Uncategorized
- Math
Buffon’s Needling Ants
The classic probability experiment known as Buffon’s needle produces a statistical estimate of the value of pi, the ratio of a circle’s circumference to its diameter. The experiment consists of randomly dropping a needle over and over again onto a wooden floor made up of parallel planks. If the needle’s length is no greater than […]
- Math
Buffon’s Needling Ants
The classic probability experiment known as Buffon’s needle produces a statistical estimate of the value of pi, the ratio of a circle’s circumference to its diameter. The experiment consists of randomly dropping a needle over and over again onto a wooden floor made up of parallel planks. If the needle’s length is no greater than […]
- Math
Tetris Is Hard
As many computer- and video-game players have long known, the insanely addictive, immensely popular game of Tetris is tough. You can’t really win; you merely try your best to improve upon previous results. The seven tetrominoes of Tetris. The game was invented in 1985 by mathematician Alexey Pajitnov, then a computer engineer at the Academy […]
- Math
Tetris Is Hard
As many computer- and video-game players have long known, the insanely addictive, immensely popular game of Tetris is tough. You can’t really win; you merely try your best to improve upon previous results. The seven tetrominoes of Tetris. The game was invented in 1985 by mathematician Alexey Pajitnov, then a computer engineer at the Academy […]
- Animals
Upside Way Down: Video turns fish story on its head
The first video of whipnose anglerfish reveals them swimming upside down and trolling for prey on the 5,000-meter deep ocean floor.
- Health & Medicine
Blood Booster: Growth signal shifts cord stem cells into high gear
A protein called Delta-1 stimulates stem cells in umbilical cord blood to proliferate in a lab dish, attach well to bone marrow when implanted into mice, and even proceed to the animal's thymus to become T cells.
- Earth
Air-Pollution Pileup: Mediterranean endures emissions from afar
Although most Mediterranean countries aren't big polluters, the area is a crossroads for pollution-carrying air currents from Europe, Asia, and North America.
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Outmuscled: Muscles, not nerve cells, fail in old worms
In aging worms, the nervous system stays intact but muscles don't.
- Astronomy
Cloudy Findings: A new population shows up in the Milky Way
A radio telescope has detected a previously unknown population of hundreds of hydrogen clouds in the gaseous halo that surrounds the disk of our galaxy.
- Anthropology
Ancient Lure of the Lakes: Early Americans followed the water
Archaeological investigations in Chile indicate that beginning around 13,000 years ago, early American settlers lived at high altitudes during humid periods, when they could set up hunting camps on the shores of lakes.
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19147
I am concerned about this article. It addresses the mass of fissile materials needed to “make a bomb,” yet it’s clear that the critical masses given–10 kilograms for plutonium-239, 50 kg for uranium-235, and 60 kg for neptunium-237–are for bare spheres with no neutron moderation, reflection, or other factors contributing to going critical. Consider that […]
- Physics
Neptunium Nukes? Little-studied metal goes critical
Researchers have measured with far greater accuracy than ever before how much neptunium it would take to make a bomb.
