25th anniversary for an unanswered message

The most distant of long distance calls celebrated its 25th anniversary on Tuesday but has still gone without a reply. Scientists blasted a three-minute signal from the 300-metre diameter radio telescope at the Arecibo Observatory, Puerto Rico, describing mankind, the fundamental chemistry of life and our place in the solar system.

The digital message is heading towards a group of stars called the Great Cluster in Hercules, some 25,000 light years away. So far, it has travelled 147 trillion miles - about one thousandth of the distance.