Å®ÉúСÊÓƵ

People have been measuring the speed of light for a few hundred years, but the universe is nearly 14 billion years old. If the speed of light changes very slowly – say a small percentage every 10,000 years – how could we tell?

While holidaying on the Greek island of Paxos, I came upon a pebble beach where many of the stones had apparently been "engraved" by some type of creature. This example (see photo) is roughly 50 by 60 millimetres, but the same sort of pattern was also present on much larger stones. What type of creature made these, and how and why? (Continued)