The Large Hadron Collider, if located in the Bay Area, would encompass a sizable piece of San Francisco. Image Credit: NASA.In about one month the world’s biggest science experiment, the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, will once again fire up. So now may be a good time to stop and remember what a stunning and ambitious project this is. Indeed, it becomes hard not to get lost in such an endless list of superlatives once you start noticing. I have gleaned a few below. See CERN’s website for more, or Jennifer Skene’s blog for a great set of LHC links.

She’s Electric: To power a standard light bulb you need 60 Watts (or 15 watts for an equivalent CFL). To power a small house you need an average of about a thousand watts. To run the LHC at full power researchers will need 120 million watts. Alternatively, you could run the LHC, supply electricity to a population the size of Berkeley, or simultaneously bake 60,000 Thanksgiving turkeys. You could only fly three 747 airplanes, though.

Life in the Fast Lane: A fundamental axiom of physics states that no information can travel faster than the speed of light. The LHC’s proton beams are no exception, but their speeds do approach light speed to within a fraction of a millionth of 1 percent. Such velocities defy comprehension. Suffice it to say that if we ever managed to accelerate a person to this velocity, time would warp so much that we could expect her to live for half a million years.

The Long and Winding Road: The LHC’s 17-mile circumference could make it a nice racetrack for a half-marathon, but don’t try racing the beam. When operational, protons will shoot around the LHC more than 11,000 times per second. Even more mind-boggling is the length of wire used in the construction of the LHC’s thousands of superconducting magnets. CERN claims there is enough wire wrapped up in these magnets to trace out more than six trips to the Sun and back.

OK Computer: When operational, the LHC is expected to generate 15 petabytes of data and simulations per year, which amounts to the hard drive space of about 30,000 high-end personal computers. At CERN in 1989, Tim Berners-Lee and Robert Cailliau revolutionized the world with their development of key pieces in the framework of the World Wide Web. The networks being developed to manage the LHC’s expected data have inspired talk of a similar revolution to come.

A Whole New World?: All of these wonders of physics and engineering have been developed for the purpose of one thing: to create a particle smasher with the capability of knocking two protons together with an energy of 14 TeV (trillions of electron volts). This is about the same energy that it takes to pick a grain of salt up off the floor. Compressed into such an acute space, however, it just might lend us insight into the most fundamental properties of our universe.

Now, if they can only get those wires hooked up correctly…

A magnet is suspended over a liquid nitrogen cooled
high-temperature superconductor (-200°C). Image source:
Wikimedia
Take a familiar metal, such as the aluminum foil from the bottom drawer of a kitchen, the mercury you might find in a household thermometer, or the titanium used to build an expensive road bike. Cool it enough, and you will find almost miraculously that electricity can be sent though the metal without losing any of its energy.

This effect, known as superconductivity, has tantalized physicists with theoretical weirdness and seduced futurists with potential applications since its discovery in 1911. Some of the applications, particularly in magnetism, have already been realized. A typical MRI machine works because, hidden within its outer casing, electricity is pumped through a superconducting wire maintained 10 times colder than the average temperature of Pluto. The soon-to-be-running Large Hadron Collider at CERN in Geneva would not have been possible without the aid of giant superconducting magnets. Scientists at the High Field Magnet Laboratory in the Netherlands have even used superconducting magnets to suspend a living frog.

Even more exotic and exciting ideas have been dreamed up, such as large-scale lossless power transmission networks or commercially-viable magnetically levitated trains. Many of these have remained elusively beyond the cusp of practicality. This is because most materials become superconductors only in the frigid neighborhood of absolute zero (0-10 Kelvin). A few do have higher transition temperatures. For example, the cuprates, a class of material based on copper and oxygen, become superconductors as high as 133 Kelvin. Unfortunately, these are also brittle, difficult to work with, and bear limited current loads. However, times may be changing.

In February of last year scientists discovered a new candidate in their quest for a better superconductor, a material based on iron and arsenic. That's right– it is possible that one of the most promising candidates for next-generation energy technology is at least partly the same stuff Aunt Abby used to poison Mr. Witherspoon. The new class of material, collectively known as the iron pnictides (pronounced "NICK-tides"), has taken the physics community by storm, inspired more than a thousand research publications and stolen the show last month at the world's largest annual gathering of materials scientists, the American Physical Society March Meeting.

Is all the hype really merited? Maybe.

Much of the excitement surrounding the iron pnictides is becuase they turn superconducting at anomalously high temperatures, to date at least as high as 56 Kelvin. To be fair, this is still not exactly a high temperature compared to normal everyday experience. Room temperature is about 300 Kelvin. At 273 Kelvin you can get frostbite. At 56 Kelvin the air you breathe liquefies and your lung cavities fill with dry ice.

In the world of superconductors, however, a material with a transition temperature of 56 Kelvin is a rock star. This is the second warmest class of superconductor we know about, overshadowed only by the cuprates.

A few scientists feel optimistic that the pnictide family's transition temperatures may yet surpass even those of the cuprates. This would be a tremendous scientific and technological discovery, not simply because it would set a new record, but because it would mean that we now have two families of materials that become superconducting above the boiling temperature of liquid nitrogen (77 Kelvin). This would be fantastic because cooling materials with liquid nitrogen is both technically easier and less expensive than using the current standard of liquid helium.

Additionally, there may be reason to believe that the new iron pnictides may not have some of the problems that plague other high temperature superconductors. The cuprates have an annoying habit of spawning tiny electrical whirlpools in the presence of a magnetic field. Unless these whirlpools, or vortices (as they are technically called), can be pinned in place, lossless power transmission is impossible. While vortices still occur in the pnictides, pinning may prove to be easier than it is in the cuprates.

Even if we never are able to capitalize on the pnictides, they may have intrinsic scientific value. Scientists are baffled at the underlying mechanism that allows a material to be a superconductor above 40 Kelvin. Figuring this out may not ultimately satiate a desire for new technologies, but the simple desire to know is exactly the sort of thing that would make Darwin or Einstein proud.