- 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 a theoretical physicist by training and inclination, but I’m not immune to awesome experiments or observatories. (Ahem.) Case in point: the new Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. This array of 66 telescopes in the high Atacama Desert is particularly well suited to hunt for the earliest galaxies and stars in the Universe. Their early scientific results—timed for the official inauguration of the array this week—bear that out, with the measurement of the distances to several star-forming galaxies that formed less than 1.5 billion years after the Big Bang. What makes it even better? My article appeared today, which is Albert Einstein’s birthday, and ALMA scientists used gravitational lensing—an effect predicted from Einstein’s general theory of relativity—to locate these galaxies.
The galaxies of the Universe’s youth worked busily at making stars—that much is certain. However, what did those galaxies look like? How many were there, and how were they distributed in space and time?
Over such huge distances, those galaxies appear faint to us, so it’s only within the last decade or so that astronomers have been able to start obtaining a reasonable view of them. The newly inaugurated ALMA (Atacama Large Millimeter/submillimeter Array) is one of the most promising telescope arrays in the world for making observations of the early Universe. [Read more…]
(Not fully alliterative, but it’s the best I can do after driving 6 hours today.)
The halos of galaxies are best known for harboring dark matter, but they also contain stars. Only a tiny fraction of the total stars in a galaxy are in the halo, so usually they’re hard to spot, but astronomers are realizing they can contribute a significant amount to the total light profile. In particular, a group of researchers using the Spitzer infrared space telescope has determined that much of the infrared haze in the sky is due to galaxies that formed in the early Universe—including their halo stars.
However, the earliest stars and galaxies should contribute to the total infrared glow of the Universe, known as the cosmic near-infrared background (CNIB). (“Near-infrared” refers to wavelengths closest to visible light in the electromagnetic spectrum; in this case, the study was in the 1 to 5 micron range.) Much of the haze in the CNIB is from the Milky Way and known galaxies, but a significant portion is not associated with any obvious sources. Astronomers have postulated it must originate in either to dwarf galaxies (which are too small to be seen at significant distances) or faint galaxies from the early Universe. [Read more….]