For once, "shadow of the atom" is not just a poetic metaphor for the nuclear age. The black dot at the center of this image is, literally, the shadow cast by a single atom of ytterbium, magnified 6500 times.

Via Discover magazine

I got to join in on a great conversation this morning on Minnesota Public Radio's "The Daily Circuit", all about the Higgs Boson and what it means for the future of physics.

This is a fascinating issue. Finding the Higgs Boson (if that is, indeed, what scientists have done) means that all the particles predicted by the Standard Model of physics have now been found. But that's not necessarily good news for physicists. For one thing, it would have been a lot more interesting to break the Standard Model than to uphold it. For another, we're now left with a model for the Universe that mostly works but still has some awkward holes — holes that it might be hard to get the funding to fill.

Daily Circuit host Kerry Miller, Harvard physics chair Melissa Franklin, and I spent 45 minutes talking about what is simultaneously a beautiful dream and a waking nightmare for the physics world. And I got to make a "Half Baked" reference in a conversation about particle physics, so you know it's a good time, too.

Listen to the whole conversation at Minnesota Public Radio's website.

Absolute zero is supposed to be the coldest cold — 0 Kelvin, the point where atoms stop moving.

But researchers at the University of Munich say it's possible to get colder than that, an idea they've demonstrated experimentally. But what does it mean to be colder than cold? Here's the scientists' totally unhelpful explanation:

another way to look at these negative temperatures is to consider them hotter than infinity, researchers added.

Cool. Thanks, guys. Luckily, journalist Charles Q. Choi makes this strange idea make a whole lot more sense. Read his explanation at LiveScience.

Image: Frozen Peas Corn Carrots IMG_1000, a Creative Commons Attribution (2.0) image from stevendepolo's photostream

After you drink some Scotch, there's usually a thin film of the liquor left clinging to the bottom and sides of the glass. If you leave it out overnight, it'll dry and be a pain to wash off in the morning. But the same dried booze leavings can also be the beginnings of some really lovely art.

Ernie Button takes photos of the waving, swirling patterns left behind on Scotch glasses. This one — part of a series called Vanishing Spirits — is a picture of glass that once held a nice measure of Balvenie.

The idea for this project occurred while putting a used Scotch glass into the dishwasher. I noted a film on the bottom of a glass and when I inspected closer, I noted these fine, lacey lines filling the bottom. What I found through some experimentation is that these patterns and images that can be seen are created with the small amount of Single-Malt Scotch left in a glass after most of it has been consumed. It only takes a very thin layer of Scotch to create; the alcohol dries and leaves the sediment in various patterns. It’s a little like snowflakes in that every time the Scotch dries, the glass yields different patterns and results. I have used different colored lights to add 'life' to the bottom of the glass, creating the illusion of landscape, terrestrial or extraterrestrial.

Interestingly, there was a recent article that was published in the Journal of Nature (I think) by Dr. Peter Yunker on the Suppression of the Coffee-Ring Effect by Shape-Dependent Capillary Interactions i.e. how are coffee rings made. I contacted him to see if he could see any obvious connection between the two liquids and the rings / patterns they create. He got back to me and unfortunately could not explain what was happening with the Scotch.

That paper Button mentioned was published in 2011. It explores the physics of particles suspended in liquid — not just coffee, but lots of things. Turns out, if you put a drop of liquid on a solid surface, it will tend to dry in a circular shape. As it dries, anything suspended in the liquid will migrate to the outside of the circle. If you put a drop of coffee on a table and leave it to dry, what you'll get is a round spot ringed by a narrow band of dark coffee gunk.

Why does the gunk form a ring, instead of evenly covering the whole circle? Yunker's research showed that it has to do with the shape of the particles that make up the gunk.

In this video, you can see those microscopic particles and how they behave.

The video is divided into five parts.

In the first, you can watch a "coffee ring" form, as spherical particles move toward the outside edge of a drop of liquid and stick there.

In the second part, ellipse-shaped particles form little blobs throughout a drop of liquid. Some of them migrate to the edge, but not all. Not even most. If this were a drop of coffee on a table, you'd get a solidly brown round spot — no coffee ring.

The third part of the video gives you a closer look at the edge of a drop of liquid filled with ellipse-shaped particles. You can see the particles clump together and move away from the edge.

The fourth part is the close-up of spherical particles as they rapidly pile up on the edge of the drop, forming a ring.

In the final part, Yunker's team shows that it's possible to get the ellipsoid particles to form a ring at the edge of the drop. The key: Using a surfactant to decrease the surface tension between the particles and the liquid. Spherical particles move right to the outside edge because the attraction between particles is weak (relative to the elliptical particles). As liquid moves to the outside edge, it just pushes the spheres along with it. Normally, the elliptical particles are attracted to one another strongly enough that they don't get swept along with the current, so to speak. But the surfactant reduces that attraction and, like the spheres, they go slip sliding away.

Button is right that this particular paper doesn't offer much of an explanation for the shapes he sees in his Scotch glasses. They aren't all as circular as the the picture at the top of this post. Some look more like undulating hills and valleys, rather than coffee rings.

This paper of Yunker's certainly suggests that there's some interesting fluid mechanics at work here, though. I'm going to look into it and will report back on what I find.

Read Peter Yunker's full paper on the "coffee ring" effect

Check out Ernie Button's full series of Scotch glass photos, called Vanishing Spirits.

The Higgs Boson is a popular, but confusing, bit of physics. You know that reality is like a Lego model, it's made up of smaller parts. We are pieced together out of atoms. Atoms are made from protons, neutrons, and electrons. Protons and neutrons are made of quarks. (Quarks and electrons, as far as we know, are elementary particles, with nothing smaller inside.) When you're talking about the Higgs Boson, you're talking about the mass of these particles. Here's an imperfect analogy: A top quark, the most massive particle we know of, is like an elephant. An electron, on the other hand, is more like a mouse. And nobody knows for certain why those differences exist.

There is a theory, though. Back in the 1960s, a guy named Peter Higgs came up with the idea that all these particles exist in a field, and their mass is a reflection of how much they interact with that field. Heavy particles have a lot of interaction. Lighter particles are relatively standoffish. If this field exists, the Higgs Boson is the tiny thing it's made of. Fermilab physicist Don Lincoln has a really great video explaining this, where he compares the Higgs field to water, and Higgs Bosons to the molecules that make up water. Everything that exists swims in an ocean of Higgses.

Tuesday morning, we learned a little more about the hunt for the Higgs Boson. But the point of the presentation wasn't really to say, "Yes, we found it" or "No, we haven't." In fact, if all you're paying attention to is that simple yes-or-no answer, you're going to miss a lot of interesting information—information that can help you better understand how science works and why the Higgs Boson is so important.

In the presentations, CERN researchers told us two big things:

First: Looking for the Higgs Boson used to be a lot harder because nobody knew its mass. Think of it like trying to find a single Lego piece, in a giant box of Legos, when you don't know what the piece you're looking for looks like. That's changed. Researchers now believe that the Higgs Boson, if it exists, probably has a mass somewhere between 115 and 131 gigaelectronvolts.

Second: Two different detectors on the Large Hadron Collider have found signals, consistent with what you'd expect to see from a Higgs Boson particle, within that mass range—at 126 and 124 gigaelectronvolts.

So why was the un-announcement so non-committal? Simple: Physicists don't like to be wrong.

You can't actually see a Higgs Boson. This isn't like sitting in the jungle and waiting for a rare species of panther to come along so you can photograph it. Instead, scientists are looking for the particles they've predicted that a Higgs Boson would leave behind as it decays. Say you have a hypothesis that a new species of panther exists, but it's invisible as long as it's alive. The only way to figure out whether or not it's actually there is to look for panther poop, or maybe some bits of bone and fur. Trouble is, there are lots of things in the jungle that could leave behind poop, bone, and fur. How do you know what you've found is actually evidence for the existence of the hypothetical panther?

That's essentially the problem physicists are faced with. Those intriguing signals could be decaying Higgs Bosons. They could also be normal things you'd expect to find in the aftermath of proton collisions. The only way to tell the difference is to look for an excess of those signals in the mass range where you'd expect the Higgs Boson to be. But, even if you see that, it could still be a coincidence. This is especially true of the hunt for the Higgs Boson, because it started out looking at a huge range of masses, says Greg Landsberg, professor of physics at Brown University.

"When you look at many, many places what is unlikely in a given place becomes more likely in one of many, many places," he says. "Ask an astronomer what is the probability of a particular star having a planet orbiting it. He’d say the probability is extremely small. However if you asked that differently, 'What the probability of any star having a planet,' the probability would be much closer to 1."

To make sure that the promising signals they're seeing aren't just flukes, the physicists at CERN will need to run their experiments, in that much-more-specific mass range, many more times. Right now, says Don Lincoln, there's a 1 in a 1000 chance that what they're seeing is a coincidence. But, in the past, particle physicists have found that 1-in-1000 chances aren't a very good bet. "That's equivalent to tossing a coin 10 times and having it always come up heads. To be comfortable saying we've found something we'd have to have the equivalent of tossing a coin 20 times and having that all come up heads—a 1 in a million chance," he says. The more coin tosses, the more you rule out coincidence. The physicists I spoke with said we're likely to have enough data to do that by next summer.

If the Higgs Boson is actually there, around 124 or 126 gigaelectronvolts, that means it's a lighter particle than many people had guessed. In fact, originally, people were looking for the Higgs Boson at masses as high as 600 gigaelectronvolts. This is interesting for a couple of reasons.

First, there's the "d'oh" factor. A big selling point on the Large Hadron Collider was the fact that it had the power necessary to study very high energies. That's what makes it different from particle accelerators that have come before, like the recently closed Tevatron. But 124-126 gigaelectronvolts is well within the range of what the Tevatron could study.

In fact, the Tevatron looked at that range. Unfortunately, it doesn't yet have enough data to make any definitive statements. That could change. Don Lincoln says that when the Tevatron researchers are finished analyzing their data, they might be able to back up the CERN findings. That's because the Tevatron noticed a small signal around 125 gigaelectronvolts. However, Lincoln also says it's a smaller signal than you'd expect if the CERN results really were correct. This could mean the Tevatron saw the Higgs Boson signal first, but couldn't verify its results before CERN got better data. It could also mean the signal from CERN is just a coincidence. Right now, it's too early to tell.*

Second, if the Higgs Boson exists and if it is light in mass, that opens up a way more awesome world for future physics research than would exist with a heavy Higgs. Physics operates on the Standard Model—a mathematical theory aimed at explaining the forces at work in the Universe and how particles interact with one another. The Standard Model requires the existence of a Higgs Boson, but a light Higgs Boson would mean that we'd have to make some changes to the way the Model works, possibly incorporating ideas like supersymmetry, says Frank Close, particle physicist at the University of Oxford.

A light Higgs also means the Large Hadron Collider has enough power to find lots of other previously unseen particles. "Strategically, if this thing turns out to be real, the fact that it is at low mass end is good news," Close says. "If it was at the high end you’d have that fear that the interesting physics was out of the LHC's reach. This suggests lots of interesting things are still available for us to find using the LHC."

Everybody is all excited about the prospect of finding the Higgs Boson particle. This is kind of the wrong way of thinking about it.

I told you before that the existence of the Higgs Boson is part of the Standard Model—finding it is a key part of verifying that the Universe works the way we think it does.

"If we don’t find it, it’s extremely weird," says Jeremiah Mans, associate professor of physics at the University of Minnesota. "We know from other measurements that properties of regular particles aren’t quite right unless there’s a Higgs around to pull them just a bit. If you take it out, then the theory, that otherwise works well, breaks down and doesn’t make the right predictions. That points to something being there."

Verifying that your big, important theory is correct is a big deal. But that outcome is also just a little boring. It would be a lot more exciting if everything we thought we knew turned out to be wrong.

And there is more than one way that the Higgs Boson could throw off the Standard Model. It could, of course, flagrantly refuse to exist. But it could also be quite a bit weirder. We could find the Higgs Boson, and it could turn out to be different than what we've been predicting. See, all this time, physicists have only really been looking for what's known as "the minimal Higgs." You can think of it as the simple version. In the minimal Higgs theory, there's only one type of Higgs Boson and it has no electrical charge, among other characteristics.

What happens if the Higgs we find turns out to have a charge? What happens if the Higgs turns out to actually be five different types of Higgses, as some versions of supersymmetry predict? If that's the case, the Standard Model could end up having to dramatically change, just like if the Higgs Boson didn't exist at all.

If, in six months, the physicists at CERN are able to say definitively that they've found the Higgs Boson, particle physicists will be gratified. They will understand the Universe in a way they didn't before and they will be able to work on some new questions. But if CERN is wrong, particle physicists won't hang their heads in shame. Instead, it could well be the most exciting day of their lives.

"If we don't find it, that would be a huge discovery," says Fermilab's Don Lincoln. "The Standard Model does work very well. We’re talking on a phone, after all, and that’s done through electricity, and how that works is part of the Standard Model. A new theory would make have to make some similar predictions, but it would rewrite textbooks."

• • • •

For more information on the Higgs Boson and particle physics, I recommend checking out a couple of books:

Frank Close has a book called The Infinity Puzzle, about the history of Peter Higgs, the Higgs field, and the hunt for the Higgs Boson.

Don Lincoln, who, over the last couple days, has become one of my favorite explainers of physics, has a book called The Quantum Frontier. It's about the Large Hadron Collider—how it works, what we can do with it, and what it might teach us about the Universe.

*This part of the story has been changed from its original version. The previous version was incorrect and read, "First, there's the "d'oh" factor. A big selling point on the Large Hadron Collider was the fact that it had the power necessary to study very high energies. That's what makes it different from particle accelerators that have come before, like the recently closed Tevatron. But 124-126 gigaelectronvolts is well within the range of what the Tevatron could study. In fact, the Tevatron looked at that range. It didn't see anything. This could mean that the signal CERN saw is just a coincidence. It could also mean that the Tevatron was in the right place, but missed seeing something really important." Thanks to Don Lincoln for helping me get this fixed, and to Joe Haley and Peter for pointing out the problem.

Image: A rendering of one of the events, captured by the Large Hadron Collider's CMS detector, that could be evidence of a decaying Higgs Boson particle. Or, it could just be stuff that happens when protons collide. Either way, it's kind of pretty.

But on Friday, September 30, the Tevatron smashed its last protons.

Ultimately, the Tevatron was simply the victim of the progress of technology. When it opened in 1983, it replaced older, lower-energy accelerators. And, in turn, the Tevatron has been replaced by the Large Hadron Collider, an accelerator capable of pushing particles to even higher energies. Once that happened, it was only a matter of time before the Tevatron felt the budgetary axe.

The end of the Tevatron doesn't mean the end of research at the Fermi National Accelerator Laboratory, and it doesn't mean the end of particle research in the United States. But it is the end of an era.

William S. Higgins is a radiation safety physicist at Fermilab, and a contributor to Tor.com. He helped build the Tevatron and he was on hand last Friday, recording his thoughts and some photos to share with us. Here, you'll find a sentimental scientific tour of the last day of a great piece of research equipment. Unless otherwise noted, all the captions were written by Higgins.

View the gallery here.