Curious? Really? Thought ad hominem attacks were all the rage lately. but consider what your venerable “expert” is saying.
First given the observation that there are “billions and billions of galaxies, with each containing billions of stars, then it is indeed possible and perhaps likely that life, even intelligent advanced civilizations exist. However what your venerable expert chooses to ignore is the immense distances that separate Earth from any purported civilization. Try to formulate the distances and speed that this cigar shaped “scout” craft would have to achieve and transverse to travel even one light year. Given the laws of physics the maximum speed any mass entity robot or biological can go is the speed of light. No mass entity could ever approach the speed of light without becoming incredibly dense. No doobt that advanced civilizations may exist but outside science fiction and unprovable, far fetched theories they cannot reach us and we cannot reach them other than through radio signals. Who knows since Earth has been broadcasting in analog for about 120 years and in digital for over 50 years, an answer and wonderful revelations may be forthcoming.
Also you would do well to recognize that homo sapiens may be the only species with the capacity if not the need to exercise mystical thought. Through most of mankind’s history this has been expressed by all sorts of superstitions and ritualistic beliefs based on unprovable thoughts. Your venerable expert at Harvard also has a mystical component to his brain. Its also likely that he has no belief in a traditional divinity to express that center of his brain. Yet it is there and continues to function. So is it so suprising that your venerable expert ignores the laws of physics, admits he does not know everything about comets, where they originate or the trajectories of their course, but instead claims that this “scout” is the probe directed toward Earth sent by an advanced civilization many light years away. No doubt the thoughts make him as happy as his ancestors thart worshipped the sky and sun.
The accepted source for those who have purportedly abducted humans is not other stars, but other dimensions.
This goes back to the point in time at which Allan Hynek stopped being a skeptic and became a believer.
Whether these aliens are real or not, they are commonly thought to be extradimensional (less than a millimeter away, not light-years).
I generally consider ad hominem attacks to be a response given when the “attacker” cannot formulate a reasoned response. Clearly you are capable of a reasoned argument as the second paragraph of your response to my curiosity so aptly demonstrates, so why didn’t you respond to the OP with that rational argument rather than ridicule?