Why would you ask a question that everyone knows the answer to? The great thinker and astronomer Carl Sagan asked this question, ‘Is there life on Earth?’ But he asked it from a different perspective; from the viewpoint of an unknowing observer far outside the Earth. In December 1990, NASA’s exploratory space probe, Galileo, was due to fly past Earth. Sagan persuaded NASA to point the craft’s instruments at our planet.
Galileo delivered remarkable results. Images of Australia and Antarctica obtained as Galileo flew overhead showed no signs of civilization. But instruments measured oxygen and methane in Earth’s atmosphere, suggesting possible life. The infrared spectrum of light from Earth indicated the likely presence of vegetation. Finally radio transmissions coming from Earth suggested intellient life. “A strong case can be made that the signals are generated by an intelligent form of life on Earth,” Sagan’s team wrote, rather cheekily.
The findings were highly instructive and have shaped how we examine very distant planets for signs of life. The project is described in this article in Nature.com.
The genius Stephen Hawking asked a ridiculous question in 2009 when he sent out invitations. He asked, ‘Would you like to come to a party which has already taken place?’ He held the event. Unsurprisingly, no-one came. He subsequently sent out many invitations. They were aimed at time travellers from any period in the future. Hawking described the whole thing as an experiment which provided evidence that time travel was not possible.
Great scientists, great philosphers and great thinkers ask questions which at first glance appear absurd. But by getting us to think about things in new ways they provide valuable insights.