Recognitions:
Gold Member
Staff Emeritus

## A&C reference library

 PhysOrg.com astronomy news on PhysOrg.com >> Three centaurs follow Uranus through the solar system>> Final curtain for Europe's deep-space telescope>> Hubble spots a very bright contortionist
 Recognitions: Gold Member Science Advisor Charles Bennet et al. http://arxiv.org/astro-ph/0302207 see table 3 on page 33---"Best" Cosmological Parameters from the article "First Year WMAP Observations, Preliminary Maps and Basic Results" Charles Lineweaver http://arxiv.org/astro-ph/0305179 "Inflation and the Cosmic Microwave Background" Michael Turner "Making Sense of the New Cosmology" http://arxiv.org/astro-ph/0202008 Wendy Freedman and Michael Turner "Measuring and Understanding the Universe" http://arxiv.org/astro-ph/astro-ph/0308418 The finiteness or infiniteness of space turns on how accurately they can measure a number called Omega. This is the first thing listed at the top of Bennett's Table 3. The current WMAP data say that Omega = 1.02 +/- 0.2 which is tantalizingly close to one. If Omega is exactly one, then space is flat and infinite. But if Omega is even slightly greater than one, then space may LOOK flat but on a very large scale it may curve around on itself and be finite. Based on observations as of right now we cannot be sure either way.
 Recognitions: Gold Member Science Advisor Nereid kindly provided a link to this article about a wide-angle deep survey of the universe called GEMS http://skyandtelescope.com/news/article_1152_1.asp GEMS covers a patch of sky as big as the full moon and took thousands of images in that patch and made a mosaic picture of that patch which is real deep, going way back in time, so you see galaxies forming and colliding and evolving. The article Nereid shows a portion of the picture. The total GEMS picture has some 3 billion pixels. ------------------------ Dark matter: Here's another Nereid link to a dark matter article (mapping it in a cluster by observing lensing) http://www.esa.int/export/esaCP/SEM...tureWeek_0.html ------------------------ Neutrino astronomy: Has a big future potential in observational cosmology. Wolram provided these neutrino-related links: http://www.space.com/scienceastrono...nos_030716.html this gives the AMANDA2 neutrino sky map---the obseratory down near south pole. http://www.lns.cornell.edu/spr/2003-07/msg0052565.html Basic facts/estimates about the cosmic neutrino background presented by Ted Bunn, one of the moderators on Usenet sci.physics.research. --------------------------- High-energy Cosmic Rays: A great survey article about high energy cosmic ray observations (another window for observational cosmology to look thru) Floyd Stecker "Cosmic Physics: the High Energy Frontier" http://arxiv.org/astro-ph/0309027

Recognitions:
Gold Member

## A&C reference library

two good online cosmology calculators:

Ned Wright's
http://www.astro.ucla.edu/~wright/CosmoCalc.html

Siobahn Morgan's
http://www.earth.uni.edu/~morgan/ajj...gy/cosmos.html

homepage for Siobahn in case you want to see who she is
http://www.earth.uni.edu/smm.html
homepage for Ned in case you want to see who he is
http://www.astro.ucla.edu/~wright/intro.html

-------
Martin Bojowald
http://arxiv.org./abs/astro-ph/0309478
"Quantum Gravity and the Big Bang"
General Relativity had a glitch and
quantizing the theory fixed the glitch so
it no longer predicts a moment of infinite
density and curvature (a type of singularity).
Evolution prior to big bang is shown in some
of the articles cited in this brief survey.
---------

Labguy provided news of a recent test of General Relativity
(which GR passed with flying colors) a binary pulsar:

http://www.astro.ucla.edu/~wright/cosmolog.htm#04Dec03

The technical article about the binary pulsar
and the most stringent verification of GR to date is:

http://arxiv.org/astro-ph/0401086

----------
 Recognitions: Gold Member Science Advisor Useful constants: One parsec = 3.857E16 meters Newton's G = 6.6742E-11 cub.meter/sq.second kg Best current estimate of Hubble parameter H = 71 km/s per Megaparsec Critical energy density derived from that = 0.85 joule per cubic km. In standard (SI) metric units H = 2.301E-18 per second H reciprocal, the "Hubble time" parameter, is 4.3E17 seconds. (As it happens this is roughly the same as the age of the universe.) The standard formula for calculating the critical density (so-called "rho crit") is $$\rho_{crit} = \frac{3c^2H^2}{8\pi G}$$ If you plug in the values for G, c, and H given here, it works out to 0.85 joule per cubic kilometer. This is the average energy density that is theoretically needed for space to be flat rather than positively or negatively curved. Since WMAP observations of the CMB indicate that it is flat or very nearly so, this is the density usualy assumed. When people say the dark energy is 73 percent they mean of this. Or dark matter is 23 percent, it is of this 0.85 joules per cubic km. Or ordinary visible matter is 4 percent, it is likewise.
 Recognitions: Gold Member Science Advisor Lineweaver's article is also online in HTML at a Caltech site and this is sometimes handy because you can link to a particular page or Figure, rather than to the whole PDF file. For instance his "Size and destiny of the universe" Figure 14 is immediately accessible in two places Figure 14 medium scale, with caption and another figure: http://nedwww.ipac.caltech.edu/level...weaver7_7.html Figure 14 larger scale, without caption: http://nedwww.ipac.caltech.edu/level...s/figure14.jpg

Recognitions:
Gold Member
 Recognitions: Gold Member Science Advisor Jimmy supplied these mosaic pictures of Europa and Jupiter http://members.aol.com/jrzycrim01/images/Europa.jpg http://members.aol.com/jrzycrim01/images/Europa2.jpg They are pretty remarkable. ---------------------------------------- Nereid supplied a good general purpose NASA link about the moons and the Jovian system in general http://galileo.jpl.nasa.gov/moons/moons.html Also some more specialized links concerning Io's ice covered ocean and concerning impact basins (of which Callisto has a couple of examples) http://www.lpi.usra.edu/research/europa/thickice/ http://www.solarviews.com/cap/index/impactbasin1.html ---------------------------------------- Enigma supplied this link to tabulated data on the Jovian moons: http://www.the-planet-jupiter.com/mo...cts-sheet.html ---------------------------------------- Here's a useful source about gravity assist maneuvers http://cdeagle00.tripod.com/omnum/flyby.pdf It gives a formula for the maximum turn angle $$2arcsin \frac{1}{1+rv_{oo}^2/\mu}$$ possible flying by a body with radius r and gravitational parameter(GM) equal to mu. Here v-infinity is the speed of approach at infinity. This can be rewritten in terms of v-infinity and v-circ, the circular orbit speed at the body's surface: $$2arcsin \frac{1}{1+v_{inf}^2/v_{circ}^2}$$ -------------------------------------------------