When Rod Carew of the Twins went 4-for-5 on Sunday and boosted his batting average to .403, he brought a flood of memories - and questions - to my geriatric generation.

Fifty years ago, a major leaguer with a .403 average in June was no sure thing to win his league's batting championship in September. Today, Carew stands alone. There is nobody within 50 points of him.

Precisely 50 years ago, the great Ty Cobb finished the 1927 season with an average of .357 - and found himself in fifth place. He was topped by Bob Fothergill at .359; Lou Gehrig, .373; Al Simmons, 392; and Harry Heilmann, .398. And there wasn't a slap hitter in the lot. Gehrig, Simmons and Heilmann were among the league's top five in slugging averages, and Cobb and Fothergill weren't far behind. Those guys hit for both average and distance.

What's more, they did it year after year. Cobb's .357 was 10 points below his lifetime average. He was 41 years-old and in his 23d year of major league competition. In his prime, when he came off a .420 year, he "slumped" to .410 the following season.

A fan who is old enough to have seen these wondrous hitters in action must wonder why Carew's .403 stands in such solitary splendor these days. What has happened to baseball's hitters to make even a .250 average worth $100,000 or more?

When I put that question to my colleagues in the sports department, three of them offered explanations.

One said, "The hitters are all down at the end of the bat handle swinging for the fences these days. They may dirve in a lot of runs, but their averages suffer."

Another pointed out that 50 years ago a manager was more likely to let his starting pitcher go all the way, and as the pitcher tired in the late innings, hitters had a chance to get a piece of the ball. These days relief pitching has become a highly developed specialty, almost an art. There's always a fresh arm in the bullpen, and therefore no surcease for the hitters.

The third man noted that the gloves worn by modern fielders are almost twice as large as the mitts worn in 1927. That might also be a factor in pulling down batting averages.

And I will concede that there is a degree of validity to all three points. But so many arguments to the contrary can be made that I'm left wondering what is the real reason modern batting averages are so anemic.

For example, one can cite the fact that the great hitters of old didn't get any help from kangaroo bounces on artificial turf. What's more, they complied their fantastic batting averages while hitting against a dead ball, not the modern ball, which Tom Boswell says "has so much rabbit in it, it eats grass." When Rogers Hornsby was hitting .424 and Nap Lajoie was hitting .426, pitchers were doing everything to the baseball from roughing up its cover to adding all sorts of foreign substances to its surface.

What's more, the men who hit so well in spite of these obstacles were a rowdy bunch, much given to carousing and therefore seldom in top physical condition. The oldtime ballplayer's idea of going into spring training was to switch from hard liquor to beer. So how did he manage to do wo well?

To the answers provided by my colleagues, I would like to add three observations of my own.

Night baseball may have been a factor in bring down batting averages. Many a hitter has complained that he couldn't follow the spin on a pitch under artificial light.

Jet lag may affect play now. But if one does, one is left to wonder about the effect on batting eyes when oldtime hitters spent a day and a half on the train between St. Louis and New York.

Most important of all, perhaps, the game was a life-and-death struggle for most of the oldtimers. Today's highly paid college graduates simply don't take it that seriously. They have other marketable skills, other interests, and - alas! - too much money in the bank.