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Sunday, October 25, 2015

Reading List: Concrete Planet

Courland, Robert. Concrete Planet. Amherst, NY: Prometheus Books, 2011. ISBN 978-1-61614-481-4.
Visitors to Rome are often stunned when they see the Pantheon and learn it was built almost 19 centuries ago, during the reign of the emperor Hadrian. From the front, the building has a classical style echoed in neo-classical government buildings around the world, but as visitors walk inside, it is the amazing dome which causes them to gasp. At 43.3 metres in diameter, it was the largest dome ever built in its time, and no larger dome has, in all the centuries since, ever been built in the same way. The dome of the Pantheon is a monolithic structure of concrete, whose beauty and antiquity attests to the versatility and durability of this building material which has become a ubiquitous part of the modern world.

To the ancients, who built from mud, stone, and later brick, it must have seemed like a miracle to discover a material which, mixed with water, could be moulded into any form and would harden into stone. Nobody knows how or where it was discovered that by heating natural limestone to a high temperature it could be transformed into quicklime (calcium oxide), a corrosive substance which reacts exothermically with water, solidifying into a hard substance. The author speculates that the transformation of limestone into quicklime due to lightning strikes may have been discovered in Turkey and applied to production of quicklime by a kilning process, but the evidence for this is sketchy. But from the neolithic period, humans discovered how to make floors from quicklime and a binder, and this technology remained in use until the 19th century.

All of these early lime-based mortars could not set underwater and were vulnerable to attack by caustic chemicals. It was the Romans who discovered that by mixing volcanic ash (pozzolan), which was available to them in abundance from the vicinity of Mt. Vesuvius, it was possible to create a “hydraulic cement” which could set underwater and was resistant to attack from the elements. In addition to structures like the Pantheon, the Colosseum, roads, and viaducts, Roman concrete was used to build the artificial harbour at Caesarea in Judea, the largest application of hydraulic concrete before the 20th century.

Jane Jacobs has written that the central aspect of a dark age is not that specific things have been forgotten, but that a society has forgotten what it has forgotten. It is indicative of the dark age which followed the fall of the Roman empire that even with the works of the Roman engineers remaining for all to see, the technology of Roman concrete used to build them, hardly a secret, was largely forgotten until the 18th century, when a few buildings were constructed from similar formulations.

It wasn't until the middle of the 19th century that the precursors of modern cement and concrete construction emerged. The adoption of this technology might have been much more straightforward had it not been the case that a central player in it was William Aspdin, a world-class scoundrel whose own crookedness repeatedly torpedoed ventures in which he was involved which, had he simply been honest and straightforward in his dealings, would have made him a fortune beyond the dreams of avarice.

Even with the rediscovery of waterproof concrete, its adoption was slow in the 19th century. The building of the Thames Tunnel by the great engineers Marc Brunel and his son Isambard Kingdom Brunel was a milestone in the use of concrete, albeit one achieved only after a long series of setbacks and mishaps over a period of 18 years.

Ever since antiquity, and despite numerous formulations, concrete had one common structural property: it was very strong in compression (it resisted forces which tried to crush it), but had relatively little tensile strength (if you tried to pull it apart, it would easily fracture). This meant that concrete structures had to be carefully designed so that the concrete was always kept in compression, which made it difficult to build cantilevered structures or others requiring tensile strength, such as many bridge designs employing iron or steel. In the latter half of the 19th century, a number of engineers and builders around the world realised that by embedding iron or steel reinforcement within concrete, its tensile strength could be greatly increased. The advent of reinforced concrete allowed structures impossible to build with pure concrete. In 1903, the 16-story Ingalls Building in Cincinnati became the first reinforced concrete skyscraper, and the tallest building today, the Burj Khalifa in Dubai, is built from reinforced concrete.

The ability to create structures with the solidity of stone, the strength of steel, in almost any shape a designer can imagine, and at low cost inspired many in the 20th century and beyond, with varying degrees of success. Thomas Edison saw in concrete a way to provide affordable houses to the masses, complete with concrete furniture. It was one of his less successful ventures. Frank Lloyd Wright quickly grasped the potential of reinforced concrete, and used it in many of his iconic buildings. The Panama Canal made extensive use of reinforced concrete, and the Hoover Dam demonstrated that there was essentially no limit to the size of a structure which could be built of it (the concrete of the dam is still curing to this day). The Sydney Opera House illustrated (albeit after large schedule slips, cost overruns, and acrimony between the architect and customer) that just about anything an architect can imagine could be built of reinforced concrete.

To see the Pantheon or Colosseum is to think “concrete is eternal” (although the Colosseum is not in its original condition, this is mostly due to its having been mined for building materials over the centuries). But those structures were built with unreinforced Roman concrete. Just how long can we expect our current structures, built from a different kind of concrete and steel reinforcing bars to last? Well, that's…interesting. Steel is mostly composed of iron, and iron is highly reactive in the presence of water and oxygen: it rusts. You'll observe that water and oxygen are abundant on Earth, so unprotected steel can be expected to eventually crumble into rust, losing its structural strength. This is why steel bridges, for example, must be regularly stripped and repainted to provide a barrier which protects the steel against the elements. In reinforced concrete, it is the concrete itself which protects the steel reinforcement, initially by providing an alkali environment which inhibits rust and then, after the concrete cures, by physically excluding water and the atmosphere from the reinforcement. But, as builders say, “If it ain't cracked, it ain't concrete.” Inevitably, cracks will allow air and water to reach the reinforcement, which will begin to rust. As it rusts, it loses its structural strength and, in addition, expands, which further cracks the concrete and allows more air and moisture to enter. Eventually you'll see the kind of crumbling used to illustrate deteriorating bridges and other infrastructure.

How long will reinforced concrete last? That depends upon the details. Port and harbour facilities in contact with salt water have failed in less than fifty years. Structures in less hostile environments are estimated to have a life of between 100 and 200 years. Now, this may seem like a long time compared to the budget cycle of the construction industry, but eternity it ain't, and when you consider the cost of demolition and replacement of structures such as dams and skyscrapers, it's something to think about. But obviously, if the Romans could build concrete structures which have lasted millennia, so can we. The author discusses alternative formulations of concrete and different kinds of reinforcing which may dramatically increase the life of reinforced concrete construction.

This is an interesting and informative book, but I found the author's style a bit off-putting. In the absence of fact, which is usually the case when discussing antiquity, the author simply speculates. Speculation is always clearly identified, but rather than telling a story about a shaman discovering where lightning struck limestone and spinning it unto a legend about the discovery of manufacture of quicklime, it might be better to say, “nobody really knows how it happened”. Eleven pages are spent discussing the thoroughly discredited theory that the Egyptian pyramids were made of concrete, coming to the conclusion that the theory is bogus. So why mention it? There are a number of typographical errors and a few factual errors (no, the Mesoamericans did not build pyramids “a few of which would equal those in Egypt”).

Still, if you're interested in the origin of the material which surrounds us in the modern world, how it was developed by the ancients, largely forgotten, and then recently rediscovered and used to revolutionise construction, this is a worthwhile read.

Posted at 23:30 Permalink

Monday, October 19, 2015

Reading List: The Road to Relativity

Einstein, Albert, Hanock Gutfreund, and Jürgen Renn. The Road to Relativity. Princeton: Princeton University Press, 2015. ISBN 978-0-691-16253-9.
One hundred years ago, in 1915, Albert Einstein published the final version of his general theory of relativity, which extended his 1905 special theory to encompass accelerated motion and gravitation. It replaced the Newtonian concept of a “gravitational force” acting instantaneously at a distance through an unspecified mechanism with the most elegant of concepts: particles not under the influence of an external force move along spacetime geodesics, the generalisation of straight lines, but the presence of mass-energy curves spacetime, which causes those geodesics to depart from straight lines when observed at a large scale.

For example, in Newton's conception of gravity, the Earth orbits the Sun because the Sun exerts a gravitational force upon the Earth which pulls it inward and causes its motion to depart from a straight line. (The Earth also exerts a gravitational force upon the Sun, but because the Sun is so much more massive, this can be neglected to a first approximation.) In general relativity there is no gravitational force. The Earth is moving in a straight line in spacetime, but because the Sun curves spacetime in its vicinity this geodesic traces out a helix in spacetime which we perceive as the Earth's orbit.

Now, if this were a purely qualitative description, one could dismiss it as philosophical babble, but Einstein's theory provided a precise description of the gravitational field and the motion of objects within it and, when the field strength is strong or objects are moving very rapidly, makes different predictions than Newton's theory. In particular, Einstein's theory predicted that the perihelion of the orbit of Mercury would rotate around the Sun more rapidly than Newton's theory could account for, that light propagating near the limb of the Sun or other massive bodies would be bent through twice the angle Newton's theory predicted, and that light from the Sun or other massive stars would be red-shifted when observed from a distance. In due course all of these tests have been found to agree with the predictions of general relativity. The theory has since been put to many more precise tests and no discrepancy with experiment has been found. For a theory which is, once you get past the cumbersome mathematical notation in which it is expressed, simple and elegant, its implications are profound and still being explored a century later. Black holes, gravitational lensing, cosmology and the large-scale structure of the universe, gravitomagnetism, and gravitational radiation are all implicit in Einstein's equations, and exploring them are among the frontiers of science a century hence.

Unlike Einstein's original 1905 paper on special relativity, the 1915 paper, titled “Die Grundlage der allgemeinen Relativitätstheorie” (“The Foundation of General Relativity”) is famously difficult to comprehend and baffled many contemporary physicists when it was published. Almost half is a tutorial for physicists in Riemann's generalised multidimensional geometry and the tensor language in which it is expressed. The balance of the paper is written in this notation, which can be forbidding until one becomes comfortable with it.

That said, general relativity can be understood intuitively the same way Einstein began to think about it: through thought experiments. First, imagine a person in a stationary elevator in the Earth's gravitational field. If the elevator cable were cut, while the elevator was in free fall (and before the sudden stop), no experiment done within the elevator could distinguish between the state of free fall within Earth's gravity and being in deep space free of gravitational fields. (Conversely, no experiment done in a sufficiently small closed laboratory can distinguish it being in Earth's gravitational field from being in deep space accelerating under the influence of a rocket with the same acceleration as Earth's gravity.) (The “sufficiently small” qualifier is to eliminate the effects of tides, which we can neglect at this level.)

The second thought experiment is a bit more subtle. Imagine an observer at the centre of a stationary circular disc. If the observer uses rigid rods to measure the radius and circumference of the disc, he will find the circumference divided by the radius to be 2π, as expected from the Euclidean geometry of a plane. Now set the disc rotating and repeat the experiment. When the observer measures the radius, it will be as before, but at the circumference the measuring rod will be contracted due to its motion according to special relativity, and the circumference, measured by the rigid rod, will be seen to be larger. Now, when the circumference is divided by the radius, a ratio greater than 2π will be found, indicating that the space being measured is no longer Euclidean: it is curved. But the only difference between a stationary disc and one which is rotating is that the latter is in acceleration, and from the reasoning of the first thought experiment there is no difference between acceleration and gravity. Hence, gravity must bend spacetime and affect the paths of objects (geodesics) within it.

Now, it's one thing to have these kinds of insights, and quite another to puzzle out the details and make all of the mathematics work, and this process occupied Einstein for the decade between 1905 and 1915, with many blind alleys. He eventually came to understand that it was necessary to entirely discard the notion of any fixed space and time, and express the equations of physics in a way which was completely independent of any co-ordinate system. Only this permitted the metric structure of spacetime to be completely determined by the mass and energy within it.

This book contains a facsimile reproduction of Einstein's original manuscript, now in the collection of the Hebrew University of Jerusalem. The manuscript is in Einstein's handwriting which, if you read German, you'll have no difficulty reading. Einstein made many edits to the manuscript before submitting it for publication, and you can see them all here. Some of the hand-drawn figures in the manuscript have been cut out by the publisher to be sent to an illustrator for preparation of figures for the journal publication. Parallel to the manuscript, the editors describe the content and the historical evolution of the concepts discussed therein. There is a 36 page introduction which describes the background of the theory and Einstein's quest to discover it and the history of the manuscript. An afterword provides an overview of general relativity after Einstein and brief biographies of principal figures involved in the development and elaboration of the theory. The book concludes with a complete English translation of Einstein's two papers given in the manuscript.

This is not the book to read if you're interested in learning general relativity; over the last century there have been great advances in mathematical notation and pedagogy, and a modern text is the best resource. But, in this centennial year, this book allows you to go back to the source and understand the theory as Einstein presented it, after struggling for so many years to comprehend it. The supplemental material explains the structure of the paper, the essentials of the theory, and how Einstein came to develop it.

Posted at 22:11 Permalink

Tuesday, October 13, 2015

Reading List: Sweeter than Wine

Smith, L. Neil. Sweeter than Wine. Rockville, MD: Phoenix Pick, 2011. ISBN 978-1-60450-483-5.
A couple of weeks after D-Day, Second Lieutenant J Gifford found himself separated from his unit and alone in a small French village which, minutes later, was overrun by Germans. Not wishing to spend the rest of the war as a POW, he took refuge in an abandoned house, hiding out in the wine cellar to escape capture until the Allies took the village. There, in the dark, dank cellar, he encounters Surica, a young woman also hiding from the Germans—and the most attractive woman he has ever seen. Nature takes its course, repeatedly.

By the time the Germans are driven out by the Allied advance, Gifford has begun to notice changes in himself. He can see in the dark. His hearing is preternaturally sensitive. His canine teeth are growing. He cannot tolerate sunlight. And he has a thirst for blood.

By the second decade of the twenty-first century, Gifford has established himself as a private investigator in the town of New Prospect, Colorado, near Denver. He is talented in his profession, considered rigorously ethical, and has a good working relationship with the local police. Apart from the whole business about not going out in daytime without extensive precautions, being a vampire has its advantages in the gumshoe game: he never falls ill, recovers quickly even from severe injuries, doesn't age, has extraordinary vision and hearing, and has a Jedi-like power of suggestion over the minds of people which extends to causing them to selectively forget things.

But how can a vampire, who requires human blood to survive, be ethical? That is the conundrum Gifford has had to face ever since that day in the wine cellar in France and, given the prospect of immortality, will have to cope with for all eternity. As the novel develops, we learn how he has met this challenge.

Meanwhile, Gifford's friends and business associates, some of whom know or suspect his nature, have been receiving queries which seem to indicate someone is on to him and trying to dig up evidence against him. At the same time, a series of vicious murders, all seemingly unrelated except for their victims having all been drained of blood, are being committed, starting in Charleston, South Carolina and proceeding westward across the U.S. These threads converge into a tense conflict pitting Gifford's ethics against the amoral ferocity of an Old One (and you will learn just how Old in chapter 26, in one of the scariest lines I've encountered in any vampire tale).

I'm not usually much interested in vampire or zombie stories because they are just so implausible, except as a metaphor for something else. Here, however, the author develops a believable explanation of the vampire phenomenon which invokes nothing supernatural. Sure, there aren't really vampires, but if there were this is probably how it would work. As with all of the author's fiction, there are many funny passages and turns of phrase. For a novel about a vampire detective and a serial killer, the tone is light and the characters engaging, with a romance interwoven with the mystery and action. L. Neil Smith wrote this book in one month: November, 2009, as part of the National Novel Writing Month, but other than being relatively short (150 pages), there's nothing about it which seems rushed; the plotting is intricate, the characters well-developed, and detail is abundant.

Posted at 22:52 Permalink

Thursday, October 8, 2015

Reading List: SJWs Always Lie

Day, Vox [Theodore Beale]. SJWs Always Lie. Kouvola, Finland: Castalia House, 2015. ASIN B014GMBUR4.
Vox Day is the nom de plume and now nom de guerre of Theodore Beale, a musician with three Billboard Top 40 credits, video game designer, author of science fiction and fantasy and three-time Hugo Award nominee, and non-fiction author and editor.

If you're not involved in the subcultures of computer gaming or science fiction and fantasy, you may not be acquainted with terms such as SJW (Social Justice Warrior), GamerGate, or Sad Puppies. You may conclude that such matters are arcana relating to subcultures of not-particularly-socially-adept people which have little bearing on the larger culture. In this, you would be wrong. For almost fifty years, collectivists and authoritarians have been infiltrating cultural institutions, and now occupy the high ground in institutions such as education, the administrative state, media, and large corporations. This is the “long march through the institutions” foreseen by Antonio Gramsci, and it has, so far, been an extraordinary success, not only advancing its own agenda with a slow, inexorable ratchet, but intimidating opponents into silence for fear of having their careers or reputations destroyed. Nobody is immune: two Nobel Prize winners, James Watson and Tim Hunt, have been declared anathema because of remarks deemed offensive by SJWs. Nominally conservative publications such as National Review, headquartered in hives of collectivist corruption such as New York and Washington, were intimidated into a reflexive cringe at the slightest sign of outrage by SJWs, jettisoning superb writers such as Ann Coulter and John Derbyshire in an attempt to appease the unappeasable.

Then, just as the SJWs were feeling triumphant, GamerGate came along, and the first serious push-back began. Few expected the gamer community to become a hotbed of resistance, since gamers are all over the map in their political views (if they have any at all), and are a diverse bunch, although a majority are younger males. But they have a strong sense of right and wrong, and are accustomed to immediate and decisive negative feedback when they choose unwisely in the games they play. What they came to perceive was that the journalists writing about games were applauding objectively terrible games, such as Depression Quest, due to bias and collusion among the gaming media.

Much the same had been going on in the world of science fiction. SJWs had infiltrated the Science Fiction and Fantasy Writers of America to such an extent that they directed their Nebula Awards to others of their ilk, and awarded them based upon “diversity” rather than merit. The same rot had corrupted fandom and its Hugo Awards.

Vox Day was near the centre of the cyclone in the revolt against all of this. The campaign to advance a slate of science fiction worthy of the Hugos rather than the pap selected by the SJWs resulted in the 2015 Hugos being blown up, demonstrating that SJWs would rather destroy a venerable institution than cede territory.

This book is a superbly written history of GamerGate and the revolt against SJWs in science fiction and fantasy writers' associations and fandom, but also provides deep insight into the seriously dysfunctional world of the SJW and advice about how to deal with them and what to do if you find yourself a target. The tactics of the SJWs are laid bare, and practical advice is given as to how to identify SJWs before they enter your organisation and how to get rid of them if they're already hired. (And get rid of them you must; they're like communists in the 1930s–1950s: once in place they will hire others and promote their kind within the organisation. You have to do your homework, and the Internet is your friend—the most innocuous co-worker or prospective employee may have a long digital trail you can find quickly with a search engine.)

There is no compromising with these people. That has been the key mistake of those who have found themselves targeted by SJWs. Any apology will be immediately trumpeted as an admission of culpability, and nothing less than the complete destruction of the career and life of the target will suffice. They are not well-meaning adversaries; they are enemies, and you must, if they attack you, seek to destroy them just as they seek to destroy you. Read Alinsky; they have. I'm not suggesting you call in SWAT raids on their residences, dig up and release damaging personal information on them, or make anonymous bomb threats when they gather. But be aware that they have used these tactics repeatedly against their opponents.

You must also learn that SJWs have no concern for objective facts. You can neither persuade nor dissuade them from advancing their arguments by citing facts that falsify their claims. They will repeat their objectively false talking points until they tire you out or drown out your voice. You are engaging in dialectic while they are employing rhetoric. To defeat them, you must counter their rhetoric with your own rhetoric, even when the facts are on your side.

Vox Day was in the middle of these early battles of the counter-revolution, both in GamerGate and the science fiction insurrection, and he provides a wealth of practical advice for those either attacked by SJWs or actively fighting back. This is a battle, and somebody is going to win and somebody else will lose. As he notes, “There can be no reconciliation between the observant and the delusional.” But those who perceive reality as it is, not as interpreted through a “narrative” in which they have been indoctrinated, have an advantage in this struggle. It may seem odd to find gamers and science fiction fans in the vanguard of the assault against this insanity but, as the author notes, “Gamers conquer Dragons and fight Gods for a hobby.”

Posted at 23:46 Permalink

Friday, October 2, 2015

Mac OS: Scaling El Capitan

Other than installing routine security patches, I haven't bothered to update the operating system of “Ansel”, the Macintosh Pro I installed in 2009 primarily to do photographic and video production. The applications I use were primarily developed for that platform, and while I prefer to avoid proprietary software, it's a much better choice than anything tainted by Microsoft.

I was finally pushed to bring the system up to date due to nagging by Apple that upgrading my iPhone and iPad to iOS 9 might cause problems synchronising with the old version of iTunes on my desktop system. (I haven't investigated the details of this, but no newer version of that regrettable application is available for the old operating system I was running.) I decided to jump all the way to the newest release, “El Capitan”, posted as an official release on 2015-09-30.

I downloaded the update and started the installer, after making sure I had a complete Time Machine backup of the existing system. The installer ran for about a minute and then said it was restarting to perform the installation. It went into a shutdown process and hung with two blue screens and nothing but the cursor on the screen.

After about 15 minutes in this state, I discovered I could log into the system with SSH, and that it was still running the old system with an uptime indicating no reboot had happened. I did a

    sudo /sbin/reboot
after which my SSH window disconnected and the cursor on the blue screen was replaced by a spinning disc icon.

This persisted for more than half an hour, during which time the system would respond to pings but not an SSH connection. Finally, it spontaneously restarted into an installer screen which said it had about half an hour to go.

After around 45 minutes, it rebooted again and came up into what looked like an initial setup screen, warning me that two applications were not compatible with the new system. As I was about to look around the new system it crashed, rebooted, and came up with the "problem" screen and then the desktop.

Just about everything I tried would bounce me out after a few seconds to what looked like a login screen, which would require me to enter the password for a few seconds more access, after which it would bounce again. I made sure screen lock and screen saver were off and even removed my login password: nothing doing.

I was also getting weird tearing on the screen, failure to refresh windows when uncovered, and a frozen cursor, after which the inevitable pop.

The network settings were lost in the “upgrade”. I re-established the WiFi connection to Fourmilab with settings as follows:

    Search: 	lan.fourmilab.ch dmz.fourmilab.ch fourmilab.ch

The “upgrade” disabled SSH logins. I went into System Settings/Sharing and set “Enable remote logins” between pops to the login screen.

Now I was able to SSH login from Hayek and access the system in text mode without pops.

Tried iTunes. Of course, it doesn't see the Apple TV. I restarted the Apple TV—nothing doing.

A wired sync of the iPhone to iTunes seems to work. I did not dare to try installing the iOS 9.0.1 “upgrade” it's been bugging me about.

I unplugged the Time Machine backup disc. If this ends up as badly as it looks right now, I'll want that as a clean backup to start over on a new machine.

Based on a discussion of the login crashes, I backed up and deleted the following in /Library/Preferences:

-rw-r--r--  1 root  wheel   229 Oct  1 21:18 com.apple.loginwindow.plist
-rw-r--r--  1 root  admin  2084 Jan 26  2010 com.apple.loginitems.plist
-rw-r--r--  1 root  admin   787 Jan 26  2010 loginwindow.plist
No improvement. It still pops.

Further research on login crashes discovered mentions of display switching on various video boards, so I unplugged the right monitor. The pops appear to have gone away, at least for the moment.

I went to the Mac App store and dowloaded 395 Mb of updates, including good old iTunes. Now I appear to be able to run iTunes without popping. It shows the Apple TV in the Preferences panel and says that it's “Syncing” but I cannot find any sync progress indicator anywhere so I have no idea what it's doing. A

    /usr/sbin/tcpdump -l -nn -x -i en2 host
doesn't see any traffic going to the Apple TV so I'm not sure I believe it. All I see is the Apple TV sending multicast broadcast “Hello. I'm here! Anybody out there?” messages.

Naturally, the new installation of iTunes created its own library file in “/home/[me]/Music/iTunes/iTunes Media” and did not respect the library I was previously using in “/Volumes/Vault/[me]/Music/iTunes/iTunes Media”. When I set the library location to there, it still didn't see the files, since it continued to use a new “iTunes Library.itl” file which it had created containing only content in the “cloud”. I had to restore the backed-up previous library:

    “/Users/[me]/Music/iTunes/Previous iTunes Libraries/iTunes Library 2015-10-01.itl”
    “/Volumes/Vault/[me]/Music/iTunes/iTunes Media/iTunes Library.itl”
then start iTunes while holding down the Option key so I could navigate to that directory where it could then find the .itl file. Now it appears to see the local content.

With iTunes repaired, I was now able to wipe the computer association of the Apple TV (because it couldn't possibly remember something like that across an event as momentous as an operating system upgrade) and start the re-sync which, if experience is any guide, will run for more than a day.

In order to get public key logins via SSH to work, I had to:

    cd .ssh
    cp -p authorized_keys2 authorized_keys
on Ansel. “authorized_keys2” no longer works.

At the moment the machine is running with one of the two monitors I paid for unplugged, dark, and useless, but at least I can use the machine without bizarre abstract art on the screen or popping back to the login screen every minute or so. I'm sure I will discover plenty more as I try to do actual productive work with this machine. I'll add the details to this post.

Posted at 02:06 Permalink