Starship Asterisk*

How about some downhome plasma tornados Harry?
http://www.newscientist.com/article/dn1 ... roras.html

harry wrote:G'day Aris

You said

How about some downhome plasma tornados Harry?
http://www.newscientist.com/article/dn1 ... roras.html

Would you like to know how they form?

makc wrote:

aristarchusinexile wrote:Jim, the article states:

"In physics, nonlocality is a direct influence of one object on another distant object, in violation of the principle of locality. In classical physics, nonlocality in the form of action at a distance appeared in corpusculas theories and later disappeared in field theories. Action at a distance is incompatible with relativity. In quantum physics nonlocality re-appeared in the form of entanglement. Physical reality of entanglement has been demonstrated experimentally[1] together with the absence of local hidden variables. Entanglement is compatible with relativity; however, it prompts some of the more philosophically oriented discussions concerning quantum theory. More general nonlocality beyond quantum entanglement, but still compatible with relativity, is an active field of theoretical investigation but has yet to be observed."

makc wrote:that's mother of all daemons I think... and adam was the father.

harry wrote:G'day from the land of ozzzzzzz

In a way Chris's attitude has proven my point.

Lilith in the Classical German period wrote:
Lilith's earliest appearance in the literature of the Romantic period (1789-1832) was in Goethe's 1808 work Faust Part I, nearly 600 years after appearing in the Kabbalistic Zohar:

• Faust:
  Who's that there?
  
  Mephistopheles:
  Take a good look.
  Lilith.
  
  Faust:
  Lilith? Who is that?
  
  Mephistopheles:
  Adam's wife, his first. Beware of her.
  Her beauty's one boast is her dangerous hair.
  When Lilith winds it tight around young men
  She doesn't soon let go of them again.

(1992 Greenberg translation, lines 4206–4211)

After Mephistopheles offers this warning to Faust, he then, quite ironically, encourages Faust to dance with "the Pretty Witch". Lilith and Faust engage in a short dialogue, where Lilith recounts the days spent in Eden.

• Faust: [dancing with the young witch]
  A lovely dream I dreamt one day
  I saw a green-leaved apple tree,
  Two apples swayed upon a stem,
  So tempting! I climbed up for them.
  
  The Pretty Witch:
  Ever since the days of Eden
  Apples have been man's desire.
  How overjoyed I am to think, sir,
  Apples grow, too, in my garden.

(1992 Greenberg translation, lines 4216 – 4223)

Lilith in the Victorian period wrote:
Dante Gabriel Rossetti wrote a sonnet entitled Lilith, which was first published in Swinburne's pamphlet-review (1868), Notes on the Royal Academy Exhibition:

• Of Adam's first wife, Lilith, it is told
  (The witch he loved before the gift of Eve,)
  That, ere the snake's, her sweet tongue could deceive,
  And her enchanted hair was the first gold.
  And still she sits, young while the earth is old,
  And, subtly of herself contemplative,
  Draws men to watch the bright web she can weave,
  Till heart and body and life are in its hold.
  The rose and poppy are her flower; for where
  Is he not found, O Lilith, whom shed scent
  And soft-shed kisses and soft sleep shall snare?
  Lo! As that youth's eyes burned at thine, so went
  Thy spell through him, and left his straight neck bent
  And round his heart one strangling golden hair.

juliaxyz wrote:What's the name of this magic trick and how do you do it? Years ago at a camp i remember some people doing a magic trick to me. I don't remember it exactly but it was something involving me holding out my fists and they touch my hands and then i flip them over and i have dirt on my palms and i have no idea out it got there.

BMAONE23 wrote:Lillith may or may not be any more mythical than Adam or Eve.
I read that Adam had a first wife, Lillith who was literally an Angel with wings. But Adam didn't like her for long because she was uncontrollable (she wouldn't do everything Adam asked). So Eve was then made from Adams rib to be his mate.

BMAONE23 wrote:

juliaxyz wrote:Years ago at a camp i remember some people doing a magic trick to me. I don't remember it exactly but it was something involving me holding out my fists and they touch my hands and then i flip them over and i have dirt on my palms and i have no idea out it got there.

The deception of the trick comes when they initially grab your hand with the palms down.
They touch their graphite covered finger to your palm while they instruct you to close your hand.

http://antwrp.gsfc.nasa.gov/apod/ap080605.html wrote:
Explanation: The Spitzer Space Telescope's encompasing infrared view of the plane of our Milky Way Galaxy is hard to appreciate in just one picture. The small portion seen here spans nearly 8 degrees. Highlighted in the false-color presentation are curving green filaments of light from complex molecules - polycyclic aromatic hydrocarbons (PAHs) - that on Earth are the common, sooty products of incomplete combustion. The PAHs are found in star forming regions, along with reddish emission from graphite dust particles.

Blue specks throughout the picture are individual Milky Way stars.

aristarchusinexile wrote:A discussion with Chris on finding the centre of the universe caused me to consider that 'Now' multiplied by Infinity = Eternal Now. Is there a math symbol for 'Now' used in math like or unlike Calculus?

aristarchusinexile wrote:'Now' multiplied by Infinity = Eternal Now.

aristarchusinexile wrote:

wikipedia wrote: ... is an active field of theoretical investigation but has yet to be observed."

makc wrote:

Why the rolling of the eyes?

BMAONE23 wrote:I read that Adam had a first wife, Lillith who was literally an Angel with wings. But Adam didn't like her for long because she was uncontrollable (she wouldn't do everything Adam asked). So Eve was then made from Adams rib to be his mate.

(d) Adam and Lilith never found peace together; for when he wished to lie with her, she took offence at the recumbent posture he demanded. 'Why must I lie beneath you?' she asked. 'I also was made from dust, and am therefore your equal.' Because Adam tried to compel her obedience by force, Lilith, in a rage, uttered the magic name of God, rose into the air and left him.

...as Don Lautman, my astronomy teacher wrote:the beauty of astronomy is that in astronomy, unlike in civil engineering, one may be 100% wrong and nobody is hurt.

In 1922, Franz Selety, university-bred philosopher and self-educated physicist and cosmologist, developed a molecular hierarchical, spatially infinite, Newtonian cosmological model. His considerations were based on his earlier philosophical work published in 1914 as well as on the early correspondence with Einstein in 1917. Historically, the roots of hierarchical models can be seen in 18th century investigations by Thomas Wright of Durham, Immanuel Kant and Johann Heinrich Lambert. Those investigations were taken up by Edmund Fournier d'Albe and Carl Charlier at the beginning of the 20th century. Selety's cosmological model was criticized by Einstein mainly due to its spatial infiniteness which in Einstein's opinion seemed to contradict Mach's principle. This criticism sheds light on Einstein's conviction that with his first cosmological model, namely the static, spatially infinite, though unbounded Einstein Universe of 1917, the appropriate cosmological theory already had been established.

The increasing prominence of general relativity in astrophysics and cosmology is reflected in the growing number of texts, particularly at the undergraduate level. A natural attitude before opening a new one is to ask i) what makes this different from those already published? And ii) does it follow the 'physics-first approach' as for instance the book by Hartle where the basic physical concepts are introduced first with as little formalism as possible, or does it follow the more traditional 'math-first approach' for which the mathematical formalism comes first and is then applied to phyics? As announced in the title, a distinctive feature of the book by Gron and Hervik is the space (almost half the book) devoted to cosmology and in particular to some of the most recent developments in this rapidly evolving field. It is also apparent that the authors have chosen, like the majority of current books on general relativity, the 'math-first approach'.

The book is divided into six parts, each of them subdivided into chapters with part VI containing a few short technical appendices. The first part of the book briefly presents in chapter I the principles of relativity, Newtonian mechanics and the Newtonian theory of gravity. In chapter II, a short introduction to special relativity is given. It seems at first surprising that the four-dimensional structure of space-time is not more fully exploited so that the reader would gain familiarity early on with notions like 4-velocity, 4-momentum and the stress energy tensor. This is in fact postponed to part II as an illustration of the mathematical formalism.

The second part is devoted to those elements of differential geometry needed in this kind of course. The authors' presentation is somewhat similar to that of the books by Misner, Thorne and Wheeler and by Straumann (2nd edition). Vectors and forms are treated separately and the formalism of differential forms is introduced in detail. The various kinds of differentiation on forms and on vectors (exterior covariant and Lie derivatives) are presented, and emphasis is given to the Cartan formalism as it is later systematically used to derive the curvature tensor and for solutions of the Einstein field equations. One also finds the properties of hypersurfaces, such as the intrinsic and extrinsic curvatures and the Gauss Codazzi relations. This makes this part of the book very useful and convenient since those important elements are gathered in one place. However the density of exposition in this part might appear a bit steep to a reader without some previous knowledge of differential geometry.

Part III deals with Einstein's field equations, and their applications to gravitational waves and black holes. The field equations are derived from a variational principle, the geometrical part (Einstein tensor) from the Einstein Hilbert action, and the matter part (stress energy tensor) from a generic action integral for matter. Various examples of stress energy tensors and in particular, for fluids, are considered, and several are used later in cosmology (for instance quintessence and Lorentz invariant vacuum energy). A short chapter on the linear approximation and gravitational waves then follows and it is good to see a section on gravito-electromagnetism. This part ends with a chapter devoted to black holes which is perhaps the weakest part of the book as it is quite sketchy. However this is to be expected in a book with an emphasis on cosmology, and such topics are extensively described in other books.

The rest of the book (parts IV and V) is essentially concerned with cosmology. The authors give a detailed description of the applications of the Einstein field equations to a universe with various matter contents, and present in a successful way the recent developments in this domain. The first chapter of part IV describes the standard homogeneous and isotropic cosmological model. It is followed by an interesting chapter dealing with universes composed of vacuum energy. There one finds, after the description of the Einstein static universe and the de Sitter solution, sections on inflation, on the Friedman Lemaître model and on models with quintessence and dark energy. This chapter ends with sections on cosmic density perturbations, temperature fluctations in the cosmic microwave background and on the history of our universe. With an additional chapter on anisotropic and homogeneous universes, part IV appears to be a very good and complete introduction to the basic and classical (i.e. non-quantum) elements of cosmology. In part V some advanced tools, such as Lie groups and the Lagrangian and Hamiltonian formalism are introduced and applied to cosmology. Also part V contains a chapter on the extrinsic curvature formalism for surface layers and its application to the recently introduced braneworld models. Finally it is a pleasant surprise to find an introduction to the Kaluza Klein theory as the last chapter of part V.

This book by Gron and Hervik certainly has its place in any good library. It covers most of the classical aspects of the theory of general relativity. The authors have made the effort to discuss many observational aspects and to illustrate the different chapters with many problems. One might regret that the authors' style is generally rather terse and not enough space is always reserved for explanation of physical concepts and for motivations of the theory (for instance, why curvature is so fundamental). This book would be most appropriate for graduate students and I will definitely recommend it as a reference textbook as well as a useful complement to other textbooks on general relativity.