Roughly half of all Americans reject the theory of evolution, believe that UFOs carry visitors from outer space, say that some people have lucky numbers and think that scientists have knowledge that makes them dangerous, according to a survey for the National Science Foundation.

Large numbers of Americans also do not understand basic scientific terms such as "molecule," "DNA" and "radiation." But substantial numbers believe in astrology, and about one in 15 has changed his or her behavior because of advice in an astrology column.

The survey results show a surprising degree of "misunderstanding of science in the American public" and difficulty in distinguishing between science and pseudoscience, said Jon D. Miller, head of the Public Opinion Laboratory at Northern Illinois University.

His findings underscore a growing national concern about widespread scientific illiteracy in the United States. They are the latest indictment, Miller said, of the failure of the public pre-college educational system to prepare Americans for an increasingly scientific and technological world.

Miller, who spoke at the American Association for the Advancement of Science (AAAS) meeting here last week, said his survey involved a random, representative national sample of 2,000 American adults reached by telephone last November and December. The margin of sampling error in a national survey of this size is about 2 1/2 percent in either direction, Miller said.

The survey indicated, Miller said, that scientific illiteracy is greatest among those with the least education, among the very young and the very old, and among women.

Miller said that astrology -- a pseudoscience purporting to show the influence of the positions of the moon, sun and stars on human affairs -- is taken seriously by many American adults. He found that almost two-thirds read astrology reports periodically and 15 percent said they read them regularly. While three of five rejected astrology as "not at all scientific," nearly two of five gave it some scientific credibility.

The survey also found that about 7 percent of Americans -- the equivalent of 12 million adults -- said they had changed their behavior because of advice in an astrology column, with 20 percent of high-school dropouts saying astrological advice had influenced them.

The survey's questions on public acceptance of basic scientific theories got mixed results. Seven of 10 participants agreed with the theory that "in the entire universe, it is likely that there are thousands of planets like our own on which life could have developed."

There was also strong agreement -- eight of 10 adults surveyed -- with the scientific view of "plate tectonics": that "the continents on which we live have been moving for millions of years and will continue to move in the future."

But on the question of evolution, Americans were almost evenly divided on the statement that "human beings as we know them today developed from earlier species of animals."

Superstition also was strongly linked to lower levels of education. Forty percent of adults surveyed agreed that "some numbers are especially lucky for some people." The figure was 60 percent among those who did not have high-school diplomas and 28 percent among college graduates.

On the question of extraterrestrial visitors, 43 percent agreed that "it is likely that some of the unidentified flying objects that have been reported are really space vehicles from other civilizations," while 46 percent disagreed. In this case, there was little difference in views among the sexes or by educational level.

One indicator of the degree to which the public feels comfortable with science is in understanding of its basic vocabulary. The survey found that:

*Only one-third of adults said they have a clear understanding of what a molecule is. Forty percent said they have a general sense and 28 percent said they have little understanding. A molecule is the smallest particle of an element or compound that can exist freely and still retain the characteristics of the element or compound.

*Only one in six adults surveyed claimed to have a clear understanding of DNA and 57 percent acknowledged that they have little or no understanding of the term. DNA is short for deoxyribonucleic acid, the chemical responsible for transmission of hereditary information in genes.

*Fewer than one-third of adults surveyed think they have a clear understanding of radiation, and one in five admits to little or no understanding of the term. Radiation is energy, in the form of particles or waves, emitted by atoms undergoing internal decay.

Miller concluded that "a substantial majority of Americans do not have a sufficient vocabulary or comprehension of concepts to utilize a wide array of scientific communication . . . . If terms like molecule and DNA are not acquired during formal schooling, it is unlikely that they will be acquired later through the media or other informal education channels."

One of the most striking overall conclusions of the survey, Miller said, was the impact of scientific illiteracy on the least educated. About 15 percent of American adults -- about 25 million people -- did not complete high school. Miller said he believes that greater misunderstanding of science and more superstition in this group has contributed to a feeling that they have "little control over their own fate."

Nearly half of the least-educated agreed with the statement that "it is not wise to plan ahead since many things turn out to be a matter of good or bad luck anyway." Only 6 percent of college graduates felt this way.

And how does the public view scientists? More than half of all adults, 71 percent of high-school dropouts and 38 percent of college graduates agreed that "because of their knowledge, scientific researchers have a power that makes them dangerous."

Nonetheless, 57 percent of adults said they agreed that "in this complicated world of ours, the only way we can know what is going on is to rely on leaders and experts who can be trusted." While 81 percent of the least-educated believed they had to depend on experts, Miller said, a majority of college graduates rejected the notion, apparently feeling that they can make some sense of the world on their own.