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Is Interstellar Travel Possible?

Overview

We often look up at the night sky, convinced that in a universe this vast, someone must be looking back. We also wonder and hope that we can visit them or that they have visited us. But what if the laws of nature themselves prevent contact? From the absolute limit of the Speed of Light, impacts of relativistic mass, to Time Dilation in Einstein’s theory of Special Relativity, to the curvature and the nature of spacetime in Einstein’s theory of General Relativity, and the Laws of Thermodynamics, interstellar travel is likely impossible, which explains why we are truly alone in the universe and why we have not been visited by alien civilizations. The Cosmic Haystack Problem also explains why SETI (Search for Extraterrestrial Intelligence) has not succeeded in detecting signals from alien civilizations. From the tyranny of the Rocket Equation to the Lorentz factor, the impossibility of interstellar travel isn't about technology; it's about the fundamental structure of reality. The Fermi Paradox also explains why UFOs are likely not what you think they are and why the silence of the universe is actually a beautiful thing.

In the original Star Trek, Chief Engineer Montgomery Scott would often exclaim, “I cannot violate the laws of Physics”. The physics of distance, time, and energy required for interstellar travel makes it impossible, and understanding that physics reminds us that we cannot violate the laws of physics. A video by Richard Feynman (one of the great physicists of the 20th century) explains the physics, “The Physics That Makes Interstellar Travel IMPOSSIBLE”, and reveals why aliens cannot reach Earth and why we are incapable of interstellar travel to other stars. Another video, by another great scientist, Brian Greene, titled “The Physics That Makes Interstellar Travel IMPOSSIBLE”, further elaborates on this impossibility. In these videos, the science fiction and Hollywood myths are stripped away to confront the brutal reality of space exploration. This is not just a theory; it is a deep dive into the hard science of Special and General Relativity, Thermodynamics, and Evolutionary Biology.

The 5 Verdicts of the Universe

Using the grounded principles of physics championed by the great minds of physics, Feynman explores the 5 Verdicts of the Universe—five insurmountable walls that ensure no civilization, no matter how advanced, can ever visit another. He structures his video as follows:

• The Silence in the Sky (Intro)
• Verdict 1: Distance - The Scale of the Universe
• Verdict 2: The Speed of Light Limit (Causality)
• Verdict 3: The Rocket Equation (Energy Crisis)
• Verdict 4: Biology vs. Space (Radiation & G-Force)
• Verdict 5: Time & The Radio Bubble
• The "UFO" Paradox (Why Videos are Blurry)
• Conclusion: The Beauty of Being Alone

Boundaries Written Into the Fabric of Reality

As Brian Greene stated at the beginning of his video:

“The universe is not indifferent to your ambitions; it is not neutral. It does not simply ignore the desire to cross the space between stars. It actively and mathematically and with absolute geometric precision makes it impossible. That is not a poetic exaggeration. That is a statement derived from the most precisely tested equations in the history of science.”

And, as he further elaborated a few moments later:

“The stars are ... separated from us by a barrier that is not made by distance alone. The barrier is woven into the very structure of space, time, mass, and energy. It is not an engineering problem. It is not a funding problem. It is a problem written into the mathematical foundation of physical reality itself.”

He ends his video by stating:

“Physics does not lie to you. It does not offer false promises. It tells you with extraordinary precision exactly what is and is not possible within the boundaries of this universe. And one of the things it tells you with the quiet certainty of an equation that has never once been proven wrong is that the distance between stars is not a challenge to be overcome. It is a boundary written into the fabric of reality itself.”

Key Concepts that Limit Interstellar Travel

The key physics concepts explained in these videos are:

• The Cosmic Haystack Problem: This problem refers to the significant challenges in finding extraterrestrial intelligence due to the vastness of space and the numerous variables involved, making it akin to searching for a needle in a haystack. Factors such as signal frequency, transmission power, and directionality complicate the detection of potential extraterrestrial signals. This concept highlights the difficulties in detecting potential signals from alien civilizations amid the immense scale of the universe, and thus in determining which star should be targeted for visitation.
• The Fermi Paradox: If aliens exist, why haven't they arrived? This paradox refers to the contradiction between the high probability of extraterrestrial life in the universe and the lack of evidence for, or contact with, such civilizations. It was named after physicist Enrico Fermi, who famously asked, "Where is everybody?" during a discussion about the existence of aliens. One of the answers lies in the energy cost of travel, and another answer lies in the evolutionary timeline of intelligent life.
• The Lorenz Factor: A mathematical expression in Special Relativity that describes how time, length, and other physical properties change for an object moving at a significant fraction of the speed of light.
• The Rocket Equation: How the velocity of a rocket changes as it expels propellant. It highlights the relationship between the rocket's mass, the effective exhaust velocity of the propellant, and the change in velocity (delta-v) that the rocket can achieve.
• Time Dilation: Time dilation is the phenomenon where time passes at different rates for observers in different frames of reference, particularly due to relative velocity or differences in gravitational potential. This effect is a key aspect of Einstein's theory of relativity, indicating that a moving clock ticks more slowly compared to a stationary clock. This dilation, when moving near light speed, slows time for the traveler, but it destroys any chance of meeting a civilization that is still alive.

Conclusion

If you are tired of easy talk about interstellar travel and sensationalist alien theories and want the hard truth grounded in real physics, these videos are for you. There are also technological and engineering problems associated with interstellar travel that I have examined in my Science Article “Science vs. Science-Fiction”, which also lead to the impossibility of interstellar travel. In this article, I discuss the issues of:

• The Fundamental Properties and Constants of the Universe
• The Significance of Thermodynamics and Entropy
• The Importance of Energy
  • Energy Storage and Generation
  • Energy for Propulsion
  • Energy for Shields
  • Energy for Spacecraft Operations
  • Energy for Weapons
  • Energy for Transporter
  • Energy for Replicators
• The Immensity of Space and Time
  • Navigation
  • Rendezvous
  • Travel Time
  • Relativity
• That Which is Seen, and That Which is Unseen
  • Impossibilities
  • Implausibilities
  • Logistics
  • Economics

For those who believe that alien races have overcome the scientific and engineering problems to make interstellar travel possible, they must also believe that our current scientific knowledge of the fundamental properties and laws of the universe will be superseded and that all engineering limitations can be overcome, a view of which a British person might exclaim, “Not Bloody Likely”. Hope and wishful thinking are not enough to overcome the problems of interstellar travel. Thus, for those who believe that interstellar travel is possible and that UFOs are visitors from another star, viewing these videos and reading this article should give them pause and, hopefully, put this belief to rest.

Disclaimer

Please note that my Science Articles disclaimer applies to this article, as it does to all of my science articles. These science articles are for the purposes of general scientific information that is understandable to a layperson, so that they can grasp the concepts of the topic being discussed. As such, they are neither as accurate nor as thorough as academics, scientists, engineers, and science writers strive to achieve. My hope is that these science articles will be informative and interesting, and that they will pique the reader's interest in exploring these topics in further detail via the hyperlinks that I have embedded into these articles.