Lifeboat Foundation

There’s a common popular science demonstration involving “soap boats,” in which liquid soap poured onto the surface of water creates a propulsive flow driven by gradients in surface tension. But it doesn’t last very long since the soapy surfactants rapidly saturate the water surface, eliminating that surface tension. Using ethanol to create similar “cocktail boats” can significantly extend the effect because the alcohol evaporates rather than saturating the water.

That simple classroom demonstration could also be used to propel tiny robotic devices across liquid surfaces to carry out various environmental or industrial tasks, according to a preprint posted to the physics arXiv. The authors also exploited the so-called “Cheerios effect” as a means of self-assembly to create clusters of tiny ethanol-powered robots.

As previously reported, those who love their Cheerios for breakfast are well acquainted with how those last few tasty little “O” s tend to clump together in the bowl: either drifting to the center or to the outer edges. The “Cheerios effect is found throughout nature, such as in grains of pollen (or, alternatively, mosquito eggs or beetles) floating on top of a pond; small coins floating in a bowl of water; or fire ants clumping together to form life-saving rafts during floods. A 2005 paper in the American Journal of Physics outlined the underlying physics, identifying the culprit as a combination of buoyancy, surface tension, and the so-called ” meniscus effect.”

The Feynman Lectures on Physics, Volume I: https://www.feynmanlectures.caltech.edu/I_toc.html.

“In this chapter, we shall discuss one of the most far-reaching generalizations of the human mind. While we are admiring the human mind, we should take some time off to stand in awe of a nature that could follow with such completeness and generality such an elegantly simple principle as the law of gravitation. What is this law of gravitation? ”

Astrophysicists have recently made a groundbreaking discovery that is sending shockwaves through the scientific community: an immense cluster of dark matter, equivalent to the mass of 10 million suns, is moving closer to our solar system. The mysterious nature of this phenomenon and its potential consequences for Earth have sparked concern and a flurry of research efforts to understand what this means for humanity and the universe itself.

Dark matter — one of the grand enigmas of astrophysics; yet there is no radiation-emission, absorption, reflection-of light. It does make stars and galaxies rotate a lot faster than they ever did before. The only clues scientists have about what 27% of its quantity is in the cosmos versus only 5% by ordinary matter are of itself.

Explained astrophysicist Dr. Lydia Harmon: “Dark matter is like the scaffolding of the universe, holding the galaxies together. Without it, the cosmic structure as we know it wouldn’t exist. But the idea of such a massive concentration headed toward us raises unprecedented questions.”

Thus, when one looks back in time, say by looking at light from a distant galaxy that has traveled billions of years to reach us, this is akin to “zooming out” on the hologram and making its details fuzzier in the process. This zooming out can continue until all the details of the hologram disappear altogether, which in the model of the universe suggested by Hawking and Hertog, would be the origin of time at the Big Bang.

“The crux of our hypothesis is that when you go back in time, to this earliest, violent, unimaginably complicated phase of the universe, in that phase you find a deeper level of evolution, a level in which even the laws of physics co-evolve with the universe that is taking shape,” Hertog said. “And the consequence is that if you push everything even further backward, into the Big Bang, so to speak, even the laws of physics disappear.”

The DESI collaboration’s latest research supports the standard model of gravity and hints at evolving dark energy, based on a detailed analysis of data from millions of galaxies and quasars. These results contribute significantly to understanding the accelerated expansion of the universe.

A physicist from the University of Texas at Dallas, alongside an international team of researchers in the Dark Energy Spectroscopic Instrument (DESI) collaboration, is conducting a multiyear mission to tackle one of astrophysics’ biggest mysteries: Why is the universe’s expansion accelerating?

Scientists have proposed competing theories to explain this phenomenon. One theory suggests that dark energy, an unknown force, is driving galaxies apart. Another theory posits that gravity—the force that binds objects together in local systems like our solar system—behaves differently on vast cosmic scales and may need to be revised to account for the accelerating expansion.

As physicists continue their struggle to find and explain the origin of dark matter, the approximately 80% of the matter in the universe that we can’t see and so far haven’t been able to detect, researchers have now proposed a model where it is produced before the Big Bang.

Their idea is that dark matter would be produced during a infinitesimally short inflationary phase when the size of the universe quickly expanded exponentially. The new model was published in Physical Review Letters by three scientists from Texas in the US.

An intriguing idea among cosmologists is that dark matter was produced through its interaction with a thermal bath of some species, and its abundance is created by “freeze-out” or “freeze-in.” In the freeze-out scenario, dark matter is in chemical equilibrium with the bath at the earliest times—the concentration of each does not change with time.

Was dark matter created some time after the Big Bang? Gravitational wave detectors could soon find the answer.

For now, the duo’s results suggest that the Dark Big Bang is far less constrained by past observations than Freese and Winkler originally anticipated. As Ilie explains, their constraints could soon be put to the test.

“We examined two Dark Big Bang scenarios in this newly found parameter space that produce gravitational wave signals in the sensitivity ranges of existing and upcoming surveys,” he says. “In combination with those considered in Freese and Winkler’s paper, these cases could form a benchmark for gravitational wave researchers as they search for evidence of a Dark Big Bang in the early universe.”

Continue reading “Delayed Big Bang for dark matter could be detected in gravitational waves” »

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Is the universe really infinite? Or could it close back on itself like a sphere? If it’s infinite, how can it expand? And is it true that there might be copies of you in it? Today I want to explain how much we know about those questions and what the expansion of space has to do with Hilbert’s Hotel.

Continue reading “Is the Universe Infinite or Finite?” »

The fabric of space and time is not exempt from the effects of gravity. Plop in a mass and space-time curves around it, not dissimilar to what happens when you put a bowling ball on a trampoline.

This dimple in space-time is the result of what we call a gravity well, and it was first described over 100 years ago by Albert Einstein’s field equations in his theory of general relativity. To this day, those equations have held up. We’d love to know what Einstein was putting in his soup. Whatever it was, general relativity has remained pretty solid.

Continue reading “Physicists Just Found a Quirk in Einstein’s Predictions of Space-Time” »