Evidence Points to the Detection of Dark Matter

[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

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.............

[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.

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.

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.