Silicon Valley has an obsession with immortality, and not just as science fiction. Many people here say they believe that the day when technology makes it possible to live forever is just around the corner.

On Wednesday, some of the tech world’s most formidable players announced an effort to get closer to that point, with a new biotechnology company to fight the aging process and the diseases that accompany it.

The company, Calico, was conceived and backed by Google, whose co-founder and chief executive, Larry Page, portrayed it as one of the company’s long-shot projects, like self-driving cars. Arthur D. Levinson, 63, the former chief executive of Genentech and the chairman of Apple, agreed to be the chief executive and is also an investor.

“This was just so out of the box that I instantly got extremely excited about it,” Dr. Levinson said in an interview. He said he had turned down other offers to run companies since stepping down as chief executive of Genentech in 2009, after the company’s acquisition by Roche.

Left: John G. Mabanglo/European Pressphoto Agency; Right: Roche

Dr. Levinson said that at first Calico would be “more of an institute certainly than a pharmaceutical company,” focusing on basic research aimed at picking apart the biological mechanisms behind aging.

He said much of that early research might be done by providing money to academic scientists, though Calico might also hire its own researchers. Dr. Levinson, who is Calico’s only employee for now, would not say when, or even if, Calico hoped to develop a drug to fight aging.

An anti-aging drug has been a long-sought goal, both by some consumers and by companies, as well as by various hucksters. Rather than treat each particular disease, retarding aging could potentially prevent or slow the development of numerous diseases.

But companies that have sprung up to try this have tended to suffer from lack of longevity themselves. Elixir Pharmaceuticals, a company started by academic experts, was shut down. Another company, Sirtris Pharmaceuticals, was acquired by GlaxoSmithKline for $720 million in 2008, but has been downsized somewhat.

Dr. Levinson said Calico hoped to surmount those issues by taking a long-term approach to better understanding the mechanisms involved, without the need to turn a quick profit.

“Larry and I share a sense of sadness that so few companies are willing to make extremely long-term bets,” he said.

He declined to say how much money was being invested in Calico, though he hinted it would be in the tens of millions of dollars. He also declined to say whether there were other investors.

Some anti-aging researchers, who have been suffering from tight federal research spending, welcomed Calico’s entrance.

“I think that if Google succeeds, this would be their greatest gift to humanity,” said David Sinclair, a professor of genetics at Harvard Medical School and co-founder of Sirtris. “I’m sure they don’t mean that they will defeat death, but if they were to give people five or 10 years of healthy life, that would change the world.”

Under Dr. Levinson, Genentech developed blockbuster cancer drugs and a reputation for allowing scientists to pursue their interests, something he said he hoped to replicate at Calico.

One issue Calico could confront is that the Food and Drug Administration does not recognize aging as a disease, so drugs would have to be approved for a specific disease. But Dr. Levinson said that if an anti-aging drug were proven to work, the agency would most likely change its mind.

He said Calico was exploring a partnership with Roche, whose board he sits on. He also said that Calico would consider using Google’s computing power.

Calico stands for California Life Company. “But if you’re thinking about cats, we like the old saying that they have nine lives,” Dr. Levinson wrote in a post on the social network Google Plus.

Though Google assures wary shareholders that these projects are small compared with the core business, the company is working to create an image of itself as the leader of innovation and long-term thinking in the industry.

Mr. Page wrote in his own Google Plus post, “Don’t be surprised if we invest in projects that seem strange or speculative compared with our existing Internet businesses.”

Google’s founders are involved in Singularity University, part of the belief system that humans and machines will at some point merge, making old age and death meaningless. Google has ventured into health before, including with company investments and personal ones related to the founders’ health issues and a failed effort at online medical records.

Dr. Levinson said that Timothy D. Cook, Apple’s chief executive, was the first outsider he told about his participation in Calico. Mr. Cook, he said, listened quietly for a few minutes and then said, “It’s not very many people who have the opportunity to reverse time.”

Claire Cain Miller reported from San Francisco, and Andrew Pollack from Los Angeles.