Interstellar Space Travel?

Well, Not So Fast!

Nearly everyone on Earth today has watched one or more episodes of Star Trek, Battlestar Galactica, Babylon 5, Stargate, Farscape, and, of course, the Star Wars movies and television series. Billions of dollars of public and private money are spent each year on the search for extraterrestrial intelligence (SETI), spurred on by historians and archaeologists who claim intelligent beings from a planet “far, far away” must have assisted ancient peoples in their remarkable construction projects and astronomical endeavors.

Many people dream about interstellar space travel and ETI visitors. However, we must ask ourselves just how practical it would be for any human-like being to travel from one planetary system to another. What kind of spaceship would be needed? How much time would it take, and how much would the journey cost? Would the conditions of space and the laws of physics even allow for interstellar travel?

Distance Challenge

The nearest planet outside our solar system, Proxima Centauri b, resides 4.25 light-years, or 40 trillion kilometers (25 trillion miles), from Earth. To imagine this great distance, consider scaling Earth’s 12,750-kilometer (7,920-mile) diameter down to the size of a mustard seed, one to two millimeters (1/32 to 3/32 inch) in diameter. On this size scale, the distance from Earth to Proxima Centauri b would be the distance from Los Angeles, California, to Providence, Rhode Island.

Of course, intelligent physical life could not survive on Proxima Centauri b. Nor could it survive on any other relatively “nearby” planet. Even the most optimistic SETI astronomers acknowledge that only by traveling 200 light-years or more from Earth would we find another planet or moon on which intelligent physical life could conceivably survive.

In reality, of the nearly 7,500 planets outside the solar system astronomers have detected, none possess the characteristics intelligent physical life requires.¹ Earth is the only known planet that resides within all fourteen of the identified planetary habitability zones, all of which are required for life to exist on the planet.² (No other planet yet discovered resides in more than three of these essential-to-life zones.) Venus ranks as the most Earth-like planet yet discovered.³ The Sun is still the only known star with all the characteristics needed to host a planet where intelligent physical life could exist.⁴

 Time & Speed Limits

If we were to travel 200 light-years on the fastest spacecraft ever launched by the world’s space agencies, the one-way trip would take 5.27 million years. “Are we there yet?” would take on new meaning! At one percent the velocity (speed) of light, the trip would be 20,000 years long. At 10 percent of light’s velocity, it would take 2,000 years.

Astronomers are exploring the possibility of sending spacecraft to Proxima Centauri b to study its physical and chemical conditions. Planning efforts have revealed both speed and size limitations on interstellar space travel, primarily due to particulates.

Interstellar space is not entirely empty. It is filled with particles, dust, pebbles, rocks, and radiation. This space debris poses a dire risk to space travel. The faster a spaceship moves through space, the greater the damage it suffers from collisions with space debris. This damage rises with the square of the spaceship’s velocity. Thus, a spaceship traveling at 10 percent of light’s velocity would suffer a hundred times the damage of a spaceship traveling at one percent of light’s velocity. In other words, a spaceship can travel only as fast as avoidance of catastrophic damage allows.

 Size Challenge

Given the presence of space debris, the larger a spaceship’s cross section (diameter), the more damage it will suffer. The number of impacts rises with the square of the spaceship’s cross section. So a spaceship with a cross section of 100 meters (328 feet) will be struck by 100 times as many impacts as a spaceship only 10 meters (33 feet) in diameter.

Astronomers have calculated that any hope of acquiring useful information about Proxima Centauri b via spacecraft sent there from Earth requires the spacecraft to be no more than 10 centimeters in diameter and to travel no faster than 20 percent of the velocity of light.

In fact, such a trip would require spacecraft, plural. If a thousand spacecraft, each a mere 10 centimeters across (about four inches), were sent to Proxima Centauri b at 10 percent the velocity of light, astronomers estimate that at least half would be destroyed on the way. All would be damaged, but among the remaining half, some would be damaged in different ways. These differences might be sufficient to allow for the gathering of some useful information about conditions there. However, this research would require extreme patience—a 43-year wait for the spacecraft to arrive at Proxima Centauri b and another 43-year wait for transmitted information to return. Astronomers wonder how many funding agencies would be willing to wait 86 years for a potential return on their investment.

Astronomers could send spacecraft to Proxima Centauri b at 20 percent the velocity of light. At this speed, the wait time to receive information would be cut in half. However, this extra speed would mean sending at least 4,000 10-centimeter-diameter spacecraft, or 1,000 five-centimeter-diameter spacecraft. (Spacecraft as small as five centimeters across, though, are not realistic. They would lack the technology and transmitting power to send useful information back to Earth.)

Who Would “We” Be?

A spacecraft 10 centimeters across might be large enough to house a tiny ant or termite, but it would be far too small to provide the food, water, and oxygen such a creature would need for a space trip of 40+ years. A far bigger problem is presented by the deadly radiation environment of interstellar space.

About 99 percent of galactic cosmic radiation is comprised of atomic nuclei (atoms stripped of their electrons), and about one percent is solitary electrons. Of the atomic nuclei, 90 percent are hydrogen (single protons), nine percent are helium, and one percent are nuclei heavier than helium. The most abundant heavier-than-helium nuclei (in order of abundance) are oxygen, carbon, neon, iron, nitrogen, silicon, magnesium, and sulfur. Note that the heavier the nucleus, the greater damage it can inflict.

Earth’s magnetosphere (see figure) shields life on Earth from deadly cosmic radiation. Outside the magnetosphere, however, life is fully exposed. Serious exposure to heavy ion galactic cosmic radiation occurs in regions beyond the outer red lines emanating from Earth.

During a brief three-year trip outside Earth’s magnetosphere, every third cell in an organism’s body would be struck by a nucleus heavier than neon, and every sixteenth cell, struck at least twice.⁵ This would be the outcome if the organism were protected by an aluminum radiation shield at least two centimeters thick, plus a layer of water 30 centimeters thick. Such a shield is far beyond what can be accommodated in a 10-centimeter-wide spacecraft.

The bottom line is clear. Even the most radiation-tolerant bacteria would not survive a trip across interstellar space in a spaceship less than two meters in diameter.⁶ The “we” is not a living being.

Help from ETI?

Scholars who suggest that ancient peoples received help in their construction projects and scientific endeavors from intelligent beings beyond the solar system appear to underestimate the scientific knowledge and technological capability of people living thousands of years ago. Ancient peoples living all over the world were at least as fascinated by the heavens and as eager to learn about the size, structure, and mechanics of heavenly bodies as people today.

Ancient peoples lacked optical telescopes, but in their determination to measure the positions and movements of heavenly bodies, ancient astronomers assembled huge stone observatories. They placed giant stones to serve as sighting aids (like gunsights) to assist them in making precise measurements. What’s more, archaeologists have determined that ancient people had developed the technology and the means to quarry these heavy stones, transport them over distances of a few hundred kilometers, and position them accurately to accomplish their research.

The best-known example of a stone observatory is Stonehenge in England’s Salisbury Plain. However, remains of thousands more of these observatories can be found throughout Europe, Asia, Africa, and North and South America, where the stone circle portions varied in dimensions from 10 meters to 330 meters across.⁷ Ancient people needed no ETI help to build these research facilities, among many other structures.

“Yes” to Exploring Interstellar Space

The fact that living organisms cannot safely traverse interstellar space does not imply that humans cannot study bodies beyond our solar system or that we’re prevented from “boldly going where no man has gone before.” Regardless of our personal travel limitations, our technology can go. Devices such as the James Webb and Hubble Space Telescopes have already revealed amazing and previously unknown features of the universe and Earth. These features enable us not only to live and thrive but also to explore the full extent and history of our cosmos and its two trillion galaxies. These discoveries on every size scale, from the cosmic web down to the interiors of the Sun, Earth, and Moon, yield evidence of exquisite design and a Designer’s intent to provide a home for billions of intelligent physical beings.⁸

Notes
1. Exoplanet TEAM, Exoplanet Encyclopaedia, Catalogue of Exoplanets (Jun. 2, 2025).
2. Hugh Ross, “Tiny Habitable Zones for Complex Life,” Today’s New Reason to Believe (blog), Reasons to Believe (Mar. 4, 2019); Hugh Ross, “Complex Life’s Narrow Requirements for Atmospheric Gases,” Today’s New Reason to Believe (blog), Reasons to Believe (Jul. 1, 2019); Hugh Ross, “Earth-Moon Coupled Magnetosphere Paved the Way for Life,” Today’s New Reason to Believe (blog), Reasons to Believe (Sep. 20, 2021); Hugh Ross, “Earth’s Magnetosphere Appears Designed for Habitability,” Today’s New Reason to Believe (blog), Reasons to Believe (Mar. 27, 2023).
3. Hugh Ross, Designed to the Core (RTB Press, 2022), 132–135.
4. Hugh Ross, Designed to the Core, 117–129.
5. S. B. Curtis and J. R. Letaw, “Galactic Cosmic Rays and Cell-Hit Frequencies Outside the Magnetosphere,” Advances in Space Research 9, no. 10 (Oct. 1989): 293–298.
6. H. J. Melosh, “Exchange of Meteorites Between Stellar Systems,” Meteoritics and Planetary Science 36, Supplement (2001): A130–A131; Henry Jay Melosh, “Exchange of Meteorites (and Life?) Between Stellar Systems,” Astrobiology 3, no. 1 (Jan. 2003): 207–215.
7. Daniel Brown, “An Introductory View on Archaeoastronomy,” Journal of Physics: Conference Series 685, issue 1 (2016): id. 012001; Alexander Thom and Archibald S. Thom, “Megalithic Astronomy,” The Journal of Navigation 30, issue 1 (Jan. 1977): 1–14; J. Donald Fernie, “Marginalia: Alexander Thom and Archaeoastronomy,” American Scientist 78, no. 5 (Sep.-Oct. 1990): 406–407; J. McKim Malville et al., “Megaliths and Neolithic Astronomy in Southern Egypt,” Nature 392 (Apr. 2, 1998): 488–491; Thomas G. Brophy and Paul A. Rosen, “Satellite Imagery Measures of the Astronomically Aligned Megaliths at Nabta Playa,” Mediterranean Archaeology and Archaeometry 5, no. 1 (Jun. 2005): 15–24.
8. Hugh Ross, Designed to the Core.