The field of physics, like any scientific discipline, is characterized by a diversity of opinions and perspectives. It is not uncommon for different physicists to hold differing views on certain topics, and this can certainly be the case when it comes to unconventional concepts such as propellantless space drives.
Marc Millis, a former NASA physicist, has been an advocate for advanced propulsion concepts and has explored the possibilities of propellantless space drives as part of the Breakthrough Propulsion Physics program. His work has focused on pushing the boundaries of our current understanding and exploring potential avenues for future space exploration.
On the other hand, Sean Carroll, a theoretical physicist, has a different perspective and has expressed skepticism towards the concept of propellantless space drives. His skepticism may arise from the fact that such propulsion systems would need to violate or greatly extend our current understanding of fundamental physics, such as Newton's laws of motion or Einstein's theory of relativity.
It's important to note that scientific opinions are not determined by consensus or popularity, but by the strength of evidence and the ability to make testable predictions. In the case of propellantless space drives, the scientific community as a whole has not yet reached a consensus, and the concept remains highly speculative and controversial.
In the scientific community, ideas and concepts go through a process of scrutiny, peer review, and empirical testing. It is through this rigorous process that scientific theories and concepts are validated or debunked. However, it is also worth noting that scientific progress often involves exploring and investigating unconventional ideas, as some of the most significant breakthroughs have come from challenging the established norms.
So, the existence of differing opinions among physicists on the feasibility of propellantless space drives is reflective of the ongoing scientific discourse and the complex nature of pushing the boundaries of our knowledge. It is through this ongoing discussion and investigation that our understanding of the universe continues to evolve.