(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.
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...]
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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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!
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 quasiparticles. These 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.
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?
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.
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.