The Spaced-Aged : 55 isn’t the limit on this highway. Senior citizens are going on-line and finding a brand-new world.

Increasingly, as home computer use explodes, the person logging on is a retiree.

“We see the senior computer-users as cutting edge,” says Mary Furlong, president of SeniorNet, a San Francisco-based organization that teaches computer skills to senior citizens and operates a network available to people 55 and older through America Online.

“There’s a tremendous reserve of talent in the older population and a computer is just the tool to utilize it,” she says. “Unlike baby boomers, they have the time to study and learn and are extremely committed.”

The emerging senior techies acknowledge trepidation. And they acknowledge it isn’t a breeze.

“People often have unreal expectations in learning the computer,” says Connie Goldman, whose book, “Secrets of Becoming a Late Bloomer,” is coming out next spring from Stillpoint Publishers.

“They say, ‘Oh, this is easy--it’ll take you no time.’ Well, it’s taking me plenty of time.”

SeniorNet’s 13,000 members are only a fraction of the men and women over 55 who sign on every day for everything from a quick look at the Dow Jones index to writing a book. “What they have found,” Furlong says, “is a place where they can use their minds.”

Here, six senior computer users discuss their relationship with cyberspace.

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Marvin Robin, 70, of Encino, bought his first home computer last year at the urging of his son, Michael, who publishes a computer magazine.

“I’d been talking about writing a family history and he encouraged me to start on a computer,” Robin says.

But there was a larger agenda. Robin, a retired Lockheed Corp. manager, needed a challenge. “You do a lot of traveling, a lot of make-do jobs, you find organizations to become active in,” he says. “But those activities don’t have any stress or strain or challenge.

“I believe that regardless of your age, you need a certain kind of stress.”

His new Macintosh filled the bill. “I’d turn it on in the morning and I’d struggle with it. You learn how to do it by practice. Eventually it takes over and pushes you--you get stuck, you keep trying and you find the answer.”

As his son provided various software packages, Robin learned to write and then finished the family history. Then he moved on to personal files, financial records and check writing and, via modem, began signing on to America Online and sending E-mail.

“It’s better than the telephone,” says Robin, who not only talks to his son and daughter in the Bay Area and longtime friends in Georgia, but updates his stocks and has sent several political opinions to the White House. (“Yes, they answer,” he says, by E-mail).

“You’ve just got to know it takes patience and tenacity and accept the idea that your ego will be deflated. I find it fantastic and stimulating.”

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“I’ve had three or four careers and I always knew what computers could do, but never got involved with them,” says Robert Kaplan, 76, of New York City, a former retail executive and city government consultant.

When New York’s 1991 budgetary squeeze abolished his city job, Kaplan wasn’t ready to retire. He enrolled in a 12-week computer class at Columbia University.

It was intimidating to sit down at an IBM PC, he says. “You’d think that somebody like me who worked with analytical stuff all his life wouldn’t be snowed, but I was scared,” he says. “I guess it was the fear of making mistakes. Even though some people in the class took to it like a duck to water, it seemed so complicated to me. And I had never learned to type--I’d always had a secretary.”

But he stuck to it, spending hours a day in the computer lab plugging through WordPerfect and learning spreadsheets on Lotus 1-2-3.

He immediately put his new expertise to work as a volunteer for the American Civil Liberties Union, researching United Nations policies on immigration rights.

“I took the material and analyzed it and started to bang out drafts,” he says. “It was so easy to create and change things on the computer. I finally conquered the keyboard and all the other things.”

Now he’s writing a summary of the ACLU report and has other projects in mind. “I had always intended to write when I got to this stage in life. I have a lot to say and the computer gives me a means of getting it out in a well-organized way.”

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Her Apple Macintosh “opened up a whole new world for me,” says Mary Jane Taft, 64, of Atlanta.

She had sworn never to have a computer. “My husband was a physicist at Yale University. We were married for 31 years and it seemed that he was always at the lab writing programs.”

But after her husband’s death, with three sons and seven grandchildren, she felt the computer age closing in on her. When her 2-year-old granddaughter drew a parrot on a computer screen, curiosity took over and Taft bought a PC and printer and started writing children’s stories.

“I’ve got quite a few pink rejection slips, but they would tell me not to give up,” she says. “And I’ve taken a course in drawing with the mouse because I’d like to write a story and illustrate it.”

Next came the modem and America Online, where Taft discovered SeniorNet.

“I just freaked out,” she says. “I do E-mail and I post messages in forums.”

Her posting in a World War II nostalgia group asked if anyone had been interned in Switzerland in 1943-44. “My mother’s second marriage was to a Swiss and we had been there when the borders closed,” she says. “I have heard from several people who remember me and remember my mother, and even had photographs of us. It’s so incredible to get those pictures.”

She spends two or three hours a day on SeniorNet. “I wish more older people would try it,” she says. “I think they should have America Online and SeniorNet in all retirement homes.”

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When Lee Case of Glendale retired four years ago as vice president of Occidental College, the school gave him a Macintosh, modem and printer. He was delighted, he says.

“I have so many friends, especially executives, who wake up their first day of retirement and think, ‘I have nothing to do.’ You can’t play golf your whole life.”

Like a natural-born hacker, Case was soon doing his taxes, developing word-processing programs for volunteer groups, and logging onto Prodigy and America Online.

Six months ago, he was invited to fill an interim post at Cal State L.A., where he stumbled into the basic computer-world gap: The administration there operated on IBM PCs.

For Case, it was like landing in a foreign country: “I felt like a total alien. At 68, I had to learn computers all over again.”

He thinks many executives of his generation have a problem with computers because they need to know how everything happens. “With computers, you just have to suspend disbelief.”

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Jeanette Popkess, 67, of Bartlesville, Okla., has five grown children around the country and they get together regularly on America Online. “We can E-mail, which is just like writing a letter to someone, or we can all get on-line at the same time.”

Her son gave her a Macintosh last Christmas. Now she talks about her “cyberspace community” on SeniorNet. The community develops, she says, from sharing thoughts on many subjects. “If anyone is sick, or someone is having surgery, everyone rushes in, just like it was a neighbor.”

For Popkess, who lives alone, life in cyberspace is super, although the launch took some courage. She spent several weeks just “lurking” on SeniorNet, reading postings without adding her voice.

Now she admits to addiction and consciously limits her on-line time. “It happens to everyone,” she says. “I’m crazy about it.”

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Larry Marinell of West Hollywood says he can’t imagine life without his computer.

“Historically, the only reason people left their homes--whether in kayaks or ships across the ocean--was in search of information,” he says. “Now, with a screen and a mouse, you can get all the information you want on any subject without leaving home.”

Marinell, 65, spends several hours a day in the nook where his IBM-compatible PC, laser and dot-matrix printers and telephone are within arm’s length.

It’s like a command post, he says, ticking off the computer’s functions.

It’s a reference library: “My sister in Chicago developed Lou Gehrig’s disease. By posting a question in the Health and Wellness Forum of SeniorNet, I was instantly put in touch with the umbrella advocacy group for the disease, I got a list of books to read and the names of several people who are family people dealing with the disease.”

It’s a shopping center: “A woman friend needed to buy a car but didn’t want to go shopping. So I called AutoVantage on America Online and found current new and used car summaries, new and used car pricing, and nearby service centers for her.”

Most important, he says, it is a community providing social life and emotional support. “No matter what’s bothering you, you’ll find a group talking about it on SeniorNet,” Marinell says.

And if you don’t find one, you can start your own: “Just post a message saying, ‘My dog just died,’ and you’ll start hearing from people.”