* Ever since her teacher took on a new assistant to teach arithmetic, Nicaraguan second grader Isabella Sanchez has loved learning math.
The assistant: a radio, broadcasting math courses.
* At the University of Hasanuddin on the Indonesian island of Sulawesi, science professor Nengah Wirawan recently had a guest lecturer tell his class how water hyacinths can be used to ease water pollution.
The lecturer spoke from a classroom 900 miles away at Bogor Agricultural Institute on the island of Java. His talk was beamed via satellite.
* In Cairo, Egyptian President Hosni Mubarak recently talked with American businessmen about how they might invest in Egypt.
Mubarak was in Cairo; the Americans in hotels in New York, Boston, Minneapolis, Los Angeles, and San Francisco. All were linked up for the two-hour meeting through a satellite ''teleconference.''
The same communications revolution that interweaves Western nations with instant-contact satellites, television, computers, and radios is rapidly reaching into the remotest corners of the planet.
Even peoples isolated in the poorest regions are beginning to receive electronic information on farming, housing, and family planning.
As early as the 1960s, media prophet Marshall McLuhan was predicting that the communication technology would unify the world in a ''global village.'' But until recently it was given surprisingly little attention as a tool for development. The technology was seen as a mere spinoff of economic growth. Even as late as 1980, the subject was totally overlooked in the acclaimed report on the global future by Willy Brandt's blue-ribbon panel.
But attitudes are shifting - almost at quantum leaps.
Meetings this year of the Society of International Development and the World Future Society proclaimed communications a precondition for development. A conference on uses of space was held a few months ago in Vienna, sponsored by the United Nations Educational, Scientific, and Cultural Organization (UNESCO). Think tanks are churning out major new studies. And now the United Nations is gathering the results in preparation for 1983, the year it has proclaimed World Communications Year.
Frank Feather, the optimistic director of the Toronto-based Global Futures Network, says: ''With the new microchip technologies, we could dramatically narrow the poverty gap between the rich and poor countries - and do it not in 150 years, but within a generation.''
Ten years ago in Africa, for instance, it was impossible to place a telephone call from one country to another without having it pass through switching centers in London, Paris, or Lisbon. In South America, Argentines could contact Chileans only via New York.
Now for the first time satellites are eliminating that costly inconvenience and giving communications a truly global base, notes a new report by Danial Deudrey of the Worldwatch Institute.
With the help of the International Telecommunications Union and the United Nations Development Program, regional all-African, all-Asian, all-South Pacific, and all-Arab telecommunications networks are moving into place. By the end of this year nearly a hundred developing countries will be linked to one another directly by satellite.
UNESCO is also designing an experiment that could dramatically increase the news flow between developing countries. It has arranged with the sky-nets of INTELSAT and (controversially) the Soviet INTERSPUTNIK to open a planetwide network by which countries can share their TV news broadcasts.
This could give developing countries access to far more news from Western networks, as well as from the developing nations themselves. The initial experiment, to begin in the new year, will last for eight weeks. If successful, it could become a permanent feature of a worldwide information system. (Participating to date are the Public Broadcasting System in America and the Canadian Broadcasting Company, though not yet the major US networks.)
The vast nation of Indonesia is experimenting with a massive inter-island satellite education program. Its PALAPA satellites will link up 8 campuses of the Eastern Islands University Association through two-way teleconferencing. The system will also make it possible for agricultural students at those campuses to chat with specialized professors hundreds, even thousands, of miles away at the Bogor Agricultural Institute near Jakarta.
A similar experiment begins shortly at the University of the West Indies this coming year. Science fiction writer Arthur C. Clarke, who now lives in Sri Lanka , predicts that the trend will sweep the third world before long.
The sale and manufacture of microcomputers have also begun to take off in some developing countries. These could eventually allow poor countries to acquire entire libraries without going through the process of buying and storing the books.
Meanwhile, scientists have been refining the powers of remote-sensing satellites to ''interpret'' the conditions of crops, forests, shipping, mining, and oil exploration. France and Japan are expected to orbit the first civilian-operated systems within five years, according to the new Worldwatch report. Seven developing countries, the largest being Brazil, have installed earth stations to draw data from America's LANDSAT sensor. A typhoon early-warning system is even being set up jointly by the nations of East Asia for mutual benefit.
The US National Aeronautics and Space Administration is pressing for a joint international research effort to pull together reliable satellite information on natural conditions that affect earth's ''habitability.''
Although technological components continue to fall in place, it is still far from certain that their full potentials for human development will be realized.
Like all new technologies, the information systems have a built-in ambiguity. Used constructively they could transform the lives of millions for the better. But manipulated for narrow self-interest by the powerful few, they could prove a tyranny.
This dilemma of promise vs. peril is rapidly becoming a premier development debate of the '80s.
''It's something like peeling off the layers of an onion,'' says Paul Boyd of the United Nations Development Program. ''In the outer layers, in outer space, we're pretty close to solving the communications problems. But once you peel away layers, once you reach the levels of inner space with all their political difficulties at the ground level, the problems get far tougher. These must be resolved if the communications development is to touch people.''
The ''inner space debates'' center on four issues:
* How to close the information gap between developing countries?
The need to reduce the information gap between rich and poor countries is obvious. But the gulf also exists between poor countries.
''Countries like India, Indonesia, and Brazil have national strategies to strengthen their information base,'' Mr. Boyd explains. ''Their communications bases can support enormous communication gains. But what about areas like Benin and Lesotho, where almost nothing is being planned? Will they just get left behind?''
Only concerted global and national planning could ensure a more even spread of gains from the communications revolution.
* Control by the few or the many?
Within developing countries the disparities between the powerful rich and the powerless poor continue to be mirrored in their inequitable access to communications. In Argentina some 85 percent of the telephones are located in cities; in Bangladesh, it is 90 percent. The rural poor are virtually out of touch.
Even within the cities, telephone service can be agonizingly slow for the lower classes. In Bombay a poor person can wait for a new phone up to 12 years; in Indonesia, 14; in Nigeria, 32, says Indian Rashmi Mayur of the Global Futures Network. A major democratization of access to information is a prerequisite for the neediest to benefit, he says.
Leaders in developing nations have also gotten much more involved in managing communications. Fearing the revolutionary potentials of the airwaves, many leaders have been tightening their control, warns Mr. Mayur. ''Speaking recently on Indian TV,'' he says, ''I criticized one little aspect of government policy and the whole show was canceled. The problem now is not so much the technology, but how freely its benefits are opened to the masses.''
The Indian government recently began its second major experiment to use satellite-transmitted TV programs to help rural villagers boost their farming and family planning. The aim is to reach 15,000 rural villages in six of India's 22 states.
* Information or ''infor-tainment?''
As TV and radio are being used more for broadcast to the rural poor, so has concern grown about the quality of information that is broadcast. Some developing countries have produced highly popular TV programs with a message of social development. A Mexican TV soap opera, for instance, is thought to have been a major factor in helping family planning efforts in that country.
The common transistor radio remains one of the cheapest, most effective developmental tools. For years the Philippines has used radio broadcasts, along with workshops, to spread agricultural information to its farmers.
But some nations are tempted to flood their networks with Western imports - a type of programming Tarzie Vittachi of the United Nations sarcastically dubs ''infor-tainment.''
* Greater dependence or greater self-sufficiency?
Developing countries are also groping for ways to decrease their dependence on Western programs. ''Almost every developing county has now set up at least one center for training in communications,'' Narrinder Aggarwala of the United Nations Development Program says. ''But even these are way, way behind.''
Developing countries are also increasingly wary about information that multinational corporations could gain over their land resources through data purchased from remote sensing satellite systems. With this in mind, Indonesia is leading a drive among developing nations to get satellite operators to withhold data about a country until the country grants its permission.
If for many the communications flurry has seemed an awesome sight to behold, the communications experts are convinced that we may not have seen anything yet. Wireless telephones, solar powered TV and radio, computers in the sky - these are but a few of the high-tech tools on the drawing board.
''By the 1990s,'' says satellite specialist Charles Gould of Rockwell International, ''inexpensive, portable . . . links to and from space give us access to whole worlds of new information - succinct, timely, and appropriate to our needs. If we want to know how to plant corn, or whether it is going to rain on our parade, a world of agricultural and meteorological knowledge backs that up. . . .''
It remains to be seen if the promise will outpace the peril.
But there is no longer any doubt that the communications technologies have carved out a permanent niche on the development map.