Month: June 2021

Enlarge / Experiments by Chinese physicists have shed further light on the intricate physics involving in skipping a stone across the water's surface. Their findings revealed key factors that could influence spaceflight water landings after re-entry. (credit: Colin Anderson Productions / Getty Images)

Learning how to skip stones across a lake or pond is a time-honored childhood tradition. The underlying physics of skipping stones could also be a useful model for landing aircraft or spacecraft on water, according to a recent paper published in the journal Physics of Fluids. Chinese physicists have built just such a model, and they used it to further clarify the key determining factors behind how many times a stone (or spacecraft) will bounce upon hitting the water.

Skipping stones is just the sort of natural everyday phenomenon that would fascinate physicists, even though at first glance the basic concepts seem simple. It all comes down to spin, speed, shape of the stone, and angle. As the stone hits the water, the force of impact pushes some of the water down, so the stone, in turn, is forced upwards. If the stone is traveling fast enough to meet a minimum velocity threshold, the stone will bounce; if not, it will sink. A round, flat stone is best, simply because its surface area displaces more water as it skips.

Experiments in 2004 by French physicists Lyderic Bocquet and Christophe Clanet demonstrated as much. They built a catapult device to toss aluminum disks at a tank of water and then recorded the splashes with high-speed video. They learned that the bouncing stone must be spinning at a minimal rate of rotation (at least once during its collision time) in order to be stable. In other words, a skipping stone relies on the gyroscopic effect, in which a body rotating around its own axis tends to maintain its own direction. (It's also what stops a spinning top from tipping over.) Experienced stone-skippers typically apply this rotation to the stone with a simple flick of the finger.

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  Everything you get when you buy the new release of Dune (1984). [credit: Arrow Films ]

The controversial yet memorable 1984 film adaptation of Frank Herbert's seminal 1965 science fiction novel Dune will be released in 4K and HDR for the first time on August 31, thanks to a new 4K UltraHD Blu-ray set from distributor Arrow Films.

According to Arrow Films, the upcoming release was mastered from the original camera negative in 4K and Dolby Vision HDR, though playback in the HDR-10 format is also supported. The set offers two audio options: uncompressed stereo and DTS-HD 5.1 surround sound.

There's one thing genre cinephiles might be hoping for that they won't get here, though: commentary from filmmaker David Lynch, who directed the film and became famous for later works like Twin Peaks and Blue Velvet. Those familiar with the film's history won't be surprised by that omission though; Lynch disowned Dune when it was released, saying that it did not represent his creative vision due to interference from the studio.

Enlarge (credit: Matthew Stockman / Getty Images)

A ransomware attack has struck the world’s biggest meat producer, causing it to halt some operations in the US, Canada, and Australia while threatening shortages throughout the world, including up to a fifth of the American supply.

Brazil-based JBS SA said on Monday that it was the target of an organized cyberattack that had affected servers supporting North American and Australian IT operations. A White House spokeswoman later said the meat producer had been hit by a ransomware attack “from a criminal organization likely based in Russia” and that the FBI was investigating.

Existential threat

The weekend attack came three weeks after a separate ransomware attack on Colonial Pipeline disrupted the availability of gasoline and jet fuel up and down the US East Coast. Late last year, ransomware attacks on hospitals hamstrung their ability to provide emergency services just as the coronavirus was already straining their capacity.

Enlarge (credit: Getty Images | s-cphoto)

Trade groups representing Facebook, Twitter, and other major websites have sued Florida to block a state law that makes it illegal for social media companies to ban politicians. The industry groups say the law violates the First Amendment—and legal experts have said the same, as we've previously written.

Florida Gov. Ron DeSantis signed the bill into law on May 24, slamming what he called the "censorship" of conservatives on social media websites such as Twitter and Facebook. The law, scheduled to take effect on July 1, gives Floridians the right to sue Big Tech companies over content-moderation decisions and prohibits the companies from "deplatforming" political candidates and journalistic enterprises. The law imposes fines of up to $250,000 per day on social media companies that ban candidates for elected office.

The lawsuit against Florida was filed by Netchoice and the Computer & Communications Industry Association (CCIA). Facebook, Twitter, Amazon, Google, and eBay are members of both groups.

Enlarge / Xiaomi's charging demo. That's a wattage meter on the left. (credit: Xiaomi)

Xiaomi has just showed off a new high mark for smartphone charging: a 200 W charging system. The company demoed "Xiaomi HyperCharge" in a new Twitter video this weekend, saying that the new tech can rocket a phone from empty to full in eight minutes. That's about as long as a trip to the gas station.

These quick-charging systems don't provide a continuous charge rate, but Xiaomi was nice enough to hook its new charger up to an electricity usage monitor so we can see what's happening. The phone charges to 10 percent in just 44 seconds, then quickly ramps up to 200 W. The phone achieves a 50 percent charge in a ridiculous three minutes. Next, the phone slowly ramps the power down, dropping to 150 W and hitting 75 percent charge in five-and-a-half minutes. Finally, the system ramps down to 40 W on its way to a full charge at eight minutes.

Behavior like this—gently topping off the battery for the last part of the charge cycle—is meant to protect battery longevity, and it is part of the reason there's no evidence that fast charging degrades your battery more quickly than regular charging.