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Physicists determine the optimal soap recipe for blowing gigantic bubbles



Enlarge / Physicist Justin Burton (left) experiments with giant soap bubbles on Emory University’s Quad with graduate student Stephen Frazier.

Everybody loves bubbles, regardless of age—the bigger the better. But to blow really big, world-record-scale bubbles requires a very precise bubble mixture. Physicists have determined that a key ingredient is mixing in polymers of varying strand lengths, according to a new paper in Physical Review Fluids. That produces a soap film able to stretch sufficiently thin to make a giant bubble without breaking.

Bubbles may seem frivolous, but there is some complex underlying physics, and hence their study has long been serious science. In the 1800s, Belgian physicist Joseph Plateau outlined four basic laws of surface tension that determine the structure of soapy films. Surface tension is why bubbles are round; that shape has the least surface area for a given volume, so it requires the least energy to maintain. Over time, that shape will start to look more like a soccer ball than a perfect sphere as gravity pulls the liquid downward (“coarsening”).

Bubbles and foams remain an active area of research. For instance, in 2016, French physicists worked out a theoretical model for the exact mechanism for how soap bubbles form when jets of air hit a soapy film. They found that bubbles only formed above a certain speed, which in turn depends on the width of the jet of air. If the jet is wide, there will be a lower threshold for forming bubbles, and those bubbles will be larger than ones produced by narrower jets, which have higher speed thresholds. That’s what’s happening, physics-wise, when we blow bubbles through a little plastic wand: the jet forms at our lips and is wider than the soapy film suspended within the wand.

In 2018, we reported on how mathematicians at New York University’s Applied Math Lab had fine-tuned the method for blowing the perfect bubble even further based on similar experiments with soapy thin films. They concluded that it’s best to use a circular wand with a 1.5-inch perimeter and gently blow at a consistent 6.9cm/s. Blow at higher speeds and the bubble will burst. Use a smaller or larger wand, and the same thing will happen.

But what about blowing gigantic bubbles or long, thin soap films that can span two stories? Justin Burton, co-author of the latest paper and a physicist at Emory University specializing in fluid dynamics, first got intrigued by the topic at a conference in Barcelona. He saw street performers producing giant bubbles about the diameter of a hula hoop and as long as a car.

He was especially intrigued by the shifting rainbow of colors on the bubbles’ surface. This effect is due to interference patterns created when light reflects off the two surfaces of the film. For Burton, this was also an indication that the thickness of the soap was just a few microns, roughly equivalent to the wavelength of light. He was surprised that a soap film could remain intact when stretched so thin into a giant bubble and started doing his own experiments, both in the lab and his own backyard.

While perusing the open access Soap Bubble Wiki, he noticed that most of the favored recipes for bubble solution included a polymer—usually natural guar (a common thickening food additive) or a medical lubricant (polyethylene glycol).

Using those recipes as a guide, “We basically started making bubbles and popping them, and recorded the speed and dynamics of that process,” said Burton. “Focusing on a fluid at its most violent moments can tell you a lot about its underlying physics.”

The ultimate goal was to determine the perfect proportions for a bubble mixture to produce gigantic bubbles: something with a bit of stretch, but not too much, where the fluid flows a little, but not too much—in other words, the Goldilocks of bubble mixtures.

As Lissie Connors writes at Physics Buzz:

For their experiment, the researchers created various mixes of water, soap, and long-chain polymers to make their bubbles. Unfortunately, blowing a 100 m3 bubble is a poor use of lab space, and quite difficult to measure accurately, so the soap films were created using a cotton string, and the thickness was measured using infrared light. In addition to measuring the thickness, they also tracked the lifetime of each film.

Burton and his team concluded that it was the polymeric strands that were the key to producing giant bubbles, confirming the collective online wisdom. “The polymer strands become entangled, something like a hairball, forming longer strands that don’t want to break apart,” said Burton. “In the right combination, a polymer allows a soap film to reach a ‘sweet spot’ that’s viscous but also stretchy—just not so stretchy that it rips apart.”

The team also found that varying the length of the polymer strands resulted in a sturdier soap film. “Polymers of different sizes become even more entangled than single-sized polymers, strengthening the elasticity of the film,” said Burton. “That’s a fundamental physics discovery.”

You can find Burton’s giant bubble recipe in the sidebar. But be forewarned: there are some factors that can’t be controlled in a real-world setting (as opposed to Burton’s laboratory environment), like humidity levels.

DOI: Physical Review Fluids, 2020. 10.1103/PhysRevFluids.5.013304 (About DOIs).

Physics secrets of giant soap bubbles.

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Facebook’s new AI teaches itself to see with less human help



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Most artificial intelligence is still built on a foundation of human toil. Peer inside an AI algorithm and you’ll find something constructed using data that was curated and labeled by an army of human workers.

Now, Facebook has shown how some AI algorithms can learn to do useful work with far less human help. The company built an algorithm that learned to recognize objects in images with little help from labels.

The Facebook algorithm, called Seer (for SElf-supERvised), fed on more than a billion images scraped from Instagram, deciding for itself which objects look alike. Images with whiskers, fur, and pointy ears, for example, were collected into one pile. Then the algorithm was given a small number of labeled images, including some labeled “cats.” It was then able to recognize images as well as an algorithm trained using thousands of labeled examples of each object.

“The results are impressive,” says Olga Russakovsky, an assistant professor at Princeton University who specializes in AI and computer vision. “Getting self-supervised learning to work is very challenging, and breakthroughs in this space have important downstream consequences for improved visual recognition.”

Russakovsky says it is notable that the Instagram images were not hand-picked to make independent learning easier.

The Facebook research is a landmark for an AI approach known as “self-supervised learning,” says Facebook’s chief scientist, Yann LeCun.

LeCun pioneered the machine learning approach known as deep learning that involves feeding data to large artificial neural networks. Roughly a decade ago, deep learning emerged as a better way to program machines to do all sorts of useful things, such as image classification and speech recognition.

But LeCun says the conventional approach, which requires “training” an algorithm by feeding it lots of labeled data, simply won’t scale. “I’ve been advocating for this whole idea of self-supervised learning for quite a while,” he says. “Long term, progress in AI will come from programs that just watch videos all day and learn like a baby.”

LeCun says self-supervised learning could have many useful applications, for instance learning to read medical images without the need for labeling so many scans and x-rays. He says a similar approach is already being used to auto-generate hashtags for Instagram images. And he says the Seer technology could be used at Facebook to match ads to posts or to help filter out undesirable content.

The Facebook research builds upon steady progress in tweaking deep learning algorithms to make them more efficient and effective. Self-supervised learning previously has been used to translate text from one language to another, but it has been more difficult to apply to images than words. LeCun says the research team developed a new way for algorithms to learn to recognize images even when one part of the image has been altered.

Facebook will release some of the technology behind Seer but not the algorithm itself because it was trained using Instagram users’ data.

Aude Oliva, who leads MIT’s Computational Perception and Cognition lab, says the approach “will allow us to take on more ambitious visual recognition tasks.” But Oliva says the sheer size and complexity of cutting-edge AI algorithms like Seer, which can have billions or trillions of neural connections or parameters—many more than a conventional image-recognition algorithm with comparable performance—also poses problems. Such algorithms require enormous amounts of computational power, straining the available supply of chips.

Alexei Efros, a professor at UC Berkeley, says the Facebook paper is a good demonstration of an approach that he believes will be important to advancing AI—having machines learn for themselves by using “gargantuan amounts of data.” And as with most progress in AI today, he says, it builds upon a series of other advances that emerged from the same team at Facebook as well as other research groups in academia and industry.

This story originally appeared on

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Under intense pressure, WHO skips summary report on coronavirus origin



Enlarge / Liang Wannian (2nd L) and Peter Ben Embarek (3rd R) both members of the WHO-China joint study team, shake hands after the WHO-China joint study press conference in Wuhan, central China’s Hubei Province, on Feb. 9, 2021.

Facing intense international pressure and criticism, the World Health Organization has abandoned plans to release a summary report of its investigation into the possible origin of the pandemic coronavirus, SARS-CoV-2.

Instead, the health agency of the United Nations is skipping the summary report and plans to release a full report the week of March 15. The WHO had previously said it would release a summary report in mid-February.

“By definition, a summary report does not have all the details,” Dr. Ben Embarek, a WHO expert who led the investigation, told The Wall Street Journal. “So since there [is] so much interest in this report, a summary only would not satisfy the curiosity of the readers.”

In a press conference Friday, the executive director of the WHO’s emergencies program, Mike Ryan, echoed the thinking, saying that skipping right to the full report will facilitate discussion given the tremendous demand for the investigation’s findings.

The limited information about the investigation’s findings that has been released so far has already fueled intense criticism and ratcheted up tension between the US and China.

Perilous probe

The investigation was conducted by a team of international researchers and WHO experts between mid-January and early February in Wuhan, China, where the pandemic first mushroomed in December of 2019. The WHO team underwent a 14-day quarantine upon their arrival, then spent about 12 days doing field work around the city.

They visited places such as the infamous Huanan seafood market, where many of the first COVID-19 cases were linked, as well as the hospital where the first patients sought treatment. The team also made a trip to the Wuhan Institute of Virology, which has become the focus of rampant speculation that SARS-CoV-2 escaped from a lab—possibly after it was picked up in the course of research on coronaviruses in bats and/or purposely engineered to infect humans. Though virologists the world over have noted that this explanation is unlikely—a natural spillover event is seen as the most likely origin—they note that it’s impossible to rule it out without more information.

In a press conference from Wuhan on February 9, the WHO team all but said they had, indeed, ruled it out. Embarek called the lab origin hypothesis “extremely unlikely” and suggested there was no need to pursue the idea further. Instead, Embarek supported researchers’ earlier thinking, calling the natural spillover hypothesis the “most likely pathway” SARS-CoV-2 took to humans. Chinese scientists, meanwhile, held up the possibility that the virus was imported into the country via frozen freight—an idea seen as unsupported by data and unlikely by international researchers.

When the WHO team members arrived back in their home countries, their conclusions appeared to soften. In a press briefing, WHO Director-General Dr. Tedros Adhanom Ghebreyesus seemed to walk back Embarek’s earlier comments on the lab origin hypothesis. “Some questions have been raised as to whether some hypotheses have been discarded,” Tedros said. “Having spoken with some members of the team, I wish to confirm that all hypotheses remain open and require further analysis and studies. Some of that work may lie outside the remit and scope of this mission.”

“Deep concerns”

Other scientists and experts criticized the investigation and the comments, saying that the team was not given the necessary unfettered access to critical places and data to come to any conclusions. One of the team’s own members bolstered that criticism. In media interviews, WHO investigation team member Dominic Dwyer reported that Chinese officials withheld key raw data that the team requested on the very first COVID-19 cases identified in Wuhan.

US officials have also expressed skepticism of the integrity of WHO’s investigation. In a February 13 statement, National Security Adviser Jake Sullivan said, “We have deep concerns about the way in which the early findings of the COVID-19 investigation were communicated and questions about the process used to reach them. It is imperative that this report be independent, with expert findings free from intervention or alteration by the Chinese government.”

Likewise, in an interview on PBS this week, Secretary of State Antony Blinken said that “China has not been fully and effectively transparent either at the start of this crisis, when it mattered most, or even today as investigations are going forward trying to get to the bottom of what happened.”

In final comments in the press conference Friday, Tedros responded to the calls for transparency, saying that everything that happened during the team’s trip to Wuhan will be presented in full in the forthcoming report.

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Rocket Report: SpaceX explains landing failure, More on New Glenn delays



Enlarge / In mid-February a Falcon 9 launch was successful, but the first stage failed to land.


Welcome to Edition 3.35 of the Rocket Report! There is an incredible amount of launch news this week, but I want to start with this: my new book on the origins of SpaceX, Liftoff: Elon Musk and the Desperate Early Days That Launched SpaceX, was published this week. Early reviews have been tremendous, and if you’re at all interested in the company, or just want a rollicking story, please check it out.

As always, we welcome reader submissions, and if you don’t want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Rocket Lab unveils plans for larger rocket. This week, the US rocket company said it had plans to go public, as well as develop a “Neutron” rocket capable of launching as much as 8 tons to low Earth orbit. “Rocket Lab solved small launch with Electron. Now we’re unlocking a new category with Neutron,” said Peter Beck, Rocket Lab founder and CEO, in a news release. The company plans an initial launch in 2024 but is only now beginning work on a new engine.

Another space SPAC … The company also said it planned to go public via a Special Purpose Acquisition Company, with Vector Acquisition Company. The public offering will allow Rocket Lab to raise the funds needed to accelerate its growth plans, including development of the Neutron vehicle. Ars has interviewed Peter Beck about these plans and will go deeper in a forthcoming article. (submitted by EllPeaTea, platykurtic, and Ken the Bin)

NASA awards Mars ascent rocket contract. The space agency has awarded the Mars Ascent Propulsion System contract to Northrop Grumman Systems Corporation as part of its efforts to retrieve rock samples from the surface of Mars. The cost-plus, fixed-fee contract has a potential mission services value of $60.2 million and a maximum potential value of $84.5 million, NASA said.

Much work to do … Coupled with the successful touchdown of the Mars Perseverance rover, this award moves NASA and ESA one step closer to realizing the Mars Sample Return mission. This two-stage rocket will be a critical element in supporting the mission to retrieve and return the samples that the Mars Perseverance rover will collect for return to Earth. There’s still a long way to go, and we shouldn’t expect samples to land on Earth before the end of the 2020. But this is a positive step forward.

The easiest way to keep up with Eric Berger’s space reporting is to sign up for his newsletter, we’ll collect his stories in your inbox.

Astra nabs NASA contracts for TROPICS missions. NASA said it has selected Astra Space to provide launch services for the agency’s Time-Resolved Observations of Precipitation Structure and Storm Intensity with a Constellation of SmallSats, or TROPICS mission. Launches of the constellation of six CubeSats will begin as early as next year.

Eye on the storm … The launch service contract for the TROPICS mission is a firm fixed-price contract valued at $7.95 million, and it will be composed of three separate launches of Astra rockets. The CubeSats will provide rapid-refresh microwave measurements that can be used to determine temperature, pressure, and humidity inside hurricanes as they form and evolve. This is a nice contract win for Astra and will likely bolster the confidence of other potential customers in its launch system. Related: Astra reveals its 100-year plan to SpaceNews. (submitted by Ken the Bin and platykurtic)

India launches its first mission of 2021. On Saturday, the Polar Satellite Launch Vehicle sent Brazil’s Amazonia-1 Earth observation satellite and 18 smaller payloads into orbit. The mission was hailed as the first dedicated commercial mission of NewSpace India Limited, a Government of India company under the Department of Space, SpaceNews reports.

Getting back on track … The launch is India’s first of a 2021, following a 2020 severely impacted by the COVID-19 pandemic. Satish Dhawan Space Center carried out its first (and only) 2020 mission in November with the launch of the EOS-1 Earth observation satellite and nine smaller payloads. India is expected to launch a number of missions in the coming months including the flight of the country’s first geostationary Earth observation satellite. (submitted by platykurtic and Ken the Bin)

SpaceX wins hypersonics heat shield contract. The Air Force Research Laboratory has awarded SpaceX an $8.5 million contract to investigate advanced materials and manufacturing techniques for heat shields that protect hypersonic vehicles in flight, SpaceNews reports. An AFRL spokesman said this was a competitive program with multiple bidders.

Re-entry gets hot … Heat protection is a critical technology to shield hypersonic vehicles from the intense heat experienced when flying at more than five times the speed of sound. SpaceX has previously developed advanced heat-shielding systems to protect the Dragon human spaceflight capsule and its next-generation Starship space exploration vehicle. (submitted by Rendgrish)

Starliner launch slips to indefinite. Recently, NASA announced that it was delaying the launch of Boeing’s Starliner spacecraft, on an Atlas V rocket, from March 25 to April 2. Now, the Orbital Flight Test-2 mission has been delayed again, with no new date set. In a news release, NASA attributed to the delay to “winter storms in Houston and the recent replacement of avionics boxes.” This set the program back about two weeks.

Launch a couple of months away … The winter storms were no picnic (trust me), but power was restored to most homes and businesses that lost electricity after about three days. NASA cited other factors it is weighing in setting a new date, including “the volume of verification and validation analysis required prior to the test flight and the visiting vehicle schedule at the International Space Station.” Sources said the launch was now likely to occur no earlier than late May. (submitted by Ken the Bin)

Relativity Space plans Falcon 9 competitor. Relativity Space, the 3D-printing rocket builder, is making another big bet: developing a fully reusable rocket, designed to match the power and capability of SpaceX’s workhorse Falcon 9 rocket. Called Terran R, the reusable rocket is “really an obvious evolution” from the company’s Terran 1 rocket, Relativity CEO Tim Ellis told CNBC.

Not skipping Terran 1 … “I’ve always been a huge fan of reusability. No matter how you look at it, even with 3D printing, and dropping the cost, and [increasing the] automation of a launch vehicle, making it reusable has got to be part of that future,” Ellis added. The company said it is still committed to developing the smaller Terran 1 rocket, which is scheduled for its first flight later this year. (submitted by gavron and Ken the Bin)

SpaceX updates on Falcon 9 landing failure. On February 16, during its sixth mission to orbit, a Falcon 9 rocket first stage successfully delivered its payload of 60 satellites into low Earth orbit. However the booster then failed to make a safe landing on a drone ship in the Atlantic Ocean.

Watch out for boot holes … This week, during a news conference for the upcoming Crew-2 mission, SpaceX’s Benji Reed provided an update on what happened. A Merlin rocket engine boot developed a hole and sent hot gas to “where it wasn’t supposed to be,” Reed said, and shut down during first stage flight. There was therefore not enough thrust for landing. The company continues to investigate. (submitted by Ken the Bin, platykurtic, and JohnCarter17)

Cape Canaveral assessing launch weather rules. Spaceflight Now has an interesting article this week on the lengths that US Space Force officials are going to work with companies like SpaceX to accommodate their launch windows and cope with weather. This includes strategies to prepare for two different launch windows on a given day to guard against weather delays.

Some fine forecasting … In an interview with the publication, SpaceX advisor Hans Koenigsmann praised the Space Force officials. He said the Space Force’s 45th Weather Squadron, which tracks launch weather conditions at Cape Canaveral, is “absolutely amazing.” “The level of detail that we get is remarkable, how good the forecast is,” Koenigsmann said. “There are launches where we work the entire time with the weather officer and try to find the right time.” All of this is being done to increase the number of launches the Cape can conduct in a given year. (submitted by Ken the Bin)

Next OneWeb launch on track. This week, Roscosmos said the next launch of OneWeb satellites, due to occur later this month, will be the second fully commercial launch from the Vostochny Cosmodrome in eastern Russia. It is being conducted by European launch-service supplier Arianespace for OneWeb, using the Soyuz launch vehicle.

Scrambling to catch up … The satellites have already arrived at the spaceport for integration with the rocket. The mission will add 36 satellites to the existing OneWeb constellation of 110 satellite. OneWeb is seeking to accelerate the implementation of its satellite Internet service as SpaceX continues launching about 120 Starlink internet satellites a month.

Starship makes its third high-altitude test flight. The Starship prototype dubbed SN10 landed this time, after the previous two flights had failed. For about 10 minutes, it stood there. Suddenly, the vehicle briefly rose upward in a violent explosion and crashed back into the pad. This landing was unquestionably a step forward, as SpaceX engineers seem to have figured out the vexing issues with propellant and Raptor relighting that had scuttled the two previous landing attempts.

But is it enough forward progress? … What we don’t know is how NASA will see this, Ars reports. Will it be deemed a positive? Or as a negative, with the third destruction of a Starship in three flights? This matters as the agency gets closer to a down-select next month for its Human Landing System contract that could see billions of dollars flow to SpaceX for its Starship program—or not. NASA may decide to go with more conventional landers under development by teams led by Blue Origin and Dynetics.

NASA vet George Abbey says SLS rocket should be reconsidered. In a policy brief for the Biden administration, Abbey—the former director of Johnson Space Center and an influential, long-time human spaceflight leader—offered an overview of the Space Launch System rocket. The goal of the document was to provide decision-makers “relevant and effective ideas” for supporting to nation’s policy goals.

Launch costs should matter … “In view of the current availability of a significant number of commercial launch vehicles with proven payload capabilities, as well as the industry’s progress in providing a launch vehicle with significantly greater lift capabilities, the Biden administration should reconsider the need for the SLS during its annual budget review,” writes Abbey, who is now a senior fellow in space policy for Rice University.

Some explanation on why New Glenn was delayed. Ars provides a behind-the-scenes report on why New Glenn is now unlikely to launch before 2023 at least. The biggest takeaway is that Blue Origin founder Jeff Bezos made the critical decision to leap directly from New Shepard to New Glenn, without an interim step in between. “It’s like if NASA had gone straight from Alan Shepard to the Saturn V rocket, but then also had to make the Saturn V reusable,” one source noted.

Step-by-step, but not always? … The story also discusses the management style of Bob Smith, who became CEO of Blue Origin in 2017 and has been trying to implement a culture transformation from hobby shop to major aerospace corporation. Some employees have struggled with his leadership style and complained that he has acted too slowly. Another factor in the delay is that Blue Origin simply has higher priorities right now, particularly finishing the BE-4 engine for United Launch Alliance and competing for the Human Landing System contract from NASA.

Next three launches

March 8: Falcon 9 | Starlink-20 | Cape Canaveral, Florida | 03:41 UTC

March 12: Long March 7A | XJY-06 02 | Wenchang Satellite Launch Center, China | 13:34 UTC

March 20: Soyuz 2.1a | Ride-share mission including Astroscale ELSA-d mission | Baikonur Cosmodrome | TBD

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