There is a lot of real estate on habitable exo-planets around other stars. Rather than compete for the limited territory on our rock, the Earth, we better explore new territories in interstellar space. Extending the footprint of our civilization from a single planet to interstellar scales is possible, as envisioned in my recent book titled “Interstellar”. My previous book was titled “Extraterrestrial”. Should my next book be titled “Intergalactic”?
Probably not. Travel on intergalactic scales is constrained by the accelerated expansion of the Universe. As I showed in a recent paper, chemical rockets cannot carry us beyond our nearest neighbor, the Andromeda galaxy, even if they travel indefinitely at their limiting speed of tens of kilometers per second. The reason is that beyond Andromeda, galaxies are receding away from us faster than chemical rockets, and our spacecraft will never catch up with them. For a while we could still detect light emitted by these distant galaxies, but even that privilege will end once the Universe will age by another factor of ten. At that time, all distant galaxies will recede away from us faster than light assuming that the cosmological constant will remain constant, as indicated by current data.
But there is still a lot of real estate for us to explore within our galaxy, which will not take part in the cosmic expansion. Our galaxy resembles a city of stars with numerous lights illuminating potential homes for our civilization to explore. For the foreseeable future, real estate agencies will be able to sell properties on habitable planets or space platforms that remain gravitationally bound to the Milky-Way.
As with real estate on Earth, the value of such properties will depend on three factors: location, location and location. Milky-Way locations are measured in light years, which naturally translate to communication time at the speed of light. Chemical rockets move ten thousand times slower than the speed of light. And so, it would take them about forty thousand years to reach the nearest star, Proxima Centauri, at a distance of 4 light years.
Instead of engaging in long trips, future earthlings might use avatars with artificial intelligence (AI) as their representative agents. Technological avatars could be resilient to high accelerations or harmful cosmic-rays and patient enough to traverse interstellar distances without getting bored. These agents could respond within a human lifetime to the wishes of customers for destinations that are tens of light years away. A recent paper listed potentially habitable worlds within that distance.
Of course, if we notice AI avatars on Earth that represent alien customers, we should be flattered that they chose the Earth as a desired destination. Good hospitality would foster interstellar tourism. By satisfying the desires of alien agents, we would attract more of them and learn about new propulsion technologies that would assist us in reaching their origin with our own AI avatars. If their gadgets reach our doorstep before our gadgets reach their doorstep, we can surely learn something from their advanced technologies.
Of course, earthlings might want to get more information from an “open house” on habitable exoplanets before investing in interstellar real estate. After all, a “potentially habitable” world at a distance might end up being a disappointing desert from up-close. One should never believe a Promised Land until witnessing it, even if it takes a journey of forty years through a desert — as experienced by the Jewish people after slavery in Egypt. The view of new worlds can be transmitted electromagnetically. Eavesdropping on video clips from extraterrestrial real-estate agents would be a fun discovery by SETI scientists.
But every long journey starts in a small step. We can start our extraterrestrial real-estate endeavors on the Moon at a distance of 1.3 light seconds, and then expand it to properties on Mars at a distance that varies between 3.2–22.3 light minutes. For these nearby destinations, travel by humans is feasible and AI avatars are not required.
One may wonder whether much faster travel is possible with advanced engines. According to Einstein’s Theory of Relativity, any material object can at best approach the speed of light but cannot exceed it. Time dilation could allow passengers to traverse long distances without much aging. But getting close to the speed of light requires a huge amount of energy and poses a health risk because of the steady bombardment by energetic dust and gas particles.
Exploring other worlds will expand our world model. So far, we benefited from our experience on Earth. Exploring new environments will broaden our imagination. Our contact with the terrestrial environment was first restricted to our motor skills and later advanced to instruments. With AI avatars as our ultimate agents, we will be able to probe new landscapes and get a better sense of what is possible in our cosmic neighborhood.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.
