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The universe of Mr Tegmark



 
 
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  #1  
Old July 7th 14, 08:43 AM posted to sci.astro.research
jacob navia[_5_]
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Default The universe of Mr Tegmark

Max Tegmark "Our mathematical universe"

OK, at least Mr Tegmark doesn't avoid the question:

What's our universe expanding into?
----------------------------------

Mr Tegmark writes about this question 16 lines. Some of those lines are
wasted with the assurance that no chocks will occur because of space
expansion. At least 4 lines reassuring us, poor souls, that no galaxy
pileup is around the corner.

Well, I am reassured Mr Tagmark. It always amazes me how cosmologists
can hide behind words.

Almost at the end of the 16 lines, almost as an afterthought Mr Tegmark
comes to two "viewpoints". You can see it either as:

Static space: Galaxies are receeding faster and faster from us in a
static space. Well, static space means that there is NO space expansion,
and galaxies are receeding from us at an accelerated rate.

Assuming that red shift equals distance this view point leads to an
horizon. Parts of the universe are receeding faster than light, in 3
dimensions there is no solution.

The other solution is static matter: volume is not constant and new
volume "is created", just like that.

Obviously space is created when nobody is looking. Space hides when
doing this kind of aberrations of course, very shy. Space hides
conveniently in "the space between galaxies".

Ahh ok. How clear.

Imagine I am traveling smoothly between galaxy A and galaxy B. Suddenly,
my space ship incrases its volume. Wow! The machine room got bumped left
of the motor B22, an empty cube of several meters appeared between two
parts of the motor, what made the connexions get loose and the computer
to shut down.

Ahh this dammed space that can't keep it steady and must bump new space
at the worst moments somewhere!

Vulgarisation is not just speaking about the questions with *some*
seriousness. Obviously Mr Tegmark hasn't done any further thoughts into
this particular question than those 16 lines...

At least not in that book. A book that tells "the layman" a story like
you tell it to a child.

Look, laymans like the target audience of this book CAN exist. Do they
actually exist? Maybe.

But in the laws of big numbers, I would bet that in thousands of laymans
about astronomy that buy this book, some of them will be pleased with a
straightforward story of how the universe came into being, nice to know,
you know?

This is all very official, with NASA satellites, etc. Precision cosmology.

I am a layman of course, but I do not agree that the answer is 16 lines
of nothing really. For me this problem is unanswered by the BB people.

The book is in itself interesting because it shows what is really the
stand of BBs.

"Volume appears", just like that!

All this bang disappears if we asssume that (for an unknown reason)
light for distant objects gets red-shifted. No Doppler effect, just
red-shift, what is something different but not related to some "space
expansion".

This conceptual advance will allow astronomers to start looking for the
reason of the red-shift instead of believing that they know what the red
shift is!

A VERY important conceptual step that Mr Tegmark doesn't do.

[Mod. note: tired light theories have well-known problems and are too
speculative to be discussed here -- mjh]
  #2  
Old July 8th 14, 09:15 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Default The universe of Mr Tegmark

In article , jacob navia
writes:

Max Tegmark "Our mathematical universe"

OK, at least Mr Tegmark doesn't avoid the question:

What's our universe expanding into?


Static space: Galaxies are receeding faster and faster from us in a
static space. Well, static space means that there is NO space expansion,
and galaxies are receeding from us at an accelerated rate.


There are indeed various viewpoints in the literature. However, all of
them agree regarding observable effects, so it's more a question of what
is useful in a given context.

Assuming that red shift equals distance this view point leads to an
horizon. Parts of the universe are receeding faster than light, in 3
dimensions there is no solution.


No. One can have a self-consistent solution in the static-space
framework. (Note that neither a horizon nor faster-than-light recession
is a problem here.)

Obviously space is created when nobody is looking. Space hides when
doing this kind of aberrations of course, very shy. Space hides
conveniently in "the space between galaxies".

Ahh ok. How clear.

Imagine I am traveling smoothly between galaxy A and galaxy B. Suddenly,
my space ship incrases its volume. Wow! The machine room got bumped left
of the motor B22, an empty cube of several meters appeared between two
parts of the motor, what made the connexions get loose and the computer
to shut down.


Calculate how much extra volume must appear in your spaceship in your
lifetime. It is not noticeable.

Vulgarisation is not just speaking about the questions with *some*
seriousness. Obviously Mr Tegmark hasn't done any further thoughts into
this particular question than those 16 lines...


You probably mean "popularization". I'm sure that he, and others, have
put more than 16 lines into this.

At least not in that book. A book that tells "the layman" a story like
you tell it to a child.


The book covers a range of topics, with an emphasis on the multiverse.
Certainly among the mainstream stuff, nothing is wrong. More detailed
explanations can be found in other books.

I am a layman of course, but I do not agree that the answer is 16 lines
of nothing really. For me this problem is unanswered by the BB people.


You need to find better evidence of a conspiracy than this.

All this bang disappears if we asssume that (for an unknown reason)
light for distant objects gets red-shifted. No Doppler effect, just
red-shift, what is something different but not related to some "space
expansion".


It is not an unknown reason, but a firm prediction. Learn all you need
to know about this and other topics in Edward Harrisons textbook
COSMOLOGY: THE SCIENCE OF THE UNIVERSE. He uses the expanding-space
picture, but Bunn and Hogg in an American Journal of Physics paper show
an equivalent formulation in terms of the Doppler effect. (However,
this is more an academic exercise in that in general no cosmological
velocity, defined as the change in (some) distance with time, is
described by the Doppler formula (relativistic or not). Harrison also
wrote an ApJ paper entitled "The redshift-distance and velocity-distance
laws", which clears up all confusion.

This conceptual advance will allow astronomers to start looking for the
reason of the red-shift instead of believing that they know what the red
shift is!

A VERY important conceptual step that Mr Tegmark doesn't do.


Again, the emphasis of Tegmark's book is elsewhere, so one can't expect
him to discuss everything in detail, especially not non-controversial
mainstream stuff.

Please read Harrison's book and the article I mentioned and ask again if
you think that there is some problem in this area which cosmologists
have got wrong.
  #3  
Old July 10th 14, 08:50 AM posted to sci.astro.research
news
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Posts: 1
Default The universe of Mr Tegmark

On Tue, 08 Jul 14 08:15:09 GMT, Phillip Helbig---undress to reply
wrote:

The redshift-distance and velocity-distance
laws

You say we should read Harrison's article, but what can you really
learn from a verbose article like this?
What are we to make of an equation for the distance to a co-moving
body where the units are so far out of balance: (where c must be the
speed of light R is dimensionless)
L = cR_0*r meters? section 6.2
I don't see how this is a useful equation and the failure to balance
units makes us doubt any of the other results
John Polasek
  #4  
Old July 11th 14, 09:50 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default The universe of Mr Tegmark

In article , news
writes:

The redshift-distance and velocity-distance
laws

You say we should read Harrison's article,


It is one of the best on the topic.

but what can you really
learn from a verbose article like this?


A wealth of information.

What are we to make of an equation for the distance to a co-moving
body where the units are so far out of balance: (where c must be the
speed of light R is dimensionless)
L = cR_0*r meters? section 6.2


Some authors have the scale factor dimensionless. Others prefer it to
have a dimension and express "distance" via a dimensionless quantity,
which has the advantage that such comoving distances do not change when
the universe expands (the physical distance is the coordinate distance
times the scale factor). However, you can be sure that Harrison's
treatment is consistent and that he has not made a simple error such as
an equation where the dimensions don't match.
 




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