The standard framing of the Fermi paradox treats the silence of the universe as a mystery to be solved. Where is everyone? The galaxy is old enough, and large enough, that a civilization with even modest expansion ambitions should have made its presence known by now.
The silence requires explanation. And so we generate explanations — civilizations destroy themselves, intelligent life is vanishingly rare, everyone is hiding, everyone is watching, the signals are there but we lack the instruments to detect them.
These explanations share an assumption worth examining: that interstellar presence is the natural endpoint of civilizational development, and absence therefore requires a special cause. The physics of interstellar travel does not support this assumption.
The distances are not obstacles to be overcome with sufficient technology. They may be the universe's answer to a question we keep asking wrong.
The nearest star system is four light-years away. At the fastest speed any human-made object has ever traveled, the journey takes roughly seventy thousand years. Chemical propulsion — the technology behind every rocket ever launched — cannot meaningfully improve on this.
The theoretical upper bound for a spacecraft, using known physics, is a significant fraction of the speed of light. Achievable only with energy expenditures that dwarf the current output of human civilization. At that speed, the journey to the nearest star takes years. The journey to the center of the galaxy takes tens of thousands.
The observable universe contains hundreds of billions of galaxies, each containing hundreds of billions of stars. The distances make even the most optimistic propulsion scenarios irrelevant to the question of contact.
This is not a temporary engineering problem. The speed of light is not a barrier that a sufficiently advanced civilization breaks through. It is a structural feature of spacetime. A civilization a million years more advanced than us is still bound by it.
What changes with advancement is not the speed limit — it is the ability to use time differently. And this is where the FHH framework becomes relevant.
If physical space is effectively closed, then time becomes the more promising dimension for any intelligence interested in exploration or contact. A civilization that has solved the problem of biological continuity — that has extended its existence across deep time — is not a civilization that travels between stars. It is a civilization that travels between eras.
The universe, in this reading, is not built for visitors from far away. It may be navigable, however, by intelligences that have learned to move through time rather than space.
The silence of the cosmos is not necessarily evidence of absence. It may be evidence of a different kind of presence — one that does not announce itself through radio waves or megastructures, but through careful, temporally-extended engagement. The universe is not built for visitors. It may be built, if it is built for anything, for inhabitants who have learned to stay.