Our Amazing Beacon

For all the problems plaguing this country’s manned space program, the unmanned program never ceases to amaze. More than 16 years ago Pioneer 10, a tiny spacecraft, was launched on a mission to explore the outer planets. Five years ago it left them behind. Now more than 4 billion miles away, it continues to send faint but usable radio signals back to Earth, and later this year it will help test part of Einstein’s general theory of relativity.

Merely maintaining communications with the Little Spaceship That Could is a remarkable feat in its own right. Pioneer 10 is so far away that it takes nearly 12 1/2 hours for a radio signal traveling at the speed of light to get to it and back to the space agency’s 230-foot deep-space antenna in the California desert. The spacecraft’s signals are excruciatingly small. Their energy received on Earth would have to be stored for 11.4 billion years to light a 7-watt nightlight for one 1/1,000th of a second. And still the spacecraft speaks and the scientists hear it.

But Pioneer is more than a technological marvel. It continues to do good science. It has changed our notion of how far the solar system extends into space. When Pioneer passed the farthest planet five years ago (which was then Neptune, though it’s usually Pluto), it was said to have left the solar system. Not so, as scientists have since found out. It has yet to leave the sun’s heliosphere of gases and magnetic field, which keep out interstellar gases and cosmic rays. Every day that Pioneer 10 continues traveling at 28,400 m.p.h. extends our knowledge of the sun’s influence into deeper space. No one knows how outgo from the sun will continue to predominate over the influx from the cosmos, but so far--45 times the distance from the sun to the Earth--the sun still holds sway.

The test of Einstein’s theory of relativity that will be done in December will be further proof of the value of this remarkable spaceship. It will also be a demonstration of how science is done and of the rock-solid structure of theory-prediction-verification on which it rests.

Einstein’s theory predicts that catastrophic events in space like exploding stars will generate gravity waves--minor perturbations that have never been detected on Earth. Later this year the Pioneer 10 research team will make intricately small measurements of the Earth and the spacecraft and the distance between them, looking for the tiny jiggles that gravity waves would cause.

There is much yet to learn about the world and the cosmos, and much that may forever remain unknown. But humanity’s push is always to find out more. That is the symbol of our species and its strength. Pioneer 10, built by TRW in Redondo Beach and now sailing the uncharted oceans of cold space, is the beacon to the universe of our planet and ourselves.