Saturday, December 18, 1999

12/18/99 7:26:14 AM

• Behind the bright full moon. Surely you've seen the email about the full moon coming on December 22. By a rare conjunction of the full moon with the winter solstice and the lunar perigee, it's supposed to be a once-in-a lifetime moonrise, according to the Old Farmer's Almanac. TBTF Irregular and crack Web historical researcher EM Ganin traced the roots of this much-forwarded meme and found two articles offering some balance to the story of the "brightest full moon in 133 years."

  In September 1998, the Old Farmer's Almanac published their 1999 edition. It contained an article enttitled "The Astonishing Lunar Illumination of December 22, 1999" by Randy Miller.

  At some point this past summer, the Almanac editors posted the article on their web site. Someone lifted the story and sent it around in email to their friends. As the summer turned to fall, the story gained momentum. It hit the newsgroups no earlier than December 1st (the oldest copy I can find on DejaNews). In the last week, the story spread by private email to many thousands of people. It reached the national media in the last few days, with articles in newspapers and TV spots.

  The Web search engines have no record of the story other than the Farmer's Almanac entry. HotBot recorded the Farmer's Almanac URL on November 17th. Other search engines also index the Farmer's Almanac story but don't list a date. No date is listed on the Farmer's Almanac web site either, but the context of the parent article indicates that it was posted before September 14, 1999.

  All of this implies that the search engines can't keep up with the growth of the Web. Alta Vista, HotBot, NorthernLight, Google, DirectHit, Lycos, Yahoo, Webcrawler all have not yet indexed relevant articles that discuss (and refute) some of the claims made in the Almanac story. Examples are:

     Sky&Telescope
     About.com

  Robot-based Web search engines appear to be a bad choice for anyone looking for information on current events.

  -- EM Ganin

Wednesday, December 15, 1999

12/15/99 10:45:09 PM

• FDA approves lenses to correct colorblindness. TBTF Irregular Eric Scheid notes that ColorMax Technologies has announced approval to sell its color enhancement lenses in the US. After proper prescription and fitting, the lenses are said to improve color discrimination in 95% of colorblind people (who number 12M in the US, 250M worldwide). How the lenses work is not obvious to me from reading this passage:

  ColorMax Lenses alter the spectral energy composition of the retinal stimulus to enhance color vision discrimination. Each lens attenuates specific portions of the visible light energy spectrum in one of five different attenuation configurations. Each attenuation configuration alters the spectral energy distribution of the retinal stimulus to permit enhanced color discrimination in the area of the visible spectrum where wavelength discrimination is reduced.

12/15/99 6:02:05 PM

• Adequate key sizes.

  (Published in TBTF -- see http://tbtf.com/archive/1999-12-16.html#s07.)

12/15/99 5:08:15 PM

• Assessing the worldwide impact of the Y2K bug.

  (Published in TBTF -- see http://tbtf.com/archive/1999-12-16.html#s09.)

12/15/99 3:16:50 PM

• Galaxies' dark-matter halos far larger than suspected. See this NY Times article (free registration and cookies required) for an an important new finding from the Sloane Digital Sky Survey. Each galaxy is embedded in a sphere of dark matter, and people have been trying for two decades to determine the size and mass of these invisible galactic "atmospheres." (It is not known whether the dark matter consists of burned-out stars, brown dwarves, exotic particles, or what exactly.) The dark matter was first inferred from the rotation rates of galaxies -- most of them are spinning too fast to hold onto their stars, so something besides the starstuff must be adding to the gravitational pull of the whole.

  Researchers from the University of Michigan used early SDSS data to look for the gravitational bending of distant galaxies' light in the dark-mater halos of nearer galaxies. They found that, on average, a galaxy's halo is 1.3 million light-years in diameter and contributes to a total mass equivalent to 5 trillion suns (preprint).

  Our galaxy is pretty typical. It's a fat spiral disk about 100,000 light-years across, consisting (as far as visible matter goes) of around 100 billion stars. According to the new research, its dark halo masses 50 times more than all the matter we can see. We can picture the Milky Way as a quarter-dollar coin at the center of an invisible basketball.

  The SDSS observatory is in New Mexico, 9150 feet above sea level. The 2.5-meter telescope uses 6 strips of CCDs to record a large swath of the sky in mosaic form. The telescope stares fixedly into the sky and the earth's rotation positions it for each successive image. In a single image the telescope can drink in a piece of the sky the size of the Big Dipper's bowl. Over 5 years the SDSS will map in detail one-quarter of the entire sky, determining the positions and brightnesses of more than 100 million objects. It will also measure the distances to more than a million galaxies and quasars. SDSS is in test mode now -- its early results, the "commissioning data," represent less than 3% of the torrent that the project will eventually pour upon astronomers' heads.

  Here is a tiny piece of the Sloan telescope's first light image (165K), captured last May. The entire image is 5,000 times larger.

Monday, December 13, 1999

12/13/99 11:55:07 AM

• The Internet Freedom Journalism Awards.

  (Published in TBTF -- see http://tbtf.com/archive/1999-12-16.html#s06.)