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As I write this it is the first week of July. In just a couple of weeks
the summer traveling begins. First, a week in Indianapolis to attend the
North American Christian Convention. Gordon Bane has graciously
provided us with a booth and accommodations to introduce geocentricity
to the attendees. Then I'll be back in Cleveland for half a week at which
time I hope to place this issue in the mail. On the 27th of July it's off to
Europe for some more promotions and visits with family and friends.
This will culminate with the presentation of a paper at the Sixth European
Creationist Congress in the Netherlands. What does it all mean? Don't
expect any correspondence or response from me until early September.
We have recently acquired a color printer and we hope to start
producing color materials in a modest way in the next issue. If all goes
well, expect only the covers to be in color until we've streamlined the
publication. If anyone would like to recommend a competitively priced
(cheap but good—I know there's no such creature, but you know what I
mean) printer who does color work, please let us know.
In this issue, J. Timothy Unruh continues his series of articles presenting
the fundamentals of astronomy and their scriptural significance. His
current article on the sun also appeared in a recent issue of ICR's Impact.
His conclusion is that the sun is especially created for man, for life on
earth. God placed it precisely, and even made it more regular than the
vast majority of stars, so that we could be the recipients of his grace and
mercy.
In his article on the biblical units of measurement, John Byl places a
slightly different tact on the issue than was done by yours truly several
issues back. I trust you'll find Dr. Byl's article interesting and informative.
Bracketing o Aql to its left and right are a series of sharp, dark lines
which are placed on the plate by an iron-arc lamp. These are characteristic
of iron. Note that between each pair (left and right) of black
(emission) lines lies a white (absorption) line in the star's spectrum. This
means that the star's light passed through a cooler (not necessarily cold,
mind you,) region of gas containing iron, most likely in the star's atmosphere.
The intervening iron gas absorbed light of its own characteristic
wavelengths, thus leaving its dark-lined “fingerprint” in the star's continuum
light. In the original negative print the lines of hydrogen can also
be seen in o Aql, although the two very broad lines to the blue (bottom)
are due to calcium and drown out the two hydrogen lines there.
If we examined the plate with a microscope with cross hairs, we could
measure the distance from each of the star's iron absorption lines to the
corresponding calibration line. Since we know the wavelengths of the
lines in the lab, we can then derive the corresponding wavelength of the
star's line. In the vast majority of cases this difference is a measure of
the star's motion relative to the earth along the line-of-sight, its radial
velocity, and is popularly called the Doppler shift. If the line is shifted to
the red, then it is called a redshift, to the blue, a blueshift. The cover
plate is of low resolution and only measures a speed accurate to about
5-10 km/sec, depending on the width of the lines. But the type of plate
astronomers use to determine radial velocities is produced by a spectrum
three or more times as long as on the cover, (more than 12 times as long
as the original plates used to create the cover) giving much more accuracy.
The width of the star's lines may be produced in several natural ways.
Generally, the width is produced by heat. Heat is a measure of atoms or
molecules in motion. The faster they move, the hotter it is. Also, the hotter
the object, the greater the spread of speeds which an atom may have.
Thus an atom at the surface of the sun, where the temperature is roughly
10,000 degrees F, may assume any speed from zero on up beyond the characteristic
speed identified at 10,000 degrees. At 20,000 degrees, the atom's
speed may be anywhere from 0 to beyond the 20,000 degree speed. With
a higher temperature, then, the lines are broadened and more “washed
out.” So it is that the lines of Gamma Aqr are wider than those of o Aql.
Gamma Aql is a type A star, albeit peculiar, with a temperature twice that
of the sun. Omicron Aql, on the other hand, has a cooler temperature, so
its lines don't suffer nearly the smearing.
There are other effects which determine line position, strength and
broadening. For example, rapid rotation of a star will broaden the lines.
Indeed, Gamma Aqr is also rotating much faster than o Aql, and so, in
addition to the temperature broadening, its lines are also rotationally
broadened. Intense atmospheric pressure can also broaden the lines, but
the shape of the lines produced by that type of broadening is different
than that caused either by temperature or rotation. Strong magnetic fields
will cause a very fine splitting of the lines so that each becomes a cluster
of several lines. This is called the Zeeman effect and is related to the fine
structure constant. The strength of a line (called its depth) is determined
by how abundant the element associated with the line is. The more atoms
there are of an element, the more light it will absorb from the surface of
the star and so the spectral line will be deeper and more pronounced.
Finally, if the star is truly massive, then light loses energy climbing out of
its gravitational field and it is thus also Doppler shifted to the red end of
the spectrum (which is to the top on the cover picture).
One final point about spectral lines. All the stars shown on the cover
are like most in the sense that they have absorption lines. These are because
the star's light passed through cooler exemplars of the elements. If
the light passes through a gas hotter than the star's surface, one may see
emission lines. The iron-arc spectrum is itself an emission line spectrum.
Some stars may thus have emission lines of hydrogen inside the broader
absorption lines, for example. P Cygni is an example of such a star. In
every case, however, each line can, in principle, be associated with an
element. In the coolest stars, where atoms can stay together to form
molecules, one can even see bands of lines made by the molecules.
Although this reproduction does not do justice to the original plate, it
is hoped that seeing what a spectrum looks like will clear up some of the
misconceptions small-universe advocates have about stellar spectra. |