As the baseball season passes its traditional Fourth of July midpoint, it's becoming obvious that the sport's first poststrike season is far different, and far better, than anyone would have dared expect.

Each day's league standings, not to mention the hallucinative Sunday averages, are enough to make any true fan rub his eyes and wonder if he's been transported through a black hole into some alternative baseball universe, one where the San Diego Padres and Seattle Mariners are, for the moment, pennant contenders, and the Atlanta Braves have the best record in the game.

In this strange yet wonderful new baseball realm:

* Fourteen teams are within 4 1/2 games of first place with the All-Star Game just a week away. Four other clubs, including the respective league champion Yankees and Dodgers, are also within 7 1/2 games of the lead. In all, 16 teams are at .500 or better, yet only one club is above .585. Nobody's great, but almost two-thirds of the teams in the game are good, or, at least, think they are.

* The poor National League West, with the promise of a mere three-team pennant race, is the game's least exciting division. The AL West has four clubs in its immediate race while the NL East has five. As for the ridiculously jammed AL East, six clubs are in a stampede there, and five of them actually look decent enough to hang in the pack until near the end.

* Rookies named Tony Pena and Willie McGee are No. 1 and 2 in the National League in batting, while Kent Hrbek leads the majors in slugging. Other rookie regulars who would be heralded in any other season--Steve Sax, Johnny Ray, Von Hayes, Dave Hostetler and Cal Ripken--are practically lost in the shuffle, although all of these players, at present, either project to hit .300, have 90 RBI or hit 25 homers.

* The best statistical bullpen in the sport in the first half, with a combined ERA of under 2.00 in more than 70 appearances, is a trio of rookie right-handers named Chiffer, Show and DeLeon. Their first names (Floyd, Eric and Luis) are as yet unknown, except in San Diego.

* The two most pleasant surprises of the year--the Padres and Mariners--have both been built with players stolen at bargain rates from hot-to-trade Yankee owner George Steinbrenner. San Diego thanks him profusely for Ruppert Jones (86 runs produced) and Tim Lollar (8-2). Seattle is in George III's debt for three-quarters of the starting rotation which has the third-best ERA in the league--young Jim Beattie (2.61) and Gene Nelson, plus reliable old castoff Gaylord Perry.

* The franchise with the best record in baseball in 1981, the Cincinnati Reds, now stands 24th out of 26 in winning percentage. And the two clubs with the most frequently praised starting pitching this spring--Oakland and Houston--each stand next to last in team ERA in their respective leagues.

* Oh, yes. The Boston Red Sox are in first place.

All this divine madness, you say, cannot last. Not only will the Padres and Mariners wilt, but so will the other down-so-long imposters like the Braves, Cardinals and White Sox. Why, say the cynics, the Tigers, losers of 17 of their last 21, have already showed the approved and time-tested way to fold a tent. Can the rest of these pipe-dream, baling-wire outfits, like the Bosox--who have dropped from third in the majors in ERA to 18th in just two weeks, thanks to Milwaukee--be far behind?

The central point of this season, however, is not that some of these romantic underdog teams, and rookie flashes, will naturally fade. Rather, the gist of 1982 is that more previously homely teams have shown more improvement, and stayed afloat longer already, than in any season in memory.

While the NFL has struggled for an artificial parity, baseball has, almost by accident, come upon a marvelous competitive balance through, it must be assumed, the open marketplace workings of free agentry.

With each year, it seems more evident that free agentry has proven to be baseball's greatest bonanza of this era.

Where is the ultrarich dynasty, buying all the best players, that would strangle the sport? It doesn't exist. The aging Yankees appear closer to disarray than dynasty. The zillionaire Dodgers, with their farm-system wealth, are simply one of a dozen stable contenders.

For every franchise that has helped itself by spending aggressively, like the California Angels with their glamor lineup of four former MVPs, there are counterbalancing clubs like Baltimore, Boston, St. Louis and Kansas City that have stayed strong while staying on a sane, if strained, budget.

Where are the decimated, poverty-stricken franchises? Except for the Minnesota Twins, who may be a Calvin Griffith special case, they're hard to find. Even the Cubs, headed for 100 loses, may be horrid, but, under Dallas Green, they're trying.

Perhaps the most invigorating aspect of free agency is the way it has improved the flow of young players into the game. Every time a free agent of quality changes teams, it opens up a position. The damaging tendency, generations old, of the best organizations stockpiling talent, keeping potential stars in the minors or on the bench as insurance, is almost a thing of the past.

If, in some ways, this season seems to contain all the new faces and dramatic shifts in team fortunes that we would normally associate with two seasons, then that may well be the case.

In retrospect, 1981 may be seen as a sort of trendless season in limbo when little of significance happened. Despite the flashy arrivals of Fernando Valenzuela and Dave Righetti, it was a sparse year for rookies; with a third of the season burned and few clubs willing to gamble on youngsters in the artificial second-season pennant races, young talent was backed up in the pipeline. Now, the spigots are turned full open and the Storm Davises are upon us.

Also, the shortened 1981 season may have helped some fading teams hide their weaknesses. Perhaps, as an example, if last season had been 162 games long, the Oakland pitching staff, worn to the nub with all Billy Martin's complete games of 1980, would have suffered its epidemic of blown arms then, rather than now.

If 1982 is, then, a sort of double season with two years worth of change and vigor packed into one summer, then it could not have come at a better time.

On the last Fourth of July, baseball was an endangered American institution.

Now, it's seldom looked better.