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Meteor

From: Brian Taves <btav~at~loc.gov>
Date: Wed, 19 Oct 2005 19:28:19 -0400 (EDT)
To: Jules Verne Forum <jvf~at~Gilead.org.il>

Thank you, Garmt!

On Sun, 16 Oct 2005, Garmt de Vries wrote:

> On Sat, 15 Oct 2005 spaceart~at~att.net wrote:
>
> > The machine used to affect the orbit of the meteor is a truly SF
> > device---although Verne (or whoever) apparently ignored the law of
> > action and reaction when describing it operating. Any force it applied
> > to shifting the meteor would have applied to the machine as well. I
> > remember thinking while reading the book that probably the only result
> > of shoving on the meteor hard enough to move it would be the flattening
> > of the device itself.
>
> It is clear from the text that the meteor was much lighter than the Earth.
> What the machine does, is create an absolute vacuum between itself and the
> meteor. The non-empty space behind the meteor then pushes it towards
> Earth. Of course, the non-empty space behind Earth would push our planet
> the other way, but this effect is much smaller, because Earth is larger.
>
> Assuming that the pressure from space is a constant, the ratio between the
> forces exerted on Earth and on the meteor goes with the square of the
> ratio between their radii, whereas the ratio between their masses goes
> with the cube of the ratio of their radii. The meteor thus experiences an
> acceleration that is larger than the accelaeration experienced by Earth by
> a factor equal to the ratio of the radii.
>
> By the way, the working of the machine is an interesting foreshadowing of
> the Casimir effect. In quantum mechanics, empty space is never empty.
> There is a constant appearing and disappearing of electron-positron pairs,
> which exist for a short time before annihilating again. But they do
> contribute to the energy density of the vacuum, which gives rise to a
> pressure exerted by the vacuum on everything around it. Another
> ingredient we need is the concept of particle-wave duality. Every
> particle can, depending on circumstances, behave as a particle or as a
> wave. The wavelength is inversely proportional to the momentum. The most
> familiar example of this duality concerns photons: light can be a wave
> phenomenon (refraction, interference, etc.), but it can also behave as
> quantised particles (photo-electric effect). Similarly, you can do
> interference experiments with electrons, which you're more used to
> thinking of as particles.
>
> Now imagine two parallel, flat, conducting surfaces, close to eachother.
> Between them, only certain energies are possible for the electron-positron
> pairs: namely those energies for which half of the corresponding
> wavelength fits exactly an integer number of times in the distance between
> the two surfaces. At the same time, outside the two planes, all energies
> are allowed. This means that there are fewer pairs inside the gap than at
> the outside. Thus, the pressure inside is lower than outside, and the two
> planes are pushed towards each other. Think about it: "empty" space
> exerting a real, macroscopic force! It takes a physicist to come with
> something like that :) But the effect has been measured, and it is as real
> as gravity.
>
> Sorry for the lecture...
> Garmt.
>


Brian Taves
Motion Picture/Broadcasting/Recorded Sound Division
Library of Congress
101 Independence Avenue, S.E. Washington, D.C. 20540-4692
Telephone: 202-707-9930; 202-707-2371 (fax)
Email: btav~at~loc.gov


Disclaimer--All opinions expressed are my own.
Received on Thu 20 Oct 2005 - 01:29:37 IST

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