Robert H. Gray
In 2016, Gray published an article in "Scientific American" about the Fermi paradox, which claims that if extraterrestrials existed, we would see signs of them on Earth, because they would certainly colonize the galaxy by interstellar travel. Gray argues that the Fermi paradox, named after Nobel Prize-winning physicist Enrico Fermi, does not accurately represent Fermi's views. Gray states that Fermi questioned the feasibility of interstellar travel, but did not say definitively whether or not he thought extraterrestrials exist.
Purcell effect
One way of seeing why this enhancement arises is by using cavity quantum electrodynamics. Fermi's golden rule dictates that the transition rate for the atom-vacuum (or atom-cavity) system is proportional to the density of final states. In a cavity at resonance, the "density" of final states is enhanced (though the number of final states may not be). The Purcell factor is then just the ratio of the cavity