A&C Reference Library - Astronomy & Cosmology Resources

[marcus]

Updating some basic cosmology links and getting a bunch of them together:

Ned Wright's cosmology tutorial
http://www.astro.ucla.edu/~wright/cosmolog.htm

Ned Wright's cosmology FAQ
http://www.astro.ucla.edu/~wright/cosmology_faq.html

Ned Wright's most basic cosmology calculator
http://www.astro.ucla.edu/~wright/CosmoCalc.html
(he has links to some more advanced or specialized calculators)

Morgan's calculator
http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html

Murphy's coordinate conversion tool
http://fuse.pha.jhu.edu/support/tools/eqtogal.html

Lineweaver and Davis' Scientific American article Misconceptions about the big bang March 2005.
AS LONG AS THIS PRINCETON LINK WORKS IT IS BETTER THAN THE OTHERS

http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf

Here are the links to the same article at the SciAm website. But these links have been going dead or else the GRAPHICS that you used to get have been disappearing. So these SciAm links may not be as good as the Princeton one

http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

The Lineweaver Davis article had some very useful SIDEBARS giving pictorial diagrams with a question together with right and wrong answers explained. For easier access, here are links to individual sidebars.

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p39.gif
What kind of explosion was the big bang?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p40.gif
Can galaxies recede faster than light?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p42.gif
Can we see galaxies receding faster than light?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p43.gif
Why is there a cosmic redshift?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p44.gif
How large is the observable universe?

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p45.gif
Do objects inside the universe expand, too?

 

[Astronuc]

marcus has posted some links to relativity.livingreviews.com, and I stumbled on a set of articles about solarphysics.

http://solarphysics.livingreviews.org/Articles/index.html

 

[Astronuc]

I found a nice little pocket handbook/guide for visual astronomers. I was discounted to $5 (normally $15) at Barnes & Noble.

Neil Bone (Illustrated by Wil Tirion), Deep Sky Observer's Guide, Firefly Books.

 

[Astronuc]

Connecting Quarks with the Cosmos:
Eleven Science Questions for the New Century

http://www.nap.edu/catalog.php?record_id=10079

Advances made by physicists in understanding matter, space, and time and by astronomers in understanding the universe as a whole have closely intertwined the question being asked about the universe at its two extremes the very large and the very small. This report identifies 11 key questions that have a good chance to be answered in the next decade. It urges that a new research strategy be created that brings to bear the techniques of both astronomy and sub-atomic physics in a cross-disciplinary way to address these questions. The report presents seven recommendations to facilitate the necessary research and development coordination. These recommendations identify key priorities for future scientific projects critical for realizing these scientific opportunities.

 

[marcus]

Fascinating article mentioned by Xantox:
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1995ApJ...446...63H&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
Edward R. Harrison
Mining Energy in an Expanding Universe
This seems not to be available at the arxiv, but is from Harvard.

 

[marcus]

Some Einstein quotes:
https://www.physicsforums.com/showthread.php?p=1386960#post1386960

“Dadurch verlieren Zeit & Raum den letzter Rest von physikalischer Realität. ..."

“Thereby time and space lose the last vestige of physical reality”.

(Possible paraphrase: space does not have physical existence, but is more like a bunch of relationships between events)

In case anyone wants an online source, see page 43 of this pdf at a University of Minnesota website
www.tc.umn.edu/~janss011/pdf%20files/Besso-memo.pdf[/URL]

==quote from the source material==
...In the introduction of the paper on the perihelion motion presented on 18 November 1915, Einstein wrote about the assumption of general covariance “[b]by which time and space are robbed of the last trace of objective reality[/b]” (“[color=blue]durch welche Zeit und Raum der letzten Spur objektiver Realität beraubt werden,[/color]” Einstein 1915b, 831). In a letter to Schlick, he again wrote about general covariance that
“[b]thereby time and space lose the last vestige of physical reality[/b]” (“[color=blue]Dadurch verlieren Zeit & Raum den letzter Rest von physikalischer Realität.[/color]” Einstein to Moritz Schlick, 14 December 1915 [CPAE 8, Doc. 165]).
==endquote==

Both quotes are from Nov-Dec 1915, one being from a paper on perihelion motion. and the other from a letter to Moritz Schlick a few weeks later.

 

[marcus]

Thanks to George Jones for this link:
http://arxiv.org/abs/gr-qc/0508052
"In an expanding universe, what doesn't expand?"
May be helpful in addressing a questions that often comes up in cosmo forum.

 

[marcus]

R. Brent Tully (of the Tully Fisher relation) has some fine outreach material,
http://www.ifa.hawaii.edu/~tully/outreach/vv1a_9-25.mpg
See this animation of a trip up out of Milky's disk and then to the Virgo Cluster, eyeballing lots of stuff along the way and ending up in a giant elliptical.

See also this, which I had trouble streaming and couldn't evaluate but which might be interesting
http://www.ifa.hawaii.edu/~tully/pecv_12min_sound_qt.mov

I should alert readers to the fact that I have just become aware of Tully's website and outreach material. Although I am impressed by by the quality and by his reputation, I cannot say anything overall. He may have some unorthodox views. From my point of view this is how science happens. Individuals should have some individualistic views and not just follow the consensus. So this would be OK. But proceed with caution. I'm just now watching the sound movie and finding it very interesting although the streaming is spasmodic.

 

[marcus]

Nobelist George Smoot talking about the CMB and what things it tells us.
Very skillful presentation with animated graphs, shows what bumps in the power spectrum mean, and why. Part of the "Honeywell Nobel" lecture series.

http://www.revver.com/video/827006/the-history-and-fate-of-the-universe-part-1-of-9/

http://www.revver.com/video/827106/the-history-and-fate-of-the-universe-part-2-of-9/

http://www.revver.com/video/827171/the-history-and-fate-of-the-universe-part-3-of-9/

http://www.revver.com/video/832550/the-history-and-fate-of-the-universe-part-4-of-9/

http://www.revver.com/video/832599/the-history-and-fate-of-the-universe-part-5-of-9/

http://www.revver.com/video/832643/the-history-and-fate-of-the-universe-part-6-of-9/

http://www.revver.com/video/832679/the-history-and-fate-of-the-universe-part-7-of-9/

http://www.revver.com/video/832724/the-history-and-fate-of-the-universe-part-8-of-9/

http://www.revver.com/video/832788/the-history-and-fate-of-the-universe-part-9-of-9/

 

[marcus]

Primer on black holes.
For nonspecialist general audience by the president of the Royal Astronomical Society.
How we observe the black holes at the center of normal galaxies and quasar galaxies.
How they generate different kinds of radiation. Models. Inference.

Color illustrated magazine article somewhat on the level of SciAm, maybe a bit more math, but still fairly accessible.
http://arxiv.org/abs/0906.2119
Black Holes at Work
Andrew Fabian
published in Astronomy and Geophysics

 

[marcus]

http://arxiv.org/pdf/0912.2809v1
Black Holes in an Expanding Universe
Gary W. Gibbons, Kei-ichi Maeda
4 pages, 1 table, 2 figures
(Submitted on 15 Dec 2009)
"An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state. It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. We find a regular horizon, which depends on one parameter (the ratio of the energy density of U(1) fields to that of the scalar field). The horizon is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature."

This short article could be useful as a review with references to a number of earlier papers on models of black hole in expanding universe.

 

[marcus]

Meteor posted this back in April 2004, almost 6 years ago. Time flies!

This paper seems interesting:
"Distance measures in cosmology"
David W. Hogg
http://arxiv.org/abs/astro-ph/?9905116

It must be good given that I really enjoyed the pdf course of special relativity of D. Hogg

Thanks to meteor for adding this to our A&C reference library. Hogg's tutorial is an excellent clear layout of the different distance measures. I recall finding it a real help at one time.
http://arxiv.org/abs/astro-ph/9905116

Of course Ned Wright's tutorial, and his cosmo calculator, should be mentioned as well.

If you don't know about this already, several different distance measures are used in astronomy. It's good to be reminded of this and of these resources. Thanks to Sylas for doing so most recently!

 

[marcus]

http://arxiv.org/pdf/0909.3983
Latest estimates about the Cosmic Event Horizon (CEH) by Egan Lineweaver.
Current distance to it ~15.7 Gly (proper i.e. freezeframe distance)
what that is converging to ~16.4 Gly (likewise proper, or freezeframe distance).

Note the CEH is not the same as the Hubble distance ~13.7 Gly.

You can picture the proper distance (at a given moment) as what you would measure if you could freezde the expansion process at that moment and use conventional radar ranging or timing of lightsignals to measure in the usual way. The Hubble law v = Hd is based on this concept of distance.

The CEH is basically the distance to a galaxy which, if you left here today and traveled at the speed of light, you could never quite get to. Something closer than CEH you could, in principle, reach. It's definition depends on the standard cosmo model.

 

[Astronuc]

Closer to home.

Nearest Star: The Surprising Science of Our Sun
Leon Golub, Jay M. Pasachoff

Leon Golub is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and is the head of one of the teams working with NASA's Transition Region and Coronal Explorer (TRACE) spacecraft .

Jay M. Pasachoff is Field Memorial Professor of Astronomy at Williams College and, having viewed 31 solar eclipses, is Chair of the Working Group on Eclipses of the International Astronomical Union.

Abstract: Unlike the myriad points of light we gaze at in the night sky, our nearest star allows us to study the wonders of stellar workings at blindingly close range--from a mere 93 million miles away. And what do we see? In this book, two of the world's leading solar scientists unfold all that history and science--from the first cursory observations to the measurements obtained by the latest state-of-the-art instruments on the ground and in space--have revealed about the Sun. Following the path of science from the very center of this 380,000,000,000,000,000,000-megawatt furnace to its explosive surface, Nearest Star invites readers into an open-ended narrative of discovery about what we know about the Sun and how we have learned it.

How did the Sun evolve, and what will it become? What is the origin of its light and heat? How does solar activity affect the atmospheric conditions that make life on Earth possible? These are the questions at the heart of solar physics, and at the center of this book. Having made optical solar observations with many solar telescopes and in the rockets and satellites, the authors bring their extensive personal experience to this story of how astronomers study the Sun, and what they have discovered about phenomena from eclipses to neutrinos, space weather, and global warming. Richly illustrated with an assortment of pictures from the latest solar missions and the newest telescopes, this book is a very readable, up-to-date account of science's encounter with our nearest star.

http://www.hup.harvard.edu/catalog/GOLNEA.html (on sale ~$18)

Nearest Star

 

[Astronuc]

OPPORTUNITIES IN NUCLEAR ASTROPHYSICS
Conclusions of a Town Meeting held at the University of Notre Dame
7-8 June 1999
http://www.nscl.msu.edu/~austin/nuclear-astrophysics.pdf

It would be interesting to do an update of this program.

Also - http://en.wikipedia.org/wiki/Joint_Institute_for_Nuclear_Astrophysics
http://www.jinaweb.org/

 

[marcus]

New textbooks about the early universe. Expensive but the department library might be willing to order copies.

http://www.worldscibooks.com/physics/7874.html
INTRODUCTION TO THE THEORY OF THE EARLY UNIVERSE
Hot Big Bang Theory
by Dmitry S Gorbunov (Russian Academy of Sciences, Russia) & Valery A Rubakov (Russian Academy of Sciences, Russia & Moscow State University, Russia)
This book is written from the viewpoint of a deep connection between cosmology and particle physics. It presents the results and ideas on both the homogeneous and isotropic Universe at the hot stage of its evolution and in later stages. The main chapters describe in a systematic and pedagogical way established facts and concepts on the early and the present Universe. The comprehensive treatment, hence, serves as a modern introduction to this rapidly developing field of science. To help in reading the chapters without having to constantly consult other texts, essential materials from General Relativity and the theory of elementary particles are collected in the appendices. Various hypotheses dealing with unsolved problems of cosmology, and often alternative to each other, are discussed at a more advanced level. These concern dark matter, dark energy, matter-antimatter asymmetry, etc.
Contents:
Cosmology: A Preview
Homogeneous Isotropic Universe
Dynamics of Cosmological Expansion
ΛCDM: Cosmological Model with Dark Matter and Dark Energy
Thermodynamics in Expanding Universe
Recombination
Relic Neutrinos
Big Bang Nucleosynthesis
Dark Matter
Phase Transitions in the Early Universe
Generation of Baryon Asymmetry
Topological Defects and Solitons in the Universe

Readership: Cosmologists, advanced undergraduate and graduate students.
500pp (approx.)

http://www.worldscibooks.com/physics/7873.html
INTRODUCTION TO THE THEORY OF THE EARLY UNIVERSE
Cosmological Perturbations and Inflationary Theory
by Dmitry S Gorbunov (Russian Academy of Sciences, Russia) & Valery A Rubakov (Russian Academy of Sciences, Russia & Moscow State University, Russia)
This book accompanies another book by the same authors, Introduction to the Theory of the Early Universe: Hot Big Bang Theory and presents the theory of the evolution of density perturbations and relic gravity waves, theory of cosmological inflation and post-inflationary reheating. Written in a pedagogical style, the main chapters give a detailed account of the established theory, with derivation of formulas. Being self-contained, it is a useful textbook for advanced undergraduate students and graduate students. Essential materials from General Relativity, theory of Gaussian random fields and quantum field theory are collected in the appendices. The more advanced topics are approached similarly in a pedagogical way. These parts may serve as a detailed introduction to current research.
Contents:
Jeans Instability in Newtonian Gravity
Cosmological Perturbations in General Relativity. Equations of Linearized Theory
Evolution of Vector and Tensor Perturbations
Scalar Perturbations: Single-Component Fluids
Primordial Perturbations in Real Universe
Scalar Perturbations Before Recombination
Structure Formation
Beyond Ideal Fluid Approximation
Temperature of Cosmic Microwave Background Radiation
CMB Polarization
Drawbacks of the Hot Big Bang Theory. Inflation as Possible Way Out
Inflation in Slow Roll Regime
Generation of Cosmological Perturbations at Inflation
Further Aspects of Inflationary Theory
Preheating After Inflation
Bouncing Universe

Readership: Cosmologists, advanced undergraduate and graduate students.
480pp (approx.)

http://www.worldscibooks.com/physics/7235.html
PRIMORDIAL COSMOLOGY
by Giovanni Montani (ENEA & ICRANet, University of Rome “Sapienza”, Italy), Marco Valerio Battisti (ICRA & University of Rome “Sapienza”, Italy), Riccardo Benini (ICRA & University of Rome “Sapienza”, Italy), & Giovanni Imponente (Queen Mary, University of London, UK)
Primordial Cosmology deals with one of the most puzzling and fascinating topics debated in modern physics — the nature of the Big Bang singularity. The authors provide a self-consistent and complete treatment of the very early Universe dynamics, passing through a concise discussion of the Standard Cosmological Model, a precise characterization of the role played by the theory of inflation, up to a detailed analysis of the anisotropic and inhomogeneous cosmological models...
This book traces clearly the backward temporal evolution of the Universe, starting with the Robertson–Walker geometry and ending with the recent results of loop quantum cosmology in view of the Big Bounce. The reader is accompanied in this journey by an initial technical presentation which, thanks to the fundamental tools given earlier in the book, never seems heavy or obscure.
Contents:
Historical Picture — From Ancient Cultures to the 20th Century
Fundamental Tools — Einstein Theory and Singularity Theorems
The Structure and Dynamics of the Isotropic Universe
Shortcomings of the Standard Model and Inflationary Theory
Inhomogeneous Quasi-Isotropic Cosmology
Homogeneous Universes — Chaotic Cosmology
Hamiltonian Formulation of the Mixmaster — The Liouville Measure
The Generic Cosmological Solution — Singularity without Symmetries
Quantum Cosmology — From the Wheeler-DeWitt Approach to Loop Quantum Cosmology

Readership: Researchers in cosmology, high energy physics and quantum physics.
616pp (approx.)

Amazon links for these and related textbooks:
https://www.amazon.com/dp/9814322245/?tag=pfamazon01-20
https://www.amazon.com/dp/9814322229/?tag=pfamazon01-20
https://www.amazon.com/dp/9814271004/?tag=pfamazon01-20
https://www.amazon.com/dp/0521195756/?tag=pfamazon01-20

 

[marcus]

Spires database has gotten a bit slow. I am currently getting somewhat better results with the German mirror site maintained by the DESY library.

Here for instance is the Stanford Spires search for post-2008 keyword Quantum Cosmology (QC) research papers:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2008&FORMAT=WWW&SEQUENCE=citecount%28d%29

Here is the corresponding DESY search:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=dk+quantum+cosmology+and+date+%3E+2008&FORMAT=WWW&SEQUENCE=citecount%28d%29

Both currently give 210 QC papers that appeared after 2008, ranked by citation count: most often cited papers shown first. But the Stanford site takes longer and sometimes times out.

 

[marcus]

Simulations of structure formation in the early universe:
http://www.mpa-garching.mpg.de/galform/virgo/millennium/
"Millennium simulations".
May be something we linked to before---like the Volker Springel 2005 movies.

 

[Astronuc]

This and the following web pages contain a database of short essays from the Astronomy and Astrophysics Encyclopedia, ed. Stephen P. Maran.
http://ned.ipac.caltech.edu/level5/ESSAYS/essays.html

 

[marcus]

Jorrie cosmo calculator

Jorrie has an online cosmology calculator that embodies the standard model of the U, just as Morgan's and Ned Wright's do
http://www.einsteins-theory-of-relativity-4engineers.com/cosmocalc.htm

It has some extra features and some advantages that make it easier to use, in certain respects. May also have additional precision at high redshifts. So it is definitely worth checking out.

If you want to use it and don't have the URL handy, you can get it by googling
"jorrie cosmological calculator" or else
"cosmological calculator 2010"

Jorrie credits another PF member, Hellfire, for originally setting it up. As I understand it, this is an updated version with whatever adjustments, based on 2010 values of the constants.

 

[Astronuc]

Want To Make A Giant Telescope Mirror? Here's How
http://www.npr.org/2012/01/26/145837380/want-to-make-a-giant-telescope-mirror-heres-how

Roger Angel is the master of making big mirrors for telescopes. For 30 years he has been using a method called spin casting to make the largest solid telescope mirrors in the world.

At the moment, he's making the second of seven mirrors, each 27 feet across, that will go into the Giant Magellan Telescope (GMT), which will be sited on a peak in the Andes Mountains in Chile.

http://www.gmto.org/

 

[marcus]

Yenchin came up with a possibly useful iconic picture of the Einstein field equation (basic GR equation)
http://www.zamandayolculuk.com/cetinbal/KO/k_Gravity_worlds.jpg

 

[marcus]

Emmy Noether's original paper, in English translation:

http://arxiv.org/abs/physics/0503066
http://arxiv.org/pdf/physics/0503066.pdf

Section 6 on page 12 discusses the fact that conservation of energy does not hold generally in the curved spacetime of GR---something pointed out by David Hilbert.
The paper first appeared in the Nachrichten der Königliche Gesellschaft der Wissenschaften zu Göttingen (1918)

 

[marcus]

Standard Solar Model, thanks to Phyzguy:
http://www.ap.stmarys.ca/~guenther/evolution/ssm1998.html

Gives percentages of H, He, and heavier elements. Derived by a computer model of fusion burning in core starting with pre-star gascloud abundances. Provides basis for estimating the remaining lifetime of the sun.

=============

The estimated total entropy as of today of the universe within our cosmic event horizon might be of interest to someone.
http://arxiv.org/abs/0909.3983 This was published in Astrophysical Journal in 2010.
One of the co-authors is Charley Lineweaver.
Here's a conference presentation writeup based on it, some nice color visuals.
http://www.mso.anu.edu.au/~charley/papers/LineweaverEganParisv2.pdf

 

[marcus]

When I type this into Google and press space, or equal sign, Google calculates the present critical energy density of the universe.
3c^2(71 km/s per Mpc)^2/(8pi*G)

that is because it can interpret "71 km/s per Mpc" which is the present value of the Hubble rate H
and because the formula for the critical energy density is
ρ_crit=3c²H²/8πG

It gives the answer in PASCALS but a pascal is the same as a joule per cubic meter. the same unit works for both pressure and energy density.
So essentially it tells you the density in question is 0.85 nanojoule per cubic meter.
It's gratifying how much the Google calculator recognizes and is able to calculate.
It knows things like "mass of earth" "mass of electron" "radius of sun".
So you can put a term like "radius of earth" into a formula you want it to calculate, like type in
2pi*radius of earth
and you get a bit over 40,000 kilometers.
I guess you could say that the Google calculator is a library resource

 

[marcus]

A nice interactive graphic illustrating the various size scales of the universe. I'm not sure if we posted it before. Indications are it's new this year, at least in this version, so probably not.
http://htwins.net/scale2/
New PF member Wakabaloola gave us the link.

 

[marcus]

A nice pedagogical thing. Pairs of masses orbiting each other send out gravity waves--yes we know this. It was the basis of the 1993 Nobel prize to Hulse and Taylor who observed a binary pulsar. But how about an example close to home?

By orbiting the sun, the Earth radiates 196 Watts of power in gravity waves. the frequency of the wave is presumably one cycle per year, very low frequency

How do you know? Wikipedia has the formula for the radiated power. Type the following into google search window, which functions as a scientific calculator:
32/5*G^4/c^5*(mass of earth*mass of sun)^2(mass of earth+mass of sun)/(1 AU)^5

It knows what G is and what c is, and what the masses of Earth and sun are. So you don't have to look any of that up. When you type that in, or simply paste it in, if you want, and press space or equal sign, it will say 196 watts.

thanks to Mfb for this idea.

 

[marcus]

A new kind of cosmological calculator. Tabular output instead of oneshot. It reveals patterns: maxima, crossovers, relationships between columns in the table... So it is somewhat better for learning than a one-shot. Perhaps quite a bit better, I don't now yet. We need a place to keep "user manual" type information---what you can do with it. At least temporarily until there is a page somewhere online you can link to. For now here is the most user-manualish information I've seen:

The 'single-step problem' has been solved in CosmoLean_A17 and the 'few issues' with the flexible rounding of column data are gone as well, or so I hope. Please try it out and report any anomalies.

The most important differences are:

1. The info-popups have been mostly reworded and include comments as received in PMs.
2. The stretch range inputs arranged to be more consistent with the output table, from highest to lowest stretch.
3. Some 'logic' built into the input processor so that 'one-shot' outputs are intuitively achieved by either making s_step zero, which gives output for s_upper only; or by making s_upper and s_lower equal to each other, irrespective of s_step.
4. The number of decimals (rounding) of column data are adjustable individually. Becomes active on clicking Calculate and will remain so until changed again, reset clicked, or the page is refreshed.
5. Overall accuracy has been improved by resolving some coding issues. It now seems to work accurately up to s =10 000.
6. Some input validation and protection against crash of program are included. More to be considered.
7. On the drawing board: "into the future" (s < 1).

 

[marcus]

This by Ruth Durrer What do we really know about dark energy?
might be good to have handy as a reference.
http://arxiv.org/abs/1103.5331
It explains what is really being measured

 

[azzkika]

This by Ruth Durrer What do we really know about dark energy?
might be good to have handy as a reference.
http://arxiv.org/abs/1103.5331
It explains what is really being measured

Sorry to be cynical, your posts are most informative to an amateur like me so many many thanks for the work you and others put in on this site, but doesn't this link just state that the observations don't fit the theory so we add in X to balance the equation and X is called dark energy. Essentially the universe doesn't behave as expected is my understanding. Maybe no dark energy is required just a better understanding of the universe.

 

[marcus]

Sorry to be cynical, your posts are most informative to an amateur like me so many many thanks for the work you and others put in on this site, but doesn't this link just state that the observations don't fit the theory so we add in X to balance the equation and X is called dark energy. Essentially the universe doesn't behave as expected is my understanding. Maybe no dark energy is required just a better understanding of the universe.

It's important to be skeptical. To have deep reserves of skepticism about manmade theories.
This could translate into a cynical attitude when one hears scientists who should know better gushing about "dark energy" to get media attention, or sell books, or get funding. But those are INDIVIDUALS.
I would not be cynical about the current cosmic models, they may actually be more solid and justified than you think and if they turn out wrong, well, that is not dishonorable! Theories are meant to be tested and eventually improved or discarded. I would rather be skeptical about the theories---no disrespect.

You might like this recorded interview with Carlo Rovelli:
http://edge.org/conversation/a-philosophy-of-physics

Rovelli is one of today's prominent physicists and is skeptical both of "dark energy" and of "string theory". But derogatory only of the HYPE. He has what I think is quite a reasonable attitude about the cosmological constant Lambda, which people CALL "dark energy" but there is no evidence that it is any kind of energy. It behaves, as far as we can tell, like a simple slight constant curvature. As such it has a natural place in the Einstein equation. For 90 years or so people knew this constant curvature naturally appeared in the GR equation but most people assumed the constant was zero.

The GR equation has room in it for TWO geometric constants, Newton's G and Lambda. Lambda is a curvature that for a long time we thought it was zero, and it happens not to be. That's all.
To see that viewpoint explained, google "rovelli prejudice". You get a paper by Bianchi and Rovelli called "Why all these prejudices against a constant".
Or go here: http://arxiv.org/abs/1002.3966 and click on PDF.

Since this is a bibliography thread, it is better to make a separate thread to discuss questions like this. If you want, start one. This thread is mainly for useful links to research papers, videos and other online resources.

 

[julcab12]

http://edge.org/conversation/a-philosophy-of-physics

Since this is a bibliography thread, it is better to make a separate thread to discuss questions like this. If you want, start one. This thread is mainly for useful links to research papers, videos and other online resources.

(Disable lurker Mode). . Awesome article and thanks for sharing Marcus. I really like his approach and mentality towards science and "how it should be". Really change my view on what is "ugly" or how it's not needed.

"I think science is not about data; it's not about the empirical content, about our vision of the world. It's about overcoming our own ideas, and about going beyond common sense continuously. Science is a continuous challenge of common sense, and the core of science is not certainty, it's continuous uncertainty. I would even say the joy of taking what we think, being aware that in everything we think, there are probably still an enormous amount of prejudices and mistakes, and try to learn to look a little bit larger, knowing that there is always a larger point of view that we'll expect in the future."

 

[marcus]

I'm glad you liked it!
I happened to see your response--was it to the article by Bianchi and Rovelli "Why all these prejudices against a constant?" or to the piece in Edge?--because I came here to post this page from Ned Wright's cosmology site:
http://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html
He thinks light travel time should not be used in press releases as a measure of distance.
And he gives an argument in support, and proposes making more use of the redshift number.
Proper distance would be another good alternative---what you would measure by any ordinary means (e.g. radar) if you could somehow stop expansion long enough to measure.

 

[marcus]

Mordred found a recent paper which gives a detailed treatment of the extent of the Habitable Zone under various conditions---different kinds of planetary atmospheres.
http://arxiv.org/abs/1301.6674

 

[marcus]

Introductory cosmology video lectures on Pirsa.
The lecturer is a young guy named Matt Johnson. I watched Lecture 1 and got a good impression of him. He seems fast, alert to questions, and well-organized. It is blackboard rather than slides, which is normal for these Pirsa introductory lecture series. That doesn't slow him down because he writes quickly and legibly. Click on enlarge, to fill the screen.

These series normally run to something on the order of ten lectures. The first three have already been given and are online. Their URLs are:
http://pirsa.org/13040062/
http://pirsa.org/13040063/
http://pirsa.org/13040064/