Re: Bill Bryson and the big bang

From: Franz Heymann (notfranz.heymann_at_btopenworld.com)
Date: 06/25/04 

Date: Fri, 25 Jun 2004 19:17:58 +0000 (UTC)

"greywolf42" <mingstb@marssim-ss.com> wrote in message
news:10dlpq6e25326b9@corp.supernews.com...
> Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in
message
> news:cbbflo$jpu$1@news.urz.uni-heidelberg.de...
> > greywolf42 wrote:
> > > Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in
message
> > > news:cb8p1t$e1c$2@news.urz.uni-heidelberg.de...
> > >
> > >>Jonathan Silverlight wrote:
> > >>
> > >>>In message <cb6fqj$pim$2@news.urz.uni-heidelberg.de>, Bjoern
> Feuerbacher
> > >>><feuerbac@thphys.uni-heidelberg.de> writes
> > >
> > >
> > >>>>By crossing two very intense laser beams, one can indeed
produce
> > >>>>matter.
> > >>>
> > >>>Interesting! Is that a practicable method of producing
antimatter?
> > >>
> > >>Depends on what you mean by "practicable"... You need a lot of
energy
> > >>to do that.
> > >
> > > And you need to understand that Bjoern made up the crossed laser
beams.
> >
> > I did not "make it up". I simply misremembered it, and freely
admitted
> > this, after it was pointed out that I am wrong.
> >
> > Stop lying.
>
> As far as I can tell, there are *no* crossed laser beam experiments.
There
> was no such experiment for you to misremember.

You've had your mileage on this. Now stop playing silly buggers. It
simply illuminates your vacuity.

> > > Theoretically, it would take gamma-ray lasers (at a minimum).
And
> > > experimentally, photons don't seem to create charged particles
except in
> > > the near vicinity of charged particles.
> >
> > Experimentally, it was shown that gamma rays interacting with a
laser
> > produce electron-positron pairs. The link to the relevant
experiment
> > was given in this thread.
>
> The experiment Franz came up with (E144) had nothing to do with
crossed
> lasers (or even gamma rays with lasers). It was an electron beam -
photon
> experiment.

Ye gods, yet again?
> > Stop lying.
>
> There are no crossed laser experiments.

You bloody arsehole
>
> There is also (AFAIK) no gamma-ray - laser experiment.
>
>
http://66.102.7.104/search?q=cache:OX1eX0yiaEAJ:www.hep.princeton.edu/~mcdon
> ald/e144/ssitalk.pdf+laser+%22positron+production%22&hl=en
>
> From the abstract of E144: "A signal of 106 +- 14 positrons above
background
> has been observed in collisions of low-emittance 46.6-GeV electron
beam with
> terawatt pulses from a Nd:glass laser at 527 nm wavelength in an
experiment
> at the Final Focus Test Beam at SLAC."
>
> And the introduction is: "This paper discusses recent experimental
results
> obtained by the E-144 collaboration on the interactions of electrons
and
> photons in very intense electromagnetic fields."
>
> It seems that you are wrong again. However, your confusion is
> understandable, if you simply read the title of the paper. Or,
perhaps you
> continue to be confused by the *theoretical* claim made in the
abstract (or
> by the title): "The positrons are INTERPRETED as arising from a
two-step
> process in which laser photons are backscattered to GeV energies by
the
> electron beam, followed by a collision between the high energy
photon and
> several laser photons to produce an electron positron pair. These
results
> are the first laboratory evidence for inelastic light-by-light
scattering
> involving only real photons." (emphasis added)

You are, of course, free to INTERPRET it in another way. Why do you
not do so?

>
> But regardless of theoretical hype and salesmanship, the experiment
remains
> one of multi-GeV electrons hitting laser photons. And multi-GeV
electrons
> hitting *anything* have sufficient energy to produce
electron/positron pairs
> (which only takes 1.022 MeV).

That was handwaving.
Please estimate the relative cross sections for the process described
by you, and the process described by the authors of that paper. Did
you really think that they did not consider as many alternatives as
they could conceive of before making such a strong statement?

How about reading the whole paper?

Franz

Relevant Pages

  • Re: Experimental disproof of the theory of Relativity
    ... reaction area and collide directly with real, observable photons. ... > positrons created by the collision of backscattered photons and a laser ... > laser pulses and a 46.6-GeV electron beam that produced backscattered ... E144 collided electrons off of a laser beam. ...
    (sci.physics.relativity)
  • Re: Simple question about a laser pushing a proton.
    ... How does the laser beam go faster than c then? ... So the photons that make up the laser beam are travelling faster than light. ... Mirror reflects photons which then push proton ...
    (sci.physics)
  • Re: Bill Bryson and the big bang
    ... >> There are no crossed laser experiments. ... >> electron beam, followed by a collision between the high energy ... >> several laser photons to produce an electron positron pair. ...
    (sci.physics)
  • Re: Bill Bryson and the big bang
    ... >> There are no crossed laser experiments. ... >> electron beam, followed by a collision between the high energy ... >> several laser photons to produce an electron positron pair. ...
    (sci.astro)
  • Re: Bill Bryson and the big bang
    ... > There are no crossed laser experiments. ... > at the Final Focus Test Beam at SLAC." ... > obtained by the E-144 collaboration on the interactions of electrons ... > process in which laser photons are backscattered to GeV energies by ...
    (sci.physics)