Not really unlikely if you consider the vast scale of time as well. A few million years is enough to reach the end of the galaxy even at very very low percent of the speed of light. That&#x27;s a long time in our terms, but a very short time given the age of the universe, or even our own planet.<p>Self replicating Von Neumann probes could handle the issue of exploring such a large number of solar systems by increasing their numbers exponentially. They could leave behind machines that could continuously monitor and survey planets for millions of years.<p>If aliens exist, then I would expect for them to have observed us like that. Unless they have no interest in the outside world at all, which seems unlikely.