What, no Big Bang?!

[Shark Bait (Stu)]

Originally Posted by sjastro

Cosmology occasionally borders on the philosophical and/or SF.

Brain Greene came closest to bringing up the Anthropic Principle, namely if the Universe was any different we wouldn't be around to observe it, hence our existence is simply coincidental with the parameters as they are, rather than the parameters being fine tuned for our existence to occur.
I much prefer this explanation.

There is much resistance in mainstream science to a Multiverse.
The Multiverse is beyond our Universe's particle horizon hence there is no way we can test for its existence. This puts it beyond the realm of Science into Philosophy.

Regards

Steven

Thanks Steven,

Prompted by the Catalyst program and this discussion, I have my battered copy of Stephen Hawking's, A BRIEF HISTORY OF TIME next to me. Time to read it from cover to cover....again.

Stu.

[sjastro]

Originally Posted by rustigsmed

i find most theories fascinating, i do start to struggle when a model is relying on some kind of 'other' that can't be tested. it seems to me a shifting of the goal posts is happening, to some degree atleast, to make a solution fit.

The Multiverse is not even a theory as by definition a theory is supported by experimental or observational evidence.
Since the Multiverse cannot be tested there is no way one can disprove it.
The term "not even wrong" has been used to describe it.

Regards

Steven

[bojan]

I find Suskind's lessons on FLRW metric most instructive and inspiring... And easy to understand.
http://www.youtube.com/watch?v=32wIKaLkvc4

He also offered talks on minimum background, necessary to understand modern theoretical physics.
http://www.youtube.com/watch?v=iJfw6lDlTuA

[sjastro]

Originally Posted by Shark Bait

Thanks Steven,

Prompted by the Catalyst program and this discussion, I have my battered copy of Stephen Hawking's, A BRIEF HISTORY OF TIME next to me. Time to read it from cover to cover....again.

Stu.

Another issue that came out of the program was the reference to John Webb's work at the Uni of NSW on the spectrum of distant quasars.
According to Hubble's Law the cosmological redshifts for all objects is a function of the distance of the object from the observer.
The position of the spectral lines is also related to the fine structure constant "a" which is the strength of the electromagnetic force.

Using the Keck and VLT telescopes, Webb found the value of "a" was slightly larger for spectra taken by the VLT and slightly smaller for the Keck.
It seemed the Universe wasn't behaving isotropically as predicted by theory.
This was reported in the program. "a" is one of those finely tuned parameters.

What wasn't reported in the program is that mainstream science have basically thrown a bucket of cold water over the whole idea claiming the measurements reflect systematic errors at Keck and VLT.

Regards

Steven

[bobson (Bob)]

If you want a brief explanation of infinity it is here in the form of a doco.

http://www.youtube.com/watch?v=NtMwAUaftSU

Watched this video on youtube. There are prominent minds from universities such as Cambridge and Berkley who openly admit that they don't understand infinity or disagree with theories. Many here claim they understand it but can't paint picture for others what is that they understand?
Sometimes things like this might be clear in our mind but when we try to explain it to others we simply can not do it. And then trouble starts as we can see from a few posts.

In this video they even mention how one infinity is bigger than other infinity and they can prove it mathematically! WOW! Sorry, but that only can confuse things even further. How on Earth one infinity can be smaller or bigger than other is beyond my understanding of infinity.

But as I mentioned at the beginning of this post, there are professors of universities such as Cambridge and Berkley who openly say they do not understand infinity.

cheers

bob

[sjastro]

Originally Posted by bobson

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Watched this video on youtube. There are prominent minds from universities such as Cambridge and Berkley who openly admit that they don't understand infinity or disagree with theories. Many here claim they understand it but can't paint picture for others what is that they understand?

The issue in this thread has nothing to do with whether the human mind can grasp the concept of infinity or not. My intuitive grasp of infinity is as limited as anyone else, but one thing I do understand is the role of infinity in Cosmology.

As highlighted in Zaps post #7, the Universe isn't expanding into existing space to which the part of the response to Zap's post was "the bounded human mind cannot understand infinity".
So what? It has no relevancy.
The observable Universe is finite, expanding and constrained to three spatial dimensions, and is supported by observation.

Then there is the entire Universe.
Is the entire Universe infinite? The evidence says yes.
This relates to my post#12.
A property of flat space is that the angles of a triangle add up to 180 degrees. Cosmologists can now directly measure this property by using the anisotropic structures in the Cosmic Radiation Background. They have found the Universe is flat.
Since the entire Universe is flat with zero curvature, the Universe can be modelled as a hypersphere of infinite radius.

Does an infinitely large Universe cause problems with Cosmologists?
No. Cosmologists are not interested in the philosophical aspects of whether the human mind can grasp infinity or not, but rather if observation supports the existence of an infinity large Universe.
In this case an infinite Universe is defined by a finite property, zero curvature.

In this video they even mention how one infinity is bigger than other infinity and they can prove it mathematically! WOW! Sorry, but that only can confuse things even further. How on Earth one infinity can be smaller or bigger than other is beyond my understanding of infinity.

This includes concepts such as uncountable infinite sets and countable infinite sets.
One can also prove mathematically that an infinite set of odd integers has the same number of elements as an infinite set of odd and even integers!

The point is these concepts are completely counter intuitive and can only be perceived through mathematics.

But as I mentioned at the beginning of this post, there are professors of universities such as Cambridge and Berkley who openly say they do not understand infinity.

cheers

bob

Cannot understand infinity or cannot intuitively grasp infinity?

Regards

Steven

[bojan]

Originally Posted by sjastro

....Cannot understand infinity or cannot intuitively grasp infinitely?

Regards

Steven

I would say they can't intuitively grasp infinity (just like everyone else)

[bojan]

More on the latest CBM results here:
http://physicsworld.com/cws/article/...-saddle-shaped

[bobson (Bob)]

They have found the Universe is flat.
Since the entire Universe is flat with zero curvature, the Universe can be modelled as a hypersphere of infinite radius.

Universe is flat? Sounds familiar, not that long ago many thought Earth was flat too.

In Bojans link:

Current observational evidence suggests that ours is a flat universe. "But the measurements still allow for a universe where the density is one-third of the critical density and the universe is still within 1% of being flat," explains Liddle. This is the crux of the researchers' argument: it may be possible that the universe appears flat but is really curved with a characteristic radius on a very large scale. This "superhorizon curvature radius" determines the wavelength of the asymmetry-generating curvaton fluctuation. This radius does extend beyond our observable horizon but by no more than an order of magnitude. "So, if the universe is within 1% of being flat, then the curvature scale is three times as big as the observable scale, but there could be some physical processes related to it that could be measured," according to Liddle.

Not that long ago there was post how galaxies above us all spin one way and galaxies bellow spin other way. Like they are all spinning around something bigger? Carl said then there is no need to have anything to spin around because galaxies can do that on their own. Well, coincidentally they spin uniformly?

The researchers then point out that their curvaton fluctuations could pop up in another set of "open inflation" theories, first proposed in the 1990s, that suggest that our observable universe forms like a bubble in a larger universe. In this theory our bubble universe is born thanks to a quantum-tunnelling event from a low-energy state and is trapped in what Liddle describes as a "false vacuum state" (click on figure above). The walls of such a bubble would expand at a velocity approaching that of light. "So, on the inside it would look to us as if we were in an open universe that is homogenous and isotropic," says Liddle, further explaining that inside the bubble, the concept of time is different from outside. "The amount of inflation inside the bubble would determine how 'flat' it will be...Will it be dominated by dark matter?...Will it suffer a heat death?"
There may be many other such bubble universes within the larger universe, but our bubble would almost never interact with them and neither would we be able to see out of our "opaque bubble" explains Liddle. But, the initial event that induced the birth of our bubble universe would also cause fluctuations in the bubble wall, which in turn imprint themselves on the curvaton fluctuations.

Don't get me wrong, I love science. And yes, even though its hard to understand "infinity" I do believe Universe is infinite, I simply can not think any other way.



cheers


bob

[Steffen]

Originally Posted by bobson

And yes, even though its hard to understand "infinity" I do believe Universe is infinite, I simply can not think any other way.

I agree. A finite universe is impossible to imagine. One immediately wonders, what's on the other side of the boundary? What's the thing called in which the finite universe bubble is suspended? The only intuitively possible universe is an infinite one for me.

Cheers
Steffen.

[sjastro]

Originally Posted by bobson

Universe is flat? Sounds familiar, not that long ago many thought Earth was flat too.

A "Flat Earth" is an example of the geometry of an object embedded in space. In this case the geometry of space itself could be anything.
A "flat" Universe describes the geometry of space itself as being flat.

A "Flat Earth" is not based on scientific evidence, a flat Universe is.

Not that long ago there was post how galaxies above us all spin one way and galaxies bellow spin other way. Like they are all spinning around something bigger? Carl said then there is no need to have anything to spin around because galaxies can do that on their own. Well, coincidentally they spin uniformly?

Sorry I can't see the relevance. Can you provide a link?

Regards

Steven

[sjastro]

Originally Posted by Steffen

I agree. A finite universe is impossible to imagine. One immediately wonders, what's on the other side of the boundary? What's the thing called in which the finite universe bubble is suspended? The only intuitively possible universe is an infinite one for me.

Cheers
Steffen.

Perhaps this will help.

Your shadow is a 2-D object projected onto a surface.
The term dimension refers to degrees of freedom. 2 D space means an object can move in terms of "length" and "width", 3-D space an object can move in terms of "length" "width" and "height".

Your shadow is constrained to the intrinsic geometry of the surface.
It can't jump off the surface hence it cannot perceive a boundary with the surrounding extrinsic geometry of space. Since the surface is finite (in this case the surface of the Earth), the shadow's Universe is in fact finite.

Its tempting to take this analogy too far by claiming our Universe is expanding into higher dimensional space. The problem is our mathematical models are based on the intrinsic geometry of the Universe, there is no "outside" or "boundary". Besides there is no evidence to support the Universe expanding into an existing space.

Regards

Steven

[bobson (Bob)]

Hi Steven,

Unfortunately the link that I posted originally doesn't work any more. I am sure if you google for it you might find more about it. Here is original link on this forum:

http://www.iceinspace.com.au/forum/s...ad.php?t=78576

And here is in short what it is about:

Is the Universe Spinning?
In a study of over 15,000 galaxies by Michael Longo and co-investigators at the University of Michigan, the researchers report that spiral galaxies preferential spin clockwise or counter clockwise depending what hemisphere of the sky they are in.

Longo sampled over 15,000 galaxies in the extensive Sloan Digital Sky Survey. The galaxies extend out to little more than 600 million light-years from Earth, less than 1/20 the distance to the farthest observed galaxies to date.

Looking northward, above the plane of our Milky Way, he found that more than half of the spirals were spinning in a counterclockwise direction in the sky. This overabundance seems small, only seven percent of the total observed galaxy sample. But the odds of it being purely due to chance are a one in a million say the researchers.

If the whole universe is rotating, then an excess number of galaxies on the opposite part of the sky, below the galactic plane, should be whirling in a clockwise direction. And indeed they are according to a separate 1991 survey of 8287 spiral galaxies in the southern galactic hemisphere.

cheers

bob

[bojan]

Found the link (after some googling)
http://www.dailygalaxy.com/my_weblog...-says-yes.html
Maybe the distance in question (600 My) is still not large enough to draw some statistically reliable conclusion on the universe as a whole..

More on this subject here, with some theoretical details:
http://iopscience.iop.org/0004-637X/..._354.text.html

[bobson (Bob)]

Steven:
A "Flat Earth" is not based on scientific evidence, a flat Universe is.

Just think about possibility that current measurements are just 0.googol1 % wrong, that would mean our Universe is not flat

[bojan]

Originally Posted by bobson

Just think about possibility that current measurements are just 0.googol1 % wrong, that would mean our Universe is not flat

I think we have to be practical here.
Such a small deviation from flat still does not mean the current (ideal) model is useless - and physicist know that very well.
Models are always idealisations.. and so is this one (flat universe).
Of course, the difference may have philosophical implications.. but we are talking science here, so.. until proven (observed) otherwise, for all practical purposes, universe is flat.

[sjastro]

A few years before the Longo project the Galaxy Zoo conducted a similar activity. Their results indicated that 52% of the spiral galaxies sampled had a counter-clockwise spin.

The result was considered suspicious so it was decided to repeat the analysis on images that had been mirror imaged.
If the initial result was a real indication of an excess of counter clockwise spinning galaxies, then the mirror images should have produced 52% of clockwise spinning galaxies.
Instead there was hardly any change to the original result.

Hence the excess was attributed to bias.

When it comes to Cosmology there is a history of observational data that seems to conflict with theory only to find the error is with the data not the theory.
The Webb project I mentioned earlier in the thread is a possible example.
Another is that redshift data was found to cluster around particular values indicating a possible redshift quantization
This was found to be caused by selection effects.

I agree with Bojan.
A 600 million light year radius represents a tiny volume of the observed Universe.
It would be an interesting exercise to resample the data to find if selection effects play any role.

Regards

Steven

[Steffen]

Originally Posted by sjastro

Perhaps this will help.

Are you conflating the alleged difficulty of grasping infinity with the very real difficulty of (intuitively) grasping more than three dimensions?

Or, are you contending that those are two sides of the same coin?

You have my ear, please expand.

Cheers
Steffen.

[Steffen]

Originally Posted by bobson

Just think about possibility that current measurements are just 0.googol1 % wrong, that would mean our Universe is not flat

Why does it matter what "shape" the universe has – flat, cubical, spherical, prismatic, or otherwise? Surely, this is not at the heart of the matter?

Kepler wasted his life (much of it anyway) trying to squeeze his, and other people's, observations into a system of simple geometric bodies.

We need to move on from our current patterns of thinking in order to achieve the next level of insight. Doing that on a rational base without sliding into metaphysics is the challenge, not arguing over old-fashioned stereotypes.

Cheers
Steffen.

[bobson (Bob)]

It would be an interesting exercise to resample the data to find if selection effects play any role.

Why does it matter what "shape" the universe has – flat, cubical, spherical, prismatic, or otherwise? Surely, this is not at the heart of the matter?

It is important, if it wasn't there wouldn't be debates about it.

cheers

bob