Replying to a radio signal from another galaxy would be pointless, since it would take millions of years to arrive at its destination, but it would change everything to know that an alien civilization exists somewhere, anywhere, in the cosmos.
Modern industrialized civilization exists because of a Faustian bargain with fossil energy: first coal, then oil, and now gas.
At one meeting of seismologists I attended, the organizers strung a banner across the front of the conference room with a quotation attributed to the historian Will Durant: "Civilization exists by geological consent, subject to change without notice".
Raffles long believed that an ancient civilization existed in Java and, now, here was his proof.
Recent carbon dating at Caral, north of Lima, has shown that an advanced civilization existed in Peru nearly 5,000 years ago, when the Egyptian pyramids were being constructed.
A significant prehistoric civilization existed on the islands prior to the arrival of the Phoenicians, who named the main island "Malat," meaning "safe haven".
Importantly, they were tested both for factual recall (How many years ago did the Indus civilization exist?) and for conceptual learning (How do Japan and Sweden differ in their approaches to social equality?).
The first four civilizations exist from 950 A.D. to 1900 A.D., which covers the first three ages: the Medieval, Gunpowder and Imperial ages.
Study co-authors Adam Frank and Woodruff Sullivan looked at recent discoveries of potentially habitable exoplanets and considered the odds of whether sophisticated civilizations existed on them in the past or present.
