Thank you, Steve Limpus, for your comment. My response follows:

My remark about uninformed juvenile speculation and gibberish referred to some of the other items in the "How Big is the Unverse" thread, not to anything you said. You impress me as very knowledgeable on the subject at hand. Sorry if I seemed to be referring to what you said.

No sweat dcl. I consider a lot of the people around here to be good friends, so I get a touch grumpy if I think someone is picking on them. But don't worry, we're all still pals. Glad you enjoyed the links.

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If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

You could be right. I don't really think anything is actually proven in cosmology. We may actually find out, someday, it is "turtles all the way down". At time, I believe that probability is considered to be quite low.

I feel the same way about inflation - it sounds sooo contrived!

Once again, Max Tagmark's 2003 paper on "Parallel Universes" at http://arxiv.org/PS_cache/astro-ph/p.../0302131v1.pdf. That is *my* source - I don't know where he got it.

I am at work. I was at work last night when I posted last. I *thought* I recalled that the SciAm rewrite agreed with the Astronomy Cast figure of 46x10⁹ ly. I discovered I was wrong. Tagmark's figure in the SciAm (I got with my new 2008 subscription with SciAm) is actually 42x10⁹ ly. I am sorry about that.

40, 42, 46 - I think these adjustment where probably due to the last adjustments of the estimate of the Hubble Horizon. I suspect there will be more. Who knows? We have more probes going out the L2 and there will be new data from CMBR and new adjustments. I would not depend on any of it to be with an order of magnitude of reality.

I know that. The key phase here was, "if we were voting". I was joking - is if God was polling us to decide how to design the universe. Actually, she does what she wants and I just have to accept her wisdom.

Thank you, Steve Limpus and Vanamonde, for your comments. My responses follow:

I'm new to the Forum in the sense that until a few days ago, it had been a number of years since I'd even looked at it, much less contributed to it. Only a few minutes ago, I suddenly discovered that "threads" can be multipage. Steve Limpus, I discovered only a few minutes ago that my attempt to respond to your message at the end of Page 1 actually did get into the thread, but at the beginning of Page 2 instead of the end of Page 1. And, Vanamode, I had noticed that you were the last to enter a message but I was mystified by my failure to find any evidence of it.

Vanamonde, I deduce from your pseudonym that you are or have been a fan of Arthur C. Clarke, who died a day or so ago. I, too, have been an Arthur C. Clarke fan, having first encountered him in 1936 while a freshman in high school, having just read his "Against the Fall of Night", later revised as "The City and the Stars.

About your remark on inflation, I agree that it seems contrived. Yet, it's the most plausible explanation we've found thus far for the homogeneity in the distribution of matter throughout the observable universe. Inflation is thought of as a response to a phase change in the nature of space itself when in a metastable state, somewhat analogous to what has been known to happen to water in a glass beaker in a microwave oven: If the beaker is so smooth and clean that the water can find no nucleation sites, the water can be heated to well above the boiling point without coming to a boil. Then any slight disturbance such as dipping a spoon into it can cause the water to suddenly change into steam, with unpleasant consequences to the holder of the spoon. If space itself can harbor dark energy, maybe it can also undergo a phase change that would trigger a superluminal expansion. I'm still waiting for a more plausible explanation.

Steve Limpus, I'm not ready to say I enjoyed the links you gave me. It's going to require a sizable mouthful to chew on, and I'm still chewing on it, not yet sure whether to swallow it or spit it out. At the very least, it's going to require more chewing before I dare try to swallow it. From the density of the stuff, I suspect that you're more into cosmology than I am. I'm a physicist with a long-term interest in cosmology, but pedestrian rather than professional. I've been through the "derivation" of the field equations of general relativity and am conversant with the Schwarzschild solution. I say "derivation" because it merely assumes a relation between the Riemann-Cristoffel curvature tensor and the stress-energy tensor that, fortunately for him, happens to make verifiable predictions.

hmmm... she you say Vanamonde.

My wife would agree.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

I remember fondly some Arthur C. Clarke short stories from my youth, one in particlular about an astronaut trapped in his spacesuit on the moon, waiting for the sun to rise (and kill him). He is rescued at the last minute by a fellow in the lunar spacecraft. It was published in Look and Learn magazine if anyone remembers it (the story or the magazine) and along with a cut out Saturn V rocket inspired a childhood interest in space and science. That interest was lost somewhat through my rebellious teens, then twenties and thirties... but in my forties I find that interest rekindled by a visit with my young son to the local planetarium, and a debate with a mate at work as to 'where is the centre of the universe' that led me to Pamela and Fraser's podcasts.

I was saddened to hear of Arthur C. Clarke's death. It was a good life. I'll have to look up some titles on my next visit to the library.

A little off topic but never mind.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

dcl, I'm very much an amateur enthusiast only (I'm a motor mechanic by trade!)... it's great to have a professional physicist participating on the board. I'm sure we will all learn a great deal from your input. At the moment my favourite reading is Brian Greene. I'm sure the local librarian is getting a bit annoyed that I'm 'hogging' his books (my library has 'The Fabric of the Cosmos' and 'The Elegant Universe' which I enjoy very much).

Not being mathematically trained I sometimes struggle, but I try hard with the simpler stuff.

Yesterday I printed out my first 'real' science paper from arXiv.org for bedtime reading, so I guess I'm making progress.

__________________
If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein

"It is beautiful to see the multi-coloured shadows on the planets of the Seven Suns"

Without a doubt, Clarke was my favorite. With Heinlein, Asimov, and Bradbury tied for a close second.

And, dcl, it is a pleasure to learn from a Real Physicist with such excellent taste in literature. I need to review that shape of universe topic over again in more detail, when I have time.

Thank you, Vanamonde, for your comments. My responses follows.

I recognize your quotation from "Don Stuart"'s (Arthur C. Clarke's pseudonym at that time) "Against the Fall of Night" and "The City and the Stars". I, too, am an avid science fiction reader, and I deplore the scarcity of good science fiction. A lot of what passes for science fiction these days makes me long for the good old days.

Back to cosmology, I agree that one should not reject an idea before considering its plausibility. Plausibility is the sole ground on the basis of which I reject arcane shapes for the universe when no data are available or can be devised against which to test the ideas experimentally. I feel that the plain 3-torus, Dr. Gay's distorted 3-torus that she describes as a doughnut, and the dodecahedron all fail the plausibility test miserably.

I just noticed that in a message addressed to Vanamonde and Steve Limpus a while back, I made an erroneous statement alleging that Arthur C. Clarke had used the pseudonym Don Stuart in some of his science fiction writings. I was confusing him with John Campbell, publisher of Astounding Science Fictoin, who used that pseudonym. Sorry about that. I have corrected that error in my original statement.