If you are fed up, like many of us, with the depressing news around the world and want to escape from Earth, preferably faster than light, please continue to read. In the paragraphs below you will find an uplifting travel plan that resolves your frustrations.
First and foremost, this plan is based on existing technologies and known physics. It will ultimately carry you away from Earth faster than light, so that your news alerts and updates on Facebook, WhatsApp, Instagram or YouTube will not catch up, and you will be automatically weaned by the laws of physics from any addiction to digital screens.
For an honest, full disclosure right from the start, let me put all cards on the table. The travel plan will become practical only after AI-assisted medicine will add more than a year to your lifespan for any passing year, namely once you reach the so-called longevity escape velocity. The reason is simple. Our existing propulsion technology and the known laws of physics require 140 billion years for a trip that will ultimately surpass the speed of light relative to Earth. As long as you are patient and immortal, you can make it. Let me repeat: this is not science fiction! At the TED2024 Conference that I attended two weeks ago, the futurist Ray Kurzweil forecasted that the longevity escape velocity will be reached within the coming decade.
The next challenge is to escape from the gravitational pull of the Milky-Way galaxy. Based on the census of nearby stars by the Gaia survey, the local escape speed from the Milky-Way is 500 kilometers per second. Fortunately and completely by coincidence, this value resembles the escape speed from the surface of the Sun, 618 kilometers per second, or from the surface of most other stars on the Main Sequence. This means that escaping from planets around most stars, irrespective of how tight their orbits are, is easier than escaping from the Milky-Way. Our galaxy is reminiscent of New-York City in Frank Sinatra’s song: “If you can make it there, you’ll make it anywhere.”
The resemblance between the escape speed from most stars and the Milky-Way offers a great benefit. It implies that gravitational-assist maneuvers at grazing incidence to stars or through tight stellar binaries, can launch a chemically-propelled spacecraft beyond the escape speed of the Milky-Way.
Thus, after some local maneuvers, our one-way trip will continue with a spacecraft travelling at about 1,000 kilometers per second out of the Milky Way. Within a billion years, the spacecraft will exit from the Local Group of galaxies, encompassing the Andromeda galaxy and its satellites out to 3 million light years. Beyond that distance, the spacecraft will be carried away by the accelerating cosmic expansion.
The subsequent part of the trip will require no engine since the recession speed and distance of the spacecraft will increase exponentially as a result of the cosmic expansion, with a doubling time of 11.4 billion years.
Here are some milestones for the trip. Within eighty billion years, our spacecraft will be half-a-billion light-years away. After travelling for 140 billion years, the passengers will be out of the cosmic horizon of Earth; and within 200 billion years the spacecraft will be located 600 billion light years away from Earth. At these late times, no communication will be possible between earthlings and the passengers. Each side will view the other as if the counterpart entered a black hole, with the counterpart’s image fading and freezing on the time that represents horizon crossing. This will be the last image that the travelers can post on their Instagram or vice versa. The structure of spacetime will not allow later signals from bridging the accelerating distance between Earth and the spaceship.
A simple way to understand these inescapable circumstances is by imagining ants walking on the surface of an expanding balloon. The walking speed of the ants is analogous to the speed of light in the Universe. But if the balloon is blown fast enough, the ants will never be able to bridge the rapidly increasing gap that opens up between them. The expansion of the balloon’s surface is the two-dimensional analog for the accelerated cosmic expansion of three-dimensional space. Once the Universe will age by a factor of ten, our spacecraft will accelerate away from Earth at a speed that exceeds the speed of light.
Yes, the universe does offer a free ride, as long as the spacecraft will escape the Local Group of galaxies. After we reach the longevity escape speed, our travel agencies could offer trips to destinations beyond our cosmic horizon. Given that these travel packages would include one-way trips and that the destination will be out of touch even at the speed of light, these cosmic travel agencies should not worry about travel insurance.
Bon Voyage!
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 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.
