[sigurdV]

JMJones0424, on 18 January 2012 - 07:36 PM, said:

If I may, I'd like to recap what I've learned from this thread in my words. Perhaps I am sympathetic to sigurd's question, as it arises naturally from a lack of understanding of what dark energy is. I do not agree that this thread belongs in silly claims, though it may better fit in the Q&A forum

My paraphrasing of the question raised in this thread is:
What observational evidence do we have that rules out centrifugal force from a rotating universe as an explanation of accelerating expansion of the universe?
After my own aimless fumblings, two answers were posted that answers this question, at least to my satisfaction.

NOTE: It is my understanding that centrifugal force is indeed the correct name for the force that sigurd is asking about, since he is asking about a rotating frame. HyperPhysics explains it better than I could, and offers us this easy to understand illustration.


NOTE2: It is not at all clear to me that universal rotation necessarily means that the universe must be rotating "in" something else.

Rotation of the universe does not adequately explain the accelerating expansion of the universe because:
1.) There is no observed axis of rotation. We observe accelerated expansion in every direction, not on a plane, and Euler's theorem shows that there cannot be numerous axes of rotation.
2.) We would need to either be at the center of rotation (which places us at a privileged location in the universe and is unacceptable for philosophical reasons) or we would need to be able to translate rotation so that every observer can see himself as the center of rotation (which can only be done with an even number of spatial dimensions).
3.) Conservation of angular momentum shows that if the universe were both rotating and expanding, the angular velocity would be slowing down, therefore the centrifugal force causing expansion would be decreasing. We observe increasing acceleration, so centrifugal force from a rotating universe still requires additional "dark energy" to explain observations, even if we ignore points 1 & 2.

Have I correctly summed up the answers given to the question as I have worded it?

sV: I always enjoy tour entries, but im suddenly wary...
On the Euler effect:
 
So the axis of a spinning object cannot be rotated, 
no matter how strong force is applied? 
Or does the second rotation affect the rotation of the first?
What happens if a stronger force is applied at the same time on both spin and axis.

On Rotation:

I Know of no object having nothing to rotate in, does anyone?
Does anyone scientifically think that our universe is such an object?
Then please show me the proof that there is nothing outside it!

AGAIN:

Unless im silly or mistaken:
1 It is a scientific fact that all observed rotating objects rotate in something.
2 Therefore: If the universe rotates then there is something for it to rotate in!

[SextonBlake]

All objects in space from the size of small moons upwards, rotate. It seems to be a property of mass when not held in place by another gravitational field. They are in a vacuum and not in "something".

Similarly, the universe itself could rotate solely because of the mass in it.

[JMJones0424]

sigurdV, on 21 January 2012 - 05:28 PM, said:

On the Euler effect: So the axis of a spinning object cannot be rotated, no matter how strong force is applied? Or does the second rotation affect the rotation of the first?What happens if a stronger force is applied at the same time on both spin and axis.

Answered by coldcreation here:

coldcreation, on 14 January 2012 - 04:15 AM, said:

According to Euler's rotation theorem, simultaneous rotation around more than one axis at the same time is impossible. If two rotations are forced at the same time, a new axis of rotation will appear.

sigurdV, on 21 January 2012 - 05:28 PM, said:

On Rotation: I Know of no object having nothing to rotate in, does anyone?
Does anyone scientifically think that our universe is such an object?
Then please show me the proof that there is nothing outside it!

AGAIN: Unless im silly or mistaken:1 It is a scientific fact that all observed rotating objects rotate in something.2 Therefore: If the universe rotates then there is something for it to rotate in!

Is having something to rotate in a necessary condition of rotation?

[sigurdV]

JMJones0424, on 04 February 2012 - 03:20 PM, said:

1 Answered by coldcreation here:
2 Is having something to rotate in a necessary condition of rotation?

1 I agree on a new axis of rotation...
Just being Silly: Let the force go on and on...

What is the outside story? (How will the axis move)
(A)Can force be so applied so the axis once,and only once, takes all
possible positions before it returns to origin?

And the inside story?
What force(s) will someone inside feel?
We are appliyng two forces...
(B)Can a third force be applied in a different direction?

2 I will swallow the bait

Yes...
I mean Yes Indeed Sir,
and: Yes Again! (For Emphasis!)

Now, please, tell us all about your "rotating object having no environment"...

(Or admit there is no such object.)

3 If somebody previously had told me I would find a spinning top interesting then...
Oh hell...Lets instantly teleport it to intergalactic space!
Ops! Now its a flying saucer!
The wolfling is not in the driver seat,he is glued to the wall and the roof...
"What more could happen to me" he seems to think?
To sum up: We are watching an observer in an approximately
two dimensional object spinning in a three dimensional environment,
and now we plan to add to his misery...
But we seem to be out of rotational possibilities, dont we?

Can we rotate his time axis?
Watch out! A black Hole is coming by...

The End of this Silly Story?
What do you think Mr Jones?
Only You! can make this...eh...make sense?

PS Read the silly continuation of the story in sigurdV posts.

[JMJones0424]

For 1 and 3, I do not follow. I don't have the time or desire to decode and follow your story.

sigurdV, on 06 February 2012 - 10:54 AM, said:

2 I will swallow the bait

Yes...
I mean Yes Indeed Sir,
and: Yes Again! (For Emphasis!)

Now, please, tell us all about your "rotating object having no environment"...

(Or admit there is no such object.)

Funny, I was going to ask the same of you. You previously stated:
1 It is a scientific fact that all observed rotating objects rotate in something.
2 Therefore: If the universe rotates then there is something for it to rotate in!

Yet you have not shown that having something to rotate in is a necessary condition for rotation. If the universe consisted of only a spaceship containing us, we would still be able to use the equations for centrifugal force and coriolis effect to determine if we were rotating or not. Statement one is irrelevant and statement two can only be valid if having something to rotate in is a necessary condition of rotation. I know of no reason to say that is true, but I admit I never really understood what was meant by the Mach principle. You seemed sure of yourself, which is why I asked.

[sigurdV]

JMJones0424, on 06 February 2012 - 03:41 PM, said:

For 1 and 3, I do not follow. I don't have the time or desire to decode and follow your story.

Funny, I was going to ask the same of you. You previously stated:
1 It is a scientific fact that all observed rotating objects rotate in something.
2 Therefore: If the universe rotates then there is something for it to rotate in!

Yet you have not shown that having something to rotate in is a necessary condition for rotation. If the universe consisted of only a spaceship containing us, we would still be able to use the equations for centrifugal force and coriolis effect to determine if we were rotating or not. Statement one is irrelevant and statement two can only be valid if having something to rotate in is a necessary condition of rotation. I know of no reason to say that is true, but I admit I never really understood what was meant by the Mach principle. You seemed sure of yourself, which is why I asked.

1 and 3 Our conversation does not depend on my story(which when/if finished needs no decoding),but at the moment it is a thought example , since black holes effect time: Perhaps they rotate it? An insider would not notice any difference in his "centrifugally stretched time" but an outsider thinks he moves slower and slower (never entering the hole), and he think its the other way around.
Also the story of an n-dimensional object rotating in a n+1 dimensional environment,needs looking into.(Still only two rotations possible?)

2 However: One can only observe an object having no environment (to rotate in) from its inside, and Im not sure we can trust our equations. Would it be the first time we were misled by equations given input they were not designed for?
Suppose we are surviving inside a black hole and our measurements and equations tell us its spinning then we are prevented from confirming the result by checking from outside.Here our memories make a difference,but if they are not there? As when you say "suppose all there is (for us insiders you dont limit it to) is a space ship with no (accessible to insiders) outside".

So far all examples of rotating objects has an environment to rotate in but its an induction step involved from getting from there to the opinion that all objects has an environment.(or that all environments have their content)

What makes us believe universes are the exception to the norm? Tradition? Our equations?

I think I(and perhaps also Mach) always assumed/interpreted rotation to be a relative concept: Rotation is such and such relation between an x and a y. THEN the existence of both is necessary.

Perhaps its funny: Wasnt I cocky since I suspected You had something up Your Sleeve! Stalemate then?

Im inclining towards the opinion that no real isolation (excepting death?) exists: Real objects have both inside and outside.Virtual (unreal)objects miss one or the other.
Seen from that view there IS neither a universe nor a point particle.

I think the germ to the idea was when i tried to "creep into the angle" realising that a diminishment of myself in the march towards the endpoint only led to an enlargement of the angle always leaving the point equally far away.

[coldcreation]

sigurdV, on 06 February 2012 - 07:09 PM, said:

[snip]
So far all examples of rotating objects has an environment to rotate in but its an induction step involved from getting from there to the opinion that all objects has an environment.(or that all environments have their content)

What makes us believe universes are the exception to the norm? Tradition? Our equations?

Having something to rotate in is not a necessary condition of rotation.
Euler's rotation theorem works for rigid bodies rotating in space, as it does for coordinate systems (what you call "environment").

In physics, according to the theory of special relativity, the Lorentz transformation describes how two observers' varying measurements of space and time can be converted into each other's frames of reference.

In a homogeneous space, the Lorentz transformation is a linear transformation. It may include a rotation of space. Since relativity postulates that the speed of light is the same for all observers, the Lorentz transformation must preserve the spacetime interval between any two events in Minkowski space. The Lorentz transformation describes transformations in which the spacetime event at the origin is fixed. These can be considered as a hyperbolic rotation of Minkowski space. The more general set of transformations that also includes translations is called the Poincaré group.

Special relativity can be considered to operate in a four dimensional space (spacetime), three spatial dimensions and one temporal. This space is linear and the four dimensional rotations (called Lorentz transformations) have practical physical interpretations. If a rotation is in the three space dimensions, i.e. about a plane that is in space, then this rotation is the same as a spatial rotation in three dimensions. But a simple rotation about a plane spanned by a space dimension and a time dimension is a "boost", a transformation between two different reference frames that together with other properties of spacetime determines the relativistic relationship between the frames. The set of these rotations forms the Lorentz group. The restricted Lorentz group is generated by ordinary spatial rotations and Lorentz boosts (which can be thought of as hyperbolic rotations in a plane that includes a time-like direction.



A visualisation of the Lorentz transformation.
Only one space coordinate is considered.
The thin solid lines crossing at right angles depict the time and distance coordinates of an observer at rest with respect to that frame;
the skewed solid straight lines depict the coordinate grid of an observer moving with respect to that same frame. (Source).




All rotations are described relative to a particular frame of reference. In two-dimensional space there is only one plane of rotation, the plane of the space itself. In a Cartesian coordinate system it is the Cartesian plane, in complex numbers it is the complex plane. Any rotation therefore is of the whole plane, i.e. of the space, keeping only the origin fixed. (See Euler's formula). In three-dimensional space there are an infinite number of planes of rotation, only one of which is involved in any given rotation.


EDIT> You may also be interested in reading this article about rotating reference frames, which discusses phenomena such as:

Quote

1 Fictitious forces
2 Relating rotating frames to stationary frames
2.1 Relation between positions in the two frames
2.2 Time derivatives in the two frames
2.3 Relation between velocities in the two frames
2.4 Relation between accelerations in the two frames
2.5 Newton's second law in the two frames
3 Centrifugal force
4 Coriolis effect
5 Euler force
6 References and notes
7 See also
8 External links

CC

[sigurdV]

Polite! Coherent! Informative! Good Entry Mr Cold ...I will read it. Hey youre adding information!

1 "Having something to rotate in is not a necessary condition of rotation."
That should depend on the definition of rotation.

I note that rotation needs a center.
Lacking that, I think "translation" is the term.

2 "coordinate systems (what you call "environment").
"Frame" is sort of "taken" by relativity...

3 Your essay as a whole has slight biase towards tecnical detail,note that the name "Einstein" is missing. Its nothing really wrong, youre familiar with the tool: The Mathematics of Relativity,and I welcome it in here: The Silly Forum

An analogy: We Swedes separate Musicians into the sets Musicants and note-icians, The first group May read poorly But perform strongly and has the best contact with the audience, the other group reads excellently (and a vista) but lacks intensity and interpretation, and is better inside the orchestra than in front of it... So Einstein is a Musicant and Minkowski a note-ician.

(Before i go on ill admit i have a grudge against Minkowski)

Looking at Mr Einstein we find him using the "Thought Experiment",
a tool, note-icians handles poorly
(If at all... why make a model when one can read the maths directly?).
The "Train"and the "Elevator" comes into mind...

In here, trying to understand the concept of rotation, I make a thought experiment...
Not that I think I am an Einstein,its because i want to understand!

So let us watch an object in intergalactic space.
In it an observator is pressed aginst the wall and roof,
and he thinks the music on the radio is slowing down...

Can his experiences be caused by rotation?

[sigurdV]

by:Greg Bernhardt
Can we tell whether the universe is rotating?

If you believe wholeheartedly in Mach's principle, then there is no way to test empirically for rotation of the universe as a whole, since there is nothing else for it to be rotating relative to. However, general relativity is not very Machian, and it offers a variety of ways in which an observer inside a sealed laboratory can detect whether the lab is rotating. For example, she can observe the motion of a gyroscope, or measure whether the Sagnac effect is zero. There are alternative theories of gravity, such as Brans-Dicke gravity, that are more Machian than GR,[Brans 1961] and in these theories there is probably no meaningful sense in which the universe could rotate. However, solar-system tests[Bertotti 2003] rule out any significant deviations from GR of the type predicted by Brans-Dicke gravity, so that it appears that the universe really is as non-Machian as GR says it is.

It is therefore possible according to general relativity to have cosmologies in which the universe is rotating. Historically, one of the earliest cosmological solutions to the Einstein field equations to be discovered was the Gödel metric, which rotates and has closed timelike curves. If we lived in a rotating universe such Gödel's example, the rate of rotation would have to be expressed in terms of angular velocity, not angular momentum. Angular velocity is what is measured by a gyroscope or the Sagnac effect, and GR doesn't even have a definition of angular momentum that applies to cosmological spacetimes.

A rotating universe does not have to have a center of rotation, and it can be homogeneous. In other words, we could determine a direction in the sky and say that the universe was rotating counterclockwise at a certain rate about the line connecting us to that point on the celestial sphere. However, aliens living somewhere else in the universe could do the same thing. Their line would be parallel to ours, but there would be no way to tell whether one such line was the real center of rotation.

To find out whether the universe is rotating, in principle the most straightforward test is to watch the motion of a gyroscope relative to the distant galaxies. If it rotates at an angular velocity -ω relative to them, then the universe is rotating at angular velocity ω. In practice, we do not have mechanical gyroscopes with small enough random and systematic errors to put a very low limit on ω. However, we can use the entire solar system as a kind of gyroscope. Solar-system observations put a model-independent upper limit of 10-7 radians/year on the rotation,[Clemence 1957] which is an order of magnitude too lax to rule out the Gödel metric.

A rotating universe must have a certain axis of rotation, so it must have a particular type of anisotropy that picks out a certain preferred direction. We can therefore look at the cosmic microwave background and see whether its anisotropy contains a preferred axis.[Collins 1973] Such observations impose a limit that is tighter than provided by solar-system measurements (perhaps 10-9 rad/yr[Su 2009] or 10-15 rad/yr[Barrow 1985]), but such limits are model-dependent.

Because all of the present observations are consistent with zero rotational velocity, it is not possible to attribute any prominent cosmological role to rotation. Centrifugal forces cannot contribute significantly to cosmological expansion, or to the way your head feels when you're hung over.

Brans and Dicke, "Mach's principle and a relativistic theory of gravitation," Phys. Rev. 124 (1961) 925, http://loyno.edu/~brans/ST-history/
Bertotti, Iess, and Tortora, "A test of general relativity using radio links with the Cassini spacecraft," Nature 425 (2003) 374
Clemence, "Astronomical time," Rev. Mod. Phys. Vol. 29 (1957) 2
Collins and Hawking, "The rotation and distortion of the universe," Mon. Not. R. Astr. Soc. 162 (1973) 307
Hawking, "On the rotation of the universe," Mon. Not. R. Astr. Soc. 142 (1969) 529
Barrow, Juszkiewicz, and Sonoda, "Universal rotation: how large can it be?," Mon. Not. R. Astr. Soc. 213 (1985) 917, http://adsabs.harvar...MNRAS.213..917B
Su and Chu, "Is the universe rotating?," 2009, http://arxiv.org/abs/0902.4575

[mpc755]

sigurdV, on 10 March 2012 - 09:31 AM, said:

by:Greg Bernhardt
Can we tell whether the universe is rotating?

Yes, the Universe spins about a preferred axis.

'Was the universe born spinning?'
http://physicsworld....icle/news/46688

"The universe was born spinning and continues to do so around a preferred axis"

The Universe spins around a preferred axis because the Universe is, or the local Universe we exist in is in, a jet; analogous to the polar jet of a black hole.

'Mysterious Cosmic 'Dark Flow' Tracked Deeper into Universe'
http://www.nasa.gov/...010/10-023.html

'The clusters appear to be moving along a line extending from our solar system toward Centaurus/Hydra, but the direction of this motion is less certain. Evidence indicates that the clusters are headed outward along this path, away from Earth, but the team cannot yet rule out the opposite flow. "We detect motion along this axis, but right now our data cannot state as strongly as we'd like whether the clusters are coming or going," Kashlinsky said.'

The clusters are headed along this path because the Universe is, or the local Universe we exist in is in, a jet.

The following is an image analogous of the Universal jet.

http://aether.lbl.gov/image_all.html

The reason for the 'expansion' of the universe is the continual emission of aether into the Universal jet. Three dimensional space associated with the Universe itself is not expanding. What we see in our telescopes is the matter associated with the Universe moving outward and away from the Universal jet emission point. In the image above, '1st Stars' is where the increase in pressure caused by the aether continually being emitted into the Universal jet causes the aether to condense into matter.

The following is an image analogous of the Universe, or the local Universe, we exist in.

http://www.astro.ucl...s/BlackHole.jpg

The following is an image analogous of the Universal spin.

http://i.space.com/i....jpg?1292259454

Dark energy is the effects caused by the aether emitted into the Universal jet.

The analogy is objects floating down a river. At the mouth of the river most of the objects move away from one another.

It's not the Big Bang; it's the Big Ongoing.

This post has been edited by mpc755: 10 March 2012 - 09:59 AM

[Little Bang]

What if, since most of this thread is about what if-ing anyway, the matter of the Universe was created from the collision of two like electric fields. Those expanding electric fields could be our dark energy?

[mpc755]

Little Bang, on 10 March 2012 - 03:03 PM, said:

What if, since most of this thread is about what if-ing anyway, the matter of the Universe was created from the collision of two like electric fields. Those expanding electric fields could be our dark energy?

The Universe is, or the local Universe we exist in is in, a jet; analogous to the polar jet of a black hole.

Dark energy is aether emitted into the Universal jet.

[Don Blazys]

For all we know, our region or sector, which we call "the observable universe" may be spinning or rotating
merely as a consequence of gravity acting upon it from another, more distant region or sector
which happens to be spinning or rotating in the opposite direction due to some kind of cosmic "instability",
the cause of which has yet to be determined.

This idea is rather abstract and hard to describe, but perhaps a somewhat decent analogy might be found in
the mathematics of fluid dynamics. Then again, you know what they say... "a picture is worth a thousand words".

http://www.youtube.c...5APRW4EIvQ&NR=1

Don.

This post has been edited by Don Blazys: 10 March 2012 - 10:13 PM

[mpc755]

Don Blazys, on 10 March 2012 - 09:28 PM, said:

For all we know, our region or sector of the observable universe may be spinning or rotating
merely as a consequence of gravity acting upon it from another, more distant region or sector
which happens to be spinning or rotating in the opposite direction due to some kind of cosmic "instability",
the cause of which has yet to be determined.

This idea is rather abstract and hard to describe, but perhaps a somewhat decent analogy might be found in
the mathematics of fluid dynamics. Then again, you know what they say... "a picture is worth a thousand words".

http://www.youtube.c...5APRW4EIvQ&NR=1

Don.

The following is an image of the actual Universe as it exists, not a timeline. Now spin the matter about a preferred axis and this is what our Universe looks like. Inflation is where the aether is emitted into the Universal jet.

http://aether.lbl.gov/image_all.html

[Don Blazys]

Quoting mpc755:

Quote

...this is what our Universe looks like...

http://aether.lbl.gov/image_all.html

Hmmm... so it appears that in a sense,
the topological properties of the universe
are identical to that of a condom!

Well, now that we all know what the universe "really" looks like,
let's all celebrate!

Don.