Many years ago, the physicist Enrico Fermi asked that, given the fact that our universe has been around for a very long time and we expect that there are many planets within it, we should have found evidence for alien life by now.
Molts anys enrere, el físic Enrico Fermi es va preguntar que, donat que l'univers ha existit  durant molt de temps i hi creiem que hi ha molts planetes, a aquestes alçades ja hauríem  d'haver trobat vida alienígena.