Magnetic monopoles are hypothetical objects that act like the isolated north or south pole of a magnet. Ordinarily when you break a magnet in half, you end up with two smaller magnets, but some theories predict independent existence for monopoles — though they obviously must be rare in nature, because we haven’t seen one yet.

When detectors fail, sometimes ingenuity can provide another way. As Richard Feynman realized, quantum systems can be used to simulate each other if the structure of their quantum states is the same. A group of researchers used a Bose-Einstein condensate — a collection of very cold atoms that behave like a single quantum system — to emulate the behavior of a magnetic monopole.

Thus, in lieu of hunting for particles that are monopolar, M. W. Ray, E. Ruokokoski, S. Kandel, M. Möttönen, and D. S. Hall emulated the behavior of a north magnetic charge using ultracold atoms. The result was behavior described as a Dirac magnetic monopole, something never before seen. This experiment relied on the quantum character of monopoles and might provide hope that isolated magnetic charges could exist in nature.

Quantum simulations work like simulations run on an analog computer: researchers construct electric circuits that obey the same basic mathematical equations as a more complicated physical phenomenon, which allows them to emulate the complicated system without trying to solve the (possibly unsolvable) equations that describe it. A quantum simulation lets physicists substitute a controllable physical system for one that might be too challenging to ever construct in the lab. [Read more….]

Emulating magnetic monopoles in Bose-Einstein condensates

(Since my weekly round-up experiment seems to have failed horribly, I’m going to try to go back to linking and summarizing individual articles I’ve written around the web on this blog. We’ll see if I keep it up!)

The great physicist Chien-Shiung Wu in 1958. [Credit: Smithsonian Institution]

The great physicist Chien-Shiung Wu in 1958. [Credit: Smithsonian Institution]

Chien-Shiung Wu is one of those physicists that everyone should know about, but not enough do. A veteran of the Manhattan Project, she went on to become the world’s expert on beta decay: the process by which an atomic nucleus changes into another element, emitting an electron (or positron) in the process. In the 1950s, she realized beta decay would be a way to test a fascinating new theory of the weak force, which predicted that there should be a fundamental asymmetry between processes occurring in different directions. Her experiment was the first observation of parity violation, which opened up a wealth of new results, leading ultimately to the discovery of the Higgs boson.

For Double X Science, I commemorated this discovery, explaining why it’s important and how weird it is. It would seem that the laws of physics shouldn’t depend on which direction a process occurs, yet that’s the way the Universe works!

Wu realized she could test this idea in the lab after discussions with her colleagues Tsung-Dao Lee and Chen-Ning Yang, who laid the theoretical groundwork for understanding the weak force. She recruited Henry Boorse, Mark Zemansky, and Ernest Ambler, who were skilled at experiments at very low temperatures. It’s a great illustration of the collaborative nature of science: Lee and Yang provided theoretical knowledge, but needed Wu to design and perform the experiment; Wu in her turn brought in experts in low-temperature physics to provide expertise in an area unfamiliar to her. (On a more sour note, Lee and Yang won the Nobel Prize for the discovery of parity violation, but Wu and her fellow lab workers were passed over.) [Read more…]

Madame Wu and the backward Universe

The week in review (August 25-31)

The more money we raise to help us go to GeekGirlCon, the more places I will go wearing my Cthulhu hat.

The more money we raise to help us go to GeekGirlCon, the more places I will go wearing my Cthulhu hat.

Welcome to the weekly round-up of stories I wrote this week, wherever they hide.

  • A tour of physics, Angry Birds style (Double X Science): The odds are good that you’ve played Angry Birds, even if (like me) you don’t own a device that will run the game. My colleague Rhett Allain wrote a book for kids, using Angry Birds as an invitation to learn quite a bit about physics, from particle trajectories to cosmology. I reviewed the book for Double X Science.
  • My book-in-progress, Back Roads, Dark Skies, hit a major snag, and its future is unclear. Based on the responses I’ve received, I will not be able to find a publisher without changing the book in an essential way, so I’m feeling a little stuck. So, to show myself (if nobody else) that I’ve accomplished something in the 18 months I’ve been working on the book, I published two excerpts from Chapter 2: Of Bosons and Bison at Galileo’s Pendulum.
  • Microcosmos: My tour of the DZero detector at Fermilab, with a digression on my favorite New Yorker cartoonist.
  • Naming the animals in the particle zoo: The hows and whys of particle detection, in the context of the Tevatron at Fermilab. This excerpt also includes what may be my best joke yet, if I can say that about my own writing.
  • The Milky Way’s black hole, like Cookie Monster, loses more than it eats (Ars Technica): Astronomers have known for many years that our galaxy harbors a supermassive black hole. Yet, it’s a very quiet black hole: the material surrounding it emits very little light compared to other galactic nuclei. A new X-ray observation may hold the key: only about 1 percent of all the material swirling around the black hole is captured, making it a Cookie Monster-level messy eater. (And yes, I’m proud of combining Cookie Monster and black holes in one article.)
  • This doesn’t count as my writing, but I’m joining a number of friends and colleagues at GeekGirlCon in late October for some do-it-yourself science! Well, I’m going if I can afford it; you can help with that by donating to our cause. We’ve already raised more than $400, so I’ve begun photographing myself around the city wearing my Cthulhu hat. If you give us more money, we’ll do even more embarrassing things. You can’t lose.
  • Atmospheric science in a bolt of lightning (Galileo’s Pendulum): Lightning is powerful enough to split molecules into their constituent atoms, and strip electrons away. For a brief moment, lightning can heat air to 30,000° C, more than 5 times the surface temperature of the Sun. An astrophotographer took an amazing snapshot of a lightning flash, with a twist: he used a diffraction grating to split the light into its component colors. The result is that we can identify some of the chemical components of air produced when the molecules and atoms were blasted by the powerful electric discharge.

This week also marked both my parents’ birthdays. Happy birthday, Mom (Monday) and Dad (Friday)!


OK, I might be feeling a little cranky about this, but my article for Ars Technica is a little more measured. I’ll have a longer analysis for Galileo’s Pendulum tomorrow, for those who want it. The short version: the Alpha Magnetic Spectrometer (AMS-02) is a particle detector installed on the International Space Station. For several months, the lead investigator has been hinting that AMS-02 detected the signature of dark matter annihilation: collisions between dark matter particles producing an excess of positrons. However, the actual research paper was rather short on dark matter, however interesting the AMS-02 results really were.

The Alpha Magnetic Spectrometer (AMS-02) is a particle detector based on the International Space Station, designed for looking at a variety of particles from many sources, among them dark matter collisions. Recently, the AMS-02 research team announced the results of its first 18 months of data collection. These results are frustratingly ambiguous: while AMS-02 found an excess of certain type of particle expected from some models of dark matter annihilation, this excess didn’t bear the hallmarks predicted for a dark matter signature. So, something interesting is going on in the AMS-02 data, but the chances of dark matter being the cause seem a bit low. [Read more…]

Update: I published my rant over at Galileo’s Pendulum, explaining exactly why I’m grumpish about the way these results were announced and characterized in much of the media.

Much ado about nothing in today’s dark matter non-announcement

question box from Super Mario BrothersWriter/editor David Manly posed a series of questions to scientists and writers, soliciting short responses on topics of broad interest. Those interviewed were shark researcher David Schiffman, paleontology writer/sauropod snogger Brian Switek, and me. If you want to know who would win an arm-wrestling contest between a human and a Tyrannosaurus, or how we know black holes exist if we can’t see them, this post is for you.

A Manly conversation

Forgive me if I get excited for a moment, but…today marks my first contribution to BBC Future! The feature I contributed is part of the “Will we ever?” series, in which science writers ask some big questions about what research may or may not be able to answer in the future. My article pondered whether we’ll ever be able to identify dark matter: the mysterious substance that comprises more than 80% of the mass of the Universe. (The link for my UK readers is here.)

Right now, a far easier question to answer is what dark matter isn’t. First of all, the name is misleading: dark matter isn’t “dark” in any usual sense of the word. “Invisible matter” is a better term: light shining on dark matter from any source passes right through without being absorbed or scattered, regardless of the type of light. This means dark matter can’t be made of atoms or of their constituent parts; that is, electrons, protons and neutrons.

In fact, dark matter doesn’t correspond to anything in the Standard Model, the best explanation we have for how the universe works. [Read more…]

Will we ever know the identity of dark matter?

Pascal the cat knows about particle physics.

Pascal the cat knows about particle physics.

It’s fundamental and natural to ask this question about an object: “how big is it?” For many things—most everyday objects, people, planets, stars—size is easy to measure. However, other things are more challenging, including the size of a proton: one of the three particles that make up every ordinary bit of matter. The major challenge is its tiny size, which precludes using light of any kind to measure it. To make matters worse, the size of a proton may depend strongly on what method you use to measure it, as I explained for Double X Science.

The simplest way to measure the size of a proton involves shooting electrons at it, and measuring the paths the electrons take as they feel the influence of the various forces. Because of those forces, in fact, the proton can’t be said to have a single size! Instead, physicists use three different size measurements, which are all pretty close to each other, but not exactly the same. The one most important to us for this post is the charge radius. Electron bombardment measurements found that to be about 0.88 femtometers.

However, electron bombardment only gets us so far; if we want better accuracy, we need another method. [Read more…]

How big is a proton?

Where do cosmic rays originate? Cosmic rays are mostly high-energy protons from deep space that hit Earth’s upper atmosphere, creating showers of other particles that can be detected at the surface. Some of these protons are so incredibly high energy—meaning they’re moving just a whisker slower than the speed of light—that only exceptional astronomical events could accelerate them. The prime suspect: supernova explosions. Up until now, though, nobody had confirmed this suspicion. However, a new observation using gamma ray emissions from supernova remnants found the telltale signature of particle collisions, which could only be present if protons were getting that extra boost of energy.

On October 15, 1991, a high-energy proton from deep space struck Earth’s upper atmosphere. Known as the “Oh My God Particle”, this proton was by far the highest energy cosmic ray ever seen. This one proton’s energy was equivalent to a regulation soccer ball traveling at 15 meters per second (34 miles per hour). In the two decades following, observers spotted several similarly energetic cosmic rays, which left a big question: what was accelerating these protons to higher speeds than anything we can achieve in on Earth? [Read more….]

High-energy cosmic rays are sped on their way by exploding stars

Macroscopic processes are usually not completely reversible: you can’t unmix or unbake cake, and perfume released from a bottle won’t spontaneously recollect. However, these phenomena involve huge numbers of particles. On the level of individual particles in elementary physics, the direction of time doesn’t matter to the forces involved. The exception to this is the weak force, one of the four fundamental forces of nature. However, no experiment thus far had been able to demonstrate time asymmetry unambiguously until now.

New results from the BaBar detector at the Stanford Linear Accelerator Center (SLAC) have uncovered this asymmetry in time. Researchers measured transformations of entangled pairs of particles, including the rates at which these transformations occurred. Through analyzing over 10 years of data, they found clear time-reversal asymmetry with an error of only one part in 1043, a clear discovery by any standard. These results are a strong confirmation of predictions of the Standard Model, filling in one of the final missing details of that theory. [Read more…]

Processes in particle physics demonstrate arrow of time

The Standard Model (SM) of particles and interactions provides a successful description of most of the matter we know of. However, physicists have known for many years that it is not complete: the SM predicted massless neutrinos, and has no place for dark matter. A new result from the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) could possibly provide another problem for the SM—and would place severe constraints on a popular alternative theory, supersymmetry (SUSY)….

Read more at Ars Technica.

Too many heavy particles could mean trouble for the Standard Model