Sometimes it feels like we arrived late to the galaxy party and everyone has already gone home.
Our species only figured out how to get into orbit in the last century. Since then, we’ve flown explorers to the Moon and sent space probes throughout our solar system. During the first few decades of space exploration, scientists launched the twin Voyager spacecraft, which have since passed into interstellar space. If you count our machines, humanity has already (just barely) become an interstellar species.
If we assume that other intelligent civilizations have similar motives – to survive, grow, expand and explore – then why haven’t we found any signs of them yet? The answer may lie in the fact that Earth exists on the edge of the galaxy, far from the hustle and bustle of the city center. Intelligent aliens may prefer warped space-time around supermassive black holes.
Why is it so hard to spread across the galaxy?
Milky Way
The universe described in novels and movies is a little different from the universe we actually understand. Here in real space, there are no faster-than-light spaceships or subspace communication systems, and you can’t teleport anywhere.
The speed of light (roughly 671 million miles per hour and denoted by a lowercase “c”) is, as the name suggests, the speed at which light travels through a vacuum, but it’s more than that. This is the cosmic speed limit, the most likely anything (matter, energy or information) can travel through space. Barring something that completely rewrites our understanding of physics, it’s likely that a spacecraft (alien or otherwise) can fly at some fraction of c, and that’s a problem.
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Even at a large fraction of the speed of light, it would take years for a spacecraft to reach the nearest star. Even worse, time dilates when traveling near the speed of light. Everyone on board will experience time much more slowly than someone resting on Earth. Star travelers would return from a mission of months or years to find a planet that had traveled decades or centuries into the future without them.
We are burdened by the twin problems of time and distance. Anything outside of your own star system is too far away to reach in a reasonable amount of time, and when traveling at sufficient speed to reach them, time has dilated, separating you from the rest of civilization. Without the seemingly miraculous technology that allows for rapid interstellar travel and without the unwanted effects of time dilation, alien societies orbiting the stars seem less and less likely.
Instead, we may have to reimagine what intelligent life in space looks like.
The benefits of living around a black hole
Black hole GIF
A new study, titled Redshift Civilizations, Galactic Empires, and the Fermi Paradox, published on the arXiv preprint server, shows how an alien civilization could overcome these limitations by orbiting a supermassive black hole.
Study authors Chris Reiss, an independent scientist, and Justin C. Feng, a PhD candidate at the Central European Institute of Cosmology and Fundamental Physics (CEICO) at the Czech Academy of Sciences’ Institute of Physics, proposed several advantages for a redshifted civilization.
Relativity describes many of the implications of the speed of light, particularly its relationship to how we experience time. If an observer is traveling at nearly the speed of light or is subject to intense gravitational forces, time begins to dilate. If you put your civilization into orbit around a supermassive black hole, it would be in a constant state of time dilation.
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Explorers could go on space missions and return home, staying relatively at the same reference point. The rest of civilization would not have moved on without them. But that would also mean that from our perspective, intelligent aliens would be incredibly sluggish and slow to react. Our own history can take centuries to unfold, while in the alien empire at the center of the galaxy only a few days or hours have passed. Such a civilization could even establish outposts and research laboratories in normal space. Then every few days they could benefit from centuries of scientific and technological progress.
Another interesting consequence of relativity is that distances shrink over time at high speeds. It’s hard to wrap your head around, but it’s true. If our alien civilization is experiencing time dilation 100 times, then everything in space would also appear (and actually be) 100 times closer.
Seen from the unique perspective of an ever-expanding rest frame, an alien civilization is suddenly confronted with a galaxy that is much smaller and can be conquered in less time. And if the explorer leaves, their friends and family will still be there when they return. The problems of interstellar travel become less serious when you live around a black hole.
Of course, trying to talk to such an intelligence that has lived for eons can be like trying to talk to a stone. Maybe we haven’t met the aliens yet because they live in a slow-time bubble around our galaxy’s supermassive black hole. From their point of view, we only came out of the trees last week and they didn’t even notice.
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