Universe and civilization

1. Is there any factual evidence that the Earth have been visited by other civilization?
2. Is important to explore the Universe looking for signals from other civilization?
3. Make a quick research about SETI institute. Is its mission important nowadays?
Are we alone in the vast universe? This a very polemic question. Most of Scientist (Astronomers, Physicists, Biologists, etc.) state that no civilization has visited our planet. Nevertheless Prof. Abraham Loeb* has written a book describing the visit of an interstellar object called “Oumuamua” that passed 15,040,000 miles from Earth; it is opinion of Prof. Loeb that the object is a piece of advanced technology created by a distant alien civilization.
Prof. Loeb based his hypothesis on the facts that Oumuamua was moving to fast along a strange orbit, it left no trail of gas, and the shape of the object was unusual.
Long time before of the discover of Oumuamua, the astronomer Frank Drake** formulated an equation to estimate the number of civilizations in our galaxy that we might be able to communicate with.