The band has stopped playing, but we keep dancing
The world keeps turning, the world keeps turning.
A lot of nonsense has been written over the years about various “prophecies” predicting the end of the world, including stuff by people who should know better. What you see in newspapers, magazines, and TV shows might lead you to believe there is credible reason to think the world will end tomorrow: December 21, 2012. Supposedly this was predicted by the Mayan calendar. However, as with so many things, the truth is much different. The Mayas didn’t predict the end of the world, and there’s no evidence they thought that way. More importantly, there’s no scientific reason to think the world will end tomorrow: nothing we know of could bring about our end so rapidly without warning. That’s a reassuring thought to me, as I wrote in Double X Science today:
My confidence comes from science. I know it sounds hokey, but it’s true. There’s no scientific reason—absolutely none—to think the world will end tomorrow. Yes, the world will end one day, and Earth has experienced some serious cataclysms in the past that wiped out a significant amount of life, but none of those things are going to happen tomorrow. (I’ll come back to those points in a bit.) We’re very good at science, after centuries of work, and the kinds of violent events that could seriously threaten us won’t take us by surprise. [Read more….]
Metal tends to be opaque. However, if you perforate it with small holes in a certain pattern, it will still transmit some light—even if the holes are smaller than the wavelength of the light! This is known as extraordinary optical transmission (EOT), which has found uses in a number of devices since its discovery in the 1990s. However, a full understanding of the phenomenon has proven elusive. (That’s such a journalist way to put it, ain’t it?) A new experiment may have shown that the transmission is driven by two separate wave effects, and sorted out the role each plays in EOT.
Ordinarily, light can pass through an opaque barrier only if the barrier is pierced with openings larger than the light’s wavelength. (This also applies to all manner of waves, including sound and water waves.) That’s why EOT is fascinating: the holes are smaller than the wavelength, yet a substantial amount of light still gets through something that would ordinarily be opaque. Oddly, making the material thinner—and therefore more transparent—decreases the EOT effect. [Read more….]
The biggest black holes in the Universe reside at the centers of the largest galaxies. However, a new study suggests they may be proportionally even larger, compared with other galaxies. The bright cluster galaxies (BCGs) are huge galaxies found in the middle of galaxy clusters, where they grew by merging with and absorbing smaller galaxies. However, based on their X-ray and radio luminosity, their black holes may have grown much bigger—perhaps as much as ten times the mass in previous estimates. That means the largest black holes in the Universe are perhaps 60 billion times the mass of the Sun…or more.
A recent study has used an independent means of estimating black hole masses, based on their brightness in X-rays and radio light. J. Hlavacek-Larrondo, A. C. Fabian, A. C. Edge, and M. T. Hogan examined the massive central galaxies in 18 galaxy clusters and found that previous measurements could be off by as much as a factor of ten. In other words, if the luminosity-based measurements are correct, a black hole currently believed to be 6 billion times the mass of the Sun could actually be 60 billion times more massive.
That leaves two possibilities: either black holes in bright cluster galaxies behave differently by producing more light than we think they should, or the biggest black holes in the Universe might be astoundingly ultramassive. [Read more…]
We have no complete, consistent quantum theory of gravity. However, clues from other theories indicate that the physics we know breaks down at a certain fundamental length scale: the Planck length. In particular, the Heisenberg uncertainty principle in quantum mechanics must be modified if you can’t measure position to arbitrary precision. However, length and energy are two ends of a teeter totter: to probe to small lengths requires vast energies, and the Planck length would necessitate energy far beyond anything our particle accelerators can provide—maybe ever. As a result, researchers are using other ideas for getting at quantum gravity in the lab, including a certain kind of gravitational wave detector based on a huge metal bar.
When theory is silent, experiment must step in. A new paper analyzed results from the AURIGA gravitational wave experiment to check for deviations from standard quantum mechanics in the vibrations of a massive metal bar at cryogenic temperatures. The AURIGA results showed no deviation from standard quantum physics, yielding an upper bound on the energy of quantum gravity modifications. The experimenters concluded that the theorists needed to get back to work so that the experimenters have a better idea of what to expect. [Read more….]
(Alas, the excellent title for this article was not my idea.)
Certain physical quantities—the fundamental electric charge, the masses of certain particles, the strengths of the basic forces of the Universe—are generally assumed to be constant in time and space. Some of our theories depend on that constancy, but it’s not an absolute certainty: it’s possible that in distant galaxies, the rules might be a little different. They can’t be drastically different, though: observations show that (for example) the hydrogen spectrum appears to be the same 12 billion years ago. A new observation has clarified the constancy of another relation: the ratio of the proton mass to the electron mass, one of the quantities that dictates the structure of all atoms. They found this by measuring the spectrum of methanol, the simplest type of alcohol.
New observations of methanol (also known as methyl alcohol) that absorbed light in a galaxy 7 billion years ago show that it behaves the same as molecules on Earth, to one part in 10 million. The spectrum of methanol depends sensitively on the ratio of the proton mass to the electron mass, considered in most theories to be one of the fundamental constants of nature. In other words, because the spectrum of methanol at a cosmologically significant distance is indistinguishable from that in the lab, at least one fundamental constant hasn’t changed measurably in at least 7 billion years. [Read more…]
Erwin Schrödinger is best known to non-scientists for his thought experiment involving a cat (or maybe his unconventional living arrangement), but he also wrote What is Life?, a book that attempted to bring the fields of physics and biology closer to each other. Today, experiment is beginning to reach the point where we can see if the specifically quantum aspects of physics play a direct role in biology. Even though in a fundamental sense, everything is quantum mechanical, the quantum state—the entity that encodes the probability of the outcomes of various interactions—doesn’t usually need to be considered for biology. However, it’s still possible life has learned to harness quantum effects, ranging from tunneling to entanglement, to gain an evolutionary advantage.
An intriguing aspect of all of these possibilities is that perhaps evolution has figured out a better way of performing tricky quantum manipulations than we have. In a sense, that’s not surprising: life has had a long time to evolve photosynthesis, photoreception, and navigation, while our understanding of quantum mechanics just began in the 1920s and ’30s. [Read more…]
The term “quasar” describes a behavior rather than an object: when a supermassive black hole (SMBH) at the center of a galaxy gorges on gas, the infalling matter produces a lot of light. While most galaxies are known to have SMBHs, not all of those exhibit quasar behavior. Similarly, black holes created from the deaths of massive stars—the stellar mass black holes—don’t generally consume matter at a rapid rate. However, a few do, and those are known as microquasars. Four microquasar candidates have been found in the Milky Way, and now one has been located in M31, the Andromeda Galaxy.
Unlike microquasars in the Milky Way, those in other galaxies potentially provide an unimpeded view of the black hole accretion process. This will allow astronomers to test whether microquasars are miniature versions of their supermassive cousins, and measure the accretion mechanism in unprecedented detail. Since the nearest “regular” quasars are much farther away than M31, a nearby microquasar provides a beautiful target for observations of how black holes beam infalling matter into jets, and the specific processes are by which they make their intense light. [Read more…]
Protostars are, as the name suggests, what we have before a star forms. Clouds of gas and dust collapse under gravitation, heat up, and (at least in some cases) begin fusing hydrogen into helium in their cores. A new observation of a protostar catches it very early in its formation, while it was still accreting mass. The researchers estimated it might have been 300,000 years old or even less, which may sound like a lot, but is a blink of an eye in cosmic terms.
The researchers measured dust in the region surrounding L1527 using the Submillimeter Array (SMA) in Hawaii and the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California. Previous observations, using one of the Gemini telescopes in Chile, determined the protostar had a disk, which appears edge-on from our perspective on Earth.
The newer results determined both the thermal emission—the broad spectrum of light directly emitted from the warm gas and dust—and absorption by carbon monoxide molecules in the disk. (Specifically, they measured 13CO, the version of carbon monoxide involving the isotope carbon-13.) The excellent resolution of the telescopes enabled the astronomers to measure the total size and mass of each component of the system. [Read more…]
Map of the Moon’s surface, as provided by the twin GRAIL spacecraft.
For most astrophysics purposes, we don’t have to worry about the details of the inner structure of planets and moons. However, if we want to reconstruct their full history, it helps to know all the variations in density and composition. The twin GRAIL spacecraft in orbit around the Moon are designed to do just that. By a bit of fancy formation flying, GRAIL-A (“Ebb”) and GRAIL-B (“Flow”) have provided the most detailed map yet of the Moon’s surface and interior, by measuring fluctuations in the gravitational pull. My editor John Timmer and I wrote a pair of stories (not named Ebb and Flow) describing the spacecraft and their discoveries. The Moon turns out to have had an even more violent past than previously suspected, including an impact so powerful it shattered the crust.
Each GRAIL spaceship is about 200kg in mass and the size of a refrigerator. The craft follow a nearly polar orbit, looping around the Moon such that, as it rotates on its axis, GRAIL was able to take measurements of the entire body in swaths (akin to the segments of an orange). [Read more…]
The moments after the Big Bang left the Universe very hot and dense. In that violent environment, the first nuclei came to be: hydrogen, helium, and lithium…but nothing heavier. The elements more massive than helium (which astronomers perversely refer to as “metals”) were forged by stars and spread through the Universe as those stars died. That means if we look far enough back in time, we should be able to see the era of transition: when the first metals in the Universe came to be. A new observation of the environment surrounding a quasar shining a mere 772 million years after the Big Bang has revealed a metal-free cosmos.
Modern galaxies like the Milky Way contain populations of stars that we can divide based on their metal content. The Sun is a Population I star, with a relatively high metal abundance; older, Population II stars near the galactic center are metal-poor. However, the earliest, metal-free stars—known as Population III—are still hypothetical. According to widely accepted models, Population III stars were massive and therefore short-lived, going supernova and spreading the first metals into interstellar space.
When did these first stars form, and did they actually correspond to our models? These questions are still unanswered. The crucial period of time when the first stars must have formed is still marked by a paucity of data. [Read more…]