Ohio State University Provost Albert J. Kuhn looked closely at the age and tenure status of his faculty in Columbus recently and came away worried.

Too many middle-aged, safely tenured professors clogging up the career paths, he concluded. No room for the bright young newcomer. Ten years ago half the faculty was tenured in. Now two out of three are.The average age is 50, which means the typical professor won't retire for 10 or 15 years.

"We're worried about losing our flexibility," Kuhn said recently. "Even if you have a whole department full of Nobel prize winners, you're in trouble because you can't bring in the guy who may win it for the next generation."

That's one glimpse of the most important demographic fact of our times, the slow aging of the American population. Collectively, we are growing older and the social and economic implications are coming into focus.

Here's a snapshot, taken down the road a bit, 50 years from now. The population will be much older. The proportion of the population 65 and over will have doubled. The Social Security system will help support more than 50 million people.For every retired person taking money out, there will be only two working to put money in. If the system works then as it does now, every payroll dollar will carry a Social Security tax of 27 cents.

Some signs of the aging of America are easily visible. Aspirin is advertised as much as an arthritic pain-reliever as a headache remedy. Campbell's Soup produces "Soup For One," aimed at the elderly living alone. There's the return of the cruise ship, a vessel once thought obsolete but now revived, in part, to attract the retirees' travel trade. Big automobiles remain popular because the middle-aged and older buyers like solidity and comfort, not raciness and glamour.

The aging process will have a ripple effect, touching almost every aspect of American life. It will accelerate population movements to the Sun Belt, the vast swath extending from Virginia through Texas to Southern California, where the elderly retire in large numbers.

Schools will close down and teaching will become a risky economic venture because of a shortage of students. Elementary and secondary schools already are feeling the pinch; between now and 1981 enrollment will decline by nearly 3 million students. College enrollment will start down in 1982.

There will be a rapid increase in what sociologists now call the "old old" -- people over 80. There are more than 2 million now; two out of every three of them are women. There will be a significnt number of families in which parents and their offspring are living in retirement.

Behind the changes is the unprecedented decline in the birth rate since 1960. People are living longer, but that's not, statistically, the important explanation for the gradual aging of the population. The significant fact is that so few are being born. After the baby boom came the baby bust, and in less than a generation American families went from having three children to two.The number of births for each 1,000 women in prime child-bearing ages last year was 65, almost half what it was in the peak birth year of 1957.

The result is a growing imbalance toward the older age groups. Forecasters say nothing ectaclysmic will happen soon. The median age will creep slowly up, from the current 29 years to about 35 in the year 2000. Ten years later, however, things will begin to change radically. The over-65 population (the baby boom grown old) will increase swiftly after 2010. One out of five people will be over 65 (compared with one out of 10 now).

The most immediate impact, many authorities agree, is an impending job crunch, a lessening of opportunities for those entering the labor force in the next decade or so. Crudely put, it means that the accumulation of middle-aged or older workers will clog the routes to jobs and promotions for the young.

"There will be more people seeking the same number of jobs," argues Jean van dei Tak of the Population Reference Bureau. "They [the newcomers] will have to lower their ambitions, particularly when they get into their 40s and 50s. There's not going to be much room at the top."

It will be particularly hard on the college-educated. Somewhere in the early 1970s a statistical watershed was crossed when the number of people with college degrees exceeded the number of jobs for which degrees are considered suitable. By 1985, according to one estimate, about a third of the people in the labor force will have undergraduate degrees and only 22 per cent of the jobs will require them.

Basil Whiting of the Ford Foundation foresees a period of great dissatisfaction. "You'll have a situation where great numbers of people are playing the game -- going to college, even getting PhDs," he said. "They are going to be dissatisfied in many ways. They are not going to have the jobs and the money and the power that they think go with that degree."

Those seeking positions in academia will be substantially blocked out by tenured professors now in their middle years. In the sciences and engineering faculties, for example, a recent study found nearly 70 per cent of the faculty spots tenured. "In some disciplines, it is not an exaggeration to fear that we may lose an entire generation of bright, young minds,' said Richard C. Atkinson, acting director of the National Science Foundation.

Peering further down the road, sociologists and demographers foresee an even more serious side of the age imbalance -- the increasing lopsidedness between the number of workers and the number of old people supported by their labors.

Some experts project a kind of generational conflict, with workers increasingly resenting the taxes levied to pay the pensions of retired firemen, for example, or the Social Security deductions required to support the elderly. A recent study of 100 cities in Illinois found that, on the average, taxpayers had to pay in $2,670 a year to finance the legal benefits for which each policeman was eligible on retirement. It had tripled in only 10 years.

The imbalance between workers and dependents shows most clearly through the projections of the Social Security system. Even those who see it in no fiscal danger concede it will be strained by the next century's burdens when the over-65 population grows suddenly.

The system's chief actuary, A. Haeworth Robertson, observes there are now 31 Social Security beneficiaries for every 100 covered workers. By the middle of the next century, there will be more than 50. That is a 65 per cent increase. The financing system probably will be drastically changed by then, but if it isn't, the payroll tax rate will have risen to 27 per cent. It's now about 11 per cent.

The heavy costs of supporting the retired already are generating a peculiar pressure to eliminate the mandatory retirement age in both public and private jobs. Those who lobby for the elderly have been pushing that for years, hoping to create a situation in which those elderly who want to work can do so. Now they're using the economic argument that letting old folks work can reduce federal, slate and local budgets by sizable amounts.

"You can save lots of public money by retiring people later," said Robert Ball, former Social Security commissioner. "If the average retirement age is raised by one year, say, from 65 to 66, the overall cost of Social Security benefit payments would be 6 to 8 per cent less."

Eliminating compulsory retirement has a plesant ring to the cost-cutters. But what happens at the other end, where the young are looking for jobs held by the old, and the middle-aged are not being promoted?

Trouble, says W. Todd Furniss of the American Council on Education. "If you cut down on pensions, you do give older people a better hedge on life --they can continue to make money. But what does it do at the other end of the employment scale? You just increase unemployment at the lower age levels."

For some, the prospect of a perpetually aging population evokes gloomy predictions of social stagnation, an epoch of conservatism and staidness. The excessive faddism of the youth culture will be replaced in this view, by a long period of excessive stability in which new ideas will be discouraged and innovations suppressed. This concern is best expressed in the often-quoted writings of French demographer Alfred Sauvy, who foresees a "population of old people ruminating over old ideas in old houses."

A countervailing argument is offered by those who see in the aging Americans of the next century a rebelliousness not often attributed to people over 65. In this view, argued most vigorously by Philip Hauser of the University of Chicago's Population Research Center, the group that will cause the population to age suddenly -- the remnants of the baby boom -- will be a uniquely militant bunch.

"They will have run the great risks of unemployment and few promotions, although they will be the most educated cohort in our history," contends Hauser." As the elderly, they will be more insistent on drastic social changes. We are building up the greatest group of malcontents in the history of this country."