a lot of confusion & frustration all around. Maybe an automated database where you just punch in who's talking.

Hope you have a good whatever holiday you celebrate, & that Santa treats you right. :D