The Voyager 1 and 2 spacecraft, launched in 1977, are now the furthest manmade objects from Earth. While it will take them tens of thousands of years to get even remotely close to another star, both contain messages on board to any aliens who happen to pick them up – however unlikely that is.
Picture the scene: You’re in a self-driving car and, after turning a corner, find that you are on course for an unavoidable collision with a group of 10 people in the road with walls on either side. Should the car swerve to the side into the wall, likely seriously injuring or killing you, its sole occupant, and saving the group? Or should it make every attempt to stop, knowing full well it will hit the group of people while keeping you safe?
One hundred years ago in November 1915, Albert Einstein presented to the Prussian Academy of Sciences his new theory of general relativity. It is fair to say the theory turned out to be a great success. General relativity was built on Einstein’s special relativity, which provided solutions to some of the greatest puzzles of the 19th century theoretical physics.