#physics

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Had to convince the language editor of my paper that "resting mass energy" is not equivalent to "rest-mass energy", it was tough.

[I mean: the language editor wanted to replace all "my" rest-mass energy with resting mass energy, and so I had to ask them to replace everything with the only possible formulation which was originally there..]

Measuring Mucus by Dragging Dead Fish

A fish‘s mucus layer is critical; it protects from pathogens, reduces drag in the water, and, in some cases, protects against predators. But little is known about how mucus could affect terrestrial locomotion in species like the northern snakehead, which can breathe out of the water and move across land. So researchers explored the snakehead’s mucus layer by measuring the force required to drag them (and two other non-terrestrial species) across different surfaces.

The team tested the same, freshly euthanized fish twice: once with its mucus layer intact and again once the mucus was washed off. Unsurprisingly, the fish’s friction was much lower with its mucus. But they also found that the snakehead was slipperier than either the scaled carp or the scale-free catfish. The biologists suggest that the snakehead could have evolved a slipperier mucus to help it move more easily …

A researcher prepares to drag a dead northern snakehead across artificial turf.

Reclaiming the Land

Lava floods human-made infrastructure on Iceland’s Reykjanes peninsula in this aerial image from photographer Ael Kermarec. Protecting roads and buildings from lava flows is a formidable challenge, but it’s one that researchers are tackling. But the larger and faster the lava flow, the harder infrastructure is to protect. Sometimes our best efforts are simply overwhelmed by nature’s power. (Image credit: A. Kermarec/WNPA; via Colossal)

Aerial view of lava overflowing a road and the surrounding landscape in Iceland.

It's the time of the year in which I challenge my students of in engineering in producing a "tomato battery", i.e. to reproduce on stage the basic functioning principle of a galvanic cell: a pair of suitable metals, an acid solution, and some connecting wires.

"one tomato" battery is not enough to generate the 1.5V tension needed for the small digital clock, so they have to realise a serie of two tomato batteries is needed.

🏆 Poster Prize at the LIGO Virgo KAGRA Collaboration Meeting 🏆

🎉 Congratulations to our colleague Lorenzo Pompili! Lorenzo is a PhD student in the “Astrophysical and Cosmological Relativity” department at @mpi_grav in Potsdam. Last week he won the prize for the best poster in the “Theory” category at the March 2025 meeting of the @LIGO Virgo KAGRA collaboration in Melbourne, Australia.

His poster presented new tests of Einstein's general theory of relativity using gravitational waves from the final stage of a binary black hole merger. During this “ringdown”, the black hole settles into its final post-merger configuration and emits gravitational waves at specific frequencies.

If Einstein's theory is correct, these frequencies depend only on the black hole's mass and spin. By measuring the frequencies, it is possible to test for deviations from Einstein's theory.

Sharepic with a picture of the prize winner and his poster.
Sharepic with a picture of the prize winner and his poster.