|A message to another world|
Forty years on the spacecraft are at the edge of the solar system and are even more intriguing than when they left, for they are not where they are supposed to be: each year they travel a few thousand kilometres less than the laws of physics say they should. This is known as the Pioneer Anomaly
One of the experiments that was designed for Pioneer was to demonstrate that the Law of Gravity works just the same all over the solar system. The unexpected result of experiment suggests - tantalisingly, impossibly - that perhaps it doesn't.
I love this inspiring passage from the latest report of the scientists investigating the anomaly:
In the short run, knowing the gravitational constant to one more decimal digit of precision or placing even tighter limits on any deviation from Einstein's gravitational theory may seem like painfully nitpicking detail. Yet one must not lose sight of the "big picture". When researchers were measuring the properties of electricity with ever more refined instruments over two hundred years ago, they did not envision continent-spanning power grids, an information economy, or tiny electrical signals reaching us from the unfathomable depths of the outer solar system, sent by manmade machines. They just performed meticulous experiments laying down the laws connecting electricity to magnetism or the electromotive force to chemical reactions. Yet their work paved the way to our modern society.That's what science is for.
Similarly, we cannot envision today what research into gravitational science will bring tomorrow. Perhaps one day humankind will harness gravity. Perhaps one day a trip across the solar system using a yet to be devised gravity engine may not seem a bigger deal than crossing an ocean in a jetliner today. Perhaps one day human beings will travel to the stars in spacecraft that no longer need rockets. Who knows? But one thing we know for sure: none of that will happen unless we do a meticulous job today. Our work, whether it proves the existence of gravity beyond Einstein or just improves the navigation of spacecraft in deep space by accounting for a small thermal recoil force with precision, lays down the foundations that may, one day, lead to such dreams.
1 From memory:
- the two circles, top left, represent a hydrogen atom
- the lines, with binary numbers along them, are distances from the sun to major pulsars (and hence our position)
- along the bottom are the planets, with distances to the same scale - our ship came from the third one
- the hand is raised because we come in peace
- the people are the same scale as the picture of the Pioneer craft behind
In 1972 that the couple were naked was a source of great controversy.