Our planet is ringed with more than 1000 working satellites, plus thousands of tonnes of space junk, and for the most part they stay up there quite happily. But surprisingly, it is only now that we properly understand why.
Ideally, a tiny satellite orbiting a perfectly spherical planet will remain there forever, assuming nothing nearby disturbs it. But Earth is not a perfect sphere, and there are plenty of other objects that can disturb artificial satellites in low-Earth orbit – first and foremost, the moon. According to the laws of motion, the moon's influence alone should cause satellites to crash into the Earth's atmosphere, where they would burn up.
Saving grace
It turns out that Earth's imperfections are a satellite's saving grace. Because of its rotation, Earth is slightly flattened at the poles and bulges around the equator.
According to computer simulations and analysis by Scott Tremaine at the Institute for Advanced Study in Princeton, New Jersey, and Tomer Yavetz of Princeton University, the gravitational pull of that bulge shifts satellites' orbits over time, preventing tugs from the moon and other sources from pulling them too far in one direction or another. If the Earth were closer to being a perfect sphere, many satellites would crash into the atmosphere and burn up in a matter of months or years.
"It's interesting that there are lots of things that could destabilise low-Earth orbits, but that things happen to combine in such a way that we have a good environment for satellites," says Gregory Laughlin, a physicist at the University of California, Santa Cruz, who was not involved with this research. "It makes you pause to think a little bit – when you look in detail at how things work, you can find surprises."
Source:http://www.newscientist.com/article/dn24309-earths-love-handles-keep-the-satellites-from-falling.html#.UscPatLuJgp
You probably don't think about pencils and erasers much in today's world of digital and mobile access to everything; while it's undeniable that the No. 2 pencil and the SAT have a long history together, pencils don't really come up much outside of standardized testing anymore. But despite our devotion to our devices, Americans still use more than 2 billion pencils every year [source: Lunsford].
Contrary to popular belief, pencils aren't really made with lead, and haven't been since Roman scribes wrote on papyrus -- that's a common pencil myth. So if you chew on your pencils, rest assured you won't become ill from lead poisoning (although that's not a free pass to snack on a No. 2). Today's pencils are made with graphite, water and clay (which is used as a binder), and pencil lead has been made this way since Nicolas-Jacques Conté invented the mixture in 1795 [source: Ritter]. They weren't topped with an eraser tip, though, until about a century later. And it's this companion to the pencil, the eraser, that we're interested in here.
Erasers eradicate pencil markings by lifting graphite from the paper you've written on. As you write, particles of graphite from your pencil mingle with and cling to particles in the fiber of the paper. Here's the science: Modern erasers are almost always made from petroleum-based synthetic rubber compounds, typically polyvinyl chloride (they're no longer made from natural latex rubber, which is an allergen for some people). Because the particles in the polymer that make up an eraser are stickier than paper, those graphite particles get stuck to the eraser instead. Some erasers are stickier than others and absorb graphite particles more easily, giving you a cleaner, less-abrasive result.
Believe it or not, one of the very first erasers used was moist bread. Let's talk about how far erasers have come since the days of day-old bread, next.
An icy moon of Jupiter has been caught spitting into space. For the first time, a towering plume of water vapour has been seen coming from Europa. The discovery strengthens the case that the moon has a liquid ocean beneath its icy crust, and may even offer a way to taste its seas and search for signs of life.
Images from the Galileo spacecraft, which orbited Jupiter from 1995 to 2003, revealed a cracked and chaotic surface dominated by dark ridges and faults. This hinted that Europa has a relatively thin crust in which fissures sometimes open up and let water escape from a subsurface ocean. Similar rifts on Saturn's icy moon Enceladus shoot spectacular water geysers. But the Galileo probe did not spot any plumes in action on Europa, and later efforts also came up empty.
Now images taken by the Hubble Space Telescope have revealed a large cloud of hydrogen and oxygen – most likely in the form of water vapour – extending from the moon's south pole. A model suggests that it is a plume 200 kilometres high that is spouting 3000 kilograms of water per second.
"This is a big discovery," says Cynthia Phillips at the SETI Institute in Mountain View, California, who was not involved in the find but had looked for plumes with Galileo. "If there are plumes erupting, there's got to be liquid water, and it's got to be pretty close to the surface."
Source:http://www.newscientist.com/article/dn24743-first-water-plume-seen-firing-from-jupiter-moon-europa.html
Now images taken by the Hubble Space Telescope have revealed a large cloud of hydrogen and oxygen – most likely in the form of water vapour – extending from the moon's south pole. A model suggests that it is a plume 200 kilometres high that is spouting 3000 kilograms of water per second.
"This is a big discovery," says Cynthia Phillips at the SETI Institute in Mountain View, California, who was not involved in the find but had looked for plumes with Galileo. "If there are plumes erupting, there's got to be liquid water, and it's got to be pretty close to the surface."
Source:http://www.newscientist.com/article/dn24743-first-water-plume-seen-firing-from-jupiter-moon-europa.html
A team of physicists has provided some of the clearest evidence yet that our Universe could be just one big projection.In 1997, theoretical physicist Juan Maldacena proposed that an audacious model of the Universe in which gravity arises from infinitesimally thin, vibrating strings could be reinterpreted in terms of well-established physics. The mathematically intricate world of strings, which exist in nine dimensions of space plus one of time, would be merely a hologram: the real action would play out in a simpler, flatter cosmos where there is no gravity.
Maldacena's idea thrilled physicists because it offered a way to put the popular but still unproven theory of strings on solid footing — and because it solved apparent inconsistencies between quantum physics and Einstein's theory of gravity. It provided physicists with a mathematical Rosetta stone, a 'duality', that allowed them to translate back and forth between the two languages, and solve problems in one model that seemed intractable in the other and vice versa. But although the validity of Maldacena's ideas has pretty much been taken for granted ever since, a rigorous proof has been elusive.
In two papers posted on the arXiv repository, Yoshifumi Hyakutake of Ibaraki University in Japan and his colleagues now provide, if not an actual proof, at least compelling evidence that Maldacena’s conjecture is true.
In one paper, Hyakutake computes the internal energy of a black hole, the position of its event horizon (the boundary between the black hole and the rest of the Universe), its entropy and other properties based on the predictions of string theory as well as the effects of so-called virtual particles that continuously pop into and out of existence. In the other, he and his collaborators calculate the internal energy of the corresponding lower-dimensional cosmos with no gravity. The two computer calculations match.
“It seems to be a correct computation,” says Maldacena, who is now at the Institute for Advanced Study in Princeton, New Jersey and who did not contribute to the team's work.
Regime change
The findings “are an interesting way to test many ideas in quantum gravity and string theory”, Maldacena adds. The two papers, he notes, are the culmination of a series of articles contributed by the Japanese team over the past few years. “The whole sequence of papers is very nice because it tests the dual [nature of the universes] in regimes where there are no analytic tests.”
“They have numerically confirmed, perhaps for the first time, something we were fairly sure had to be true, but was still a conjecture — namely that the thermodynamics of certain black holes can be reproduced from a lower-dimensional universe,” says Leonard Susskind, a theoretical physicist at Stanford University in California who was among the first theoreticians to explore the idea of holographic universes.
Neither of the model universes explored by the Japanese team resembles our own, Maldacena notes. The cosmos with a black hole has ten dimensions, with eight of them forming an eight-dimensional sphere. The lower-dimensional, gravity-free one has but a single dimension, and its menagerie of quantum particles resembles a group of idealized springs, or harmonic oscillators, attached to one another.
Nevertheless, says Maldacena, the numerical proof that these two seemingly disparate worlds are actually identical gives hope that the gravitational properties of our Universe can one day be explained by a simpler cosmos purely in terms of quantum theory.
This story originally appeared in Nature News.
Fiber optics is a technique and a technology for transmitting information on computer networks. Once reserved for inter-enterprise links, optical fiber can be generalized as a means of access to the Internet because it allows downloads very high speed (up to 100 Mbits / s against 22 Mbit / s for ADSL 2 +).The optical fiber cable means a yarn which contains a glass or plastic capable of carrying light. It is this light that will be transported in the network and interpreted upon receipt. The optical fiber also has the advantage of being naturally insensitive to external electrical interference. We can thus establish a fiber optic link across thousands of kilometers.
Fiber-optic cables have greater "bandwidth": they can carry much more data than metal cable. Because fiber optics is based on light beams, the transmissions are more impervious to electrical noise and can also be carried greater distances before fading. The cables are thinner than metal wires. Fiber-optic cable delivers data in digital code instead of an analog signal, the delivery method of metal cables; computers are structured for digital, so there is a natural symbiosis. The main disadvantage is cost: fiber optics are much more expensive than traditional metal cable.
Modern fiber optic cables can carry a signal quite a distance -- perhaps 60 miles (100 km). On a long distance line, there is an equipment hut every 40 to 60 miles. The hut contains equipment that picks up and retransmits the signal down the next segment at full strength.
Fiber-optic cables are currently the best way to carry very high rates of digital information, and the needs in this area are likely to increase sharply in the near future. It is likely that the demand for a simple Internet connection, the next few years will be identical to what we have come to expect a LAN (100 Mbit / s at least). Under these conditions, the panorama of information has completely changed. Telephony, radio, television and transfers "computer" data will be provided by the same connection, the interpenetration of these various means of information will be much larger, at least this is a quite realistic scenario.
In1816,Karl von Drais de Sauerbrun, of Germany, invented a model with a steering bar attached to the front wheel, which he called a Draisienne. It has two wheels (of the same size), and the rider sat between the two wheels, but there were no pedals; to move, you had to propel the bicycle forward using your feet (a bit like a scooter). He exhibited his bicycle in Paris on April 6, 1818.
Kirkpatrick MacMillan (1812-1878), a blacksmith from Dumfriesshire, Scotland, invented the first bicycle with foot pedals in the 1830 to 1840's, but he never patented it and his idea did not catch on locally.
A French father-and-son team of carriage-makers, Pierre and Ernest Michaux, invented an improved bicycle in the 1860's. Many early bicycles (called velocipedes, meaning "fast foot," or, more descriptively, "bone shakers") had huge front wheels - it was thought that the bigger the wheel, the faster you could go. Early tires were wooden - metal tires were an improvement, and solid rubber tires were added later. A chain with sprockets was added to the bicycle in the 1880's; this was called the "safety bicycle." Air-filled tires were also added in the 1880's. The derailleur gear system was added in the 1970's..
2 - Have a U.S. nationality, was born in 1847 and died in 1931 at the age of 84 years.
3 - Edison religion was Deism , a religion believes of the existence of the Creator of the universe and that this makes sense , but without the need to have a religion.
4 - He did not invent the light bulb , but it exists before him, he invented the light bulb practical capable of permanence for a long time .
5 - He has 1,093 registered patents .
6 - His tenure at the school did not exceed a few months so His mother taught him at home ,and this is what made him say, "I felt that there is a human should not being disappointed, and that there is something i should live for him. "
7 - Work in the offing as operator Telegraph He worked for Western Union and then worked in the agency AP News in some administrative functions .
8 - Married twice ( his first wife died ) , and fathered 6 children, scored one 80 and the other patented arrived for governor of New Jersey , while the rest were without significant achievements .
9 - Other of the most famous inventions is the oldest phonograph, the oldest device used to record and restore the sound, and the first animation camera , which is the basis of evolution in video and television, and he was the first man think to make an integrated laboratory for industrial experiments .
10 - Edison was accused of being an businessman ,Thomas did not deny that, but assured them that he invented everything for money, but saying "to helpme to invent more things"
Was used Steel tubing. He worked with the receiving device in one room, while his assistant Thomas Watson runs a transmitter in the other room.
Watson picked up steel rod to make it oscillate, fired a ringing voice. Suddenly Bill hustling income, shouting to his friend Watson: Do not change anything. What did you do then? Let me see. He found that a vibrating steel rod above the magnet has caused a strong current flows through a variety tape. This is what makes the Tube in Chamber Bill fluctuate and issued a ringing voice.
The next day was made the first telephone and voice votes can be identified via the first telephone line, which was top of the building down to two floors and was the first phrase heard on the phone on 10 March of the following year: Mr Watson, come here, I want you.
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