The Distance Between Galaxies Is Worse Than You Think

Pick any galaxy in tonight's sky and ask the simplest question imaginable. How long would it take to get there? For a few, there is an answer, however staggering. For most, there isn't. Not because the number is too large to write, but because there is no number at all. 94% of the galaxies in the observable universe are already permanently beyond reach, even at the speed of light, even starting right now. Let's travel outward, one stop at a time, until the travel times grow longer than the universe itself, and then, at one exact distance, stop existing altogether. On the 18th of November, 2026, Voyager 1 becomes the first human-built object to sit one full light day from Earth, 16 billion miles, a gap light crosses in 24 hours. Voyager needed 49 years. It cruises at about 38,000 miles per hour, engines off since 1980. Our fastest creation, the Parker Solar Probe, hit 430,000 miles per hour in 2024, 11 times quicker than Voyager, yet still just 6 hundredths of 1% of light speed. So every stop below gets three numbers, Voyager for what we actually do, Parker for our fastest achievement, and one-tenth light speed, a wish nothing we've built comes within a factor of a hundred of. One scale to hold onto, shrink the Milky Way to a 10-inch dinner plate. The Magellanic clouds become a saucer 16 inches away, Andromeda, a second plate 21 feet across the room, the Virgo cluster 450 feet out, and the point where travel time stops making sense sits 28 miles away. The large Magellanic cloud sits about 163,000 light years out, its smaller companion around 200,000. Voyager would take 2.9 billion years to arrive. Parker, 254 million years. One-tenth light speed, 1.6 million years, a span before dinosaurs reached their largest size. In 1987, a star there exploded, its light arriving after 163,000 years in flight, a message sent long before our species existed. Both clouds sit inside the Milky Way's gravitational grip. Wherever the rest of the universe goes, gravity has already decided these two are coming with us. Andromeda, 2.5 million light years away, is the last stop that behaves the way intuition expects. Voyager needs 44 billion years. Parker, 3.9 billion, long enough that the sun would destroy Earth first. But Andromeda is racing toward us at roughly 250,000 miles per hour. The old story gave a collision in 4 to 4.5 billion years. In 2025, a team led by ran over 100,000 simulations with Hubble and Gaia data and put the odds within 5 billion years at under 2%, within 10 billion years at about 50. A coin flip for our galaxy's most famous scheduled event. Even if it happens, stars are so sparse that two galaxies can pass through each other with almost no collisions. Gas clouds ignite, spiral arms stretch into streamers, and after a billion years, the two settle into one elliptical blob, a slow rearrangement of the night sky rather than a crash. What never changes? Andromeda, the Milky Way, the Magellanic clouds, and several dozen smaller galaxies form one gravitationally bound local group. Merge or miss, they're never leaving each other. The local group spans roughly 10 million light years, with its far edge about 5 million light years out. Voyager would take 88 billion years to reach it, over six times the age of the universe, a number that still writes down but no longer means anything usable. Parker takes 7.8 billion years, one-tenth light speed, 50 million. This edge is the last true boundary. Inside it, gravity holds. Outside, space expands faster than gravity can pull back, and the gap keeps growing every year. Run the clock forward a hundred billion years, and everything outside the local group fades from view entirely, leaving a future civilization looking up, and reasonably carefully, concluding that their lone, merged galaxy is the whole universe. They would be wrong only because the evidence itself would be gone. We're lucky enough to live while it's still visible. The Virgo Cluster, about 54 million light years away and home to over a thousand galaxies, would take Voyager 952 billion years to reach, and Parker 84 billion, six times the age of the universe, at our fastest real speed. Only the one-tenth light speed figure still means anything. 540 million years, roughly as long as complex animal life has existed on Earth, reachable only by a civilization we are not. Virgo is also pulling us toward it, as part of a vastly larger structure called Laniakea, a supercluster about 500 million light years across holding the Milky Way, Virgo, and around 100,000 times our galaxy's mass. We live inside it, and we'll still never cross most of it, since dark energy will pull Laniakea apart long before anything could. One distinction matters here. When a galaxy is to be 10 billion light years away, that's usually how long its light has traveled, not where the galaxy sits now. While that light was in flight, space itself stretched, carrying the galaxy further out, which is why the observable universe measures 46 billion light years in radius, despite being only 13.8 billion years old. The road grew longer while the light was still traveling it. Right now, at a present distance of about 18 billion light years, the arithmetic simply ends, the 28-mile mark on our dinner plate. Beyond that line, space is being added between us and everything else, faster than light could ever cross it. A ship leaving today at light speed would never arrive, not in a trillion years. It's like swimming up a river that has been accelerating for roughly 5 billion years. Match its current, and you go nowhere forever. Let it outpace you, and there's a point upstream you'll never reach at all. Of the roughly 2 trillion galaxies in the observable universe, only about 6% sit inside that reachable boundary. 94% are already gone, in the only sense that matters to a traveler. And the fraction keeps shrinking, roughly 20,000 stars cross that line every second. Their light from a moment ago will reach us eventually, their light from right now never will. The boundary isn't approaching, it has stood here for billions of years. So for the Magellanic Clouds, the answer is a number too large to ever use. For Andromeda, it may come to you on a coin flip. For Virgo, it demands a civilization we are not. And for 94% of everything else, there is no answer, and there never will be.