Re: Bill Bryson and the big bang

From: Bjoern Feuerbacher (feuerbac_at_thphys.uni-heidelberg.de)
Date: 06/23/04 

Date: Wed, 23 Jun 2004 17:59:51 +0200

Jim Jastrzebski wrote:
> "Bjoern Feuerbacher" <feuerbac@thphys.uni-heidelberg.de> wrote in message
> news:cbbgrv$k5c$1@news.urz.uni-heidelberg.de...
>
>
>>So you didn't *predict* Hubble's constant, you simply inserted
>>a made-up number for the density so that the result comes out right?!?
>
>
> Right. I predicted density of space.

Nice. Now you have to show that this prediction is right.

> Or showed that one "predicts" the other, whichever is known more
> exactly.

Well, as I pointed out, the mean density is known to an accuracy
of less than 7%. Using that value and putting it into your formula,
one gets the wrong result for H...

>>Err, if the universe is originally homogeneous and isotropic,
>>light should be radiated at *every* point into *every* direction
>
>
> Maybe it should according to your opinion but
> experience shows that it is not even possible to
> predict when an atom decides to emit a photon
> unless you kick him in his pants as e.g. in a laser.

But emission of photons happens in *very* short times,
on the order of 10^(-9) seconds or less. Such small time
differences should be negligible on cosmological scales.

> As a particle physicist you should have heard
> about it.

I have. This is irrelevant here.

> It makes impossible for all the atoms
> of the universe to radiate their photona at the
> same time and even more difficult to do it
> isotropically since each radiates only one
> photon at a time. So I assume that laws of
> physics work also when only one place in the
> universe radiates, and others just sit and react
> to this radiation.

So in essence, the part of the universe which radiates
first becomes it center. (you *do* realize that the
metric you propose describes a universe with a center,
don't you?)

[snip]

>>>So please read the stuff again, this time without skiping
>>>every second paragraph,
>>
>>I read the stuff above. It is wrong.
>>
>>Oh, BTW, using only the mass of a *shell* for the gravitational force
>>acting on a photon also makes no sense. You have to use the mass inside
>>the enclosed *sphere*.
>
>
> You made two errors in the two sentences.
>
> (1) I don't use "mass of a *shell* for the gravitational
> force acting on a photon". As I mentioned elswere
> using "gravitational force acting on photon" is illegal
> in Newtonian approximation that I use.

Why is that illegal?

> (2) I do use the mass inside the enclosed *sphere*
> but of course not "for the gravitational force acting
> on a photon".

I quote from your paper:
"The Newtonian gravitational force (derivative of gravitational energy
with respect to r) acting on the dust particles between sphere at r and
a parallel sphere at r + dr and so of mass dM(r) = (4pr^2dr r) is dM(r)g
therefore
   d^2E = 4p G r m(r) dr^2"

You clearly use only a mass shell here.

> It makes me to think that you didn't read the paper
> more carefully neither the second time.

Well, either there are really some sentences or part of sentences
missing, or my browser displays the page wrong. Some sentences
do not make any sense grammatically, e.g. the following:
"Newtonian gravitational field g(r) created by the missing mass that
has been carried away in photons, assuming that the movement of dust
particles caused by the influence of photons is negligible, or that
g(r), once created by the passage of the sphere of photons, doesn't
change with time, which assures the lack of feedback effects of matter
in the space on photons in the sphere, by elementary Newtonian magic
(droping the vector form and because of spherical symmetry doing the
magic with magnitudes only) is"

(directly before equation 1)

> After second
> time your misunderstanding of the paper shouldn't be
> that spectacular, but it is only may opinion that may
> be wrong.

It is my opinion that due to the missing sentences (or sentence fragments,
or bad grammar), it is quite easy to misunderstand what you mean.

Bye,
Bjoern

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