Are there really aliens in the universe?

Since human beings explored extraterrestrial life, we haven't found any footprints about extraterrestrial life, let alone aliens. If it really exists, it will be a sensational event in the world. Obviously, whether you guess or not, the result is the same "no evidence".

But science pays attention to evidence. Since there is no evidence of aliens now, the answer is definitely "no", so from the existing science, there is no need to dispute.