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jurasovaib

Speed of light - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...Speed_of_light

shared by jurasovaib on 24 Jun 14 - Cached
  • The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its value is exactly 299,792,458 metres per second, a figure that is exact because the length of the metre is defined from this constant and the international standard for time.[1]
  • The first quantitative estimate of the speed of light was made in 1676 by Rømer (see Rømer's determination of the speed of light).[83][84] From the observation that the periods of Jupiter's innermost moon Io appeared to be shorter when the Earth was approaching Jupiter than when receding from it, he concluded that light travels at a finite speed, and estimated that it takes light 22 minutes to cross the diameter of Earth's orbit. Christiaan Huygens combined this estimate with an estimate for the diameter of the Earth's orbit to obtain an estimate of speed of light of 220000 km/s, 26% lower than the actual value.[105]
  • Beginning in the 1880s several experiments were performed to try to detect this motion, the most famous of which is the experiment performed by Albert A. Michelson and Edward W. Morley in 1887.[128] The detected motion was always less than the observational error. Modern experiments indicate that the two-way speed of light is isotropic (the same in every direction) to within 6 nanometres per second.[129]
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  • In 1972, using the laser interferometer method and the new definitions, a group at NBS in Boulder, Colorado determined the speed of light in vacuum to be c = 299792456.2±1.1 m/s. This was 100 times less uncertain than the previously accepted value. The remaining uncertainty was mainly related to the definition of the metre.[Note 8][104] As similar experiments found comparable results for c, the 15th Conférence Générale des Poids et Mesures (CGPM) in 1975 recommended using the value 299792458 m/s for the speed of light.[136]
jurasovaib

Rømer's determination of the speed of light - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...mination_of_the_speed_of_light

determination speed light

shared by jurasovaib on 24 Jun 14 - No Cached
  • Order of magnitude[edit] Rømer starts with an order of magnitude demonstration that the speed of light must be so great that it takes much less than one second to travel a distance equal to Earth's diameter. The point L on the diagram represents the second quadrature of Jupiter, when the angle between Jupiter and the Sun (as seen from Earth) is 90°.[note 6] Rømer assumes that an observer could see an emergence of Io at the second quadrature (L), and also the emergence which occurs after one orbit of Io around Jupiter (when the Earth is taken to be at point K, the diagram not being to scale), that is 42½ hours later. During those 42½ hours, the Earth has moved further away from Jupiter by the distance LK: this, according to Rømer, is 210 times the Earth's diameter.[note 7] If light travelled at a speed of one Earth-diameter per second, it would take 3½ minutes to travel the distance LK. And if the period of Io's orbit around Jupiter were taken as the time difference between the emergence at L and the emergence at K, the value would be 3½ minutes longer than the true value. Rømer then applies the same logic to observations around the first quadrature (point G), when Earth is moving towards Jupiter. The time difference between an immersion seen from point F and the next immersion seen from point G should be 3½ minutes shorter than the true orbital period of Io. Hence, there should be a difference of about 7 minutes between the periods of Io measured at the first quadrature and those measured at the second quadrature. In practice, no difference is observed at all, from which Rømer concludes that the speed of light must be very much greater than one Earth-diameter per second.[5]
  • However Rømer also realised that any effect of the finite speed of light would add up over a long series of observations, and it is this cumulative effect that he announced to the Royal Academy of Sciences in Paris. The effect can be illustrated with Rømer's observations from spring 1672. Jupiter was in opposition on 2 March 1672: the first observations of emergences were on 7 March (at 07:58:25) and 14 March (at 09:52:30). Between the two observations, Io had completed four orbits of Jupiter, giving an orbital period of 42 hours 28 minutes 31¼ seconds. The last emergence observed in the series was on 29 April (at 10:30:06). By this time, Io had completed thirty orbits around Jupiter since 7 March: the apparent orbital period is 42 hours 29 minutes 3 seconds. The difference seems minute – 32 seconds – but it meant that the emergence on 29 April was occurring a quarter-hour after it would have been predicted. The only alternative explanation was that the observations on 7 and 14 March were wrong by two minutes.
jurasovaib

Ole Rømer - Wikipedia, the free encyclopedia - 1 views

en.wikipedia.org/...Ole_R%C3%B8mer

people astronomy

shared by jurasovaib on 24 Jun 14 - No Cached
  • Ole Christensen Rømer (Danish pronunciation: [o(ː)lə ˈʁœːˀmɐ]; 25 September 1644, Århus – 19 September 1710, Copenhagen) was a Danish astronomer who in 1676 made the first quantitative measurements of the speed of light.
  • Rømer and the speed of light
  • jurasovaib on 24 Jun 14
     
    The guy who measured the speed of light.
lilymg

Social Media vs. Police Brutality | Sinan Ülgen - 1 views

www.huffingtonpost.com/...ia-vs-police-br_b_3785672.html

social media police brutality

shared by lilymg on 26 Jun 14 - No Cached
  • social media fulfilled the role of real-time reporting
  • powerful instrument of public scrutiny
  • Still, social media cannot prevent police brutality on its own.
  • ...5 more annotations...
    • lilymg
      lilymg on 26 Jun 14
       
      Many countries experience police brutality, some experience severe violence from it
    • lilymg
      lilymg on 26 Jun 14
       
      survey shows impact of social media 
    • lilymg
      lilymg on 26 Jun 14
       
      Media can sometimes cover up violent outbreaks
    • lilymg
      lilymg on 26 Jun 14
       
      But social media can still show the real story, sharing stories + pictures that can go viral
    • lilymg
      lilymg on 26 Jun 14
       
      Many times social media can only bring to light issues and violence, but this does not mean change will happen
George Neff

Your Brain While Watching Orange Is the New Black - Shape Magazine - 0 views

www.shape.com/...your-brain-binge-watching-tv

#ThoughtVectors bingewatching media netflix brain

shared by George Neff on 15 Jul 14 - No Cached
  • Like a perfectly addictive drug, almost every aspect of the television viewing experience grabs and holds your brain’s attention, which explains why it’s so tough to stop watching after just one (or three) episodes of Orange is the New Black.
  • Characters run or shout or shoot accompanied by sound effects and music. No two moments are quite alike. To your brain, this kind of continuously morphing sensory stimulation is pretty much impossible to ignore, explains Robert F. Potter, Ph.D., director of the Institute for Communication Research at Indiana University.
  • “Our brains are hardwired to automatically pay attention to anything that’s new in our environment, at least for a brief period of time,” he explains. And it’s not just humans; all animals evolved this way in order to spot potential threats, food sources, or reproductive opportunities, Potter says.
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  • “This also explains how you can sit in front of the TV and binge for hours and hours at a time and not feel a loss of entertainment,” he says. “You brain doesn’t have much time to grow bored.”
  • 
Studies show that, by this point, most of your brain activity has shifted from the left hemisphere to the right, or from the areas involved with logical thought to those involved with emotion. There has also been a release of natural, relaxing opiates called endorphins, research indicates.
  • You’re noodle isn’t really analyzing or picking apart the data it’s receiving. It’s basically just absorbing. Potter calls this “automatic attention.” He says, “The television is just washing over you and your brain is marinating in the changes of sensory stimuli.”
  • At the same time, the content of your television show is lighting up your brain’s approach and avoid systems, Potter says. Put simply, your brain is pre-programmed for both attraction and disgust, and both grab and hold your attention in similar ways. Characters you hate keep you engaged just as much (and sometimes more) than characters you love.
  • 
Like any addictive drug, cutting off your supply triggers a sudden drop in the release of those feel-good brain chemicals, which can leave you with a sense of sadness and a lack of energy, research shows. Experiments from the 1970s found that asking people to give up TV for a month actually triggered depression and the sense that the participants had “lost a friend.”
abdulrahmanabdo

More NSA revelations: backdoors, snooping tools and worldwide reactions - 0 views

www.sciencedirect.com.proxy.library.vcu.edu/...S1353485814700017

NSArevelations

shared by abdulrahmanabdo on 04 Jul 14 - No Cached
  • “I cannot imagine a more ‘indiscriminate’ and ‘arbitrary invasion’ than this systemic and high-tech collection and retention of personal data on virtually every single citizen for purposes of querying and analysing it without prior judicial approval,” he wrote
    • abdulrahmanabdo
      abdulrahmanabdo on 04 Jul 14
       
      US Judge displays his vital view on what the NSA did to the American people, can be important in making an argument in the inquiry paper.
  • A Presidential Task Force set up by Barack Obama to examine the NSA issue has issued its first report and has concluded that: “Excessive surveillance and unjustified secrecy can threaten civil liberties, public trust, and the core processes of democratic self-government.”
    • abdulrahmanabdo
      abdulrahmanabdo on 04 Jul 14
       
      What the executive branch things of this whole NSA issue. This also states the possible outcomes that may have come with this issue.
  • Many people in the security industry remain unconvinced by RSA's denials.
    • abdulrahmanabdo
      abdulrahmanabdo on 04 Jul 14
       
      Illustrates that the truth isn't always easily obtained, and that this story may dig deeper than anyone once anticipated before.
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  • Some members of the group wanted him to step down following his part
    • abdulrahmanabdo
      abdulrahmanabdo on 04 Jul 14
       
      This may prove to help shed some light on the big question of, is this issue, making the NSA fall apart.
  • abdulrahmanabdo on 04 Jul 14
     
    First of my three sources for Nugget Research #1.
Mirna Shaban

The Revolution Will Be Tweeted - 1 views

www.aucegypt.edu/...articledetails.aspx

socialmedia revolution internet

shared by Mirna Shaban on 06 Jul 14 - No Cached
  • Much of the organization and mobilization occurred through the Internet, particularly on social media such as Facebook and Twitter. But social media also played a vital role as a democratic model. Its inclusive space indirectly taught lessons in democracy to a wide sector of Egyptian youth that was not necessarily politically inclined. When the right moment arrived, they were ready to join the revolt.
  • What happened in January 2011 in Egypt did not start in January 2011. It began at least ten years earlier, and it’s not over yet
  • The main catalyst for the January 25 revolution was the Internet, so it may be accurate to describe this as an Internet-based revolution. Not that the Internet was the only factor involved, or that Internet users were the only ones protesting. But the Internet was the tool that showed every dissident voice in Egypt that he or she is not alone, and is indeed joined by at least hundreds of thousands who seek change.
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  • Facebook did not go to Tahrir Square. The people did. Twitter did not go to Al-Qaied Ibrahim Square. The people did.
  • More than one-third of Egypt’s population of eighty million remains illiterate, and just 25 percent of Egyptians use the Internet. However, Facebook and Twitter were instrumental in organizing, motivating, and directing these crowds as to where to go and what to do. Egypt’s revolution was created as an event on Facebook eleven days in advance. People clicked “I’m attending.” Certainly, this was a people’s revolution, yet one based on and accelerated in many ways by the Internet. What happened in Tahrir and every square in Egypt was the accumulation of years and years of activism, including Internet activism. Social media prepared Egyptians for the revolution and enabled them to capitalize on an opportunity for change when the time came.
  • The Internet, by definition, is a democratic medium, at least in the sense that anyone with Internet access is a potential publisher of information.
  • The mere presence of the Internet as a source of information helps open up a freer space for public debate, and makes it much more difficult for governments to censor information.
  • Internet activism started in Egypt with the appearance of Web 2.0 technology in the country around 2003
  • Blogging was the first valuable brainchild of Web 2.0 technologies.
  • The phenomenon exploded in the Arab world, with Egyptian bloggers pioneering and leading the scene. Blogger numbers in the region approached half a million by the beginning of 2009, the great majority of them coming from Egypt.
  • Political blogging in particular became more popular, as users felt that they could remain anonymous if they so wished
  • Nevertheless, most Egyptian political bloggers choose to blog under their real names, which frequently got them in trouble with the regime. The state security crackdown on bloggers was testimony to their potential impact.
  • Undoubtedly, blogging created a space for the voiceless in Egypt.
  • It was the first time individuals felt they could make themselves heard. That in itself was important, whether or not the content was political, and whether or not anyone was reading the blogs. The phenomenon created a venting space for people who had long gone unheard.
  • Early on, Alaa Abdel Fattah and Manal Hassan were awarded the Special Award from Reporters Without Borders in the international Deutsche Welle’s 2005 Weblog Awards (Best of Blogs) contest, where their blog was cited as an instrumental information source for the country’s human rights and democratic reform movement. The husband-and-wife team had created one of Egypt’s earliest blogs, “Manal and Alaa’s Bit Bucket,” where they documented their off-line activism and posted credible information on protests and political movements, election monitoring and rigging, and police brutality.
  • Another award-winning blogger was Wael Abbas. He received several honors, including the 2007 Knight International Journalism Award of the International Center for Journalists for “raising the standards of media excellence” in his country. This was the first time that a blogger, rather than a traditional journalist, won the prestigious journalism award, a testament to the important work such bloggers were doing. In the same year, CNN named Abbas Middle East Person of the Year. He has been instrumental in bringing to light videos of police brutality in Egypt, a topic that was taboo before he and other bloggers ventured into it. As a result of these efforts, the Egyptian government at one point brought three police officers to justice on charges of police brutality for the first time in Egypt’s history; they were convicted and sentenced to three years in jail.
  • As blogging was becoming a phenomenon in Egypt, some political movements started having a strong on-line presence, and taking to the streets based on their on-line organization. The most important was probably the Kefaya movement, whose formal name is The Egyptian Movement for Change. The movement was established in 2004 by a coalition of political forces, and became better known by its Arabic slogan. The word kefaya is Arabic for ‘enough,’ and as the name implies, the movement called for an end to the decades-old Mubarak regime, and for guarantees that his son would not succeed him as president. Kefaya was instrumental in taking people to the streets, thus bridging the gap between the on-line and the off-line worlds. Many of its supporters were bloggers, and many of the street protesters started blogging. So, increasingly, reports on the demonstrations found their way into blogs and were provided media coverage even when the traditional media ignored them or were afraid to cover them. One result was that many more Egyptians gained the courage to write blogs that openly criticized the authoritarian system and crossed the ‘red line’ of challenging their president.
  • nternet applications such as the video-sharing platform YouTube, which appeared in 2005, took blogging to a higher level.
  • hey were also capable of videotaping street protests and uploading the clips on YouTube. Watching people chanting “Down with Hosni Mubarak” in the mid-2000s was a totally new, riveting experience, which led many other brave Egyptians to join these demonstrations. Internet activists and blogger stars such as Wael Abbas, Alaa Abdel Fattah, Manal Hassan, Hossam El-Hamalawy, Malek Mostafa, and others uploaded hundreds of videos of police brutality, election rigging, and different violations of human and civic rights.
  • media, the platforms that allow for wider user discussions and user-generated content such as MySpace, Facebook, and Twitter
  • he next important development came with the introduction of what is typically known as social
  • The structure of social media taught Egyptians that space exists that you can call your own, your space, where you can speak your mind. To many in the West, this is probably no big deal. There are countless venues where they can express their opinions relatively freely. But for people in Egypt, and in the Arab world in general, this was a new phenomenon, and one I believe to be of profound importance.
  • horizontal communication.’ Before social networks, Egyptian youth were accustomed to being talked at, rather than talked to or spoken with. Communication was mostly vertical, coming from the regime down to everyone else
  • Authoritarian patterns of communication do not allow for much horizontal interaction. But social networks do, and eventually their existence on the Internet taught Egyptian youths a few lessons in democratic communication, even if the essence of the conversations carried out was not necessarily political in nature.
  • The bulk of those that I believe were affected by these lessons in democratic expression were clusters of the population that were not previously politically oriented. These form a good sector of those who took to the streets on January 25, and were joined by millions who held their ground in Tahrir Square and in every square in Egypt until Mubarak was toppled. The majority of these millions, including myself, were people who had never participated in a demonstration before. They were not political activists before January 25, but they saw or heard the call for action, and it touched a nerve as they found safety in numbers
  • another function that social networks served: making you realize that you’re not alone.
  • Perhaps the first time Egyptians learned about the power of social networks was on April 6, 2008. Workers in the Egyptian city of Al-Mahalla Al-Kobra planned a demonstration to demand higher wages. Esraa Abdel Fattah, an activist then twenty eight years old, felt for the workers and wanted to help them. She formed a group on Facebook and called it ‘April 6 Strike’ to rally support for the workers.
  • he knew it was too much to ask people to join in the protest, so she simply asked them to participate in spirit by staying home that day, not going to work, and not engaging in any monetary transactions such as buying or selling. The group was brought to the attention of the traditional media and was featured on one of Egypt’s popular talk shows, thus getting more exposure. What ensued surpassed all expectations. To Abdel Fattah’s own surprise (and everyone else’s), the Facebook group immediately attracted some seventy three thousand members. Many of these, and others who got the message through traditional media, decided to stay home in solidarity with the workers. Others were encouraged to stay home by a bad sandstorm that swept across parts of Egypt that day, and yet others stayed home for fear of the strong police presence on the streets.
  • The overall outcome made political activists realize that social networks could be a vital tool in generating support for a political cause, and in encouraging people to join a call for action.
  • The April 6 event was meaningful because it provided a sense that people were actually willing to take an action, to do something beyond clicking a mouse
  • three months before the January 25 revolution, Malcolm Gladwell argued in a much-discussed article in The New Yorker under the title “Small Change: Why the revolution will not be tweeted” that social media can’t provide what social change has always required. He said that social media is good when you’re asking people for small-scale, low-risk action, but not for anything more. “Facebook activism succeeds,” he wrote, “not by motivating people to make a real sacrifice but by motivating them to do the things that people do when they are not motivated enough to make a real sacrifice.” He explained that this is because high-risk activism is a “strong-tie phenomenon,” meaning that those who carry out such acts of activism have to personally know each other well and develop strong personal ties before they would risk their lives for each other or for a common cause. Since Facebook and Twitter provide mostly “weak-tie” connections, since users typically have a strong off-line social tie with only a small percentage of their ‘friends’ or ‘followers,’ these social networks were therefore not capable of motivating people for a high-risk cause. He therefore concluded that a social network “makes it easier for activists to express themselves, and harder for that expression to have any impact.”
  • nowing that you are in the company of many who share your utter belief in the same cause. That is something that social networks delivered
  • ne of the Facebook pages that played a major role in this regard was the Khaled Said page. Khaled Said was a young Egyptian who was brutally beaten to death by police informants outside an Internet café in Alexandria in June 2010. He had an innocent face that everyone could identify with. He could be anyone, and anyone could’ve been him. The Facebook page “We Are All Khaled Said” appeared shortly thereafter. It started asking its members, whose numbers increased steadily, to go out on silent standing protests in black shirts with their back to the streets. The demonstrations started in Alexandria and soon spread to every governorate in Egypt. Numbers increased with every protest. More and more people gained a little more courage and tasted the freedom of dissent.
  • One of the main advantages of the Khaled Said page was how well organized the events were. Protesters were provided with exact times and locations, and given exact instructions on what to wear, what to do, as well as who to contact in the case of any problems with security forces.
  • t was the Khaled Said page that eventually posted the ‘event’ for a massive demonstration on January 25, Egypt’s Police Day.
  • The administrators usually polled their users, asking them to vote for their place or time of preference for the next protest. The responses would be in the thousands, sometimes tens of thousands, and the administrators would read them all, and give a breakdown, with exact numbers and percentages, of the votes.
  • The January 25 demonstration was motivated and aided by an important intervening variable, the revolt in Tunisia. When Tunisian protesters succeeded in ousting President Zine El-Abidine Ben Ali on January 14, Egyptians felt that toppling a dictator through demonstrations was finally possible.
  • he Khaled Said page, which by then had about six hundred thousand followers, demonstrated its strong ability to organize. They listed all the major squares in every Egyptian governorate where they expected people to gather, and again gave specific instructions on what to wear, what to take with you, and who to contact in times of trouble. They then alerted the users that the listed venues for demonstration would change at midnight on January 24 to give police forces a lesser chance of mobilizing against them the next day. On the morning of January 25, there were close to half a million people who had clicked “I’m attending” the revolution. Today, the Khaled Said page has more than 1.7 million users, by far more than any other Egyptian Facebook page.
  • nd indeed that was what happened. We witnessed another key moment illustrating the power of the interaction between social media, traditional media, and interpersonal communication. Newspapers, broadcasters, and on-line outlets had been discussing the potential ‘Facebook demonstration’ for a few days prior to January 25. As groups of demonstrators marched through the streets enroute to main squares chanting “Ya ahalina endamo lina,” (“Friends and family, come join us”), people watching from their balconies and windows heeded the calls and enabled the protests to snowball to unprecedented numbers. People were galvanized by the sight. The core activists, who attended every demonstration for years, were suddenly seeing new faces on January 25, mostly mobilized by the Internet. They came by the thousands, and then by the hundreds of thousands, numbers larger than anyone had expected.
  • Twitter played an important though slightly different role. Crucial messages relayed in short bursts of one hundred and forty characters or less made protesters ‘cut to the chase.’ Most activists tweeted events live rather than posting them on Facebook. Twitter was mainly used to let people know what was happening on the ground, and alert them to any potential danger. It usually was ahead of Facebook in such efforts. Twitter also enabled activists to keep an eye on each other. Some managed to tweet ‘arrested’ or ‘taken by police’ before their mobile phones were confiscated. Those words were incredibly important in determining what happened to them and in trying to help them. Most activists are, to this day, in the habit of tweeting their whereabouts constantly, even before they go to sleep, because they know that fellow activists worry if they disappear from the Twittersphere.
  • When the Egyptian regime belatedly realized on January 25 how dangerous social networks could be to its survival, the first thing it did was block Twitter. Internet censorship is a ridiculously ineffective strategy, though. Users were tech-savvy enough to find their way onto proxy servers within minutes, and to post on Facebook how to gain access to Twitter and how to remain on Facebook if the regime blocks it, which indeed happened later. The government felt it didn’t have any other option but to block all Internet access in the country for five days starting January 27 (as well as mobile telephone communications for one day). By then it was too late. People had already found their way to Tahrir and nearly every square in Egypt. Ironically, some were partly motivated by the Internet and communication blockage to take to the streets to find out what was happening and be part of it. And they were joined by workers’ movements in many governorates that expanded the protester numbers into the millions. The major squares of Egypt were full of people of every age, gender, religion, creed, and socio-economic status
  • Gladwell, it turned out, was wrong. These people didn’t know each other personally, but the “weak” personal ties had not proved a barrier to high-risk activism. Egyptians discovered the strong tie of belonging to the common cause of ousting a dictator
  • ocial network users were not the only ones revolting, and social networks were not the only reason or motivation for revolt. However, the role that social media have played over the years in indirectly preparing sectors of Egyptian youths for this moment, and in enabling them to capitalize on an opportunity for change when the time came, cannot be understated.  It can also be said that the role of social networks in Egypt has hardly ended. The revolution is not yet complete. 
peppermara

Interview with Jawole Willa Jo Zollar - 0 views

www.youtube.com/watch

#tv008 #ThoughtVectors

shared by peppermara on 07 Jul 14 - No Cached
  • peppermara on 07 Jul 14
     
    founder and artistic director of Urban Bush Woman out of New York City. -speaks of inspiration, influences of her movement/project -sheds light on intertwined history of the Black Art's Movement -reflects on community-what individual voices provide -"I can be me, and I can create from that place. I can create from who I am and from the strengths and vulnerabilities of my community."
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