Do aliens exist? Could Earth really be the only planet hosting intelligent life?

Debates over the existence of extraterrestrials date back to the earliest Indigenous and western thought.

The tools generating the evidence within western science, however, have changed — from the philosophical and theological arguments of the Ancient Greeks to the development of increasingly sophisticated telescopes and space travel and exploration.

These include NASA’s missions to Mars, using a fleet of robotic orbiters, landers and rovers, and the development of the James Webb Space Telescope, which orbits the sun 1.5 million kilometres away from the Earth.

Philosophy and theology

Aristotle’s views on the nature of the cosmos dominated the Ancient Greek world. He argued that there’s only one world, at the centre of which is an immobile Earth. The planets move around the Earth. Beyond them is the sphere of the stars, or heaven.

“It is clear then that there is neither place, nor void, nor time, outside the heaven,” he wrote in On the Heavens. “Hence whatever is there, is of such a nature as not to occupy any place, nor does time age it.”

Aristotle’s teachings later created a storm in the Catholic Church, with various theologians worrying that Aristotle’s ideas were becoming too dominant. Étienne Tempier, bishop of Paris, responded to these criticisms by issuing the Condemnation of 1277, prohibiting the teaching of........

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