Gravitons, the particles thought to carry gravity, have never been seen in space – but something very similar has been detected in a semiconductor.
Physicists have been searching for gravitons, the hypothetical particles thought to carry gravity, for decades. These have never been detected in space, but graviton-like particles have now been seen in a semiconductor. Using these to understand gravitons’ behaviour could help unite the general theory of relativity and quantum mechanics, which have long been at odds.
“This is a needle in a haystack [finding]. And the paper that started this whole thing is from way back in 1993,” says Loren Pfeiffer at Princeton University. He wrote that paper with several colleagues including Aron Pinczuk, who passed away in 2022 before they could find hints of the elusive particles. READ MORE...
A 13-sided tile called “the hat” forms a pattern that covers an infinite plane yet it cannot repeat, making it a long-sought shape known as an “einstein.” A sample of that pattern is shown here.
D. SMITH, J.S. MYERS, C.S. KAPLAN AND C. GOODMAN-STRAUSS (CC BY 4.0)A 13-sided shape known as “the hat” has mathematicians tipping their caps.It’s the first true example of an “einstein,” a single shape that forms a special tiling of a plane: Like bathroom floor tile, it can cover an entire surface with no gaps or overlaps but only with a pattern that never repeats.“Everybody is astonished and is delighted, both,” says mathematician Marjorie Senechal of Smith College in Northampton, Mass., who was not involved with the discovery. Mathematicians had been searching for such a shape for half a century. “It wasn’t even clear that such a thing could exist,” Senechal says.Although the name “einstein” conjures up the iconic physicist, it comes from the German ein Stein, meaning “one stone,” referring to the single tile. The einstein sits in a weird purgatory between order and disorder. Though the tiles fit neatly together and can cover an infinite plane, they are aperiodic, meaning they can’t form a pattern that repeats.With a periodic pattern, it’s possible to shift the tiles over and have them match up perfectly with their previous arrangement. An infinite checkerboard, for example, looks just the same if you slide the rows over by two. While it’s possible to arrange other single tiles in patterns that are not periodic, the hat is special because there’s no way it can create a periodic pattern. READ MORE...
MEXICO CITY, Nov 3 (Reuters) - The most historic legacy of President Andres Manuel Lopez Obrador, a left-leaning resource nationalist who casts his administration as a turning point in the annals of Mexico, may be to pave the way for the country's first woman leader.
Mexico City Mayor Claudia Sheinbaum, a 60-year-old physicist, environmentalist and longstanding ally of Lopez Obrador who has governed as mayor in tandem with his presidency, has emerged as early front-runner to be his party's candidate in 2024, despite hints she could be more moderate than him. READ MORE...
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A conjecture called superdeterminism, outlined decades ago, is a response to several peculiarities of quantum mechanics: the apparent randomness of quantum events; their apparent dependence on human observation, or measurement; and the apparent ability of a measurement in one place to determine, instantly, the outcome of a measurement elsewhere, an effect called nonlocality.
Einstein, who derided nonlocality as “spooky action at a distance,” insisted that quantum mechanics must be incomplete; there must be hidden variables that the theory overlooks. Superdeterminism is a radical hidden-variables theory proposed by physicist John Bell. He is renowned for a 1964 theorem, now named after him, that dramatically exposes the nonlocality of quantum mechanics.
Bell said in a BBC interview in 1985 that the puzzle of nonlocality vanishes if you assume that “the world is superdeterministic, with not just inanimate nature running on behind-the-scenes clockwork, but with our behavior, including our belief that we are free to choose to do one experiment rather than another, absolutely predetermined.”
In a recent video, physicist Sabine Hossenfelder, whose work I admire, notes that superdeterminism eliminates the apparent randomness of quantum mechanics. “In quantum mechanics,” she explains, “we can only predict probabilities for measurement outcomes, rather than the measurement outcomes themselves. The outcomes are not determined, so quantum mechanics is indeterministic. Superdeterminism returns us to determinism.”
“The reason we can’t predict the outcome of a quantum measurement,” she explains, “is that we are missing information,” that is, hidden variables. Superdeterminism, she notes, gets rid of the measurement problem and nonlocality as well as randomness. Hidden variables determine in advance how physicists carry out the experiments; physicists might think they are choosing one option over another, but they aren’t. Hossenfelder calls free will “logically incoherent nonsense.”
Hossenfelder predicts that physicists might be able to confirm superdeterminism experimentally. “At some point,” she says, “it’ll just become obvious that measurement outcomes are actually much more predictable than quantum mechanics says. Indeed, maybe someone already has the data, they just haven’t analyzed it the right way.” Hossenfelder defends superdeterminism in more detail in a technical paper written with physicist Tim Palmer.
AUTHOR - John Horgan directs the Center for Science Writings at the Stevens Institute of Technology. His books include The End of Science, The End of War and Mind-Body Problems, available for free at mindbodyproblems.com. For many years he wrote the popular blog Cross Check for Scientific American.
Scientists have observed a stunning demonstration of classic physics giving way to quantum behavior, manipulating a fluid of ultra-cold sodium atoms into a distinct tornado-like formation.
Particles behave differently on the quantum level, in part because at this point their interactions with each other hold more power over them than the energy from their movement.
Then, of course, there's the mind-boggling fact that quantum particles don't exactly have a certain fixed location like you or I, which influences how they interact.
By cooling particles down to as close to absolute zero as possible and eliminating other interference, physicists can observe what happens when these strange interactions take hold, as a team from MIT has just done.
"It's a breakthrough to be able to see these quantum effects directly," says MIT physicist Martin Zwierlein.
The team trapped and spun a cloud of around 1 million sodium atoms using lasers and electromagnets. In previous research physicists demonstrated this would spin the cloud into a long needle-like structure, a Bose-Einstein condensate, where the gas starts to behave like a single entity with shared properties.
"In a classical fluid, like cigarette smoke, it would just keep getting thinner," says Zwierlein. "But in the quantum world, a fluid reaches a limit to how thin it can get."
In the new study, MIT physicist Biswaroop Mukherjee and colleagues pushed beyond this stage, capturing a series of absorption images that reveal what happens after atoms' have switched from being predominantly governed by classical to quantum physics. READ MORE...
