Physicists, to their credit, are notoriously unsentimental and future-oriented. "Today's sensation is tomorrow's calibration" describes their modus operandi.

Nevertheless! Today America's flagship collider, the Tevatron at Fermilab in Illinois, will cease operation, and Europe's Large Hadron Collider (LHC) at CERN, near Geneva, will lead the exploration of the deep microcosmos. That changing of the guard inspires reflection, and merits celebration too.

Some historical perspective will highlight the special role of colliders in fundamental physics. The goal of experimental work in fundamental physics, crudely speaking, is to find out what the smallest, most basic building-blocks of the material world are, and how they behave (which, if you think about it, effectively defines what they are). In the early days of science, optical microscopes revealed the existence of tiny creatures and the cellular structure of life in general. But light cannot resolve structures much smaller than its wavelength, and the wavelength of ordinary light is tens of thousands of times larger than the size of atoms.

X-rays, discovered much later, get closer to atomic scales. Rosiland Franklin's x-ray pictures of DNA crystals enabled Crick and Watson to decipher DNA's molecular structure. At this point, a simple question may suggest itself: Why was any deciphering necessary--can't you just look at the darned picture? The answer is profound, and central to our story. It's easy to take for granted a most fortunate and unusual feature of ordinary light, namely that lenses can bend it and (when suitably arranged) automatically form images of illuminated objects. Our very own eyes do that trick, which is what makes it so easy to overlook! But there are no good lenses for x-rays. Instead of images, when we scatter x-rays off matter we get patterns of greater or lesser brightness called diffraction patterns. Then we've got to use our brains to make models, using everything else we know about x-rays and matter, for what could have caused the observed diffraction pattern.

To probe structures much smaller than atoms we must get well beyond x-rays, using more extreme forms of illumination. Energetic particles are the tools for this job; and the smaller the structures we aspire to "see," the higher the energies we need. Physicists study what emerges when those projectiles impact on matter--or, in the jargon, scatter on targets. Then, like Crick and Watson, they make models of what could be responsible. (Actually, nowadays theorists usually provide myriad models in advance, and then experimentalists disprove all but one of them!) In the early days of nuclear physics, particles emitted in natural radioactivity (especially "alpha particles," later identified as helium nuclei) were the workhorse probes; later cosmic rays--high-energy particles raining down from space--despite their obvious inconvenience, and unreliability, took the lead. Those techniques led to some tantalizing discoveries, but their limitations were crippling.

Further progress required that experimentalists wean themselves from natural sources. They had to learn how to pump up the energy of particles, collect them, and guide them to targets. A long series of brilliant innovations led to the modern collider. One innovation in particular is so unlikely-sounding, yet so crucial, that it deserves special mention. According to the theory of relativity, particles moving close to the speed of light are flattened in the direction of motion, but retain their size in the transverse direction, so that they appear as narrow pancakes. For our purposes, that's great--it allows the probes to be sharply localized, so they can take high-resolution pictures. It's so advantageous that physicists double down on it. Rather than impacting energetic particles on a stationary target, at a modern collider highly energetic particles moving in one direction impact other highly energetic particles moving in the opposite direction. At the Tevatron protons collide with antiprotons; at the LHC it's protons on protons. To make such collisions happen, though, is no mean feat, because the targets are comparatively few, and each is very small indeed. It takes powerful, intricately patterned electric and magnetic control fields, and ultra-fast monitoring and feedback, to bring tight counter-circulating beams to the same place at the same time.

For this and many other reasons modern colliders are fantastic engineering projects. They employ instruments and ideas more complex and much more varied than are involved, for example, in space exploration. They are big, and expensive. The main Tevatron ring, where the beams circulate, is almost four miles around, and the various pieces of the project cost about $1 billion altogether. The LHC is about five times as big, and five times as expensive.

These great colliders are, I think, monuments to our dynamic scientific civilization. They are our Pyramids; but they are better motivated and much better engineered than the originals. There's been some progress in five thousand years!

A bittersweet corollary of dynamism, however, is that once-great things eventually become passé. With the coming of the LHC, which makes more and more energetic collisions, the Tevatron, its glory days gone, is ready for retirement.

What did the Tevatron teach us? I think most physicists would agree that its single most spectacular achievement was the discovery of the top quark, in 1995. The top quark is the next-to-last piece in the wildly successful Standard Model of fundamental physics. That set of ideas provides a reasonably compact census of the building blocks of matter, and precise, beautiful equations for their observed interactions; but it is less informative when it comes to their masses. The mere existence of the top quark was a firm prediction of the Standard Model since at least 1977, but theory gave no firm prediction for its mass. In fact the large value of that mass--about 185 times the mass of a proton, and more than 40 times the mass of the next-heaviest quark (bottom)--came as a shock to most. Together with the large mass comes an extraordinarily short lifetime, estimated at 5 ×10⁻²⁵ seconds. Its large mass makes the top quark difficult to produce, and its short lifetime makes it challenging to detect, so the discovery was a tremendous technical achievement.

How can a single elementary particle be so heavy? We still don't know the answer to that question, or even whether it's a sensible question to ask. (A better question, I think, is why the other quarks are so light; but that's a story for another time.) In any case, the striking divergence among masses of otherwise very similar particles--i.e., different kinds of quarks--brings us face to face with our ignorance.

Pending deeper understanding, we can already draw important inferences from the large top-quark mass. Masses of quarks, within the Standard Model, reflect the strength of their interaction, or coupling, with the mass-giving Higgs field. The large top-quark mass implies quite a strong coupling. That coupling is in effect a powerful new force, that must be taken into account in constructing more encompassing models of physics. Its ultimate significance is presently unclear, but it makes the idea of supersymmetry--a most interesting and attractive hypothesis on other grounds--work more smoothly; so that is the direction it might be pointing us toward.

Several other pretty discoveries were made at the Tevatron, but I think its other most important result, besides the top quark discovery, was to confirm, in many demanding quantitative tests, the correctness of the core theories of the Standard Model. These triumphs of a beautiful, economical theory put many gratuitous speculations to rest, and demonstrated Nature's good taste. As a practical matter, this result provides a firm platform upon which we can stand, as we reach toward still more beautiful, unified, and encompassing understanding.

What's next?

The last, still missing piece of the Standard Model is the so-called Higgs particle. Just as it predicted the top quark, theory firmly predicts the existence of the Higgs particle, but not the value of its mass. The Tevatron was able to constrain that mass to a fairly narrow range (between about 122 and 160 proton masses), but ran out of time before reaching a conclusive result. The LHC will get to the finish line, very likely, within the next year or so. A Higgs particle in that mass range would be yet another favorable omen for supersymmetry. Unless Nature is a shameless tease, we'll see supersymmetry itself--that is, some of the new particles supersymmetry predicts--discovered at the LHC, though that might take longer. Should those profound discoveries occur, as I hope and expect, they will bring our understanding of Nature's foundational principles to a new, higher level. We will build upon the Tevatron's achievements even as we transcend them.

The enormous tsunami which swept Japan in the March 11th earthquake was an enormous shock to those of us involved in making scientific programming. Every year, NHK's science team had produced programs warning of the fatal dangers of natural disasters: earthquakes, typhoons, landslides. We rang alarm bells hoping to save the lives of viewers. But it was all to no avail, and the tsunami took over 20,000 lives. How can we learn from this tragedy, and pass on those lessons to future generations? What can we bring to the table as makers of science programs? We bent all our energies to the task, with this question ringing in our minds.

Damage in the city of Kesennuma. Image courtesy of Takeshi Shibasaki.

Our first task was to collect the extensive footage of the enormous tsunami, and to thoroughly analyze it. The earthquake had struck in the daytime, so many local residents had captured the tsunami on digital cameras and mobile phones. Minutes after the earthquake, NHK bureaus in the region dispatched camera crews to record the event, and the NHK helicopter was miraculously able to take off from Sendai Airport just before it was consumed by the tsunami. This meant the NHK could secure an unprecedented volume of tsunami footage. Tens of hours of footage were carefully played on a huge screen and we searched for pictured residents who might be able to offer eyewitness accounts.

In particular the clear HD footage captured by a reporter at the NHK Kamaishi bureau shows an astonishing sight. Residents were seen fleeing from homes that were being swallowed up by the tsunami. Immediately after the disaster our team had gone to every evacuation center and residential area with a local map and portable DVD player in hand in order to capture the testimony of those who had, against all odds, survived the onslaught of the tsunami. The extraordinary experiences and bravely captured footage show just how fast the tsunami hit the coast and swallowed up those who had no chance to flee. It is a chilling testament to the destruction and speed of this tsunami.

While gathering residents' testimony, we also examined the captured footage, GPS wave buoy and other records showing tsunami movements. We had decided to attempt the CGI recreation of the tsunami using this data. Having been created offshore, how did its height change, in what order did it hit the coast, and how fast and how far had it come inland? We were certain that answering these questions would be vital to future tsunami planning. We asked the leading scientist in tsunami simulation to handle the calculations, while NHK's CGI team used the resulting data to create top-quality CGI. A particularly useful network came to light: the unattended cameras set up by NHK across Japan, usually referred to as "weather-cams." These cameras recorded everything from the moment after the quake to the coming of the tsunami, with no break. It made it possible to see the tsunami's route and size at any given moment. As many governmental wave gauges set up along the coast were destroyed by the tsunami, this footage was a key component in calculating the tsunami simulation.

Other important factors were the tsunami spawning point and the mechanism by which it was created. A scientist researching seabed faults around Japan gave us data on the position of the fault and the size of the movement which was reflected in the calculations. As they also used geographical data inland, such as elevation and breakwaters, we were able to recreate in detail just how a vast tsunami swept so far inland. It shows exactly how the shapes and depths of coastal bays affected the size and shape of the vast tsunami.

Immediately after the quake, our cameraman and colleague Takashi Hokoi leapt onto a helicopter to shoot the tsunami from above. He explains: "I watched countless tragedies unfold in front of my eyes. One that stayed with me was a man trapped on the bed of a truck. Another was a group of young children stranded on the rooftop of a school building. I was later able to meet them through the program. Despite all our losses, there were some lives saved that day. Being able to share that with viewers has been a great comfort to me."

The analysis of residents' testimony and the footage has shown how evacuating to high ground as fast as possible was vital in saving lives. We must ensure this important lesson is passed on to future generations, and work to minimize any future loss of life. To that end we plan to continue a scientific examination of the earthquake and tsunami. Today Japanese researchers are planning submersible studies and drilling research of the Japan Trench. We hope to constantly follow its movements, and keep viewers informed of the changes occurring beneath our feet. We must give meaning to the many lives taken by the tsunami.

When you're homesick, you start seeing traces of home everywhere you look.

When I went away to college, my heart would skip a beat every time a particular Ford Escort drove by, because it was the exact same model my best friend from home drove--even though I knew she was five hundred miles and four states away.

At one of my first jobs after college, I felt a surge of affection for the building custodian just because he was a dead ringer for my dad--from thirty feet away, if you stood at the right angle, and if he was wearing his glasses.

And here on Earth, we see--or think we see--planets that look like home when we look out into the cosmos. In this case, "looking like home" means having a solid surface and the capacity to support liquid water. It doesn't sound like much to ask, but in fact finding such planets with today's technology is like reading the very last row of the eye chart at the optometrist's office--possible, but just barely. Of the 600 or so known exoplanets, only a handful could maybe, possibly, be capable of supporting life.

An artist's impression of the potentially habitable planet orbiting the Sun-like star HD 85512. Credit: ESO/M. Kornmesser.

Now, astronomers have announced the discovery of a new planet that just might fit the bill. It's 3.6 times the mass of Earth and orbits at the inner boundary of the habitable zone--meaning that it is hot, but (with enough cloud cover) perhaps not so hot that water would vaporize. The planet, called HD 85512 b (because it is in orbit around the star HD 85512), was discovered using the HARPS spectrograph at the La Silla Observatory in Chile, which enables astronomers to track the gravitational wobbles that planets induce in their parent stars. It was announced along with a batch of 49 other exoplanets. (For more on how this technique works, see NOVA scienceNOW's Hunt for Alien Earths.)

Though scientists who discovered the planet are calling it "the best candidate for exploring habitability to date," it isn't the first potentially habitable planet we've found. Back in January I wrote about a planet called Gliese 581 g, which could be habitable--if it actually exists, which is controversial. And Gliese 581 g followed a string of other false alarms.

That's not to say that we shouldn't be excited about this new discovery--just that we should be cautious before, you know, running across the quad with our arms outstretched to give it a big hug, only to realize that it isn't quite who--or what--we thought it was.