| Planck_Satellite ESA mission designed to find the three cosmological parameters: the Hubble parameter, the density and the deceleration parameter from variations in the cosmic background radiation. |
| Revved-Up_Universe Astronomers are convinced that the expansion of the Universe accelerates. |
| Sloan_Digital_Sky_Survey A dedicated 2.5 meter telescope which uses sensitive electronic light detectors to systematically map a quarter of the sky, building a catalog of celestial objects, galaxies, and quasars. |
| Supernova_Cosmology_Project This Berkeley labs site is based on observation of red shift in stars going supernova. |
| Tufts_Institute_of_Cosmology The Cosmology group at Tufts University with links to other cosmology sites |
| The_Big_Bang_(One_More_Time) A new model of the universe says it repeats itself in an endless cycle. Article from Christian Science Monitor. (May 9, 2002) |
| Turning_On_the_Universe Astronomers say the Universe's expansion has been accelerating recently. A new model for repulsive 'dark energy' may help explain the acceleration in a more natural way than other models. From Physica |
| Review_of_Mistake_of_Einstein Cosmologists have used recent data to constrain the type of 'dark energy' that may fill all of space. (July 30, 1999) |
| Coalition_for_Plasma_Science A group of institutions, organizations, and companies joining forces to increase awareness and understanding of plasma science and its many applications and benefits for society. |
| Helicon_Plasma_Thesis PhD thesis on helicon wave plasmas by Darryn Schneider. |
| MATLAB_Instruction_Modules_for_Introductory_Plasma_Physics Modules to teach single particle motion, dispersion relation, particle simulation and ray-tracing. |
| NRL_Plasma_Formulary Revised Edition. The NRL Plasma Formulary has been the handbook of plasma physicists for the past 20 years. It is available in PostScript, PDF, and TeX formats. |
| Plasma_Dictionary All terms and definitions presented in alphabetical order. |
| Plasma_Everywhere Introduction on plasmas from NASA. Plasmosphere surrounding our world. |
| Plasma_on_the_Internet Plasma-gate. Lists of Plasma Physics servers on the internet. (From WIS Institute). |
| Plasma_Physics_and_Nuclear_Fusion_Experiments List of web sites describing experiments world-wide to study the physics of nuclear fusion by magnetic confinement. |
| Plasma_Physics_Research_Center Plasma Physics Research Center Tehran-Iran |
| Plasma_Simulation_Projects Projects on numerical plasma simulation, including HPEM code, Monte Carlo Module, and Feature Profile Model, developed at the Computational Optical and Discharge Physics Group, University of Illinois. |
| Plasma_TV_Science Guide to plasma science used within the plasma television technology. Includes educational resources and links to related information. |
| Theoretical_Principles_of_Plasma_Physics_and_Atomic_Physics Essential facts and formulae. |
| Who_is_Who_in_Atomic_and_Plasma_Physics_(WWAPP) Database from Plasma Laboratory at Weizmann Institute of Science, Israel. |
| AP_Statistics_at_the_College_Board The College Board's official AP Statistics page. Course description, sample exam questions, teacher resources and contact information. |
| Business_Statistics Covers averages, normal distribution, best curve fit and skewness. Includes resource links. |
| Center_for_Statistics_Education The American Statistical Association sponsors educational resources for K-12 and above. ASA's LearnStat program provides continuing education for professional statisticians and educators. |
| Computer-Assisted_Statistics_Teaching_(CAST) A complete web-based course in introductory statistics. Registration required. |
| Curve_Fit Beginner's guide to nonlinear regression. Emphasizes how to interpret results. |
| The_Data_and_Story_Library Online library of datafiles and stories that illustrate the use of basic statistics methods. The goal is to provide data from a wide variety of topics so that statistics teachers can find interesting, |
| DISCUS Discovering Important Statistical Concepts Using Spreadsheets. Uses Excel spreadsheets to investigate statistical concepts. |
| Intro_Stat__EPR_Approach This site contains information about the Entity-Property-Relationship (EPR) approach to the introductory statistics course by Donald Macnaughton. |
| Introduction_to_Mathematical_Statistics Lecture notes from a year-long course in mathematical statistics. |
| Introductory_Statistics___Concepts,_Models,_and_Applications_by_David_Stockburger An online, searchable introductory statistics text. By David Stockburger of Southwest Missouri State University. |
| Intuitive_Biostatistics Harvey Motulsky, OUP (1995). Site for the book, with online extracts (PDF). |
| K-12_Statistics_Education Resources in statistics including lessons and useful data sets. |
| Number_Watch Monitors the media in search of misleading numbers in news, politics and science. |
| Numeracy_in_the_News Features sections on data collection and sampling, creating graphs, probability and inference. Also, includes special topic articles and teacher spreadsheet programs. |
| Primer_in_Statistics Covers mean, mode, median, standard deviation, area approximation, charts and testing for normality. |
| Resources_in_Statistics,_Quantitative_Methods_and_Experimental_Design Statistics-related exercises and humour, for courses from high school to graduate level. |
| Rice_Virtual_Lab_in_Statistics This resource for teaching statistics includes java simulations, case studies, an online text, and an analysis lab. |
| SAS_JMP Tutorials for SAS's JMP Statistical Analysis Software. |
| Seeing_Statistics Tutorial using graphs to illustrate concepts. Includes glossary of terms. Online purchase. |
The figure on the left is based on Plate IV in Adriaan van Maanen's 1921 paper (MA21) which shows astrometrically measured internal motions for M81. "The arrows indicate the direction and magnitude of the mean annual motions. Their scale (0.1 arcsec) is indicated on the illustration."
The photo on the right was made with Mt. Wilson's 100 inch reflector. (Source NASA). This photo was
digitally quantized into six brightness levels to form the background for the van Maanen information on the left.
Both photographs above are misleading to a degree because over-exposure in the central region of M81 makes it look as though that region is comprised of thousands or millions of stars (which may or may not
be true). To see a clearer picture of the central region, go to the Space.com article
Stunning View of Galaxy M81 Released and click on the full XMM-Newton graphic inside the Images box.
The authors of that article say that the strangely active center of M81 might represent a maturing black hole or a starburst. If it turns out that M81 is about where van Maanen suggested, i.e., nearby to the Milky Way, then some other interpretation of the small nucleus might be in order.
For further evidence of a small (star like?) core for M81 see NRAO's
page Radio Images of Galaxies.
[Added 05 Sep 2003.]
See the related articles M33 Internal Motions
and
On Spiral Nebulae, van Maanen et al.
Recommended sites for other photographs of M81.
M81,
Spiral Galaxy in Ursa Major - CCD Masterpiece by Robert Gendler
M81 - Spiral Galaxy (Type Sb) - Multi-wavelength photos.
Note of Caution
Van Maanen's investigations on internal motion in spiral nebulae have
(since about 1935) been relegated to the status of "nonsense" by
astronomers who subscribe to the idea of an expanding universe. That said,
two articles which seem to suggest that the expanding universe idea
may not be on as solid ground as commonly assumed are, "Edwin Hubble and a
Relativistic, Expanding Model of The Universe"
(HN71)
and "Walter S. Adams and the Imposed Settlement Between Edwin Hubble and
Adriaan van Maanen"(HB92). In the first of these it is stated:
"Hubble's preference for a recessional or expanding model is further
revealed in a 1936 paper communicated to the National Academy of Sciences.
In this paper he reviewed previous counts of nebulae and reported the
results of two new surveys. The data, enlarged from that of the previous
year, still pointed to the same conclusion: the observations more nearly
fit the non-expanding model." [Emphasis added.]
* * *
It is fitting to quote van Maanen's tribute to James Jeans in the final
two paragraphs of his 1921 paper (MA21) on Messier 81.
The close agreement of the displacements in direction with the spiral arms
suggests that we have here a realization of the motions described by Jeans
in Problems of Cosmonogy and Stellar Dynamics, from which I quote
freely.
"If so, we must then suppose that before the formation of the spiral arms
the nebular masses were rotating and had reached a lenticular shape. The
formation of Laplace's ring requires perfect symmetry of mass about the
axis of rotation. The distances of adjacent masses in space are in
general so great that their gravitational influence will be extremely
small, but even the slightest external gravitational field will be
sufficient to preclude the formation of a ring; instead of this, the matter
will will be thrown off at two antipodal points. The masses first thrown
off at the antipodal points form in themselves a tide-generating system
which concentrates the region of ejection more and more at two points. The
result is an extension farther and farther into the equatorial plane as
the evolution of the nebula proceeds. The determination of the shape of
the arms seems at present to be beyond the reach of mathematical analysis,
but the long streams of gaseous matter must become longitudinaly unstable
and will tend to break up into condensations or nuclei." [Adams Prize
Essay, University of Cambridge, 1917.]
Jeans' other publications on spiral nebulae (JJ17), (JJ23), and (JJ25)
should be of interest to students of the History of Astronomy.
* * *
Readers are encouraged to see the Hubble Site 07 Feb 2002 release,
Hubble Reveals
'Backwards' Spiral Galaxy". Future findings may invalidate the picture
but, at present, astronomers suggest that "the galaxy called NGC 4622
appears to be rotating in the opposite direction to what they expected."
The apparent direction of rotation is similar to that for van
Maanen's measured internal motions for M81 shown above. [Added 06
August 2003.]
See Jay Bitterman's Astronomy Bio...
Adriaan
van Maanen. [Added 27 August 2003.]
Adriaan van Maanen (left), Bertil Lindblad (center), Unidentifed man
(right), on the platform for observation at the Newton focus of the
1 meter reflector of the Stockholm Observatory in Saltsjöbaden Sweden.
August 1938.* (Lindblad was Director of the Stockholm Observatory from
1927 to 1965.)
Photograph by Dorothy Davis Locanthi,
courtesy AIP
Emilio Segrč Visual Archives,
Dorothy Davis Locanthi Collection
* Thanks to Per Olof Lindblad for the location and date of the photograph.
References
HN71 - Hetherington, N., Astronomical Society of the PacificLeaflet
509, 473-480 (1971) -
NADS
HB92 - Hetherington, N., Brashear, R., Journal for the History of
Astronomy 23, 53-56 (1992).
JJ17 - Jeans, J., Internal Motion in Spiral Nebulae, The Observatory
40 60-61(1917) -
NADS [No article or abstract]
JJ23 - Jeans, J., Internal Motions in Spiral Nebulae, MNRAS
84, 60-76 (1923) -
NADS
JJ25 - Jeans J., Note on the Distances and Structure of the Spiral Nebulae,
MNRAS 85, 531-534 (1925) -
NADS
MA21 - van Maanen, Adriaan, Investigations on Proper Motion - Fifth Paper:
The Internal Motion in the Spiral Nebula Messier 81, Astrophysical
Journal 54, 347-356 (1921) -
NADS
See: On Spiral Nebulae, van Maanen et al.
Messier 33 Internal Motions.
Useful Links
Photos Focus: Categorized resource
directory for everything about photos.
Shade Tree Physics
Send comments/questions to Bob Fritzius at
fritzius@bellsouth.net
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