O, what entangled photons we weave!

(OK, it doesn’t scan. So sue me.) Quantum entanglement is a challenging topic, and one which has tripped up a lot of people (including many physicists!) over the decades. In brief, entanglement involves two (or more) particles constituting a single system: measurement on one particle instantly determines the result of similar measurements on the second, no matter how far they are separated in space. While no information is transferred in this process, it’s still at odds with our everyday experience with how the world should work. I updated my earlier explanation of entanglement, which hopefully can help clear up some of the confusion.

Recent work either assumes entanglement is real and probes some of the more interesting implications, or tests some mathematical relations known as Bell’s inequalities. The latter are aimed at quantifying the difference between the predictions of quantum physics and certain alternative models. In that spirit, a group of researchers proposed using light from quasars to randomize the measurement apparatus in entanglement experiments, to eliminate the tiny possibility of a weird loophole in quantum theory.

If a detector has some correlation with the hidden variables of the particles being measured, then the two detectors don’t act independently. That’s true even if only a very tiny amount of information is exchanged less than a millisecond before measurements take place. The interaction would create the illusion that the particles are entangled in a quantum sense, when in fact they are influencing the detectors, which in turn dictate what measurements are being taken. This is known as the “detector settings independence” loophole—or somewhat facetiously as the “free will” loophole, since it implies the human experimenter has little or no choice over the detector settings. [Read more...]

Final note: this is probably the first paper I’ve covered that involves both my undergraduate research focus (quantum measurement) and my PhD work (cosmology), albeit in a much different way than both.

Stephen Hawking, black holes, and scientific celebrity

The active galaxy Centaurus A, rendered in several different types of light. Note in radio waves (the central image at right), the galaxy itself seems to disappear, replaced by crossing jets of radio-emitting jets. Those are produced by the supermassive black hole at the galaxy’s core.

The active galaxy Centaurus A, rendered in several different types of light. Note in radio waves (the central image at right), the galaxy itself seems to disappear, replaced by crossing jets of radio-emitting jets. Those are produced by the supermassive black hole at the galaxy’s core.

For the upcoming ScienceOnline 2014 meeting, I’m leading a session titled “Reporting Incremental Science in a World that wants Big Results“. It’s an important topic. We who communicate science to the general public have to evaluate stories to see if they’re worth covering, then translate them in such a way that conveys their significance without hyping them (ideally at least). That’s challenging to do on deadline, and we’re not always or maybe even usually experts on the topics we report. I know a fair amount about cosmology and gravitational physics, but very little about galactic astronomy or planetary science — yet I must write about them, because it’s my job.

So Stephen Hawking’s recent talk on black holes is an interesting case study. I won’t rehash the whole story here, but I wrote not one but two articles on the subject yesterday. Article 1 was in Slate:

Hawking’s own thinking about black holes has changed over time. That’s no criticism: Evidence in science often requires us to reassess our thinking. In this case, Hawking originally argued that black holes violated quantum mechanics by destroying information, then backed off from that assertion based on ideas derived from string theory (namely, the holographic principle). Not everyone agrees with his change of heart, though: The more recent model he used doesn’t correspond directly to our reality, and it may not have an analog for the universe we inhabit. The new talk suggests he has now moved on from both earlier ideas. That’s partly what raises doubts in my mind about the “no event horizons” proposal in the online summary. Is this based on our cosmos or yet another imaginary one of the sort physicists are fond of inventing to guide their thinking? In my reading, it’s hard to tell, and in the absence of a full explanation we are free to project our own feelings about both Hawking and his science onto the few details available. [Read more...]

Article 2 was a follow-up on my own blog:

But at the same time, we have to admit that nobody—not Nature News, not Slate.com—would have covered a paper this preliminary had Hawking’s name not been attached. Other people are working on the same problem (and drawing different conclusions!), but they can’t command space on major science news sites. So, by covering Hawking’s talk, we are back on that treacherous path: we’re showing how science works in a way, but we risk saying that a finding is important because somebody famous is behind it. [Read more...]

Two weeks in review (October 27-November 9)

The Universal Marathon: 13.8 billion years! You run this race whether you like it or not, so might as well enjoy it.

Evidently I forgot to post one of these roundups last week, so here’s two weeks’ worth of writing all at once! Also, I have a new sticker design you can order, for those of you (like me) who don’t willingly run for exercise, but want to feel you’ve accomplished something anyway. At least in a cosmological sense, we all run this marathon we call existence.

  1. Drown your town, drown the world (Galileo’s Pendulum): My colleague Andrew David Thaler asked how much water would be required to flood the whole world to the height of Mount Everest, so I took up the challenge.
  2. Hellish exoplanet has Earth-like density and composition (Ars Technica): It’s difficult to measure both the mass and the size of exoplanets (planets orbiting other stars), because discovery methods are complementary to each other. A new pair of papers described the first exoplanet with a density similar to Earth’s, meaning it probably has a similar composition. However, the planet is hot enough to melt most rocks. Don’t plan your vacation there.
  3. New LUX experiment: No dark matter in this corner (Ars Technica): Researchers operating the Large Underground Xenon (LUX) dark matter detector announced the results of the first three months of operation. They found: nothing. Well, specifically they found nothing where some other detectors might have found a possible dark matter signature.
  4. Ghosts in the detector: why null results are part of science too (Galileo’s Pendulum): To follow up that previous article, here’s why the LUX detector wasn’t a failure, and definitely why we shouldn’t think dark matter doesn’t exist.
  5. A comment on comments, with cats (Galileo’s Pendulum): Comments on websites have always been a point of some debate. Do we have them? How do we moderate them? What constitutes reasonable commenting, and who makes that decision? Because of an ongoing “debate” between a few vocal people about pterosaur flight (of all things) on an old post about gravity, which I simply don’t have time or willingness to moderate, I decided to close down comment threads on older posts. That riled some people up.
  6. So close, yet so far (Galileo’s Pendulum): The closest star to the Solar System is invisible to the unaided eye, but in many ways it’s a more typical star than the Sun — much less the other stars we see in the night sky.
  7. The census of alien worlds (Galileo’s Pendulum): The Kepler observatory’s primary mission is over, but its legacy lives on. Based on Kepler data, scientists have estimated the possible number of Earth-class planets orbiting at habitable distances from Sun-like stars. Here’s my take on that study.
  8. I don’t believe in science (Galileo’s Pendulum): Oftentimes, big ideas in science — the Big Bang model, evolution, climate change — are regarded as optional, matters of belief. Here are some of my musings about science, belief, and what it means to trust science in the face of bad behavior, fraud, and controversy.
  9. Weekly Space Hangout (Universe Today): Yesterday, I participated in the weekly round-up of space and astronomy news, in conversation with other science writers. Much fun was had!

The week in review (October 20-26)

Evidently, Nicole "the Noisy Astronomer" Gugliucci did not like it when I quoted Star Wars at her. All I said was "Aren't you a little short for a Stormtrooper?" [Credit: Melanie Mallon]

Evidently, Nicole “the Noisy Astronomer” Gugliucci did not like it when I quoted Star Wars at her. All I said was “Aren’t you a little short for a Stormtrooper?” [Credit: Melanie Mallon]

I had a wonderful time at GeekGirlCon; thanks again to Dr. Rubidium, AKA Nick Fury, for putting together the DIY Science Zone, and to everyone who made it a great event. I have a more formal wrap-up post in the works, but in the meantime, have some science writing.

  • The river of spacetime (Galileo’s Pendulum): As a follow-up to my earlier post, I extended the metaphor of dynamic spacetime. If spacetime is the river, gravity is the current, carrying matter and light along with it.
  • New type of quantum excitation behaves like a solitary particle (Ars Technica): In materials, the relevant entities aren’t particles, but quasiparticlesThese are quantum excitations that have mass, charge, spin, and all that jazz, but those properties depend on the specifics of the material…and of external influences. So, physicists would like to create quasiparticles that are less finicky, and behave more like free, solitary particles. That type of excitation is a leviton, and experimenters created them for the first time, as described in this new paper.
  • Taking Measure: A ‘New’ Most Distant Galaxy (Universe Today): It seems that every week, we see a new “most distant galaxy” announcement. However, this new find is special for two reasons: it’s a rare case where astronomers have measured the distance accurately using the galaxy’s spectrum, and the specific galaxy is producing new stars at a much higher rate than expected. Also, this is my first contribution to Universe Today!
  • For the love of Gauss, please stop (Galileo’s Pendulum): A somewhat ranting post in which I get grumpfy about the over-use and misuse of certain examples from the history of science in popular science writing.
  • What do we call a theory that is no longer viable? (Galileo’s Pendulum): As a follow-up to that previous post, I ponder better ways to think about the history of science, and propose (somewhat seriously) a term to describe theories that were once viable, but are now ruled out by evidence.

The week in review (October 13 – 19)

I’m at GeekGirlCon this weekend, so I’m busy with non-writing activities as part of the DIY Science Zone. Thanks to our Fearless Leader Dr. “Nick Fury” Rubidium for putting our part of the event together!

  • Where Nature Hides the Darkest Mystery of All (Nautilus): Even though there’s no solid barrier, the event horizon of a black hole provides a boundary through which we can’t see or probe. That leads to a troubling idea: will we ever know what’s really inside that event horizon? Is there any way to learn about the interior by indirect measurements?
  • Black hole hair and the dark energy problem (Galileo’s Pendulum): Building off that article, what happens if our standard theory of gravity is modified? That’s not an entirely crazy idea: several modifications to general relativity have been proposed, inspired by inflation (the rapid expansion during the cosmos’ earliest moments) or dark energy. A recent paper examined that idea, and here’s my take.
  • Strongly magnetic pulsar could explain anomalous supernovas (Ars Technica): Some supernovas are particularly bright, especially some from the early Universe. These, known as “pair-instability” supernovas, are the explosion of very massive stars made of nearly pure hydrogen and helium. However, some of these super-luminous supernovas don’t quite fit that profile, including being too close. A new set of observations may show they are actually driven by a magnetar, a highly magnetized pulsar.
  • Gravitational waves show deficit in black hole collisions (Ars Technica): Mergers of supermassive black holes should happen frequently enough to produce a bath of gravitational radiation permeating the cosmos. While that gravitational wave background (GWB) possesses wavelengths too large for ground-based detectors like LIGO, astronomers realized it might be visible in the fluctuations of light from pulsars. However, they didn’t see what they expected, leading to the big question: why not?

Two weeks in review (September 29 – October 12, 2013)

The center of the Milky Way lies at the upper left of this image from the 2MASS survey of galaxies. [Credit: 2MASS/G. Kopan, R. Hurt]

My black holes class and other responsibilities ate my brain the last two weeks, so I forgot to post a “week in review” last week. So, here’s the highlights from the last two weeks. If it’s more heavily weighted toward black holes even than usual, that’s hardly surprising.

  • Of fire and ice and Harlow Shapley (Galileo’s Pendulum): In 1918, a poet named Robert Frost met an astronomer named Harlow Shapley. The result, according to Shapley, was “Fire and Ice”. Most people probably don’t remember who Shapley was anymore, but in his day he was one of the most prominent astronomers, helping to map the galaxy and measuring its size.
  • Portrait of a black hole, part 1 (Galileo’s Pendulum): When trying to understand the curved four-dimensional spacetime of gravity, we have to resort to metaphor and simplified pictures. Here’s my attempt to describe spacetime around a (non-rotating) black hole using a dynamic analogy: a flowing current, against which objects must move.
  • A scientific love affair (Galileo’s Pendulum): Like many (most?) little kids, dinosaurs captured my imagination, sparking me to think about science for the first time. However, black holes, pulsars, and other products of extreme gravity inspired me in a different direction when I was in sixth grade. Here’s a partial story of my love affair with gravity.
  • The 2013 Nobel Prize in physics: the Higgs boson (Galileo’s Pendulum): The 2013 Nobel Prize was awarded this week to François Englert and Peter Higgs for the theoretical prediction of what is now known as the Higgs boson. This post celebrates that award, but also delves into how the Nobel Prize fails. In promoting the “lone (male) genius” view of science and thereby failing to acknowledge contributions by the others who deserve recognition for the Higgs boson, the Nobel Prize does a disservice to that which it seeks to honor. Bonus: what the Nobel Prize has to do with the leg lamp from A Christmas Story.
  • Measuring a superconducting qubit by manipulating its environment (Ars Technica): Now for something completely different! Quantum systems are complicated, involving interactions between the objects we want to study, the environment of those objects, and our measuring apparatus. A new experiment shows a way of measuring an object’s properties indirectly by performing environmental measurements instead. The result is a picture of a superconducting quantum bit (or qubit) as it evolves in time.

The week in review (September 22-28)

I spent much of the week sick, but that doesn’t stop me. I care about you, people.

  • All black holes, great and small (Galileo’s Pendulum): As my regular readers have probably figured out, I love black holes. I could probably find an excuse to write about them most days. So, why not take an online class from me and learn about black holes? The class begins this Tuesday (October 1), and runs for four one-hour sessions. Sign up today!
  • A Holographic Big Bang: Did the universe start with a five-dimensional black hole? (Slate): Much as I love black holes, however, I cast a skeptical eye on a new paper proposing that the Big Bang had an event horizon. This Slate piece examines what we mean by the “Big Bang model” (which isn’t quite how it’s often described), and the reasons why this five-dimensional theory probably won’t solve the mystery of our Universe’s origins.
  • Scientific grumpfiness and open-mindedness (Galileo’s Pendulum): All three pieces I’ve written for Slate thus far, in addition to a number of other articles published elsewhere, are critical responses to scientific reporting. Generally, I find myself on the opposite side to those who promote radical new theories, which makes me worry sometimes that I’m just a naysayer with no positive commentary to make. Here’s my examination of that worry. (Yes, it’s a bit meta, I suppose.)
  • Pulsar’s magnetic field strong enough to clean up after nuclear explosion (Ars Technica): While pulsars are all fast-spinning objects, some are extremely so, rotating hundreds or thousands of times each second. A new observation caught one of these pulsars in the act of feeding off material from a companion star, lending strong support to the theory of how they spin so fast. Bonus: runaway nuclear explosions! on the surface of a dead star! Who needs science fiction?
  • Snobbish photons forced to pair up and get heavy (Ars Technica): Photons don’t usually interact in the usual sense that matter particles do. Researchers produced a weird medium by pumping a diffuse gas of rubidium atoms with laser light until they puffed up. The result: the interactions between the atoms made an environment where photons have an effective mass (!) and attract each other, forming pairs. Beyond being really cool, this could have all sorts of applications in quantum logic and even “photon materials”.

And just because I can, here’s Cookie Monster playing with his Newton’s cradle again.

Cookie Monster is me brother from another mother.

 

The Solar System boundary and the week in review (September 8-14)

Cthulhu at NASA Wallops, for the LADEE launch last weekend. (I didn't wear the hat the whole time. I'm not that weird.)

Cthulhu at NASA Wallops, for the LADEE launch last weekend. (I didn’t wear the hat the whole time. I’m not that weird.)

‘Twas a busy week!

  • High-resolution observations show how black hole jets churn galactic gas (Ars Technica): One portion of my PhD thesis involved galactic feedback. That’s the process by which jets from black holes at the center of galaxies push material away, potentially affecting star formation and other activity. This article addressed the observation of galactic feedback, showing exactly where the hot jet of plasma from the black hole meets the colder atoms in galactic clouds. Very awesome stuff!
  • Parallel Earth and the Evil Matthew Hypothesis (Double X Science): I don’t know if Star Trek was the original source of the “evil twin from a parallel world” trope, but it’s the most famous. The idea is that there’s a mirror universe to ours, in which things are almost the same, but not quite. I discussed that trope in light of the multiverse, the concept that during rapid expansion right after the Big Bang, the Universe split into a number of disconnected regions that might obey different laws than our own.
  • Do-it-yourself science at GeekGirlCon (Galileo’s Pendulum): We’re still raising money to send a group of us to GeekGirlCon in Seattle next month! We’re willing to embarrass ourselves in public to accomplish this! However, the real purpose is to have hands-on science activities at the con.
  • Status of the book-in-progress (Galileo’s Pendulum): On a more somber note, I have suspended work on my book indefinitely and released my agent. I haven’t completely given up on either the book or getting it published, but the frustrations around the whole process have exhausted me, so it’s time for a break.
  • Cosmic coincidence and a potato eclipse (Double X Science): The Moon is nearly the same size as the Sun in our sky, which has led to all sorts of mystical musings and apocalyptic fears, especially during eclipses. However, that appearance is a coincidence, which we can understand using simple geometry. What’s even more fun to contrast our Moon to Phobos, the larger of Mars’ two moons, which is much smaller than our own but manages to create its own eclipses.
  • Voyager 1 really has left the Solar System…probably (Ars Technica): Sometime last year, the venerable spacecraft Voyager 1 crossed into interstellar space. While there have been a lot of announcements along these lines (I compared the number with Spinal Tap drummers), this time the probe seems to have actually done it. The necessary measurement is the plasma density, which is much higher in interstellar space, but Voyager’s plasma instrument had been knocked out by a solar flare. Researchers pieced together the appropriate data from other instruments. There’s still an anomalous measurement that needs to be accounted for — the magnetic field doesn’t behave as predicted — but I think it’s pretty safe to say that’s an issue for theorists, not ambiguity about Voyager’s position. (See below for a discussion of whether Voyager has actually “left the Solar System” or not.)
  • Mapping the dark matter in the tiniest of galaxies (Galileo’s Pendulum): Dwarf spheroidal galaxies don’t look like galaxies at all. They have so few stars and so little gas or dust, they’re nearly see-through, yet they have as much as 1000 times more dark matter than ordinary matter. (In regular galaxies, dark matter is more like 10 times the amount.) Two astronomers analyzed the motion of stars within dwarf spheroidals to see if they could map the distribution of dark matter, and they found something similar to what is seen in larger galaxies.
  • Finally, I participated in the Weekly Space Hangout, sponsored by Universe Today and CosmoQuest. I joined hosts Fraser Cain and Nicole Gugliucci, along with Amy Shira Teitel, David Dickinson, and Nancy Atkinson to talk about the space and astronomy news from the last week. The whole thing is archived at Google+, or you can watch the video on YouTube.

Where’s the edge of the Solar System?

Returning to Voyager 1, I think stories about its passage into interstellar space fell into two major categories: those saying “Voyager 1 has left the Solar System!” and variations on “Stop saying Voyager 1 has left the Solar System!” Despite what the headline on my story said, the second group of people (which includes writers I respect like Phil Plait and Amy Shira Teitel) is correct: the Solar System includes the Oort Cloud, a diffuse region of icy bodies loosely bound to the Sun by gravity.

A radio image of Voyager 1, as seen by the Very Long Baseline Array (VLBA) and the Green Bank Telescope. Click for a larger image and more information. [Credit: Alexandra Angelich, NRAO/AUI/NSF]

A radio image of Voyager 1, as seen by the Very Long Baseline Array (VLBA) and the Green Bank Telescope. Click for a larger image and more information. [Credit: Alexandra Angelich, NRAO/AUI/NSF]

However, if you want to say Voyager has left the Solar System, I’ll back you up: the boundary between the Oort Cloud and the “rest of the galaxy” isn’t very well defined. Gravity technically extends forever, though it weakens substantially with larger distances. As a result, the Oort Cloud is a fuzzy edge, and one we can’t measure. Is the end of the Solar System the point where the last Oort Cloud body resides?

Now, I agree with the pedants that the Oort Cloud truly does define the end of the Sun’s influence, and therefore is the edge of the Solar System. But the magnetic boundary of the Solar System, which is arguably the more important one from the point of view of astronomy, is defined by the edge of the heliopause, where the solar wind hits interstellar gas. That boundary, while it fluctuates with solar weather, is a much clearer division, and one we could conceivably measure near other stars.

So, I’m a both/and kind of guy in this case. Since there’s no single, sharp boundary between the Solar System and “everything else”, let’s just say there are two edges: one for the Sun’s electromagnetic influence (the heliopause), and one for its gravitational influence (the Oort Cloud). Voyager crossed the first one, but won’t reach the second one for 300 years. Now, can we get back to talking about how awesome Voyager is?

The week in review (September 1-7)

A full-size wooden mock-up of the Lunar Atmosphere and Dust Environment Explorer (LADEE). [Credit: moi]

A full-size wooden mock-up of the Lunar Atmosphere and Dust Environment Explorer (LADEE). [Credit: moi]

The last week was especially busy because I attended the launch of the Lunar Atmosphere and Dust Environment Explorer (LADEE) at NASA’s Wallops Flight Facility. I will have a lot to say about that launch, LADEE, and related topics later on, but suffice to say it was a great experience — increased because it was my first successful rocket launch viewing. (I attempted to watch the Antares rocket test in April, but that was scrubbed at the last minute and I couldn’t attend the rescheduled launch.) So, here’s my very small list of articles published this week.

  • Turbulence ahead: Interstellar wind changes direction, blows faster (Ars Technica): The Solar System orbits the center of the Milky way, and as it does, it’s passing through a diffuse nebula known as the Local Interstellar Cloud (LIC). Various satellites and probes have measured the passage of atoms through the Solar System since the 1970s; analysis of that data shows that the direction of this wind has changed and its rate has picked up. That reveals some interesting new detail about the environment surrounding the Solar System.
  • Of maps and math and Buckminster Fuller (Galileo’s Pendulum): Mapmaking will never be perfect because there’s no way to create a flat representation of the curved surface of Earth without some distortions. This post goes a little into the math of projection, the art of converting positions on a globe onto a flat map, and how the eccentric utopian architect Buckminster Fuller tried to solve the problem. The result was his wonderful Dymaxion map, which as a physicist I’m very fond of.

I also wrote a brief viewing guide for the LADEE launch, which is now necessarily obsolete. However, you can find a lot of photos and video from the launch at NASA’s LADEE site.

 

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)!