Martin

there is a sense in which I can give a strictly personal opinion if I were in grad school right now I sure as hell would stay clear of string theory! too many people in it no testable predictions no experimental guidance and from the standpoint of GR the whole approach looks wrong because it isnt background independent so I'd probably get together with someone who is good with computers and try to repeat Jan Ambjorn and Renate Loll's work massive monte carlo simulation of geometry of universe using a beautifully simple model it's a wide open field, with a lot of new research to be done there (like, introducing matter into the model, now that we know that it generates 4D spacetime) the problem would be finding someone on the faculty to be the research advisor

nobody can say that, no one knows the future and in some sense all rigorously conducted research is to the good balancing research funding (where theory has gone for a long time without guidance from research) is a complex business Peter Woit (a mathematician at Columbia who watches theoretical physics closesly) has a blog where people are discussing these issues (as well as just yakking and gossiping for fun) the field is overhyped and overfunded just because of sheer momentum (a lot of people dont know how to do anything else) so it is due for a readjustment. meanwhile there is anecdotal and some statistical evidence that people are getting out of string (where the results have been poor lately) and even sometimes out of HEP and into things closer to astrophysics some kind of shift is happening. Woit's opinion may count for something, I cant say I have a definite opinion here's Woits blog http://www.math.columbia.edu/~woit/blog/ here's an arXiv bar graph showing hep versus astro-ph research http://arxiv.org/Stats/hca_avg.gif astrophysics used to be less than 1/7 of hep, in the heyday of string in the 1990s but hep peaked in 2002 and has declined some (mainly the decline in string which was a major part of high energy physics research) and astrophysics is now approximately equal to hep. look at the graph, picture worth a lot of words

I noticed that the Wikipedia entries for string and LQG give no inkling of these changes in the picture It is possible that a degree of favoritism has crept in. Lubos Motl, a string stalwart and moderator of sci.physics.strings, has been one of the main authors of the Wikipedia pages on these subjects.

in string research it's fairly straightforward to show theres been a decline in quantity and quality---you just look at the Spires citation numbers (as a gauge of quality) and the NASA ADS numbers at the Harvard site show in overall numbers of published papers a decline of at least 13 percent 2002 to 2003, which continues at the same rate this year, if you go by arXiv as a leading indicator so let's look at the flip side----there's been an increase in Non-string quantum gravity research. The numbers there will provide a contrast. I've provided links so you can get the annual preprint counts directly from the arxiv search engine if you care to. 2001 92 2002 113 2003 129 LTM 138 2001: http://arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+doubly+special/0/1/0/2001/0/1 2002: http://arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+doubly+special/0/1/0/2002/0/1 2003: http://arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+doubly+special/0/1/0/2003/0/1 Last Twelve Months: http://arXiv.org/find/nucl-ex,astro-ph,nucl-th,math-ph,hep-ex,physics,cond-mat,hep-lat,quant-ph,gr-qc,hep-ph,hep-th/1/OR+OR+abs:+AND+AND+loop+quantum+OR+cosmology+gravity+abs:+AND+AND+quantum+gravity+OR+OR+discrete+phenomenology+OR+canonical+nonperturbative+abs:+OR+OR+spinfoam+AND+spin+foam+AND+doubly+special/0/1/0/past/0/1 this is just one of several possible boolean searches that can be done for non-string QG, by clicking on the link you will get the search function showing the keywords used, so I wont list them here. anyway it is a more cheerful picture, even though field is small and has less funding and fewer people

correct me if I am wrong I believe that SpaceShipOne is capable of carrying two passengers (is this correct?) but that on today's flight there was just the pilot as I understand it, there have to be two flights (with passengers) in a 2 week period if the craft is capable of carrying 3 including pilot then it seems eligible to win the prize

http://www.freep.com/news/latestnews/pm20366_20040621.htm from Detroit Free Press a few minutes ago first commercial space(?) flight at 100 km was nominally out of the atmosphere?

the image blurs distinctions between a hillbilly moonshiner and an alchemist, the moonshiner's "still" for distilling whiskey being indeed an alembic so there is a circle of associations philosopher's stone -> pitchblende rock -> illegal nuclear alchemy -> illegal whiskey still -> alembic -> alchemist -> back to the beginning Marquez (100 years of solitude) could have written a story on this image but perhaps he had too great a sense of responsibility to allow it, if the thought crossed his mind

Some striking turns of phrase especially where Nisou says "SO empty that there is no emptiness." which could be a line by a good poet. I will try to respond too, but I dont see how right at the moment. Nisou: "like.. how can space go on forever,.. ive always imagined space to be a big box of empty space.. but.. sooner or later, won't you reach a stop?.. and if you do reach that "wall".. what's after that wall.??? if space loops.. then what's outside of that loop? so confused :?" Vague: Missed to answer this one. It seesm as if you regard Space as "something" but anything that comes up after the wall you are talking about, would also occupy space or volume...so the Space just keeps on going on and on and on and on... Nisou: how can there be TOTALLY empty space? and how can our macho/wimpy space go on forever, i still picture space as one big box.. and outside of that box is .. like.. SO empty that there is no emptiness ------------------------ I dont see why space cant keep going on and on. that is what it looks like it does when you go outside on a clear night. What is wrong with simple straightforward infinite space. And no "outside" All I can see that might be a mental stumbling block in this case is that it means there has to be unlimited amounts of stuff----unlimited numbers of galaxies and stars and dark matter constituents (whatever you think they are and choose to call them). Whether or not you find it a problem that the stars keep going and there's no limit to how many-----I guess it depends on you.

I think it must be very easy to see that there cannot be only a finite number of primes because if there were then one could multiply them all together and add one to it. then one would have a number that is not divisible by any of them It would be that monstrosity which we know is not! It would be a number which cannot be written as a product of primes. just like if 2,3,5, and 7 were the only primes one could multiply them all together to get 210 and then add one to it to get 211 and that would not be divisible by 2,3,5, or 7 because when you divided by any of them you always get the remainder of one.

sorry for the misunderstanding, I was just offering a proof for what Dave said, namely any number is a product of primes please tell me if you see a mistake I think what I said proves that any number can be written as a product of primes (because if not then pick the smallest number that cant be...etc) would you like a proof that there are infinitely many prime numbers?

jana's comment had some really interesting points---the thoughtfulness is almost as if the toronto undergraduate jana had asked a chief string-controversialist like Lubos Motl how he parries the AJL paper. I am missing jana and hope she/he returns to contribute to the discussion. the AJL paper is not exactly a Regge model but it is reggeesque. -----exerpt from jana------- "My understanding is that these sort of reggeesque theories are deficient in a number of ways. Here are a few: 1) Since spacetime dimension is dynamical in them, the associated fundamental degrees of freedom are not fixed in number and so these theories ultimately can't be unitary. ... 3) They can't really explain the emergence of GR since the hilbert action is used as input..." -----end quote---- I started a thread about the AJL paper in Cosmology Forum http://www.scienceforums.net/forums/showthread.php?t=4482 the AJL approach is to get a quantum model of the 4D geometry of the whole universe from beginning to end (if there is end) and this should be done very simply as a weighted Feynmann-like average over all the paths it could take and so in some sense the AJL model is "cosmology" because it is a quantum picture of the whole 4D thing but also it is a quantum model of microscopic spacetime, where fields and particles live----so it is "modern/particle physics" too Ambjorn Jurkiewicz Loll preprinted their papers including this one in the hep-th part of ArXiv----hep-th is the "High Energy Physics-Theory" category. http://arxiv.org/hep-th/0404156 so it really belongs in both cosmology and high energy physics anyway I put the thread about AJL in cosmology forum (this thread is about the decline of string theory which is a separate topic)

suppose it were not true then there is a natural number that you cant write as a product of primes pick the smallest such number either it is prime (in which case it is writable as a product of primes namely itself) or it is not prime (in which case it can be factored into two smaller numbers which can each, by assumption, be factored into products of primes)

A strange recollection. The Pied Piper of Hamlin before he became famous: "I am reminded of a friend from the early 1970s, Edward Witten. I liked Ed, but felt sorry for him, too, because, for all his potential, he lacked focus. He had been a history major in college, and a linguistics minor. On graduating, though, he concluded that, as rewarding as these fields had been, he was not really cut out to make a living at them. He decided that what he was really meant to do was study economics. And so, he applied to graduate school, and was accepted at the University of Wisconsin. And, after only a semester, he dropped out of the program. Not for him. So, history was out; linguistics, out; economics, out. What to do? This was a time of widespread political activism, and Ed became an aide to Senator George McGovern, then running for the presidency on an anti-war platform. He also wrote articles for political journals like the Nation and the New Republic. After some months, Ed realized that politics was not for him, because, in his words, it demanded qualities he did not have, foremost among them common sense. All right, then: history, linguistics, economics, politics, were all out as career choices. What to do? Ed suddenly realized that he was really suited to study mathematics. So he applied to graduate school, and was accepted at Princeton. I met him midway through his first year there--just after he had dropped out of the mathematics department. He realized, he said, that what he was really meant to do was study physics; he applied to the physics department, and was accepted..."

So Urs Schreiber picked up on your antedeluvian metaphor I tracked back to the original post: http://golem.ph.utexas.edu/string/archives/000298.html#c000613

the image works fine here also you added explanatory notes to that image (making it easier to understand) but not to the other image id=309 I, for one, could use even more explanation, and maybe others could as well. (or pointers to the appropriate places on your webpage if that is where this is explained in more basic terms)

Woit's view of the future (19 March Not Even Wrong) "...Quite possibly the LHC will revolutionize physics by showing us what is really causing the spontaneous breaking of the electroweak gauge symmetry. If this happens, everyone will abandon string theory and start working on this, 1984-2008 then becoming a period in the history of physics that particle theorists try and not think about...." http://www.math.columbia.edu/~woit/blog/archives/000002.html it is possible, as one of your posts suggests, that the intellectual over-investment in string is more a problem in US universities than in Europe, so coming from Zaragoza you may have a different assessment the funny thing was that Thomas Larsson commented that it looked as if Witten was coming around to Woit's view as expressed here (which prompted an immediate disclaimer: Woit saying it wasnt especially his point of view but just a commonplace)

here was Woit's blog about the Nature article: http://www.math.columbia.edu/~woit/blog/archives/000032.html it should have some clue as to whether Witten is imagining a post-string-bubble future and what it looks like to him what you describe----each generation of graduate students, in order to find a cooperative Thesis Advisor, must choose a field of research that the previous generation understannds----does not augur well now there is a big glut of people trained in a possibly irrelevant branch of theory how will the stampeed ever stop?

this conversation was back in April 2003. we didnt actually hear the end (I dont have Greene's book so i cant check arivero's guess either)

As for most recession speeds being FTL put redshift z = 2 into the calculator here http://www.scienceforums.net/forums/showthread.php?p=56565#post56565 to set things up you first need to put 0.27 for matter and 0.73 for dark energy and 71 for the hubble parameter, which are standard cosmology estimates. galaxies as distant as z =10 have been observed, so way more are out there with z > 2 than are with z < 2 that is why it is typical or normal for a galaxy in the observable part of the universe to have redshift z > 2 so accordingly it is normal for them to be receding FTL

one should be careful not to throw anything too hard or jump too high, I guess

Im curious as to why it's your second favorite. both about why favorite at all, and why second and is it your second favorite as a place to establish a manned base among the jovian moons I'm aware that as someone located at a military base in antarctica you are probably rather broad-minded about habitats as compared with Northerncalifornians like myself personally I like the feel of gravity and am always happiest when I get some regular physical exercise and so I would imagine hollowing out a cave under the Callisto ice to serve as an ice-skating rink but I would not know what to do if I lived on Phobos and Deimos and my health might deteriorate---also they do seem a might dry. do you suppose that human musclepowered flight would be possible on Callisto or Ganymede---that seems like a good aerobic exercise too: if a big under-ice stadium were hollowed out to provide room for swooping please reply! I urgently desire your opinion on these important matters