Science Loop on Youtube talks about the visualization of the great famous Drake equation. This equation calculates the number of alien civilizations in our fantastic Milky way galaxy. "Are we alone in the whole universe" - this question is asked from ancient times. Humans are still wondering about this.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.
The equation was written in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first scientific meeting on the search for extraterrestrial intelligence (SETI). The fascinating equation summarizes the main concepts which smart scientists must contemplate when considering the question of other radio-communicative life. It is more properly thought of as an approximation than as a serious attempt to determine a precise number.
There is some criticism of the equation. Most criticism related to the Drake equation focuses not on the equation itself, but on the fact that the estimated values for several of its factors are highly conjectural, the combined multiplicative effect being that the uncertainty associated with any derived certain value is so large that the equation cannot be used to draw really firm conclusions.
Many scientists are searching for microbial life forms on other planets and moon in our solar system (Mars, Venus, Europa, Saturn). However, scientists in SETI (Search for extraterrestrial intelligence) are searching for extraterrestrial intelligent life forms.
There seems to be no sure "no evidence" of those alien beings. You might think that there is no way we could know any of these things right now.
The Fermi paradox, named after Italian-American physicist Enrico Fermi, is the apparent contradiction between the lack of evidence for extraterrestrial civilizations and various high estimates for their probability.
Below: The Drake Equation: See more information here: https://en.wikipedia.org/wiki/Drake_equation