Physics Week in Review: June 23, 2018

Among this week’s physics highlights: the physics of how cracks spread; resonating peacock crests, and Einstein’s general relativity still holds at the galactic scale. (Takeaway: Don’t bet against Einstein.)

Why Some Cracks Repel: A theoretical study of crack propagation provides an explanation for the observed repulsion between certain pairs of cracks on collision courses. To properly account for whether approaching cracks will repel or attract, models must take into account length-scales much smaller than the crack length. [PDF]

Peahens have fan-shaped crests on their heads, and it seems male peacocks can make these crests resonate by making a specific noise with their tails.  See also my 2016 Gizmodo article on the physics of peacock feathers.

In the 1970s, Roger Penrose proposed that the general relativity-breaking boundary inside a black hole could be disregarded as a mathematical novelty. That idea has been disproven.

Stealth sheets can make you appear invisible to infrared cameras. “A bendable sheet of silicon can hide 95 percent of infrared light, rendering objects essentially invisible to heat-sensing night vision goggles or infrared cameras.”

Scientists Find Stronger Evidence for New Kind of Black Hole. “These intermediate-mass black holes are hard to spot, mainly because it’s thought that they form in clusters of stars, outside of the dense galactic centers.”

Fifth State of Matter May Challenge the Second Law of Thermodynamics. In the quantum realm, “for certain situations equilibrium is not reached, regardless of the amount of time allowed to pass.”

How Does the Strange and Probabilistic Quantum World Cross Over Into the Deterministic Classical World of Our Everyday Lives? New experiments aim to probe where—and why—one realm passes into the other.

Shape-Shifters: These 3D Printed Smart Materials Can Jump, Crawl, And Play Catch.

New Glowing Dichroic Glass Installations by British artist Chris Wood are Activated by Sunlight. “The artist forms seemingly spare geometric shapes in windows and on on white panels, which come to life with streaks of color when hit with sunlight.” [Image: Chris Wood]

A team of scientists explained the paradoxical phenomenon of the mutual annihilation of particles and antiparticles in graphene. The theoretical justification for this process was until recently one of the most complex riddles of solid-state physics.

Physics of knitting shows why your sweater is so nice and comfy. The spacing of stitches in knitted fabrics lets friction cascade through the material, which allows it to stretch without the yarn getting any longer.

Spiders can float in the air, and scientists just figured out how they lift off.

“Under the right (or, perhaps more accurately, wrong) circumstances, the clatter of ceramics like porcelain can be dangerously loud, as engineer Phil Metzger discovered when repairing his toilet.”

A Cleaner Cosmological Ruler Could Shed Light on Dark Energy. Related: Why Cosmology’s Expanding Universe Controversy Is An Even Bigger Problem Than You Realize. The Universe is expanding, but different techniques can’t agree on how fast. No matter what, something major has got to give.

Einstein’s Greatest Theory Validated on a Galactic Scale. Astronomers have used a pair of galaxies far beyond the Milky Way to test general relativity with unprecedented precision.

Finally, A Problem That Only Quantum Computers Will Ever Be Able to Solve: Computer scientists have been searching for years for a type of problem that a quantum computer can solve but that future classical computers cannot. Now they’ve found one.

To build quantum networks we need a scalable way of sharing entanglement between nodes. Two methods to deliver entanglement deterministically are now reported in Nature, which could facilitate the building of large-scale quantum networks.

How Correlated Weather Fluctuations Take Down Power Grids. Line failures can emerge and propagate in power grids because of varying power injections such as those from wind and solar plants.

The Twinkle in Mother Earth’s Eye: Laser Blasts Produce Promising Fusion Advances.

Scientists Propose a New Kind of Matter Inside the Densest Stars. However, “More investigation of the topic is necessary before turning two-flavored quark matter into a strong candidate for what is in the interior of neutron stars.”

Astronomers watch the aftermath of a star ripped apart by a huge black hole.

Weird Low-Light Bacteria Could Potentially Thrive on Mars. The photosynthetic organisms subsist on redder, lower-energy light than other species, and could be a new source of fuel and air for interplanetary outposts.

Why Does Exploding Dots Work? “[James] Tanton’s “Exploding Dots” approach to precollege math is designed to bring illumination and joy to a subject that students all too often associate with mystery and misery.”

Twenty Years of Network Science: “The idea that everyone in the world is connected to everyone else by just six degrees of separation was explained by the ‘small-world’ network model 20 years ago. What seemed to be a niche finding turned out to have huge consequences.”

Frozen Bubble Formations and Shards of Snow Captured in Alaska’s Swamps and Ponds by Japanese Photographer Ryota Kajita. The artist “has captured the strange ice patterns of Alaska’s interior swamps and ponds for the last eight years as a part of his Ice Formations series. The ephemeral structures look like fanciful desserts discovered in the wild, with frozen shavings lightly dusting the formations’ edges.”  [Image: Ryota Kajita]

How Surfing Helped These Scientists Make Waves. From the oceans’ depths to the insides of atoms, researchers of all stripes have found inspiration in the surf.

The Drake Equation & Seager Equation – Calculating the chance of extraterrestrial life. Are we alone in the universe? Is there life on other planets? Or has the Fermi Paradox kicked in?

Stars gravitate to Stephen Hawking’s memorial. “Mischievous even beyond the grave, this was pure Hawking.”

No, World Cup Fans Didn’t Trigger an Earthquake. Here’s Why. Mexico’s win over Germany rocked Mexico City. But not literally.

Are Superhero Capes Aerodynamic? “The consensus seems to be that capes are not really that aerodynamic at all, when you get right down to it. Just the opposite, really. But the mechanics here are interesting.”

A physicist ponders the universe’s most mysterious questions—in a comic book.

Facebook Researchers Develop a Neural Network That Predicts Body Movement Using Musical Input.

The Incredible Harmonic Complexity Found Within Each Part of the Iconic Eagles Song ‘Hotel California.’

Introducing the National Science Policy Network: A new wave of scientists and engineers are recognizing the importance of their seat at the policy table.

The strange allure of decayed daguerreotypes. “The faces on daguerreotypes become lost, like features reflected in a misted bathroom mirror.”

Finally, for your weekend viewing pleasure, I moderated a panel in Santa Fe this week, as part of a workshop at the Santa Fe Institute on the implications of time for complex adaptive systems. The all-star line-up: Sean Carroll (beloved spouse and Time Lord), UCSB physicist Jim Hartle, and SFI director David Krakauer. Per the description: “This panel discusses the challenges of time in physics, biology, and culture. Panelists focus on the idea that time flies forward, like an arrow, as a way of distinguishing what we call “the past” from “the future.” They discuss the latest understanding of the relationship between the arrow of time, entropy, and the second law of thermodynamics as they move from physics fundamentals to time and information in adaptive systems. Along the way, they also reflect on limits to mortality.”