This Place is Taken

Sunday, December 16, 2012

How The Speed of Light Was Measured in 1676

How The Speed of Light Was Measured in 1676:

Orbits of Jupiter and Earth

Roemer measured the speed of light by timing eclipses of Jupiter's moon Io. In this figure, S is the Sun, E1 is the Earth when closest to Jupiter (J1) and E2 is the Earth about six months later, on the opposite side of the Sun from Jupiter (J2). When the Earth is at E2, the light from the Jupiter system has to travel an extra distance represented by the diameter of the Earth's orbit. This causes a delay in the timing of the eclipses. Roemer measured the delay and, knowing approximately the diameter of the Earth's orbit, made the first good estimate of the speed of light. Illustration by Diana Kline.
In 1676, the Danish astronomer Ole Roemer (1644–1710) became the first person to measure the speed of light. Until that time, scientists assumed that the speed of light was either too fast to measure or infinite. The dominant view, vigorously argued by the French philosopher Descartes, favored an infinite speed.
Roemer, working at the Paris Observatory, was not looking for the speed of light when he found it. Instead, he was compiling extensive observations of the orbit of Io, the innermost of the four big satellites of Jupiter discovered by Galileo in 1610. By timing the eclipses of Io by Jupiter, Roemer hoped to determine a more accurate value for the satellite’s orbital period. Such observations had a practical importance in the seventeenth century. Galileo himself had suggested that tables of the orbital motion of Jupiter’s satellites would provide a kind of “clock” in the sky. Navigators and mapmakers anywhere in the world might use this clock to read the absolute time (the standard time at a place of known longitude, like the Paris Observatory). Then, by determining the local solar time, they could calculate their longitude from the time difference. This method of finding longitude eventually turned out to be impractical and was abandoned after the development of accurate seagoing timepieces. But the Io eclipse data unexpectedly solved another important scientific problem—the speed of light.
The orbital period of Io is now known to be 1.769 Earth days. The satellite is eclipsed by Jupiter once every orbit, as seen from the Earth. By timing these eclipses over many years, Roemer noticed something peculiar. The time interval between successive eclipses became steadily shorter as the Earth in its orbit moved toward Jupiter and became steadily longer as the Earth moved away from Jupiter. These differences accumulated. From his data, Roemer estimated that when the Earth was nearest to Jupiter (at E1), eclipses of Io would occur about eleven minutes earlier than predicted based on the average orbital period over many years. And 6.5 months later, when the Earth was farthest from Jupiter (at E2), the eclipses would occur about eleven minutes later than predicted.
Roemer knew that the true orbital period of Io could have nothing to do with the relative positions of the Earth and Jupiter. In a brilliant insight, he realized that the time difference must be due to the finite speed of light. That is, light from the Jupiter system has to travel farther to reach the Earth when the two planets are on opposite sides of the Sun than when they are closer together. Romer estimated that light required twenty-two minutes to cross the diameter of the Earth’s orbit. The speed of light could then be found by dividing the diameter of the Earth’s orbit by the time difference.
The Dutch scientist Christiaan Huygens, who first did the arithmetic, found a value for the speed of light equivalent to 131,000 miles per second. The correct value is 186,000 miles per second. The difference was due to errors in Roemer’s estimate for the maximum time delay (the correct value is 16.7, not 22 minutes), and also to an imprecise knowledge of the Earth’s orbital diameter. More important than the exact answer, however, was the fact that Roemer’s data provided the first quantitative estimate for the speed of light, and it was in the right ballpark.
Roemer returned to Denmark in 1681, where he pursued a distinguished career in both science and government. He designed and built the most accurate astronomical instruments of his time and made extensive observations. He later served as mayor and prefect of police of Copenhagen and ultimately as head of the State Council. Roemer is remembered today of course not for his high political office but for being the first person to measure the speed of light.

Thursday, December 13, 2012

Let it Snow

Let it Snow:





For those who desire a layer of snow with their holiday season it's been mainly green and brown so far this year in the Boston area. Since the start of December, here are some places that have already had the chance to experience the beauty and sometimes annoyance of a winter wonderland. -- Lloyd Young ( 32 photos total)

A train of the Brocken Railway steams through a winter landscape with snow covered pine trees as it approaches its destination on the Brocken mountain in the Harz mountainous region of Germany on Dec 8. (Stefan Rampfel/European Pressphoto Agency)

A dog, covered with hoarfrost and snow, looks on during a snowfall outside Russia's Siberian city of Krasnoyarsk. (Ilya Naymushin/Reuters) #

Davide Simoncelli of Italy descends the course on the first run en route to third place in the men's Giant Slalom at the Audi FIS World Cup on Dec. 2 in Beaver Creek, Colorado. (Doug Pensinger/Getty Images) #

Children ride sleds down a hill as the first snowfall of the season hits Brussels, Belgium on Dec. 2. (Francois Lenoir/Reuters) #

Saint Basil's Cathedral is seen peeping over snowdrifts at Red Square in Moscow, Russia, on Dec. 4. Heavy snowfall reportedly caused traffic jams and disruption to air travel. (Sergei Ilitsky/European Pressphoto Agency) #

The sun shines behind the weather station and snow covered trees on the Fichtelberg mountain, in Oberwiesenthal, south eastern Germany, on Dec. 8. Parts of eastern and central Europe were hit hard by heavy snow and freezing temperatures. (Uwe Meinhold/Associated Press) #

A man clears snow in Ilmenau, central Germany, on Dec. 11. (Michael Reichel/European Pressphoto Agency) #

A car drives after a heavy snowfall on Dec. 9 in Liebenau, eastern Germany. (Arno Burgi/AFP/Getty Images) #

A local walks with his ponies during the season’s first snowfall in the northern hilltown of Shimla, India on, Dec. 11. (AFP/Getty Images) #

A boy rides his bicycle in a park as the first snow fall covers Sofia, Bulgaria, on Dec. 3. (Dimitar Dilkoff/AFP/Getty Images) #

A woman clears snow from a car in the Austrian province of Salzburg on Dec. 10. The weather forecast predicts continuing snowfall for the next few days. (Kerstin Joensson/Associated Press) #

Airplanes on the tarmac at Schiphol airport in Amsterdam on Dec. 7. (Ruud Taal/European Pressphoto Agency) #

A man rides a horse-drawn cart during heavy snow fall near the village of Petravinka, Belarus, on Dec. 5. (Vasily Fedosenko/Reuters) #

People jog in the snow in Aarhus, Denmark, on Dec. 9. (Dago/Polfoto, via Associated Press #

Lenin's statue is covered with snow during heavy snowfall over Kiev on Dec. 11. (Sergei Supinsky/AFP/Getty Images) #

A boy holding a snowball runs over a street as snow falls on Dec. 1 in Berlin. (Hannibal Hanschke/AFP/Getty Images) #

A man walks at a park during a snowfall in downtown Sofia, Bulgaria, on Dec. 11. (Stoyan Nenov/Reuters) #

A child walks in a park after heavy snowfall in Kiev, Ukraine, on Dec. 11. (Anatolii Stepanov/Reuters) #

Snow covers roses in Duesseldorf, Germany, on Dec. 7. ( Martin Gerten/European Pressphoto Agency) #

A man films with a tablet device after heavy snowfall in Kiev. (Anatolii Stepanov/Reuters) #

A North Korean man scrapes off snow from the monument of anti-Japanese revolutionary fighters on Mansu Hill in Pyongyang, North Korea, on Dec. 10. (Kyodo News/Associated Press) #

A man rides his bicycle holding an umbrella as light snow covers the roads in Amsterdam on Dec. 7. Temperatures have dropped below freezing and more snow is expected to fall during the day, but the Dutch ride their favorite means of transport come rain or snow. (Peter Dejong/Associated Press) #

A recovery worker tries to retrieve a car lying in a dyke on the side of the road after skidding off due to ice and snow on the roads near Zurich, Netherlands, on Dec. 6. (Catrinus Van Der Veen/European Pressphoto Agency) #

A couple walk under an umbrella during a heavy snowfall in Pristina, Kosovo, on Dec. 5. (Arment Nimani/AFP/Getty Images) #

Fans wait in the snow before the NFL football game between the Green Bay Packers and the Detroit Lions in Green Bay, Wisconsin, on Dec. 9. (Darren Hauck/Reuters) #

A young polar bear wallows in snow at the public zoo in St Petersburg, Russia, on Dec. 7. (Olga Maltseva/AFP/Getty Images) #

A snowboarder takes a jump at the Erbeskopf near Deuselbach, western Germany, on Dec. 9. The highest point in the state of Rhineland-Palatinate has opened for the 2012/2013 winter season. (Thomas Frey/AFP/Getty Images) #

People struggle against wind and drifting snow in Stockholm, Sweden, on Dec. 5. (Andres Wiklund/AFP/Getty Images) #

Workers clean a model replica of Cheops Pyramid of Giza, after snowfall in landscape park Miniwelt (Miniworld), in Lichtenstein, eastern Germany, on Dec. 7. The cultural park Miniworld presents about 100 original and true-to detail buildings and technical facilities at a 1:25 scale. (Jens Meyer/Associated Press) #

People ski off piste at Val d'Isere, in the French Alps, on Dec. 11. Recent snowfalls have encouraged skiers to hit the slopes and the Val d'Isere authorities have opened certain slopes early. (Philippe Desmazes/AFP/Getty Images) #

A runner dressed as Father Christmas runs in heavy snow during the 'Nikolaus Run' in the East German town of Michendorf on Dec. 9. Around 800 participants took part in the Santa Claus running competition that is hosted by the Laufclub Michendorf running association. (Wolfgang Rattay/Reuters) #

Two girls play in the snow on the bank of an island in the middle of the Yenisei River, where the air temperature reached minus 22 degrees Celsius (minus 7.6 degrees Fahrenheit), in Russia's Siberian city of Krasnoyarsk on Dec. 6. (Ilya Naymushin/Reuters) #






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Wednesday, December 12, 2012

The Making Of OpenERP

The Making Of OpenERP:
I needed to change the world. I wanted to ... You know how it is when you are young; you have big dreams, a lot of energy and naïve stupidity. My dream was to lead the enterprise management market with a fully open source software. (I also wanted to get 100 employees before 30 years old with a self-financed company but I failed this one by a few months).
To fuel my motivation, I had to pick someone to fight against. In business, it's like a playground. When you arrive in a new school, if you want to quickly become the leader, you must choose the class bully, the older guy who terrorises small boys, and kick his butt in front of everyone. That was my strategy with SAP, the enterprise software giant.
So, in 2005, I started to develop the TinyERP product, the software that (at least in my mind) would change the enterprise world. While preparing for the "day of the fight" in 2006, I bought the SorrySAP.com domain name. I put it on hold for 6 years, waiting for the right moment to use it. I thought it would take 3 years to deprecate a 77 billion dollars company just because open source is so cool. Sometimes it's better for your self-motivation not to face reality...
To make things happen, I worked hard, very hard. I worked 13 hours a day, 7 days a week, with no vacations for 7 years. I lost friendships and broke up with my girlfriend in the process (fortunately, I found a more valuable wife now. I will explain later why she is worth 1 million EUR :).
Three years later, I discovered you can't change the world if you are "tiny". Especially if the United States is part of this world, where it's better to be a BigERP, rather than a TinyERP. Can you imagine how small you feel in front of Danone's directors asking; "but why should we pay millions of dollars for a tiny software?" So, we renamed TinyERP to OpenERP.
As we worked hard, things started to evolve. We were developing dozens of modules for OpenERP, the open source community was growing and I was even able to pay all employees' salaries at the end of the month without fear (which was a situation I struggled with for 4 years).
In 2010, we had a 100+ employees company selling services on OpenERP and a powerful but ugly product. This is what happens when delivering services to customers distracts you from building an exceptional product.
It was time to do a pivot in the business model.

The Pivot

We wanted to switch from a service company to a software publisher company. This would allow to increase our efforts in our research and development activities. As a result, we changed our business model and decided to stop our services to customers and focus on building a strong partner network and maintenance offer. This would cost money, so I had to raise a few million euros.
After a few months of pitching investors, I got roughly 10 LOI from different VCs. We chosed Sofinnova Partners, the biggest European VC, and Xavier Niel the founder of Iliad, the only company in France funded in the past 10 years to have reached the 1 billion euro valuation.
I signed the LOI. I didn't realize that this contract could have turned me into a homeless person. (I already had a dog, all I needed was to lose a lot of money to become homeless). The fund raising was based on a company valuation but there was a financial mechanism to re-evaluate the company up by 9.8 m€ depending on the turnover of the next 4 years. I should have received warrants convertible into shares if we achieved the turnover targeted in the business plan.
The night before receiving the warrants in front of the notary, my wife checked the contracts. She asked me what would be the taxation on these warrants. I rang the lawyer and guess what? Belgium is probably the only country in the world where you have to pay taxes on warrants when you receive them, even if you never reach the conditions to convert them into shares. If I had accepted these warrants, I would have had to pay a 12.5% tax on 9.8 m€; resulting in a tax of 1.2m€ to pay in 18 months! So, my wife is worth 1.2 million EUR. I would have ended up a homeless person without her, as I still did not have a salary at that time.
We changed the deal and I got the 3 million EUR. It allowed me to recruit a rocking management team.

Being a mature company

With this money in our bank account, we boosted two departments: R&D and Sales. We burned two million EUR in 18 months, mostly in salaries. The company started to grow even faster. We developed a partner network of 500 partners in 100 countries and we started to sign contracts with 6 zeros.
Then, things became different. You know, tedious things like handling human resources, board meetings, dealing with big customer contracts, traveling to launch international subsidiaries. We did boring stuff like budgets, career paths, management meetings, etc.
2011 was a complex year. We did not meet our expectations: we only achieved 70% of the forecasted sales budget. Our management meetings were tense. We under performed. We were not satisfied with ourselves. We had a constant feeling that we missed something. It's a strange feeling to build extraordinary things but to not be proud of ourselves.
But one day, someone (I don't remember who, I have a goldfish memory) made a graph of the monthly turnover of the past 2 years. It was like waking up from a nighmare. In fact, it was not that bad, we had multiplied by 10 the monthly turnover over the span of roughly two years! This is when we understood that OpenERP is a marathon, not a sprint. Only 100% growth a year is ok... if you can keep the rhythm for several years.
 
OpenERP Monthly Turnover
As usual, I should have listened to my wife. She is way more lucid than I am. Every week I complained to her "it's not good enough, we should grow faster, what am I missing?" and she used to reply; "But you already are the fastest growing company in Belgium!". (Deloitte awarded us as the fastest growing company of Belgium with 1549% growth of the turnover between 2007 and 2011)

Changing the world

Then, the dream started to become reality. We started to get clues that what we did would change the world:
Something is happening... And it's big!
OpenERP 7.0 is about to be released and I know you will be astonished by it.
The official release is planned for the 21th of December. As the Mayas predicted it, this is the end of an age, the old ERP dinosaurs.
It's time to pull out the Ace: the SorrySAP.com domain name that I bought 6 years ago.
Fabien Pinckaers,
OpenERP Founder

Tuesday, December 4, 2012

Windows 8 — Disappointing Usability for Both Novice and Power Users

Windows 8 — Disappointing Usability for Both Novice and Power Users:
Jakob Nielsen's Alertbox, November 19, 2012

Summary:
Hidden features, reduced discoverability, cognitive overhead from dual environments, and reduced power from a single-window UI and low information density. Too bad.
With the recent launch of Windows 8 and the Surface tablets, Microsoft has reversed its user interface strategy. From a traditional Gates-driven GUI style that emphasized powerful commands to the point of featuritis, Microsoft has gone soft and now smothers usability with big colorful tiles while hiding needed features.
The new design is obviously optimized for touchscreen use (where big targets are helpful), but Microsoft is also imposing this style on its traditional PC users because all of Windows 8 is permeated by the tablet sensibility.
How well does this work for real users performing real tasks? To find out, we invited 12 experienced PC users to test Windows 8 on both regular computers and Microsoft's new Surface RT tablets.

Double Desktop = Cognitive Overhead and Added Memory Load

The Roman god Janus; Dr. Jekyll and Mr. Hyde; even Batman's arch-foe Two-Face — human culture is fascinated by duality. We can now add Windows 8 to this list. The product shows two faces to the user: a tablet-oriented Start screen and a PC-oriented desktop screen.
Unfortunately, having two environments on a single device is a prescription for usability problems for several reasons:
  • Users have to learn and remember where to go for which features.
  • When running web browsers in both device areas, users will only see (and be reminded of) a subset of their open web pages at any given time.
  • Switching between environments increases the interaction cost of using multiple features.
  • The two environments work differently, making for an inconsistent user experience.

Lack of Multiple Windows = Memory Overload for Complex Tasks

One of the worst aspects of Windows 8 for power users is that the product's very name has become a misnomer. "Windows" no longer supports multiple windows on the screen. Win8 does have an option to temporarily show a second area in a small part of the screen, but none of our test users were able to make this work. Also, the main UI restricts users to a single window, so the product ought to be renamed "Microsoft Window."
The single-window strategy works well on tablets and is required on a small phone screen. But with a big monitor and dozens of applications and websites running simultaneously, a high-end PC user definitely benefits from the ability to see multiple windows at the same time. Indeed, the most important web use cases involve collecting, comparing, and choosing among several web pages, and such tasks are much easier with several windows when you have the screen space to see many things at once.
When users can't view several windows simultaneously, they must keep information from one window in short-term memory while they activate another window. This is problematic for two reasons. First, human short-term memory is notorious weak, and second, the very task of having to manipulate a window—instead of simply glancing at one that's already open—further taxes the user's cognitive resources.

Flat Style Reduces Discoverability

The Windows 8 UI is completely flat in what used to be called the "Metro" style and is now called the "Modern UI." There's no pseudo-3D or lighting model to cast subtle shadows that indicate what's clickable (because it looks raised above the rest) or where you can type (because it looks indented below the page surface).
I do think Metro/Modern has more elegant typography than past UI styles and that the brightly colored tiles feel fresh.
But the new look sacrifices usability on the altar of looking different than traditional GUIs. There's a reason GUI designers used to make objects look more detailed and actionable than they do in the Metro design. As an example, look at this settings menu:
Screenshot from Surface RT of the settings menu at the bottom of the charm bar when activated from the start screen.
The bottom of the Windows 8 settings menu on Surface RT.
Where can you click? Everything looks flat, and in fact "Change PC settings" looks more like the label for the icon group than a clickable command. As a result, many users in our testing didn't click this command when they were trying to access one of the features it hides.
(In that task, we asked users to change the start screen background color. As a further problem, the very command label had misleading information scent for some users; they thought of the Surface as a tablet, not a "PC.")
We also saw problems with users overlooking or misinterpreting tabbed GUI components because of the low distinctiveness of the tab selection and the poor perceived affordance of the very concept of clickable tabs.
Icons are flat, monochromatic, and coarsely simplified. This is no doubt a retort to Apple's overly tangible, colorful, and extremely detailed "skeuomorphic" design style in iOS. For once, I think a compromise would be better than either extreme. In this case, we often saw users either not relating to the icons or simply not understanding them.
Icons are supposed to (a) help users interpret the system, and (b) attract clicks. Not the Win8 icons.

Low Information Density

The available advice on designing for the "modern UI style" seems to guide designers to create applications with extraordinarily low information density. See, for example, the following screenshots:
Screenshots from two Surface RT apps: Bing Finance and the Los Angeles Times.
Start screens from the Bing Finance (top) and Los Angeles Times (bottom) apps for the Surface tablet.
Despite running on a huge 10.6-inch tablet, Bing Finance shows only a single story (plus 3 stock market quotes) on the initial screen. The Los Angeles Times is not much better: this newspaper app's initial screen is limited to 3 headlines and an advertisement. In fact, they don't even show the lead story's full headline and the summary has room for only 7 words. Come on, this tiny amount of news is all you can fit into 1366 × 768 pixels?
Screenshot of the Los Angeles Times website: the homepage as seen above the fold on the Microsoft Surface TR tablet in Internet Explorer.
www.latimes.com in the tablet-mode browser.
Visiting the newspaper's website in Internet Explorer gives you much more information, though it's remarkable that the site still doesn't exploit the real estate offered by the widescreen aspect ratio on the Surface (and many full-sized computers). The website shows 9 stories (and 3 ads) in the same space as the 3 stories offered by the Metro app. Plus we get full summaries of the top articles.
Yes, big photos are nice. Yes, spacious layouts are nice. But you don't have to be a fanatic follower of Edward Tufte to want a bit more "data ink" on the screen.
As a result of the Surface's incredibly low information density, users are relegated to incessant scrolling to get even a modest overview of the available information.
As it turns out, users didn't mind horizontal scrolling on the Surface, which is interesting given that horizontal scrolling is a usability disaster for websites on desktop computers. Still, there's such a thing as too much scrolling, and users won't spend the time to move through large masses of low-density information.

Overly Live Tiles Backfire

Live tiles are one of the UI advances in Windows 8. Instead of always representing an app with the same static icon, a live tile summarizes current information from within the app. This works well when used judiciously. Good examples include:
  • Weather app showing current (or predicted) temperature and precipitation
  • Email app showing the subject line of the latest incoming message
  • Calendar app showing your next appointment
  • Stock market app showing the current market level
Unfortunately, application designers immediately went overboard and went from live tiles to hyper-energized ones. To illustrate …
Quick, without reading the caption, which apps do the following 4 tiles represent?
4 live tiles from Surface RT: Urbanspoon, LA Times, Newegg, Epicurious.
Live tiles for (clockwise from upper left): Urbanspoon, Los Angeles Times, Newegg, and Epicurious.
Newegg is the only app that includes its full name in the tile. When we asked participants to use the other apps, they couldn't find them. This on a new tablet with only a few applications installed. We know from our user testing of other tablets and mobile devices that users quickly accumulate numerous applications, most of which they rarely use and can barely recognize—even with static icons that never change.
The theory, no doubt, is to attract users by constantly previewing new photos and other interesting content within the tiles. But the result makes the Surface start screen into an incessantly blinking, unruly environment that feels like dozens of carnival barkers yelling at you simultaneously.

Charms Are Hidden Generic Commands

One of the most promising design ideas in Windows 8 is the enhanced use of generic commands in the form of the so-called "charms." The charms are a panel of icons that slide in from the screen's right side after a flicking gesture from its right edge (on a tablet) or after pointing the mouse to the screen's upper-right corner (on a computer).
The charms panel includes features like Search, Share (including email), and Settings that apply to whatever content the user is currently viewing. In principle, it's great to have these commands universally available in a single, uniform design that's always accessed the same way.
In practice, the charms work poorly — at least for new users. The old saying, out of sight, out of mind, turned out to be accurate. Because the charms are hidden, our users often forgot to summon them, even when they needed them. In applications such as Epicurious, which included a visible reminder of the search feature, users turned to search much more frequently.
Hiding commands and other GUI chrome makes sense on small mobile phones. It makes less sense on bigger tablet screens. And it makes no sense at all on huge PC screens.
Furthermore, the charms don't actually work universally because they're not true generic commands. In our test, users often clicked Search only to be told, "This application cannot be searched." Enough disappointments and users will stop trying a feature. (Also, of course, it violates basic usability guidelines; that is, you shouldn't tease users by offering a feature that isn't actually available.)
Finally, not all users understood that the commands are context dependent and do different things on different pages.
Many other features are initially hidden and are revealed only when users perform specific and often convoluted gestures. For example, all of our users had great difficulty with an extraordinarily basic task: changing the city in the weather app. Obvious gestures, such as clicking the name of the current city to change locations, didn't work. Users' difficulties were exacerbated by the fact that the "Modern" GUI style doesn't indicate which words and fields are active and/or can be changed.
What's the long-term usability of the hidden features in Windows 8? We might expect users to grow accustomed to the need to reveal the charms and other non-visible commands, even though this imposes additional cognitive overhead on using the system. That is, people must think to do something, rather than being reminded to do something, and thus users will sometimes neglect useful Win8 features.
Also, the familiarity bred by long-term use might be counteracted by the fact that well-designed websites have trained users to expect important features to be shown directly in the context in which they're needed. You simply can't design a website with hidden features and expect it to be used: website features are usually ephemeral, meaning that they must be explicitly represented if they're to gather any use.
Thus, people's experience with the web excerpts a powerful pull in the direction of expecting visible features. It remains to be seen whether the Surface tablet's physical presence creates enough of an opposing pull to remind people to look for hidden features when they're using Surface apps.

Error-Prone Gestures

The tablet version of Windows 8 introduces a bunch of complicated gestures that are easy to get wrong and thus dramatically reduce the UI's learnability. If something doesn't work, users don't know whether they did the gesture wrong, the gesture doesn't work in the current context, or they need to do a different gesture entirely. This makes it hard to learn and remember the gestures. And it makes actual use highly error-prone and more time-consuming than necessary.
The worst gesture might be the one to reveal the list of currently running applications: you need to first swipe from the screen's left edge, and then immediately reverse direction and do a small swipe the other way, and finally make a 90-degree turn to move your finger to a thumbnail of the desired application. The slightest mistake in any of these steps gives you a different result.
The UI is littered with swipe ambiguity, where similar (or identical) gestures have different outcomes depending on subtle details in how they're activated or executed. For example, start swiping from the right to the left and you will either scroll the screen horizontally or reveal the charm bar, depending on exactly where your finger first touched the screen. This was very confusing to the users in our study.

Windows 8 UX: Weak on Tablets, Terrible for PCs

As mentioned in the introduction, Windows 8 encompasses two UI styles within one product. Windows 8 on mobile devices and tablets is akin to Dr. Jekyll: a tortured soul hoping for redemption. On a regular PC, Windows 8 is Mr. Hyde: a monster that terrorizes poor office workers and strangles their productivity.
Although Win8 has usability issues on tablets, there's nothing that a modest redesign can't fix. In fact, usability could be substantially improved by revising the application guidelines to emphasize restrained use of active tiles, higher information density, better visibility of key features, and many other usability guidelines we've already discovered in testing other tablets.
(I was stunned to see the Architectural Digest app for Surface replicate a host of well-documented usability bloopers, such as not making the cover headlines clickable. Swipe ambiguity ran rampant, and users were often lost in this app's confusing combination of vertical and horizontal scrolling. All of this could have been avoided by reading reports we have published for free. I can just barely understand companies that ruin their user experience because they don't want to pay $298 to find out what the usability research says. But to create a bad app to save no money seems a puzzle.)
I have great hopes for Windows 9 on mobile and tablets. Just as Windows 7 was "Vista Done Right," it's quite likely that the touchscreen version of Windows 9 will be "Windows 8 Done Right."
The situation is much worse on regular PCs, particularly for knowledge workers doing productivity tasks in the office. This used to be Microsoft's core audience, and it has now thrown the old customer base under the bus by designing an operating system that removes a powerful PC's benefits in order to work better on smaller devices.
The underlying problem is the idea of recycling a single software UI for two very different classes of hardware devices. It would have been much better to have two different designs: one for mobile and tablets, and one for the PC.
I understand why Microsoft likes the marketing message of "One Windows, Everywhere." But this strategy is wrong for users.

I Don't Hate Microsoft

Because this column is very critical of Microsoft's main product, some people will no doubt accuse me of being an Apple fanboy or a Microsoft hater. I'm neither. I switched from Macintosh to Windows many years ago and have been very pleased with Windows 7.
I am a great fan of the dramatic "ribbon" redesign of Office (we later gave several awards to other applications that adapted this UI innovation), and I proclaimed the Kinect an "exciting advance in UI technology." I have many friends who work at Microsoft and know that it has many very talented usability researchers and UI designers on staff.
I have nothing against Microsoft. I happen to think that Windows 7 is a good product and that Windows 8 is a misguided one. I derived these conclusions from first principles of human–computer interaction theory and from watching users in our new research. One doesn't have to hate or love a company in order to analyze its UI designs.
I'll stay with Win7 the next few years and hope for better times with Windows 9. One great thing about Microsoft is that they do have a history of correcting their mistakes.

Learn More

293-page report on Usability of Mobile Websites and Applications with 237 design guidelines and 479 screenshots is available for download.
Full-day training courses at the annual Usability Week conference: