The era of limits has become the era of possibilities. Whale Day has become Space Day, and California Gov. Edmund G. (Jerry) Brown Jr., the onetime darling of the environments, is soothing big business leaders with talk of lower taxes and greater economic growth.

"I think there's a certain evolution in one's program," Brown said blandly in an interview this week. "All life is growth and I think I'm growing along with everyone else."

The evolution of which Brown speaks has manifested itself in opposition to two taxes which California corporations don't want, in a series of meetings with business leaders and in Brown's repeated assertions that California must take the lead in encouraging national space programs that will benefit the state's aerospace industry.

Despite the suspicion of some businessmen that it is mostly talk, Brown's transformation has been politically successful. His performance as governor gets high marks in public opinion surveys. California Manufacturers Association President Bob Monagan, a former Republican state legislative leader and frequent critic of Brown, concedes the governor is "a cinch to be re-elected next year."

What is immediately at stake for Brown is winning the center ground in the 1978 campaign. All of California's successful governors have been centrists, a position which Brown's predecessor, Ronald Reagan, reached from the opposite political direction.

But some Democratic politicians think that Brown's political shift also signifies long-range strategy. They say that the governor, still boyish-looking at 39, remains intrigued by the presidency and has realized that he is unlikely to reach the White House as the candidate of the Democratic Party's liberal wing.

Brown defeated Jimmy Carter whenever the two men faced each other in last year's state presidential primaries, but no one close to the governor foresees him challenging Carter in 1984. Instead, Democratic politicians tend to regard Brown as a candidate of the future, probably a contender for the presidential nomination against Vice President Mondale in 1984.

That election is so far away that such talk would seem preposterous except for Brown's history of long-distance political planning. Growing up in a political household headed by former two-term governor, Pat Brown, Jerry Brown developed a natural sense of political timing that even his foes find remarkable. Friends of Brown say he senses his course, rather than plots it, and that he frequently anticipates a public mood.

Recently, for example, Brown positioned himself on the Lost Angeles school integration issue by observing on a television program that people would move out of Los Angeles if they "don't like what they see in the schools."

This remark drew an angry rebuke from civil rights leaders, who said Brown was encouraging white flight in the face of an anticipated school desegregation plan. When questioned about it afterward Brown said he would match his integration record with anyone's.

The economic course Brown is now steering started last January when Dow Chemical Co., frustrated at its inability to win approval from state and local agencies for a $500 million petro-chemical plant near San Francisco, abruptly withdrew its application.

In the wake of Dow's decision, critics of the governor accused him of fostering a poor business climate in California by requiring industries to clear a bewildering variety of pollution-control hurdles, one frequently cited example is the long-stalled plan of Standard Oil of Ohio to build a massive terminal in Long Beach harbor that would serve as an exchange point for Alaskan crude oil.

The Sohio terminal has failed repeatedly to win approval from the California Air Resources Board which is headed by Tom Quinn, Brown's 1972 campaign manager. Until recently, it seemed unlikely that the terminal would ever be built.

Now, Quinn is talking about possible approval of the terminal by October. And Brown is moving to alleviate concerns of multinational companies over the state's "unitary tax," which taxes corporations on the basis of their combined world holdings rather than just on their California earnings.

"The unitary tax creates some real problems and has got to be changed, and I'm going to change it," Brown said in the interview with The Washington Post. He added that he didn't even know of the existence of the tax until six months ago.

The California governor also has talked about repealing the state's controversial tax on business inventories. This tax, amounting to $440 million a year, has encouraged the growth of warehousing in neighboring Nevada and discouraged warehousing in California.

California's business conditions are mixed.Corporate and personal income remain high and the state last month led the nation in housing starts. But California has one of the highest business tax burdens in the nation and companies large and small face a state and local regulatory maze which can be discouraging. Brown has vowed to improve this regulatory process.

"As yet, there haven't been that many substantial changes, but I basically think Gov. Brown has made some progress," says Kirk West, Sacramento lobbyist for the California Taxpayers Association and a former finance official in the Reagan administration. West's view is shared in large measure by other business lobbyists, many of whom emphasize that the changes so far are mostly rhetorical.

Rhetoric, of course, is part of political leadership and it provides the most instructive clues to the changes in the Brown administration.

Last year the governor proclaimed Whale Day and celebrated the preservation of the endangered mammals as vital to human civilization. This year, at a Los Angeles extraganza called Space Day, the emphasis was on technological achievement.

With the characteristic overstatement that seems to be part of his political charm, Brown declared that the future of California and mankind were inexplicably linked with other space.

"California needs space for jobs, but America needs space for its predominance in the world and the survival of the human species," he said.