Does Newton’s law of gravity work when gravity is very weak?

This video takes a look at Newton’s law of gravity that is written in the form F=GMm/r2 and points out that although the law is referred to as a ‘universal’ law of gravity, it does not hold for very strong gravitational forces involving very large masses (where the General Theory of Relativity needs to be used). He also points out that the law has not been tested very precisely in cases where the force is very weak, such as with small masses, but that we assume it holds true in that regime.


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Fun with neodymium magnets

Neodymium magnets are extremely strong, as anyone who has ever handled them knows. This video shows how strong the forces generated by them are. One should be very careful though, because you can hurt yourself and any nearby electronic equipment with these magnets.

One of the practical uses of these magnets is to have cows swallow them. Yes, really. This is because cows often swallow bits of metal (nails bits of wore, staples, etc.) that are in the pastures where they feed and this can harm them. These powerful ‘cow magnets’ settle in a part of the digestive system called the rumen, where they collect the metal pieces that pass by and prevent them from going further into the system and causing harm.

Physics envy of economists

Physics has long been considered the canonical science. It is not the oldest mathematical science, since astronomy predates it by centuries but that discipline lacked an experimental basis. Physics deals with the inanimate world and so is free of the messiness and ethical constraints that complicate other disciplines that deal with living things. It has an empirical basis of observations and experiments and yet has a high level of abstraction that enables simplified models to approximate reality. And the mathematical framework in which its theories are expressed gives its predictions a level of precision and rigor.
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The Libet free will experiment revisited

I have long been interested in the question of free will and back in 2010 even wrote a 16-part series (!) looking into what was known about it. Many people are Cartesian dualists where they view the brain and mind as distinct, the former being a physical organ while the latter is an immaterial entity, dubbed the ‘Ghost in the Machine’ by Gilbert Ryle, that controls the cognitive processes of the former, though how that actually happens has not been made clear.
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Sonic attack? Crickets? Insecticide? Update on the Havana mystery

There is a new twist to the long-running saga about the mysterious ailment that struck personnel working at the American and Canadian embassies in Havana, Cuba. Initially the US accused Cuba of using some kind of sonic weapon to attack their diplomats. But this seemed highly implausible, not least because there did not seem to be any evidence that such a weapon existed and it was not clear why the Cuban government, even if it had such a weapon, would do such a thing at a time when they were trying to improve relations with the US.
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Richard Stallman will not be the last clueless nerd to fall

The fall of computer scientist Richard Stallman, forced to resign his position at MIT because of his apologetics for rape and sexual abuse is now widely known. But Steven Levy says that the entire nerd culture that these people were steeped in that found their eccentricities amusing is also one that made them oblivious from seeing that their views on so many matters were utterly appalling.
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Chess and weight loss

In my history and philosophy of science course, I used to start by asking students whether cheerleading was a sport. This aroused lively discussion because they usually had surprisingly strong feelings for and against this issue. But my real goal was to introduce them to the idea of demarcation criteria, setting up necessary and sufficient conditions that would establish whether some thing X belonged definitely to class A or definitely did not belong to class A. An important and unresolved question in the philosophy of science is the effort to identify necessary and sufficient conditions that would determine whether some theory was scientific or not, and this early exercise on cheerleading was meant to be an introduction to that more abstract question later in the semester.
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Danger to pedestrians is increasing in the US

Kevin Drum looks at data that suggests that being a pedestrian in the US has gotten a lot more dangerous over the past decade, while it has got safer in Europe. Pedestrian fatalities in the US dropped steadily from 6,482 in 1990 to 4,109 in 2009 before growing rapidly to 6,227 in 2018.

Why? He quotes an article that says that the reasons for the steady drop in Europe are design changes in cars that were required to be implemented by manufacturers there 14 years ago but are not as yet required here.

The focus of the new EU standards has been on safer front-end design to minimize injuries to the legs and head in 25 mph crashes. They will require passenger cars and light vans to pass tests involving the A-pillar, bumper, the hood’s leading edge and windshield to determine if they protect adults and children from leg and head injuries in frontal impact accidents. Automakers will also be required to install flexible bumpers and hoods that crumple and to add 8 inches of space between the exterior structure and the under-hood structure from the front bumper to the windshield to better disperse the impact energy of a person hitting the front end. More stringent rules are expected to be phased in beginning in 2010, when the number of tests doubles to four — two for leg injuries and two for head injuries. The changes are expected to save 2,000 lives annually.

But while this could explain the disparity between the US and Europe, it does not explain the recent rise in the US. Are car drivers in the US getting more aggressive and reckless? Is road rage rising? Are drivers and pedestrians getting more distracted?

UPDATE: In the comments Dunc has a helpful comment that takes into account population numbers and vehicle numbers traveled that provide a better measure than the raw fatality numbers in my post. The conclusion of a drop and then a rise does not change.

Utterly revolting treatment of climate scientists by Trump administration

Will Happer has resigned as a member of the Trump administration’s National Security Council. Since Trump never got around to filling the position of Science Advisor to the president, Happer tried to play that role. Happer is one of those physicists who seems to think he is an expert on many things and even though he is not a climate scientist, he was a fierce climate change denialist and had a plan to thwart the scientific consensus on the causes and dangers of global warming by following the playbook that had been adopted by earlier generations of industry-funded skeptics on things like the dangers of smoking, and that was to sow doubt on the scientific consensus.
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