[Cosmo-torun] the shape of the universe (fwd)

Boud Roukema boud w astro.uni.torun.pl
Czw, 16 Lut 2006, 14:11:35 CET

hi everyone,

We have a media question :).

i don't want to spam people, so anyone interested, please respond on
cosmo-media@ ...  rather than cosmo-torun.

Below are my proposed "compact" answers.  Any corrections before i
respond "officially"?  Remember the number one rule of the dependent media:
"anything you say may and will be misquoted against you". Which is why having
this on the cosmo-media archive will at least, in principle, provide some

i don't know what time frame the journalist has in mind - but presumably
the sooner the better for any answers. IMHO probably a day or two should
be OK.


> ---------- Forwarded message ----------
> Date: Wed, 15 Feb 2006 23:38:49 +0100
> From: t.rozek at fz-juelich.de
> To: boud at astro.uni.torun.pl
> Subject: the shape of the universe
> Dear Sir,
> I'm a physicist and scientific writer. Within the new project of Axel Springer publishing house (editor of Newsweek in Poland and Die Welt in Germany) in Poland I would like to invite you to the discussion about the shape of the universe.
> As I know scientific group you are the leader, in 2004 went public with the information that in the microwave background radiation picture there are some indications, that our universe has a shape of dodecahedron.
> Questions I'm asking you are the same like these I have sent to other expert in this field. I will not hide, that his opinion about the shape of the universe is different than your.
> I will be pleased to get from you compact answers to questions which are listed below. Please keep in mind that new Axel Springer daily will be addressed to nonspecialists in physics or astronomy.
> Let me thank you in advance for time you will spend to answer my questions. I'm looking forward to your respond.
> With the best regards
> Tomasz Rozek

> Questions:

> 1.  Analysis of the microwave background radiation are the only way
> - I guess - to collect information about the shape of the
> universe. Isn't it risky to draw conclusions resulting from only one
> experiment ?

Yes, it is risky to draw conclusions from only one experiment. We
expect other scientists to read our paper carefully and make their own
analyses of microwave background and other data.

The most independent test of our work will be testing the prediction
that the average, total density parameter of the Universe, including
ordinary matter, dark matter and dark energy together, should be about
0.9% to 1.1% higher than the density which would make the Universe
perfectly flat ("flat" means that Pythagoras' Theorem is true). This type
of test is highly independent of our analysis method.

> 2. Why this is commonly believed, that data from WMAP probe, brought
> down the concept of flat and infinite universe ?

The flat and infinite universe model is still consistent with the WMAP
data.  It is not the best model, but it is still consistent with the
data and most observational cosmologists still take it as the best
approximation we have.

Please remember, however, that no theoretical cosmologists take the
flat and infinite model as a serious model of the entire Universe - it
is only treated as a limiting case inside the observable sphere.

> 3. There are many ideas concerning the shape of the universe. Maybe
> it is like a sphere, cylinder, funnel, but it can also be like bell,
> horn or dodecahedron. Why do you claim that space is
> dodecahedron-like ?

We don't.

The first misunderstanding is that "shape" means the shape of *space
itself*, not the shape of *space inside of space*. Our intuition is developed
to think of objects inside of three-dimensional, Euclidean, infinite space.
In order to understand what is meant by the shape of the Universe, you first
need to develop a method of thinking about the shape of space itself.
A good place to start would be http://pl.wikipedia.org/wiki/Ksztalt_Wszechswiata .

One example of a shape of space itself is a space with the name "Poincare
dodecahedral space" (PDS). One "ordinary" shape, inside of space, which
helps to think about the PDS, is the dodecahedron.

The second misunderstanding is that so far our group only claims to
have a "hint" of that the shape of space is the PDS. Our analysis follows that
by Jean-Pierre Luminet's group. Ralf Aurich's group and Jesper Gundermann have
also found similar (though not exactly identical) results.

> 4. What are the errors or defects of the idea of horn-like space ?

None as far as I am aware of.

> 5. Could you in the very easy way explain the expression, that space
> has a shape ?

Imagine that space only has two dimensions, instead of three.

Now we can use our existing intuition about three-dimensional space to
imagine many different possible two-dimensional spaces inside of three-dimensional
space. In this way, we use one dimension as a purely psychological dimension.
It's used by our brain, but has no physical meaning for the two-dimensional
space we're thinking about.

Of course, real space has three dimensions (we can ignore the time dimension
for discussion of "the shape of space"), so if you can now start thinking in
four dimensions, then you can use the fourth dimension as a psychological
dimension and think of differently shaped spaces, each having three dimensions.

> 6. Do efforts to establish a shape of the universe have any
> practical meaning or you are doing that just to know ?


It is practical to know the shape of a footpath or a tree or a
mountain or an atom or a molecule, so it is practical to know the
shape of the Universe.

But it is also good to knowing the shape of a work of Picasso or a
beautiful woman or man, even if this has no practical use.

> 7. Did universe have a beginning, and ones will have the end ?

The standard hot big bang model is very well established, and this model
has a limiting time we can call "time equals zero". If we start today and
think backwards towards "time equals zero", then our model of the Universe
becomes more and more speculative as we get towards "time equals zero".

So it is more realistic to say that we have a standard model which
goes *towards* having a beginning rather than saying the Universe
actually "had" a beginning.

However, theoretical cosmologists have some ideas of universe models extending
earlier than "time equals zero".


Więcej informacji o liście Cosmo-torun