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A new study of the Gobi Wall in the Gobi highland desert of Mongolia reveals a multifunctional role beyond defense; data from the James Webb Space Telescope is bringing physicists closer to resolving the Hubble tension; and a U.S.-based team of astronomers stumbled on a new dwarf planet in the outer solar system while searching for Planet Nine.

Additionally, researchers found that within a socioeconomic system based on private ownership of the means of production, workers need to be paid, challenging long-held notions of plutocrats. Teeth—the very ones in your head—may have evolved from the sensory odontodes of marine life. And a Japanese research team hopes to resolve the mystery of dark matter by searching for primordial black holes:

Incentives required

A researcher at the Norwegian University of Science and Technology reports that countries with the lowest minimum wages tend to compel workers to choose unemployment benefits over working. Economically, it's beneficial for countries to ensure that working is more attractive than benefits, and in many countries with both low minimum wage and low unemployment benefits, workers may decide that employment isn't worth it.

"The work incentive principle no longer works when both the minimum wage and welfare benefits are so low that the financial return from both approaches is close to the subsistence level," author Roberto Iacono said. This is the welfare-versus-work paradox; the only way to prevent it is to ensure that the minimum wage always remains above the subsistence threshold.

Ow, my crab nodes!

What types of pain can you endure? Most people experience muscle pain from exertion, the occasional headache, joint pain, and maybe abdominal discomfort from suboptimal eating choices. But basically anyone who develops a toothache transforms into a highly motivated, dentistry-seeking automaton. It's one of the least endurable types of pain, and an international team of researchers reported this week on its evolutionary origins.

Researchers believe the evolutionary precursors of teeth are odontodes, hard tissue structures that comprised the armor of marine organisms starting around 500 million years ago. In the new study, the researchers explored the hypothesis that odontodes were originally used as sensory organs.

Researcher Yara Haridy at the University of Chicago was trying to determine the oldest species to develop a backbone. While examining vertebrate specimens, she began focusing on dentin, the calcified tissue that sends sensory information to nerves in the pulp. A fossil from the Cambrian period had exoskeletal tubules beneath its odontodes that may once have contained dentin.

Comparison with other species suggested that these tubules resembled sensilla, sensory organs of arthropods. These have features that have changed little over time, and the study's upshot is that the teeth of modern organisms could have evolved over time from the odontodes of marine precursors.

Very old holes

To settle a debate about the nature of cold dark matter, researchers in Japan have proposed a search for primordial black holes by studying gravitational waves. The leading candidates for cold dark matter are sterile neutrinos, weakly interacting massive particles, and axions. But physicists have proposed that primordial black holes could account for the missing matter in the universe.

Theorized primordial black holes would have formed during the first seconds after the Big Bang from dense agglomerations of subatomic particles. Over time, they are believed to evaporate via Hawking radiation, and the only remaining primordial black holes would have to weigh trillions of kilograms.

However, there's a theoretical phenomenon called the memory burden effect, discovered in 2018, in which the load of information contained in a black hole stabilizes it against evaporation; thus, PBHs may still occupy the modern universe and could be the source of currently unexplained gravitational effects.

Future gravitational wave observatories, like the Laser Interferometer Space Antenna, could detect the expected wave frequency spectra to confirm or disconfirm the existence of primordial black holes; finding them could revolutionize physics.

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