Around his left wrist Tad Hogg wears a bracelet engraved with an emergency number to call in case he dies. Hogg, a 43-year-old research scientist with Hewlett-Packard Co., only takes it off at night to sleep. "It's like wearing a watch," he said, only instead of keeping time he hopes this band of stainless steel will freeze time -- or at least put it on hold.

Hogg is a member of Alcor Life Extension Foundation, the largest organization supplying cryonics services. When he dies, his body will be immediately packed in ice and flown to Scottsdale, Ariz., where his head will be surgically removed, injected with preservatives, placed in a large metal vat and cooled in liquid nitrogen. Hogg believes the sub-zero temperatures will preserve his mind -- thoughts, feelings, memories, knowledge -- until medical and scientific advances can bring him back to life.

For this shot at immortality, he has filled out reams of paperwork, taken out a life insurance policy to cover the expense of preservation and storage, and pays membership dues to Alcor.

"No one can say whether it will work or not," Hogg said. "It's an unknown."

It's just that unknown, that otherworldly possibility of life after death, that tantalize techies of all stripes -- mathematicians, physicists, software developers, computer programmers -- who make up a vast majority of those who have signed up for cryonics suspension. The family feud over deep-freezing baseball slugger Ted Williams has only intensified interest in cryonics in Silicon Valley and in the greater Bay Area, already a hotbed for the experimental and controversial process.

Canadian author Heather Pringle first noted that cryonics "captivates the hearts and minds of many in Silicon Valley" while researching modern mummification for her book, "The Mummy Congress: Science, Obsession and the Everlasting Dead" (Theia/Hyperion), which explores the age-old human obsession with cheating death.

"I wondered why on Earth would software people, bit heads and hardware people be so interested in this?" said Pringle, who estimated in 1998 that more than 25 percent of the more than 400 people then signed up with Alcor toiled in either the computer or engineering industries. "It's really because of their faith in technology. They are very future-oriented. They are constantly looking ahead in their own minds to the future."

A Michigan math and physics teacher, Robert C.W. Ettinger, laid the groundwork for cryonics in his book "The Prospect of Immortality," which was commercially published in 1964. A slew of technologists was drawn to the fringe, avant-garde scientific movement, including Ralph Merkle and K. Eric Drexler, two respected theorists in the emerging field of nanotechnology, which aims to build molecular machines that would give humans mastery over matter.

Other high-profile techies have warmed to cryonics, from artificial intelligence expert Marvin Minsky of the Massachusetts Institute of Technology to Ray Kurzweil, who invented reading machines for the blind. Most hail from the Bay Area, where innovators and free thinkers come to chart new scientific frontiers. One in five Alcor members lives in the Bay Area, Merkle said. The Bay Area is also home to the American Cryonics Society, the longest-running such organization in the country.

"The Bay Area is a high-tech Mecca," said Merkle, a former Xerox PARC research scientist who helped develop the encryption technology that facilitates secure transactions over the Internet and sits on Alcor's board. "A lot of people are directly involved in advances in technology."

Bringing people back to life by freezing and then thawing them has long captured the American imagination in science-fiction novels and on the big screen in Woody Allen's "Sleeper" and Mike Myers' "Austin Powers."

Cryonics, derived from the Greek word for cold, holds a very real fascination for the digerati that has seen time and again the power of technology to turn fantasy into reality. Cryonics converts rebut mainstream scientists who insist it's unlikely anyone will develop technology that can reanimate dead people. How many scientists centuries ago could have envisioned today's advances: artificial hearts, space travel, cloning, computers? these techies ask. Could the notion of sitting in the bleachers watching Williams again bat .400 really be so far-fetched?

Their final question is nearly always the same: If these are the clinical trials, which control group would you rather be in 100 years from now: the one playing cryonics roulette suspended in liquid nitrogen or the one dead and buried?

That's pure hokum, says Kenneth B. Storey, a biochemistry professor at Canada's Carleton University who experiments with freezing small animals and bringing them back to life. Storey firmly believes that "we cannot freeze whole humans in order to revive them intact and functional in the future.

"Desperate cryonics organizations and their followers have responded to scientific skepticism about failed human cryopreservation by classic tactics of changing the base of the argument from reality to 'future magic' to keep the paying public coming into their circus tent," he said. "By confusing the public into believing that magical machines, strange cryo solutions and unnamed 'medical advances' will be available and allow them to live after preservation, they keep the converts coming."

Dr. Michael Shermer, a Pasadena psychologist who publishes Skeptic magazine, says it's possible but not at all probable that scientists will develop the ability to wake the dead at some nebulous point in the future. "Cryonics is almost a faith-based secular religion in the sense that it is based on the idea of achieving immortality and being resurrected," he said. "There is not a shred of evidence that this ever could be done. It all depends on having faith in the future of science."

Ettinger, 83, ("the same age as Ted Williams") has dedicated his life's work to faith in just that. In 1976, Ettinger formed the Cryonics Institute, a Clinton Township, Mich.-based cryonics facility where his two wives and mother are among the 41 patients. "Most people would rather be alive than dead," he said matter of factly.

Cryonics taps into the innate human longing for immortality that is fueling this minuscule yet fervid movement -- albeit at glacier speed. Fewer than 1,000 people have made the cryonics commitment; only about 100 are "patients," meaning they have already been dunked in liquid nitrogen. Yet in the past decade, Alcor's ranks have swelled from 312 to 580 people waiting to be frozen, according to Merkle. Half of the Cryonics Institute's 400 members joined in the past three years, Ettinger said.

Take Tim Freeman, 36, a former computer programmer at Infoseek. He signed himself up and then convinced his wife, mother and stepfather to sign up. "It's like doing a back-up of your computer; you save the data and someone will eventually figure out something useful to do with it," Freeman said.

A disproportionate number of the new recruits are in computer-related occupations. They don't fit the stereotype of credulous, new-age dreamers. They have high IQs and ambitions, loads of education and technical expertise. Ettinger's theory? "They are not only accustomed to relying on trains of logic, they are accustomed to radical change. They not only accept the possibility of it; they accept the likelihood of it."

Kennita Watson, a 41-year-old software engineer with Sun Microsystems, dreams about the future. "Techies know how many things that used to be science fiction are now science," said Watson, who signs e-mail correspondence with the tag line "may you live long and prosper" and her Alcor identification number, A-1490.

Watson signed up to be frozen from head to toe nine years ago after attending a cryonics presentation at a conference sponsored by the Extropy Institute, a think tank that promotes "transhumanism," the belief that humans can overcome biological limits through advances in science and technology. Planning for her own death changed her life: She met and fell in love with William Wiser, 39, a life-extension consultant and another Alcor member, when he spotted her Alcor bracelet and struck up a conversation.

Like many in the cryonics movement, Watson believes giant steps in science and technology ultimately will allow people to stay younger, healthier and live longer. More than ever, she hopes she will wake up disease-free. Nicknamed "kinetic" for her boundless energy, Watson used to tear up the dance floor -- jazz, ballet, "pretty much anything I could get my hands and feet on" -- until she was diagnosed with multiple sclerosis four years ago. "Even though they are making a lot of progress on MS, I might have to wait until I'm frozen and reanimated before it's cured," she said.

Proponents say cryonics has gained some momentum with techies in recent years because science and technology are catching up to the vision. Experiments with lowering the body temperatures of surgical patients to near freezing have shown promise in keeping brain tissue alive longer during surgical procedures, staving off brain death and protecting transplant organs for longer periods. Berkeley-based BioTime Inc., which according to published reports was at one time affiliated with the San Leandro-based cryonics facility Trans Time Inc., is working on artificial plasma, a blood substitute for organ transplants and cold-temperature surgery. (See related story).

Nanotechnology -- a term Drexler came up with in the early 1980s while a graduate student at MIT -- also figures prominently in the cryonics blueprints. Merkle is confident that one day scientists will build nanobots, robots little bigger than atoms that will repair tissue damage caused by aging, disease and freezing at the molecular level.

"Medicine will benefit from nanotechnology," he said. "We will have a better ability to detect illness, to respond to illness, to heal and cure. Disease and ill health are caused by damage at the molecular and cellular level, and medical tools are too large to deal with that."

Ettinger believes cryonics will eventually perfect freezing techniques to the point some patients won't even require the use of nanotechnology, just that scientists discover a cure for what killed them.

Are these quixotic hopes or prescience worthy of H.G. Wells? Luke Nosek, 27, a high-profile Silicon Valley executive who most recently was PayPal's vice president of marketing, thinks of it as a wager. He first read about cryonics in a popular science magazine when he was 12. He got hooked on the Internet when he saw Marc Andreesen's first Web browser Mosaic in 1993 while he was a computer-engineering student at the University of Illinois at Urbana-Champaign. He ventured to Silicon Valley, where his fascination with cryonics reawakened.

"You make a bet on the technology. Sometimes you are wrong, and the technology doesn't work like the Apple Newton. Other times it works like the PalmPilot, and millions of people are thrilled," Nosek said. "Many people are making that bet on cryonics."

Ka-Ping Yee is making that bet. The 26-year-old computer science graduate student at UC Berkeley got into cryonics when a high school friend lent him Ed Regis' "Great Mambo Chicken and the Transhuman Condition: Science Slightly over the Edge," which explored fringe scientific theories. Then he picked up Drexler's "Engines of Creation: The Coming Era of Nanotechnology." He met Merkle five years ago while working for the summer at Xerox PARC and then took the plunge at a Silicon Valley sign-up party, where an insurance agent and notary helped guide him through the complicated process. "It's cheaper than basic cable," Yee said.

Cryonics isn't exactly cheap, though it would be a small price to pay for eternal life. Alcor charges about $120,000 for a full-body suspension and storage or $50,000 for the head only. (Those who elect to freeze just their heads imagine they will wake up with bodies that are cloned, genetically engineered or manufactured using nanotechnology. Others speculate that technology will evolve to the point that a brain can be uploaded to a computer where consciousness will exist digitally.)

The Cryonics Institute offers full-body suspension for $28,000 but doesn't do heads. The organizations also charge a lifetime membership fee or annual membership dues.

Yee pays $133.75 a year for life insurance and $180 a year for the Alcor student membership, which works out to about $26 a month. He plans to have just his head frozen because the more rapid cool down curtails biological deterioration. "You have to set aside aesthetics and figure out what is actually going to assure the highest probability of survival," he said.

Nosek, who plans to have his whole body frozen, shells out $160 a year for life insurance plus annual Alcor membership dues of $398. "It's less than the cost of having a cup of coffee a day in Palo Alto," Nosek said. "It's cheap if you think there is any chance it will work."

As much as Yee hopes he will open his eyes hundreds of years from now to live again in a brave new world, logic prevails. "The probability is quite low that I will be suspended in the first place or revived if I am suspended," he said.

People die in many destructive ways -- in car accidents, natural disasters -- that would leave little to preserve. Medical advances in coming years may help Yee live longer than Alcor, he reasons. Once frozen, anything could happen. Despite its many assurances and provisions to fund its operations for decades to come, the cryonics organization could run out of money and shut down, the corpses thawed and buried. It has happened before. And should technology deliver the power to grant eternal life a la the Vampire Lestat, who's to say future generations will want to bring a bunch of geeks on ice back to life?

Pringle points out a lot can go wrong "when the dead are unable to lift a finger to defend themselves." Even the most dedicated mummifiers, the Egyptians, were prone to mistakes: they took out the wrong organs, used too much boiling resin, let limbs rot and then tied them together with the Egyptian equivalent of duct tape, then plundered those they had embalmed.

"Who knows what (future generations) will make of all these 21st century mummies?" Pringle wrote in "The Mummy Congress." "Will they size up this trove of ancient human flesh for its commercial potential and auction off its primeval DNA and untainted blood cells on some future version of eBay?"

"I'm not holding any illusions about this. This is not a cheap ticket to eternal life," Yee said. "This is a gamble, but it's a case of informed risk. If you bet against cryonics, you are not betting against a particular technology, you are betting against the entire future, no matter how long that stretches out."