Granulation on the surface of the Sun, created by rising bubbles of hot plasma. Fluctuations in these bubbles can be measured on distant stars, which provides a way to calculate the stars’ surface gravity. [Credit: Hinode JAXA/NASA/PPARC]
I’ve been remiss in blogging at Bowler Hat Science, largely because…well, I’ve been writing too much elsewhere. So, I’m going to try something different: instead of blogging each new article I write in a separate entry, I’ll write a single post summarizing everything in one go.
How I learned to stop worrying and love tolerate the multiverse (Galileo’s Pendulum): My explanation of cosmology involving parallel universes is a response to a piece placing the multiverse in the same category as telepathy. While I’m not a fan of the multiverse concept, I reluctantly accept that it could be a correct description of reality.
An Arguably Unreal Particle Powers All of Your Electronics (Nautilus): Electrons in solids behave differently than their wild cousins. In some materials, the electronic and magnetic properties act as though they arise from particles that are lighter or heavier than electrons, or multiple types of particles with strange spins or electric charges. Are these quasiparticles real?
Kepler finds stars’ flickers reveal the gravity at their surface (Ars Technica): The Kepler observatory’s primary mission was to hunt for exoplanets, but arguably it’s been equally valuable for studying stars. A new study revealed a way to measure a star’s surface gravity by timing short-duration fluctuations — the rippling of hot plasma bubbles on the surface known as granulation (see above image).
Destruction and beauty in a distant galaxy (Galileo’s Pendulum): The giant galaxy M87 has a correspondingly huge black hole at its heart. That black hole in turn generates an enormous jet of matter extending 5,000 light-years, which fluctuates in a way we can see with telescopes. In that way, an engine of destruction shapes its environment and produces a thing of beauty.
The Freaky Celestial Events We See—and the Ones We Don’t (Nautilus): In another faraway galaxy, a black hole destroyed a star, producing a burst of gamma rays that lingered for months. This event is the only one of its kind we’ve yet seen, prompting the question: how do we evaluate events that are unique? How can we estimate how likely they truly are, especially if we’re seeing them from a privileged angle?
This isn’t writing, but after listing two black hole articles in a row, it seems a good time to advertise my Introduction to Black Holes online class in October! Sign up to learn all* about black holes. *All = what I can cover in four hours of class time.
Warp Speed? Not So Fast (Slate): Many articles have appeared over the last year or so profiling a NASA researcher, whose research supposedly could lead to a faster-than-light propulsion system. The problem: very little actual information about his work is known, and what he’s said publicly contradicts what we understand about general relativity and quantum physics.
Statistics is rarely sexy, sometimes satisfying, occasionally misused, but useful enough that more people should know how to use it than do. (Insert obvious condom joke here.) However, a particular method in statistics got additional attention last fall during the United States national elections: Bayesian inference. I wrote two pieces last week, drawing from a recent Science article, that highlighted Bayesian methods. The first (written for Ars Technica, now picked up at WiredUK!) was about Bayes’ theorem and why its use is still controversial for some people.
Bayes’ theorem in essence states that the probability of a given hypothesis depends both on the current data and prior knowledge. In the case of the 2012 United States election, Silver used successive polls from various sources as priors to refine his probability estimates. (In other words, saying he “predicted” the outcome of the election is slightly misleading: he calculated which candidate was most likely to win in each state based on the polling data.) In other cases, priors could be the outcome of earlier experiments or even educated assumptions drawn from experience. The wise statistician or scientist constructs priors that are informative, but that isn’t always easy to do. [Read more…]
My second, follow-up piece was for my own blog, and included a tutorial introduction to Bayes’ theorem. Admittedly, this example is very simple and doesn’t do justice to the power of Bayesian methods, but a better example would be pretty involved, so I decided to hold off for now. (I may revisit the topic later, though, depending on time and inspiration.)
So, Bayes’ theorem reads: the probability of a hypothesis being true (based on the data and prior information) depends on the probability of the hypothesis from prior knowledge, multiplied by the likelihood of that particular data showing up, divided by the chance of the data showing up based on the priors alone. Using Bradley Efron’s example from his Science article, consider the case of a couple whose sonogram showed they were due to give birth to male twins. Given that data, they wanted to know what the chances were that the twins would be identical as opposed to fraternal — a genetic question undecidable by sonogram. [Read more…]
White dwarfs are the remnants of the cores of stars like our Sun. They have the mass of a star packed into the volume of Earth, but when they die, their light can be detected across the observable Universe. Researchers using the Hubble Space Telescope identified the farthest white dwarf supernova yet seen, one which exploded more than 10 billion years ago.
Only 8 white dwarf supernovas have been identified farther than 9 billion light-years away. (Some core-collapse supernovas, which are the explosions of very massive stars, have been seen farther than Supernova Wilson.) Since all such explosions happen in a similar way, cosmologists use them to measure the expansion rate of the Universe. [Read more…]
I gotta say, though: this supernova was nicknamed “Woodrow Wilson”, which kind of bugs me. Wilson was a war president, which means we Americans tend to give him a pass on a lot of things, but both his foreign and domestic policies reeked of racism. He worked against racial equality at home and abroad, stamping on egalitarian movements in the League of Nations and segregating the Federal Government. (The previous Republican administrations, for all their faults, had been making efforts to give African-Americans a voice after the Civil War.) Anyway, that’s mostly beside the point. If you want to read about a supernova named for someone whose work I do admire (prickly though he was), see my post about Supernova Mingus.
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…]
The cosmic pie, via Planck. [Credit: ESA/Planck Collaboration]
For cosmology-lovers like me, yesterday was a full, busy day. The Planck telescope released its first full set of data, refining the estimates of the age of the Universe and its contents. I wrote two big pieces, one for Ars Technica and one for Galileo’s Pendulum.
First Planck results: the Universe is still weird and interesting [Ars Technica]. “By comparing theoretical models to the real CMB, cosmologists determined that dark energy—the mysterious substance driving cosmic acceleration—comprises 68.3 percent of the energy content of the Universe, down slightly from earlier estimates of 72.8 percent. Similarly, dark matter’s contribution was boosted from 22.7 percent to 26.8 percent, while ordinary matter’s share went from 4.5 percent to 4.9 percent.”
Planck results: our weird and wonderful Universe [Galileo’s Pendulum]. “The big news today is that our Universe is a little older than we thought, has a little more matter in it, and is every bit as strange as we’ve come to expect. Some numbers got shifted around a bit, but things are pretty much what we cosmology-watchers expected. It’s not a bad thing, in my opinion. After all, we still don’t know what dark matter is, we still don’t know what dark energy is, and we still don’t understand inflation completely. Adding weirdness to weirdness is probably more than our poor brains could take right now.”
Today I begin a new feature, which I will try to update once a week: the Alphabet of Cosmology. In these entries, I’ll highlight a concept, experiment, or observation in cosmology—the study of the history, contents, and evolution of the Universe—that may not be as familiar to non-specialists.
(I stole borrowed this idea from Brian Switek, whose Dinosaur Alphabet series is a great way to learn about dinosaur species that aren’t the usual famous ones covered in books or on TV shows.)
The dark matter problem in boxer brief
About 80% of the mass in the Universe isn’t the same stuff familiar from daily life. The name we give our ignorance is dark matter, and we generally assume it to be a particle of some kind. We see its effects in the motion of stars and gas in galaxies, in the way galaxies cluster…
Somewhere, something incredible is waiting to be known. – Carl Sagan, born November 9, 1934
Carl Sagan in 1980. [Credit: NASA/JPL]
Like many science writers, I count Carl Sagan as one of my inspirations and influences. However, I think there’s a tendency to mourn his absence (he died relatively young) in the wrong way: by negatively contrasting current science communicators with him, as though there needs to be One True Sagan, with everyone else failing to meet his standard. That’s a fallacy of thought and a failure of imagination.
I think there is a tendency to idolize Sagan, which is (as usual with idolization) unfair both to him and to others who would try to communicate science. In this era of media fragmentation, it may not even be possible for a single figure to be as popular or recognizable, but I don’t think that’s necessarily a bad thing. Instead of a single Sagan, why not many? [Read more…]
The business end of a Rocketdyne F-1 rocket engine, used in the first stage of the Saturn V rockets. Five of these engines were used to launch the Apollo missions into space. Note the picnic tables at left for scale comparison.
For the next two weeks, I am on the move, traveling to various observatories in the American south and southwest, as part of the research for my book-in-progress Back Roads, Dark Skies: A Cosmological Journey. This morning, I will be visiting the Laser Interferometer Gravitational-wave Observatory (LIGO) near Livingston, Louisiana, before heading west to other observatories in Texas, New Mexico, and Arizona. My full itinerary is over at Galileo’s Pendulum:
Being a travel book, though, I am also seeking a new way to see through travel and exploration. Cosmology is a very familiar field to me, but often the person closest to a subject is the worst to try to explain it to a lay audience. By going to particle physics labs and astronomical observatories, I am learning to see my own discipline in a new way, in hopes that it will help me bring it to my readers. As you can tell, this book is different from most cosmology books (A Brief History of Time is perhaps the best example), where the focus is on highly speculative ideas and Big Theories. While theory will always inform the research I discuss—and, being a theorist myself, I can’t help but discuss theory—the primary emphasis of Back Roads, Dark Skies is on experiment and observation. Without these things, theory is nothing but the ramblings of creative people, unconnected to reality. [Read more…]
While the scientific part of the agenda begins today, I haven’t been idly driving without keeping an eye out for interesting things. To wit: yesterday, I saw a wild alligator and one of the engines from the Saturn V rockets, which were used to launch the Apollo missions and the Skylab space station.
Every exoplanet discovery seems to bring us closer to understanding the variety of planetary systems out there in our galaxy. The latest find is particularly exciting: an Earth-mass planet orbiting around Alpha Centauri B, one of three stars in the closest system to the Solar System. The planet isn’t very Earthlike in most respects, but it’s still an incredibly exciting discovery.
However, the discovery is still exciting for a number of reasons. First is the proximity of the star system to us: Alpha Centauri is 4.4 light years away, a tiny distance in cosmic terms. The stars Alpha Centauri A and B are some of the brightest in the sky in the Southern Hemisphere. (Sorry, fellow Northern Hemisphere-dwellers; we can’t see them from here.) We don’t have starship technology to travel there, but we could conceivably send a robotic probe that could arrive within my lifetime, and 4.4 years isn’t a terribly long time for data to travel back to Earth. No one has such a probe in the works yet, but the mere fact of discovery of a planet might encourage investment in that direction. [Read more…]
Last year, I celebrated Emmy Noether, perhaps the greatest mathematician of the 20th century. This year (largely because I’m swamped with other work), I’m stealing a great idea from Ed Yong, and celebrating living writers who are my friends, colleagues, and influences. This list is in no particular order, isn’t anywhere close to complete, and has some overlap with Ed’s list. My main criteria are that these are writers I read regularly, so their interests mix with mine to some degree. (Writers marked with an asterisk* are people I have met in Real Life, whatever that signifies.) Leave your own favorites and influences in the comments! [Read more….]