Lifeboat Foundation

Calculations involving a higher dimension are guiding physicists toward a misstep in Stephen Hawking’s legendary black hole analysis.

Scientists hope that the future of gravitational wave detection will allow them to directly observe a mysterious kind of black hole.

Gravitational wave detectors have seen direct evidence of black holes with roughly the mass of giant stars, while the Event Horizon Telescope produced an image of a supermassive black hole billions of times the mass of our Sun. But in the middle are intermediate-mass black holes, or IMBHs, which weigh between 100 and 100,000 times the mass of the Sun and have yet to be directly observed. Researchers hope that their new mathematical work will “pave the way” for future research into these black holes using gravitational wave detectors, according to the paper published today in Nature Astronomy.

Physicists use two types of measurements to calculate the expansion rate of the universe, but their results do not coincide, which may make it necessary to update the cosmological model. “It’s like trying to thread a cosmic needle,” explains researcher Licia Verde of the University of Barcelona, co-author of an article on the implications of this problem.

More than a hundred scientists met this summer at the Kavli Institute for Theoretical Physics at the University of California (U.S.) to try to clarify what is happening with the discordant data on the expansion rate of the universe, an issue that affects the very origin, evolution and fate of our cosmos. Their conclusions have been published in Nature Astronomy journal.

“The problem lies in the Hubble constant (H0), a parameter which value—it is actually not a constant because it changes with time—indicates how fast the Universe is currently expanding,” points out cosmologist Licia Verde, an ICREA researcher at the Institute of Cosmos Sciences of the University of Barcelona (ICC-UB) and the main author of the article.

Artificial muscles will power the soft robots and wearable devices of the future. But more needs to be understood about the underlying mechanics of these powerful structures in order to design and build new devices.

Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have uncovered some of the fundamental physical properties of artificial muscle fibers.

“Thin soft filaments that can easily stretch, bend, twist or shear are capable of extreme deformations that lead to knot-like, braid-like or loop-like structures that can store or release energy easily,” said L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics. “This has been exploited by a number of experimental groups recently to create prototypical artificial muscle fibers. But how the topology, geometry and mechanics of these slender fibers come together during this process was not completely clear. Our study explains the theoretical principles underlying these shape transformations, and sheds light on the underlying design principles.”

The prestigious academic physics journal Physical Review Letters published a paper this week about cutting-edge laser tech — and, if bloggers are to be believed, it could have juicy ramifications.

The paper itself is dry and technical, but the prominent tech blog Ars Technica’s interpretation of its findings is anything but. According to Ars, in fact, the tech it describes could pulse a laser “through fabric of the Universe.”

For years, physicists have assumed that Cooper pairs, the electron duos that enable superconductors to conduct electricity without resistance, were two-trick ponies. The pairs either glide freely, creating a superconducting state, or create an insulating state by jamming up within a material, unable to move at all.

But in a new paper published in Science, a team of researchers has shown that Cooper pairs can also conduct electricity with some amount of resistance, like regular metals do. The findings describe an entirely new state of matter, the researchers say, that will require a new theoretical explanation.

“There had been evidence that this metallic state would arise in thin film superconductors as they were cooled down toward their superconducting temperature, but whether or not that state involved Cooper pairs was an open question,” said Jim Valles, a professor of physics at Brown University and the study’s corresponding author. “We’ve developed a technique that enables us to test that question and we showed that, indeed, Cooper pairs are responsible for transporting charge in this metallic state. What’s interesting is that no one is quite sure at a fundamental level how they do that, so this finding will require some more theoretical and experimental work to understand exactly what’s happening.”

Stars explode. But how?

A recent press release asks, “What happens when a star explodes?” The answer, not surprisingly, is, “…the same thing that happens when gas explodes here on Earth.”

The Electric Universe agrees with modern physics: a supernova is an exploding star. However, there is much more to the story that involves plasma. Electricity flowing through plasma creates regions of charge separation isolated by double layers. Could charge separation be the foundation for supernovae?

3D printers are revolutionizing manufacturing by allowing users to create any physical shape they can imagine on-demand. However, most commercial printers are only able to build objects from a single material at a time and inkjet printers that are capable of multimaterial printing are constrained by the physics of droplet formation. Extrusion-based 3D printing allows a broad palette of materials to be printed, but the process is extremely slow. For example, it would take roughly 10 days to build a 3D object roughly one liter in volume at the resolution of a human hair and print speed of 10 cm/s using a single-nozzle, single-material printhead. To build the same object in less than 1 day, one would need to implement a printhead with 16 nozzles printing simultaneously!

Now, a new technique called multimaterial multinozzle 3D (MM3D) printing developed at Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) uses high-speed pressure valves to achieve rapid, continuous, and seamless switching between up to eight different printing materials, enabling the creation of complex shapes in a fraction of the time currently required using printheads that range from a single nozzle to large multinozzle arrays. These 3D printheads themselves are manufactured using 3D printing, enabling their rapid customization and facilitating adoption by others in the fabrication community. Each nozzle is capable of switching materials at up to 50 times per second, which is faster than the eye can see, or about as fast as a hummingbird beats its wings. The research is reported in Nature.

“When printing an object using a conventional extrusion-based 3D printer, the time required to print it scales cubically with the length of the object, because the printing nozzle has to move in three dimensions rather than just one,” said co-first author Mark Skylar-Scott, Ph.D., a Research Associate at the Wyss Institute. “MM3D’s combination of multinozzle arrays with the ability to switch between multiple inks rapidly effectively eliminates the time lost to switching printheads and helps get the scaling law down from cubic to linear, so you can print multimaterial, periodic 3D objects much more quickly.”

Adding energy to any material, such as by heating it, almost always makes its structure less orderly. Ice, for example, with its crystalline structure, melts to become liquid water, with no order at all.

But in new experiments by physicists at MIT and elsewhere, the opposite happens: When a pattern called a charge density wave in a certain material is hit with a fast laser pulse, a whole new charge density wave is created—a highly ordered state, instead of the expected disorder. The surprising finding could help to reveal unseen properties in materials of all kinds.

The discovery is being reported today in the journal Nature Physics, in a paper by MIT professors Nuh Gedik and Pablo Jarillo-Herrero, postdoc Anshul Kogar, graduate student Alfred Zong, and 17 others at MIT, Harvard University, SLAC National Accelerator Laboratory, Stanford University, and Argonne National Laboratory.