Now it can be told: I will be writing a weekly post for The Daily Beast (making me The Weekly Beast?), on space, astronomy, and such things. My first column is about inflation, and why it’s a big deal:
If you compare any two points on the night sky, their temperature as measured in microwave light is identical to a few millionths of a degree. That light, known as the cosmic microwave background, comes to us from nearly the beginning of the Universe, so it has been traveling for 13.8 billion years. Even with the expansion of the cosmos, two points on opposite sides of the sky were never in the same place, yet they have the same temperature… assuming the current rate of the expansion of the Universe has been roughly the same since the beginning.
But maybe it hasn’t. The cosmic temperature coincidence (which would be a great band name), along with several other annoying aspects of the Universe, led a group of researchers to propose the theory of inflation. [read more…]
If you shine light on a barrier with two openings, it produces a distinct pattern of light on a distant screen. Measuring that pattern is standard in introductory physics laboratories. (You could even do it at home, but I recommend a very dark room and a bright laser pointer if you hope to see anything at all.) Where things get fun, though, is if you have a light source capable of sending a slow stream of photons — particles of light — through: you still get the interference pattern, but it emerges slowly from individual points of light. In other words, the photons behave as though the entire wave interference pattern is already present, even though they are single particles.
My latest article for Nautilus shows how researchers have taken this classic experiment, but use single photons to manipulate the interference pattern via the phenomenon known as entanglement. The result is a mind-bending experiment known as the “quantum eraser”:
The best way to see the quantum eraser is to couple the double-slit experiment with another fascinating quantum phenomenon: entanglement. In a typical implementation, light from a laser stimulates a certain kind of crystal, which in turn emits two photons with opposite polarization—one could oscillate left-right, while the other oscillates up-down. (You can see how this works by putting one pair of polarized sunglasses in front of another and rotating one pair. At certain angles, the light going through both lenses will fade to almost nothing, a sign that the light is passing through two filters with perpendicular orientations.)
The polarization of each photon is unknown before measurement, but because of how they’re generated, they are entangled, and measuring one can instantly affect each the other. That holds true no matter how far apart the two particles are or when the measurements are taken. [read more….]
I’m in a magazine!
Physics is largely a matter of finding patterns in natural processes and translating that to mathematical expression. That’s a horribly oversimplified view, of course, but there’s no question that physics (and other branches of science) seeks to find symmetries. The huge successes of modern particle physics have largely arisen from identifying symmetries — and when those symmetries break down. To cite just one: physicists understand the weak force, which governs neutrinos and processes like nuclear beta decay, using a mathematical symmetry. That symmetry isn’t perfect, however, and one outward manifestation of that imperfection is the Higgs boson.
This pattern-seeking behavior among physicists is the theme of Dave Goldberg’s book The Universe in the Rearview Mirror: How Hidden Symmetries Shape Reality. I reviewed the book for Physics World, which marks my first publication in a print magazine. (It also may be the first time The Decemberists were quoted in Physics World.) You can read my review online, though the site requires a free registration to do so. In brief, I enjoyed the book, but found a few problems with it as well.
Inevitably, Goldberg’s explanations vary in quality. I found his discussion of the Casimir and Unruh effects (weird quantum phenomena in the vacuum) to be very good introductions for non-specialists. He also provides an excellent summary of the problems facing attempts to unify the different forces of nature, and specifically the question of pro- ton decay. On the other hand, his explanation of Lagrangians and the principle of least action (both essential topics in a mathematical sense) falls short, since it requires him to define a lot of new terminology in just a few pages, most of it barely mentioned again. The book also misses an opportunity to explain how specific symmetries shaped the development of the Standard Model; while it outlines a few of the important symmetries (including parity or reflection symmetry, time-reversal, time-translation, and exchange of matter and antimatter) early on, it fails to bring them back into the picture when the Standard Model is discussed. [Read more…]
The BICEP2 telescope (foreground) with the South Pole Telescope (SPT) behind. [Credit: Steffen Richter (Harvard University)]
Today was an exciting and stimulating day: the BICEP2 collaboration announced the first measurement of the cosmic microwave background that might tell us whether or not inflation happened. Inflation is the hypothetical rapid expansion of the Universe during its first instants, which explains a lot about why the cosmos appears the way it does. However, data on inflation itself, as opposed to its side-effects, are hard to come by. This new observation could help resolve that
…assuming we can figure out why some of its aspects don’t agree with prior observations.
While they do not constitute a direct detection of either primordial gravitational waves (the distortions causing the light polarization) or inflation, the BICEP2 results could provide the best evidence for both that could not be easily explained away by other theories. This observation cannot be the end of the story, however. The measurement of polarization is significantly larger that what is seen in the results of prior observations in a way that cannot be immediately dismissed. Whether the problems are with the interpretation and analysis of the BICEP2 data, or if something more subtle is at work, remains to be seen. [Read more….]
A visual representation of the “axis of evil”: the strange alignment of temperature fluctuations on the largest scales on the sky. [Credit: Craig Copi]
On the largest scales — far bigger than any galaxy or galaxy cluster — the Universe is remarkably smooth and regular. Tiny irregularities in the early cosmos are what gave rise to all the structures we see today, including us, but there’s another irregularity covering the whole sky. The Universe appears to be ever-so-slightly lopsided, an anomaly facetiously known as the “axis of evil”. Cosmologists are concerned with trying to understand whether the anomaly is a significant challenge to our understanding of some of the laws of physics, or whether it can be understood either as a new astronomical source or a random fluke based on the fact that the whole cosmos is much larger than our observable Universe.
In my latest feature article at Ars Technica, I explored why the “axis of evil” could be a big deal and how some physicists are trying to understand it.
The lopsidedness is real, but cosmologists are divided over whether it reveals anything meaningful about the fundamental laws of physics. The fluctuations are sufficiently small that they could arise from random chance. We have just one observable Universe, but nobody sensible believes we can see all of it. With a sufficiently large cosmos beyond the reach of our telescopes, the rest of the Universe may balance the oddity that we can see, making it a minor, local variation.
However, if the asymmetry can’t be explained away so simply, it could indicate that some new physical mechanisms were at work in the early history of the Universe. [Read more….]
Astronomers measured the rotation of a black hole from halfway across the Universe.
What, I need to say more?
Astronomers have now used gravitational magnification to measure the rotation rate of a supermassive black hole in a very distant galaxy. From four separate images of the same black hole, R.C. Reis, M.T. Reynolds, J.M. Miller, and D.J. Walton found it was spinning nearly as fast as possible. That likely means it was spun up by a small number of mergers with other black holes rather than a gradual increase from eating smaller amounts of mass.
This marks the first measurement of black hole rotation outside the local Universe…. [Read more]