Issues of 2005
This page lists the home pages for this web site for the year 2006. These pages constitute
volume 2 of The Astrophysics Spectator.
- Issue 2.37, November 30, 2005.
In the last issue for the year, The Astrophysics Spectator presents a page
that discusses the lens produced by a galaxy. These lenses and the lenses of the stars
within each galaxy cover a significant fraction of the sky, so they affect the appearance
of the most distant objects in our universe.
- Issue 2.36, November 16, 2005.
The discussion of stellar gravitational lenses is extended with this issue to include
a description of how we can use the gravitational lenses in our own galaxy to find objects
that do not emit light.
- Issue 2.35, November 2, 2005.
A simulator of a point gravitational lens is added to the “General Relativty”
path in this issue of the web site. This simulator shows the image of a distant object
after the image passes through the gravitational field of an intervening star.
- Issue 2.34, October 19, 2005.
This week a page is added to the “General Relativity” survey path of
The Astrophysics Spectator that describes the gravitational lens produced
by a star. With this issue, the “Gravitational Wave” survey path is
incorporated into the “General Relativity” survey path.
- Issue 2.33, October 5, 2005.
With this issue of The Astrophysics Spectator, we begin our exploration of
general relativity, our modern theory of gravity. This new “General Relativity”
survey path begins with a discussion of the principles underlying general relativity; it
then moves to a discussion of where in our universe we see the effects of general relativity.
- Issue 2.32, September 21, 2005.
The discussion of helium, carbon, and oxygen fusion on the “Stars” survey path
has been expanded with this issue of The Astrophysics Spectator. This discussion
is now spread over three pages. The first page discusses helium fusion, the second page
shows in a live figure the dependence of the helium thermonuclear fusion rates on temperature,
and the third discusses the carbon and oxygen fusion processes.
- Issue 2.31, September 7, 2005.
This issue of The Astrophysics Spectator presents an improved version of the
helium fusion simulator. This version permits the user to set the temperature to
a broader range of temperatures than the previous simulator, and it allows the reader
to change the composition of the gas undergoing fusion. A second plot is added that
shows the power generated through fusion.
- Issue 2.30, August 24, 2005.
This issue of The Astrophysics Spectator adds a new simulator to the web site.
This simulator calculates the thermonuclear fusion of helium within a star. The simulator page
is part of the “Stars” survey path. This week a commentary is also added to the
web site that argues for dropping Pluto from the planet category.
- Issue 2.29, August 3, 2005.
Three survey pages are added in this week's issue of The Astrophysics Spectator.
One page on the “X-ray Astronomy” survey path discusses x-ray emission from
clusters of galaxies, a second page on the “Cosmology” survey path discusses
the microwave background, and a third page on the “Cosmology” survey path
discusses how the influence of a galactic cluster on the microwave background gives
us a means of finding the distance to the cluster.
- Issue 2.28, July 27, 2005.
This issue of The Astrophysics Spectator adds a page about active galactic nuclei
to the “X-ray Astronomy” survey path. The issue also adds a commentary
about fluke results in science.
- Issue 2.27, July 20, 2005.
With this issue of The Astrophysics Spectator, I introduce
The Astrophysics Spectator Gift Shop. This shop, which is hosted by CafePress.com,
sells items carrying images from this web site.
- Issue 2.26, July 13, 2005.
This week's issue of The Astrophysics Spectator adds a new page to the
“X-ray Astronomy” survey path that discusses what might be learned from
the observation of isolated neutron stars at x-ray energies. The commentary for
the week discusses the rush to publish theoretical papers when an observation undercuts
a favored theory.
- Issue 2.25, July 6, 2005.
For this issues of The Astrophysics Spectator, a page is added to the
“X-ray Astronomy” survey path that describes stellar corona, which
produce observable x-rays from nearby stars.
- Issue 2.24, June 22, 2005.
This week, additional pages are added to an “X-ray Astronomy” survey path. The
first page gives a short overview of the sources of x-rays in the sky; a second page
describes a particularly luminous source of x-rays, the compact binary star. The commentary
for this week discusses the prevalence of unethical behavior in scientific research.
- Issue 2.23, June 15, 2005.
This week, The Astrophysics Spectator continues the discussion of x-ray astronomy
with pages that describe what can be learned by observing x-rays from a astronomical source
and that discuss the three x-ray observatories in operation as of June 15, 2005. This issue
also contains a background page on the frequency of light and photon energy.
- Issue 2.22, June 8, 2005.
A page is added to the web site that discusses the physics behind x-ray telescopes.
The commentary for the week discusses the link between fantasy literature and the more
speculative scientific theories.
- Issue 2.21, June 1, 2005.
This week's issue expands the discussion on the “Stars” survey path
on how light interacts with matter in the interior of stars. A new page discusses
the four processes that couple light to matter, and a rewritten page discusses
the diffusion of light out of a star.
- Issue 2.20, May 25, 2005.
In this week's issue, three pages are added to the “Astrophysical Disks” survey path
that describe accretion disks. Accretion disks are found around young stars, massive
black-hole candidates, and compact stars in binary star systems. The new pages describe
the general physics, the structure, and the temperature of accretion disks.
- Issue 2.19, May 18, 2005.
In this issue, the “Astrophysical Disks” survey path is started with an overview
of the physics of disks. The commentary for the week discusses the claim that there are
too few advanced degrees being awarded in physics and engineering. The news item for
the week is that the Swift gamma-ray observatory has determined the location of
a short-duration burst, allowing ground telescopes to search for an optical counterpart
to this mysterious event.
- Issue 2.18, May 11, 2005.
This issue adds a simulator to the “Special Relativity” survey path.
The simulator calculates the free-fall motion of an object for a traveler accelerating
at a constant rate. The simulator shows both the motion as measured in a coordinate grid
and the motion as seen by the traveler. Effects such as the bending of light and
the slowing of motion as an object falls to the event horizon of the traveler
are demonstrated by the simulator. These effects are also seen at the event horizon
of a black hole.
- Issue 2.17, May 4, 2005.
This week, a page that discusses time dilation, length contraction, the skewing
of simultaneity, and the twins problem is added to the “Special Relativity”
- Issue 2.16, April 27, 2005.
This issue discusses what an interstellar traveler would see when he makes a round trip
to a distant star or galaxy in a rocket that can accelerate at a constant rate.
The pages describe both the time dilation experienced by our traveler and the
apparent distortion of time back on Earth. Live figures show these effects;
the reader can adjust the acceleration and the destination distance in these figures.
The commentary thumps the cliche that our universe is stranger than we can imagine.
- Issue 2.15, April 20, 2005.
Special relativity, the theory of how our measurements of time and length change
as we accelerate, cannot be ignored in astronomy. Its effects are seen in the
jets of gas flowing out of compact binary star system and out of the centers of galaxies,
they are seen in the gases in supernovae remnants, and they are seen in the cosmic rays
striking Earth. This week we add pages discussing the theory of special relativity
and its consequences for an observer experiencing constant acceleration. These pages
motivates this week's commentary, which discusses the distinction between the appearance
of an object and the abstract description we give for an object.
- Issue 2.14, April 6, 2005.
The third and final hydrogen fusion simulator is added to the web site with this edition of
The Astrophysics Spectator. This simulator combines both the processes
of the proton-proton fusion chains and the carbon-nitrogen-oxygen hydrogen fusion cycles
into a single simulation. With this simulator, the reader can learn how temperature
and gas composition affect the fusion of hydrogen into helium. The commentary for this
week describes how the author came to use Harvard College Observatory's Great Refractor.
- Issue 2.13, March 30, 2005.
This issue introduces a second hydrogen fusion simulator, the CNO hydrogen fusion simulator.
This simulator models the carbon-nitrogen-oxygen fusion processes that are found in the
massive stars of our epoch. Along with this simulator, pages are added that explain
the results of this and the PP simulator introduced in the previous issue.
- Issue 2.12, March 23, 2005.
A new simulator is added to the web site with this issue of The Astrophysics Spectator.
The simulator is a nuclear reaction network for the PP processes of hydrogen fusion.
These processes dominate the nuclear fusion of hydrogen into helium at low temperatures
or in environments with very little nitrogen, carbon, and oxygen. The simulator permits
the reader to examine this process for various temperatures and gas compositions.
- Issue 2.11, March 16, 2005.
This issue of The Astrophysics Spectator adds a page on Uranus and Neptune
to the “Solar Planetary System” path. The commentary for the week discusses
the role of academic freedom at the university and how this relates to the Ward Churchill
controversy at the University of Colorado. A discussion of Nicolaus Copernicus's
On the Revolutions of Heavenly Spheres appears in this issue.
- Issue 2.10, March 9, 2005.
A store is added to the web site this week. Under the store page, found under the link
Store at the top of the home page, the reader will find reviews of
worthwhile books, and links to Amazon, where the books can be bought. The commentary for
this week argues that tenure and a tight job market
discourage unorthodox thinking in the sciences.
- Issue 2.09, March 2, 2005.
In this week, two new pages are added to the web site: a page on the hydrogen nuclear
reaction rates, and a commentary page on how government funding affects academic freedom.
The page on hydrogen nuclear reaction rates includes a live figure of the rates for
the PP and CNO processes. The commentary is the third in the series on academic freedom.
- Issue 2.08, February 23, 2005.
This week adds a page about polytropic stellar models. These very simple models display
how the pressure dependence on density modifies the structure of a star. With these models,
we can see the conditions that lead to the expansion of a star's surface and to the collapse
of a star's core. The commentary for this issue recounts the controversy between
Immanuel Velikovsky and Harlow Shapley, and the implications for free speech and
- Issue 2.07, February 16, 2005.
A variety of topics appear in the 2.07 issue of The Astrophysics Spectator.
A page describing the structure of main-sequence stars is added to the “Stars” path.
A research page on the Huygens probe and its landing on Titan is added to the
“Solar Planetary System” path. The commentary for the week is the first
in a series of articles on academic freedom.
- Issue 2.06, February 9, 2005.
This week I add pages on atmospheres in local thermal equilibrium and on Cepheid variables to the
“Electromagnetic Radation” path and the “Distance” path.
An Applet Control Guide is also added to the site, and two applets are updated.
The commentary for this week discusses how we use our vision to understand physical phenomena.
- Issue 2.05, February 2, 2005.
The “Electromagnetic Radiation” survey path is begun this issue with a page
on thermal radiation. This page includes the site's first “live” figure.
The commentary for this issue discusses the difficulty of seeing the world as we know
it to be. This issue also includes an index page of live figures.
- Issue 2.04, January 26, 2005.
This issue of The Astrophysics Spectator adds three pages to the “Stars”
path; these pages discuss the internal structure of stars, radiative transport in stars,
and convection in stars. The landing of the Huygens probe on Titan inspires a commentary
on how we see the same processes in quite different corners of the universe. A redesigned
home page is presented.
- Issue 2.03, January 19, 2005.
This issue of The Astrophysics Spectator presents several pages of the
“Distance” path that develop the natural distance scales for the Solar System,
the Galaxy, and the observable universe. The commentary discusses a form of argument
about the origin of observed phenomena that the author calls “Natural Design.”
- Issue 2.02, January 12, 2005.
This issue of The Astrophysics Spectator continues the discussion of orbits with
the discussion of stellar orbits in isotropic stellar systems. A simulator page that
models stellar orbits in the plane of a spiral galaxy is included. The news of the week
is the imminent landing of the Huygens probe on Titan. The commentary is on the intelligent
design argument for the existence of God.
- Issue 2.01, January 5, 2005.
In the first issue of 2005, I add a Keplerian orbit simulator page to the
“Gravitational Physics” path.