Sudoku

Sudoku (数独, sūdoku?), also known as Number Place, is a logic-based placement puzzle. The aim of the puzzle is to enter a numerical digit from 1 through 9 in each cell of a 9×9 grid made up of 3×3 subgrids (called "regions"), starting with various digits given in some cells (the "givens"); each row, column, and region must contain only one instance of each numeral. Completing the puzzle requires patience and logical ability. Although the puzzle was first published in a U.S. puzzle magazine in 1979, it initially caught on in Japan in 1986 and attained international popularity in 2005.

The name "Sudoku" is the Japanese abbreviation of a longer phrase, "Suuji wa dokushin ni kagiru" , meaning "the digits must remain single". It is a trademark of puzzle publisher Nikoli Co. Ltd. in Japan. In Japanese, the word is pronounced in English, it is usually spoken with an Anglicised pronunciation. Other Japanese publishers refer to the puzzle as Number Place, the original U.S. title, or as "Nanpure" for short. Some non-Japanese publishers spell the title as "Su Doku".

The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are irrelevant. Any set of distinct symbols will do; letters, shapes, or colours may be used without altering the rules (Penny Press' Scramblets and Knight Features Syndicate's Sudoku Word both use letters). Dell Magazines, the puzzle's originator, has been using numerals for Number Place in its magazines since they first published it in 1979. Numerals are used throughout this article.

The attraction of the puzzle is that the rules are simple, yet the line of reasoning required to reach the solution may be complex. Sudoku is recommended by some teachers as an exercise in logical reasoning. The level of difficulty of the puzzles can be selected to suit the audience. The puzzles are often available free from published sources and may also be custom-generated using software.

Sudoku

Sky and Telescope

Did you know you can see a galaxy 2½ million light-years away with your unaided eyes? Craters on the Moon with binoculars? Countless wonders await you any clear night. The first step is simply to look up and ask, "What's that?" When you do, you're taking the first step toward a lifetime of cosmic exploration and enjoyment.

But what, exactly, comes next? Too many newcomers to astronomy get lost in dead ends and quit in frustration. It shouldn't be that way.

What advice would help beginners the most? A while ago, the Sky & Telescope editors got together to brainstorm this question. Pooling thoughts from more than 100 years of collective experience answering the phones and mail, we came up with the following pointers to help newcomers past the most common pitfalls and onto the route to success.

Sky and Telescope

Emerging Technologies and their Impact

Researchers at IBM have overcome an important obstacle to building computers based on carbon nanotubes, by developing a way to selectively arrange transistors that were made using the carbon molecules. The achievement, described in the current issue of Nano Letters, could help make large-scale integrated circuits built out of carbon nanotubes possible, leading to ultrafast, low-power processors.

For decades, the size of silicon-based transistors has decreased steadily while their performance has improved. As the devices approach their physical limits, though, researchers have started looking to less conventional structures and materials. Single-walled carbon nanotubes are one prominent candidate -- already researchers have built carbon nanotube transistors that show promising performance. According to estimates, carbon nanotubes have the potential to produce transistors that run 10 times faster than even anticipated future generations of silicon-based devices, while at the same time using less power.

Emerging Technologies and their Impact

Mummy of Tattooed Woman Discovered in Peru Pyramid

An exquisitely preserved and elaborately tattooed mummy of a young woman has been discovered deep inside a mud-brick pyramid in northern Peru, archaeologists from Peru.

The 1,500-year-old mummy may shed new light on the mysterious Moche culture, which occupied Peru's northern coastal valleys from about A.D. 100 to 800.

In addition to the heavily tattooed body, the tomb yielded a rich array of funeral objects, from gold sewing needles and weaving tools to masterfully worked metal jewelry.

Such a complete array has never been seen before in a Moche tomb.

Surprisingly, the grave also contained numerous weapons, including two massive war clubs and 23 spear throwers.

The unusual mix of ornamental and military artifacts has experts speculating about the woman's identity and her role in Moche society.

"The war clubs are clear symbols not only of combat but of power," said John Verano, an anthropologist at Tulane University in New Orleans, Louisiana, who is part of the research team.

Peruvian archaeologists, under the direction of lead scientist Régulo Franco, made the discovery last year at an ancient ceremonial site known as El Brujo.

The tomb lay near the top of a crumbling pyramid called Huaca Cao Viejo, a ruin near the town of Trujillo that has been well known since colonial times.

Mummy of Tattooed Woman Discovered in Peru Pyramid