The Fermi paradox questions why aliens have never visited Earth despite the Universe being so old and so vast that races should have evolved interstellar travel and come calling by now.

Now two scientists believe they may have the answer.

Astrobiologists Dr Michael Wong, of the Carnegie Institution for Science in Washington, and Dr Stuart Bartlett, of California Institute of Technology, have hypothesised that civilisations burn out when they grow too large and technical.

Faced with an ever-growing population and eye-watering energy consumption, worlds hit a crisis point known as a “singularity” where innovation can no longer keep up with demand.

The only alternative to collapse is to abandon “unyielding growth” and adopt a balance that allows survival but prevents the society moving any further forward, or venturing far from its own spot in the universe.

Read more: yahoo