Month: December 2020

Enlarge / The secret to a stable sandcastle primarily lies in the right proportion of water to sand. Mathematically, the forces at play are described by the "Kelvin equation," first referenced in 1871. (credit: ac productions/Getty Images)

Building sandcastles at the beach is a time-honored tradition around the world, elevated into an art form in recent years thanks to hundreds of annual competitions. While the basic underlying physics is well-known, physicists have continued to gain new insights into this fascinating granular material over the last decade or so. The latest breakthrough comes from Nobel Laureate Andre Geim's laboratory at the University of Manchester in England, where Geim and his colleagues have solved a mathematical puzzle—the "Kelvin equation"—dating back 150 years, according to a new paper just published in Nature.

All you really need to make a sandcastle is sand and water; the water acts as a kind of glue holding the grains of sand together via capillary forces. Studies have shown that the ideal ratio for building a structurally sound sandcastle is one pail of water for every eight pails of sand, although it's still possible to build a decent structure with varying water content. But if you want to build the kind of elaborate, towering sandcastles that win competitions, you'd be wise to stick with that ideal ratio.

Back in 2008, physicists decided to delve a little deeper into why sand becomes sticky when it gets wet. Using x-ray microtomography, they took 3D images of wet glass beads of similar shape and size as grains of sand. When they added liquid to dry beads, they observed liquid "capillary bridges" forming between individual beads. Adding more liquid caused the bridges to grow larger, and as that happened, the bead surfaces came into contact with more water, further increasing the binding effect. However, the increased binding effect was canceled out by a corresponding decrease of the capillary forces as the bridge structures grew bigger. The team concluded that even if the moisture content changes, the forces binding the beads together do not change.

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  The Sun glints around the lower fin of Starship SN8 on Dec. 9, 2020. [credit: Trevor Mahlmann ]

Original story 12:45pm EST: SpaceX is readying its Starship prototype vehicle for a second launch attempt on Wednesday afternoon from its South Texas Launch Site. The launch window extends until 5pm local time (23:00 UTC), and sources suggested any liftoff would occur no earlier than 2pm local time.

The company got very close to launching the "SN8" prototype on Tuesday evening before the attempt automatically aborted with just 1.3 seconds left in the countdown. It is not clear what caused the last-second scrub—perhaps a pressure or temperature reading just outside of acceptable levels—but SpaceX engineers appear to have addressed the issue.

The weather at the coastal launch site remains nearly perfect on Wednesday, with light winds and clear skies. Should a technical issue arise again, there are additional opportunities on Thursday and Friday. However, the South Texas weather will be much more windy on those days, perhaps too much for a flight.

Enlarge / Margaret Keenan, 90, who was the first patient in the United Kingdom to receive the first of two doses of the Pfizer-BioNTech COVID-19 vaccine, reacts as she talks with healthcare assistant Lorraine Hill, while preparing to leave University Hospital Coventry, in Coventry on December 9, 2020, a day after receiving the vaccine. (credit: Johnny Weeks | Getty Images)

People with a significant history of allergies should not receive the Pfizer/BioNTech coronavirus vaccine, the UK medical regulator has said after two NHS staff experienced an adverse reaction.

June Raine, chief executive for the Medicines and Healthcare products Regulatory Agency (MHRA), told a UK parliamentary committee that the two individuals had the allergic reaction shortly after receiving the vaccine and that the regulator was investigating. Both people had a history of serious allergies and carried adrenalin pens.

“We know from the very extensive clinical trials that this wasn’t a feature but if we need to strengthen our advice... we get that advice to the field immediately,” Dr. Raine said.

Enlarge / This demonstration of Microsoft's Project xCloud as played with a Razer Kishi controller, attached to a standard Android smartphone, could be a hint of what's to come to iOS devices in spring of 2021. (credit: Microsoft)

In a blog post today outlining everything from upcoming games to plans for Xbox Series X/S, Microsoft announced that Xbox cloud gaming will come to iOS mobile devices and Windows PCs in spring of 2021.

On Windows PCs, the games will stream through the Xbox app or a Web browser, whereas the service will be limited to the mobile Web browser on iOS devices.

Microsoft's game-streaming features require an Xbox Game Pass Ultimate subscription, which also includes an on-demand library of downloadable games for both Xbox platforms and Windows PCs, the EA Play downloadable game library, and Xbox Live Gold, Microsoft's online multiplayer service.

Enlarge (credit: Tasos Katopodis/Getty Images)

For the last month, President Donald Trump and his allies have tried to cast doubt on President-elect Joe Biden's victory in the presidential election. However, they've failed to produce evidence of irregularities in Pennsylvania, Michigan, Georgia, or other states sufficient to overcome Biden's substantial lead in the electoral college. Now YouTube says it has had enough.

"We will start removing any piece of content uploaded today (or anytime after) that misleads people by alleging that widespread fraud or errors changed the outcome of the 2020 US Presidential election," the Google-owned service announced.

YouTube acknowledged that it had previously allowed the airing of "controversial views on the outcome or process of counting votes of a current election as election officials have worked to finalize counts." But now that most of Trump's legal challenges have been thrown out of court, YouTube says that the legitimacy of Biden's election is no longer up for debate.