First major CERN test complete, scientists cheer

The world’s largest particle collider successfully completed its first major test by firing a beam of protons all the way around a 17-mile (27-kilometre) tunnel on Wednesday in what scientists hope is the next great step to understanding the makeup of the universe.

After a series of trial runs, two white dots flashed on a computer screen at 10:36 a.m. (0836 GMT) indicating that the protons had travelled the full length of the 3.8 billion US dollar Large Hadron Collider. (Watch).

Cheers erupted from the assembled scientists, including project leader Lyn Evans, in the collider’s control room at the Swiss-French border when the beam completed its lap.

Champagne corks popped in labs as far away as Chicago, where contributing scientists watched the proceedings by satellite.

Physicists around the world now have much greater power than ever before to smash the components of atoms together in attempts to see how they are made.

The European Organisation for Nuclear Research, known as CERN began firing the protons – a type of subatomic particle – around the tunnel in stages less than an hour earlier. (See pics).

Now that the beam has been successfully tested in clockwise direction, CERN plans to send it counterclockwise.

Eventually two beams will be fired in opposite directions with the aim of recreating conditions a split second after the big bang, which scientists theorise was the massive explosion that created the universe.

The start of the collider – described as the biggest physics experiment in history – comes over the objections of some skeptics who fear the collision of protons could eventually imperil the earth.
The skeptics theorised that a byproduct of the collisions could be micro black holes, subatomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.
James Gillies, chief spokesman for CERN dismissed this as nonsense before Wednesday’s start.

CERN is backed by leading scientists like Britain’s Stephen Hawking in dismissing the fears and declaring the experiments to be absolutely safe.

Gillies said that the most dangerous thing that could happen would be if a beam at full power were to go out of control, and that would only damage the accelerator itself and burrow into the rock around the tunnel.

Nothing of the sort occurred on Wednesday, though accelerator is still probably a year away from full power. The project organised by the 20 European member nations of CERN has attracted researchers from 80 nations.

Some 1,200 are from the United States, an observer country which contributed 531 million US dollar. Japan, another observer, also is a major contributor.

The collider is designed to push the proton beam close to the speed of light, whizzing 11,000 times a second around the tunnel.

Smaller colliders have been used for decades to study the makeup of the atom. Less than 100 years ago scientists thought protons and neutrons were the smallest components of an atom’s nucleus, but in stages since then experiments have shown they were made of still smaller quarks and gluons and that there were other forces and particles.

The CERN experiments could reveal more about “dark matter,” antimatter and possibly hidden dimensions of space and time.

It could also find evidence of the hypothetical particle – the Higgs boson – believed to give mass to all other particles, and thus to matter that makes up the universe

How a detector works

The job of a particle detector is to record and visualise the explosions of particles that result from the collisions at accelerators. The information obtained on a particle’s speed, mass, and electric charge help physicists to work out the identity of the particle.

The work particle physicists do to identify a particle that has passed through a detector is similar to the way someone would study the tracks of footprints left by animals in mud or snow. In animal prints, factors such as the size and shape of the marks, length of stride, overall pattern, direction and depth of prints, can reveal the type of animal that came past earlier. Particles leave tell-tale signs in detectors in a similar manner for physicists to decipher.

Modern particle physics apparatus consists of layers of sub-detectors, each specialising in a particular type of particle or property. There are 3 main types of sub-detector:

• Tracking device – detects and reveals the path of a particle
• Calorimeter – stops, absorbs and measures the energy of a particle
• Particle identification detector – identifies the type of particle using various techniques

To help identify the particles produced in the collisions, the detector usually includes a magnetic field. A particle normally travels in a straight line, but in the presence of a magnetic field, its path is bent into a curve. From the curvature of the path, physicists can calculate the momentum of the particle which helps in identifying its type. Particles with very high momentum travel in almost straight lines, whereas those with low momentum move forward in tight spirals.

Tracking devices

Tracking devices reveal the paths of electrically charged particles through the trails they leave behind. There are similar every-day effects: high-flying airplanes seem invisible, but in certain conditions you can see the trails they make. In a similar way, when particles pass through suitable substances the interaction of the passing particle with the atoms of the substance itself can be revealed.

Most modern tracking devices do not make the tracks of particles directly visible. Instead, they produce tiny electrical signals that can be recorded as computer data. A computer program then reconstructs the patterns of tracks recorded by the detector, and displays them on a screen.

They can record the curvature of a particle’s track (made in the presence of a magnetic field), from which the momentum of a particle may be calculated. This is useful for identifying the particle.

Muon chambers are tracking devices used to detect muons. These particles interact very little with matter and can travel long distances through metres of dense material. Like a ghost walking through a wall, muons can pass through successive layers of a detector. The muon chambers usually make up the outermost layer.

Calorimeters

A calorimeter measures the energy lost by a particle that goes through it. It is usually designed to entirely stop or ‘absorb’ most of the particles coming from a collision, forcing them to deposit all of their energy within the detector.

Calorimeters typically consist of layers of ‘passive’ or ‘absorbing’ high–density material (lead for instance) interleaved with layers of ‘active’ medium such as solid lead-glass or liquid argon.

Electromagnetic calorimeters measure the energy of light particles – electrons and photons – as they interact with the electrically charged particles inside matter.

Hadronic calorimeters sample the energy of hadrons (particles containing quarks, such as protons and neutrons) as they interact with atomic nuclei.

Calorimeters can stop most known particles except muons and neutrinos.

Particle identification detectors

Two methods of particle identification work by detecting radiation emitted by charged particles:

• Cherenkov radiation: this is light emitted when a charged particle travels faster than the speed of light through a given medium. The light is given off at a specific angle according to the velocity of the particle. Combined with a measurement of the momentum of the particle the velocity can be used to determine the mass and hence to identify the particle.
• Transition radiation: this radiation is produced by a fast charged particle as it crosses the boundary between two electrical insulators with different resistances to electric currents. The phenomenon is related to the energy of a particle and distinguishes different particle types.

 

Images of CERN Experiment

 

 

 

CERN Experiment

 

 

 

 

 

 

 

 

 

 

 

A view of the LHC (large hadron collider) in its tunnel at CERN (European particle physics laboratory) near Geneva, Switzerland. One huge scientific experiment being launched Wednesday, September 10, 2008 is described as an Alice in Wonderland investigation into the makeup of the universe, or dangerous tampering with nature that could spell Doomsday for the Earth. The first beams of protons will be fired around the 27-kilometer (17-mile) tunnel at the launch on Wednesday to test the controlling strength of the world’s largest superconducting magnets. It will still be several weeks before beams traveling in opposite directions are brought together in collisions that some skeptics fear could create micro “black holes” they theorize could endanger the planet. (AP)

 

 

 

 

 

CERN Experiment
People stand next to the giant magnet Compact Muon Solenoid (CMS) being placed underground in the Large Hadron Collider (LHC) accelerator at CERN, the European Particle Physics laboratory, in Cressy near Geneva, France. (AP)

 

 

 

CERN Experiment

 

 

 

 

 

 

 

 

 

 

 

A general view of the island SPS (Super Proton Synchrotron) of the CERN Control Centre (CCC) where the operators prepare the commissioning of the LHC (Large Hadron Collider) at the European Particle Physics laboratory (CERN) in Prevessin, France, at the Swiss border, near Geneva. (

AP)

 

 

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The photo shows the tunnel of the LHC particle accelerator at the European Organisation for Nuclear Research CERN in Geneva, Switzerland. (AP)

 

 

 

CERN Experiment 

 

 

 

 

 

  

 

 

Project leader for CERN’s Large Hadron Collider (LHC) Lyn Evans, left, speaks with Carlos Fernandez Robles, right, engineer, in the island LHC of the CERN Control Centre (CCC) at the European Particle Physics laboratory (CERN) in Prevessin, France, at the Swiss border, near Geneva. (AP

 

 

CERN Experiment  

 

 

 

 

 

A technician working in a computing center of the CERN, the worlds largest particle physics laboratory of the European Organization for Nuclear Research in Meyrin, near Geneva, Switzerland. (AP)

 

 

CERN Experiment 

 

 

 

 

 

 

A view of the LHC (large hadron collider) in its tunnel at CERN (European particle physics laboratory) near Geneva, Switzerland. One huge scientific experiment being launched Wednesday, September 10, 2008 is described as an Alice in Wonderland investigation into the makeup of the universe, or dangerous tampering with nature that could spell Doomsday for the Earth. The first beams of protons will be fired around the 27-kilometer (17-mile) tunnel at the launch on Wednesday to test the controlling strength of the world’s largest superconducting magnets. It will still be several weeks before beams traveling in opposite directions are brought together in collisions that some skeptics fear could create micro “black holes” they theorize could endanger the planet. (AP)

Dark secrets of the Universe

It’s perhaps natural that we don’t know much about how the Universe was created – after all, we were never there ourselves. But it’s surprising to realise that when it comes to the Universe today, we don’t necessarily have a much better knowledge of what is out there. In fact, astronomers and physicists have found that all we see in the Universe – planets, stars, galaxies – accounts for only a tiny 4% of it! In a way, it is not so much the visible things that define the Universe, but rather the void around them.

Cosmological and astrophysical observations indicate that most of the Universe is made up of invisible substances that do not emit electromagnetic radiation – that is, we cannot detect them directly through telescopes or similar instruments. We detect them only through their gravitational effects, which makes them very difficult to study. These mysterious substances are known as ‘dark matter’ and ‘dark energy’. What they are and what role they played in the evolution of the Universe are a mystery, but within this darkness lie intriguing possibilities of hitherto undiscovered physics beyond the established Standard Model.

Dark matter

Dark matter makes up about 26% of the Universe. The first hint of its existence came in 1933, when astronomical observations and calculations of gravitational effects revealed that there must be more ’stuff’ present in the Universe than telescopes could see.

Researchers now believe that the gravitational effect of dark matter makes galaxies spin faster than expected, and that its gravitational field deviates the light of objects behind it. Measurements of these effects show that dark matter exists, and they can be used to estimate the density of dark matter even though we cannot directly observe it.

But what is dark matter? One idea is that it could contain ‘supersymmetric particles’ – hypothesized particles that are partners to those already known in the Standard Model. Experiments at the Large Hadron Collider may be able to find them.

Dark energy

Dark energy makes up approximately 70% of the Universe and appears to be associated with the vacuum in space. It is homogenously distributed throughout the Universe, not only in space but also in time – in other words, its effect is not diluted as the Universe expands.

The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the Universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the Universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of this mysterious substance exists.

 

WiFi

If you’ve been in an airport, coffee shop, library or hotel recently, chances are you’ve been right in the middle of a wireless network. Many people also use wireless networking, also called WiFi or 802.11 networking, to connect their computers at home, and some cities are trying to use the technology to provide free or low-cost Internet access to residents. In the near future, wireless networking may become so widespread that you can access the Internet just about anywhere at any time, without using wires.

One wireless router can allow multiple devices to connect to the Internet.

WiFi has a lot of advantages. Wireless networks are easy to set up and inexpensive. They’re also unobtrusive — unless you’re on the lookout for a place to use your laptop, you may not even notice when you’re in a hotspot. In this article, we’ll look at the technology that allows information to travel over the air. We’ll also review what it takes to create a wireless network in your home.

First, let’s go over a few WiFi basics.

What Is WiFi?

A wireless network uses radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here’s what happens:

1. A computer’s wireless adapter translates data into a radio signal and transmits it using an antenna.
2. A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection.

The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to the computer’s wireless adapter.

The radios used for WiFi communication are very similar to the radios used for walkie-talkies, cell phones and other devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s and 0s. But WiFi radios have a few notable differences from other radios:

• They transmit at frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.
• They use 802.11 networking standards, which come in several flavors:
  • 802.11a transmits at 5 GHz and can move up to 54 megabits of data per second. It also uses orthogonal frequency-division multiplexing (OFDM), a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver. This greatly reduces interference.
  • 802.11b is the slowest and least expensive standard. For a while, its cost made it popular, but now it’s becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complementary code keying (CCK) modulation to improve speeds.
  • 802.11g transmits at 2.4 GHz like 802.11b, but it’s a lot faster — it can handle up to 54 megabits of data per second. 802.11g is faster because it uses the same OFDM coding as 802.11a.
  • 802.11n is the newest standard that is widely available. This standard significantly improves speed and range. For instance, although 802.11g theoretically moves 54 megabits of data per second, it only achieves real-world speeds of about 24 megabits of data per second because of network congestion. 802.11n, however, reportedly can achieve speeds as high as 140 megabits per second. The standard is currently in draft form — the Institute of Electrical and Electronics Engineers (IEEE) plans to formally ratify 802.11n by the end of 2009.
• Other 802.11 standards focus on specific applications of wireless networks, like wide area networks (WANs) inside vehicles or technology that lets you move from one wireless network to another seamlessly.
• WiFi radios can transmit on any of three frequency bands. Or, they can “frequency hop” rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously.

WiFi Hotspots

If you want to take advantage of public WiFi hotspots or start a wireless network in your home, the first thing you’ll need to do is make sure your computer has the right gear. Most new laptops and many new desktop computers come with built-in wireless transmitters. If your laptop doesn’t, you can buy a wireless adapter that plugs into the PC card slot or USB port. Desktop computers can use USB adapters, or you can buy an adapter that plugs into the PCI slot inside the computer’s case. Many of these adapters can use more than one 802.11 standard.

Once you’ve installed your wireless adapter and the drivers that allow it to operate, your computer should be able to automatically discover existing networks. This means that when you turn your computer on in a WiFi hotspot, the computer will inform you that the network exists and ask whether you want to connect to it. If you have an older computer, you may need to use a software program to detect and connect to a wireless network.

Being able to connect to the Internet in public hotspots is extremely convenient. Wireless home networks are convenient as well. They allow you to easily connect multiple computers and to move them from place to place without disconnecting and reconnecting wires. In the next section, we’ll look at how to create a wireless network in your home.

Building a Wireless Network

If you already have several computers networked in your home, you can create a wireless network with a wireless access point. If you have several computers that are not networked, or if you want to replace your Ethernet network, you’ll need a wireless router. This is a single unit that contains:

1. A port to connect to your cable or DSL modem
2. A router
3. An Ethernet hub
4. A firewall
5. A wireless access point

A wireless router allows you to use wireless signals or Ethernet cables to connect your computers to one another, to a printer and to the Internet. Most routers provide coverage for about 100 feet (30.5 meters) in all directions, although walls and doors can block the signal. If your home is very large, you can buy inexpensive range extenders or repeaters to increase your router’s range.

A wireless router uses an antenna to send signals to wireless devices and a wire to send signals to the Internet.

As with wireless adapters, many routers can use more than one 802.11 standard. 802.11b routers are slightly less expensive, but because the standard is older, they’re slower than 802.11a, 802.11g and 802.11n routers. Most people select the 802.11g option for its speed and reliability.

Once you plug in your router, it should start working at its default settings. Most routers let you use a Web interface to change your settings. You can select:

• The name of the network, known as its service set identifier (SSID) — The default setting is usually the manufacturer’s name.
• The channel that the router uses — Most routers use channel 6 by default. If you live in an apartment and your neighbors are also using channel 6, you may experience interference. Switching to a different channel should eliminate the problem.
• Your router’s security options — Many routers use a standard, publicly available sign-on, so it’s a good idea to set your own username and password.

Security is an important part of a home wireless network, as well as public WiFi hotspots. If you set your router to create an open hotspot, anyone who has a wireless card will be able to use your signal. Most people would rather keep strangers out of their network, though. Doing so requires you to take a few security precautions.

It’s also important to make sure your security precautions are current. The Wired Equivalency Privacy (WEP) security measure was once the standard for WAN security. The idea behind WEP was to create a wireless security platform that would make any wireless network as secure as a traditional wired network. But hackers discovered vulnerabilities in the WEP approach, and today it’s easy to find applications and programs that can compromise a WAN running WEP security.

To keep your network private, you can use one of the following methods:

• WiFi Protected Access (WPA) is a step up from WEP and is now part of the 802.11i wireless network security protocol. It uses temporal key integrity protocol (TKIP) encryption. As with WEP, WPA security involves signing on with a password. Most public hotspots are either open or use WPA or 128-bit WEP technology, though some still use the vulnerable WEP approach.
• Media Access Control (MAC) address filtering is a little different from WEP or WPA. It doesn’t use a password to authenticate users — it uses a computer’s physical hardware. Each computer has its own unique MAC address. MAC address filtering allows only machines with specific MAC addresses to access the network. You must specify which addresses are allowed when you set up your router. This method is very secure, but if you buy a new computer or if visitors to your home want to use your network, you’ll need to add the new machines’ MAC addresses to the list of approved addresses. The system isn’t foolproof. A clever hacker can spoof a MAC address — that is, copy a known MAC address to fool the network that the computer he or she is using belongs on the network.

  Sources

  • Borisov, Nikita, Ian Goldberg and David Wagner. “Security of the WEP algorithm.” University of California, Berkeley. (Aug. 7, 2008)
    http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html
  • Geier, Jim. “802.11 WEP: Concepts and Vulnerability.” Wi-Fi Planet. June 20, 2002. (Aug. 6, 2008)
    http://www.wi-fiplanet.com/tutorials/article.php/1368661
  • IEEE. (Aug. 6, 2008)
    http://www.ieee.org
  • IEEE. “IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements.” (Aug. 6, 2008) http://standards.ieee.org/getieee802/download/802.11-2007.pdf

Wimax Vs WiFi

Wireless LANs based on Wi-Fi have been a resounding success, and now the focus in wireless is shifting to the wide area. With product shipments due out at the end of 2004, WiMax will be the next wireless WAN technology to debut. With increased market recognition for WiMax comes comparisons to Wi-Fi. While the two share some common technical characteristics, they approach wireless from completely different perspectives. This paper by Michael Finneran of dBrn Associates provides a technical and market comparison of Wi-Fi and WiMax technologies, highlighting similarities and differences and identifying applications that each will address in the coming years.

you can fe detailed information at the given link

http://searchmobilecomputing.techtarget.com/searchMobileComputing/downloads/Finneran.pdf