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with respect to the Sun's frame. But there's a difficulty. Suppose there was a
streetlamp beyond the telescope, directly in line with the star being
observed. If some kind of motion through an ether were responsible, you'd
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think that light from one would follow the same path as the light from the
other, and the same aberration should be observed. It isn't. No measurable
effect occurs at all.
Relativists chuckle and say, "We told you so. It's because there's no relative
motion between the street light and the observer." But the considerations
above are enough to say that can't be true either. It's more as if different
ethers were involved, one containing the Earth and the streetlamp, inside
which there is no aberration, the other extending out to somewhere less than
the Sun's distance such that its annual motion within the Sun's frame produces
the effect on starlight. There are further complications too, such as why
long-baseline radio telescope arrays should detect aberration when there's no
tube for photons to move sideways in, and the theories and arguments currently
doing the rounds to try and account for them could bog us down for the rest of
this book. I've dwelt on it this far to show that the whole subject of
aberration is a lot more involved than the standard treatments that dismiss it
in a few lines would lead one to believe.
Field-Referred Theories
Petr Beckmann, a Czech professor of electrical engineering at the University
of Colorado, developed an alternative theory in which the second of SRT's two
founding premises that the speed of light is constant with respect to all
observers everywhere is replaced by its speed being constant with respect to
the dominant local force field through which it propagates. (SRT's first
premise was the relativity principle, by which the same laws of physics apply
everywhere.) For most of the macroscopic universe in which observers and
laboratories are located, this means the gravitational field that happens to
dominate wherever one happens to be. On the surface of the Earth it means the
Earth's field, but beyond some distance that gives way to the Sun's field,
outside which the field of the local part of the galactic realm dominates, and
so on. This gives a more tangible form to the notion of embedded "ether
bubbles," with light propagating at its characteristic speed within fields
that move relative to each other
like the currents and drifts and doldrums that make up a real ocean, as
opposed to a universally static, glassy abstraction. And since, as with any
conservative vector field (one in which energy potentials can be defined), any
point of a gravity field is described by a line of force and the equipotential
passing through it, the field coordinate system can serve as a local standard
of rest.
Does this mean, then, that the gravitational field is, in fact, the long
sought-for "ether"? Beckmann asks, in effect, who cares? since the answers
come out the same. Marklin is more of a purist, insisting on philosophical
grounds that whatever its nature finally turns out to be, a physically real
medium must exist.
A "field," he pointed out when I visited him at his home in Houston while
researching this book, is simply a mathematical construct describing what a
medium does. The smile can't exist without the Cheshire cat.
I'm not going to attempt to sit in judgment on heavyweights like Petr and
George. The purpose of this essay is simply to inform interested readers on
some of the ideas that are out there.
The cause of all the confusion, Beckmann argues, is that what experiments have
been telling us about motion relative to the field has been mistakenly
interpreted as meaning motion relative to observers who have always been
attached to it. Since every experiment cited to date as supporting or
"proving"
relativity has been performed in a laboratory solidly at rest on the Earth's
surface, the same experiments are consistent with either theory. Both theories
account equally well for the same results. Except that doing the accounting
can be a far more involved business in one case than in the other. As an
example of how the same result is explained simply and straightforwardly by
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one theory but requires elaborate footwork from the other, let's consider the
Michelson-Gale experiment of 1925, which rarely finds its way into the
textbooks.
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Michelson-Morley had failed to detect any motion of the Earth relative to an
ether in its orbit around the Sun. This could be because there is no ether
(SRT), or there is but the distortion of measuring standards obscures it
(LET), or because the local ether moves with the Earth
(Beckmann-type field-referred theories). Does the local ether bubble rotate
with the Earth also, or does the Earth spin inside it?
Michelson and Gale set up an experiment to try to answer this at Clearing,
Ilinois, using a rectangular interferometer large enough to detect the
difference in velocity between the north and south arms due to the southern
one's being slightly nearer the equator and hence moving slightly faster. It
was a magnificent affair measuring over 2,000 feet east-west and 1,100 feet
north-south, with evacuated pipes
12 inches across to carry the beams, and concrete boxes for the mirrors,
lenses, and beam splitters.
Two hundred sixty-nine measurements were taken in sets representing various
conditions.
And fringe shifts were observed not only of a magnitude consistent with the
"hypothesis of a fixed ether" (Michelson's words) within the limits of
observational error, but from which the experimenters were able accurately to
calculate the rotation speed of the Earth.
Beckmann's theory predicts this on the theoretical argument that if the
gravitational field describes an outward propagation, the effect would
"decouple" from the source as soon as it leaves, somewhat like bullets from a
rotating machine gun still radiating outward in straight lines. In other
words, the field's effects shouldn't share the source's rotation, and hence
the speeds of the light beams in the two arms of the interferometer will be
different. This doesn't contradict Einstein, though, where the General Theory
is invoked to arrive at the same result on the grounds that each beam has its
own idea of time. But whereas
Beckmann's conclusion follows from Galilean principles and a few lines of
high-school algebra, GRT
requires multidimensional tensors in spacetime and non-Euclidian geometry.
Electromagnetic Mass Increase Without Einstein
The law of inertia says that a mass tends to keep its momentum constant, i.e.,
it resists external forces that try to change that momentum. That's what the
definition of mass is. The same is true of an electromagnetic field. A steady
electric current produces a steady magnetic field. If the field is changed by
changing the current, it will, by Faraday's law, induce an electric field that
will seek to restore the current and its field to its original value all [ Pobierz całość w formacie PDF ]