Where is Everyone?

Sctattered in time.

Our galaxy - The Milky Way - is a collection of 100-400 billion stars all in orbit around a supermassive black hole. Estimated to be over 13 billion years old, time enough has passed for over one trillion planets to have formed around those stars. One trillion planets.

The physical laws, processes, and materials that allowed for intelligent life to arise from inanimate matter here on earth are to be found everywhere in our universe. Intelligent life has had more than ample time and opportunity to have come into existence many times over in the last billions of years and then to have moved into space and spread out to every corner of our galaxy.

It would take about 1 million years for an alien intelligence dedicated to the colonization of the galaxy to become ubiquitous throughout it. Enough time has passed where this should have occurred multiple times. But so far dedicated attempts at detecting them has failed, resulting in only an eerie, empty, silence.

Enrico Fermi, an Italian-born physicist first asked - if intelligent alien life has arisen and had more than ample time to have spread out throughout our galaxy - where is everybody?

The answer to this paradox may lie in the manner in which alien civilizations expand out into the galaxy from their home planets, and in our methods of detecting them.

There are essentially two ways to travel the vast distances of space ( warp drives, subluminal warp bubbles, Krasnikov tubes, worm holes, and cosmic-string travel aside)

1. Slower moving generational travel where the original occupants of a spacecraft never see their goal - leaving that for future generations after a trip lasting hundreds or even thousands of years.

2. The second is to travel at near light speed, allowing for relativistic effects to become pronounced. Such effects allow the original crew to reach their destination in their lifetimes, but it isolates them from their home planet, not only in distance, but in time as well.

Slow moving generational space travel is really neither practical or likely. Given the vast distances between star systems - taking hundreds, if not thousands of years to travel between star systems seems as daunting a task as developing craft that can travel at near the speed of light.

Generational travel to a star system 50 light years from home would take hundreds of years. Upon arrival at their destination meaningful communication with their home world would have become impractical decades earlier and besides everyone still alive would have never even seen ‘home’. Even if they wanted to contact home, at 50 light years distant, messages would now take 100 years round trip.

Traveling at near the speed of light (c) would be more practical even while being even more isolating - for not only are the distances vast but relativistic effects begin to come into play. Going to the same 50 light year away star system traveling with a constant acceleration of 1.5g to the midpoint then decelerating at 1.5g to your goal you would reach a maximum speed of 99.55% c. The relativistic effects of traveling at such speeds begin to cause noticeable time dilation and length contraction - slowing your clocks and shortening the distance to one’s goal. At that speed it would take you about 5.7 years ship-time to arrive at your goal, but about 51 years would have passed on your home planet. So now everyone you knew is 51 years older while you aged only 5.7 years. Additionally any messages to home would still take 100 years round trip.

Our galaxy is 110,000 lights years across. If you travelled to a star system 1000 light years distant, accelerating and decelerating at a constant 1.5g, you would reach a maximum speed of 99.97% c. It would take you about 9.5 years ship-time but about 1,001 years would have passed back ‘home” and any messages would now take 2000 years round trip. You get the idea.

Isolated is isolated be it through distance or time - so why employ generational travel to colonize the galaxy when the original crew can reach their destinations in manageable periods of time?

Here’s the thing though. The faster you travel the more scattered in distance and in time you become.

It becomes clear then that building a galactic empire in ‘real’ time in the traditional sense becomes an impossibility (sorry Star Wars). A civilization could still have a loose, delayed, protocol-based network, shared archives, automated governance, or cultural continuity without real-time control but I would argue as each colonization branch evolves they would eventually become unrecognizable to those left behind both physically and culturally - thus becoming completely independent and in a sense alone.

And so the colonization of intra-galactic space would most likely be a one‑way, near‑c hopping colonization, where returning home seems pointless given the time differences, and the vast distances render meaningful communication impossible and cultural continuity very unlikely.

Nevertheless colonization would move forward. But such colonization actually reduces the odds that we would ever encounter them, even if they end up filling large parts of the galaxy.

Each colony ship makes a high‑speed hop to a nearby star, settles it, and then its descendants launch further near‑c hops outward, never really returning home because of relativistic time isolation. Such a network of ever forward colonization can, in principle, spread across the galaxy in less than a million years, a blink of the eye on a galactic time scale.

But you do not necessarily get a smooth, “every star visited” front. If each new colony has only some probability P of itself becoming a colonizer, you end up with clusters of colonized stars separated by large untouched voids. It is similar to the branches on a tree - there will always be voids.

Furthermore I would argue that P is quite low. After each relativistic space jump a new society would develop on a new home planet. Having been given the technological prowess for intra-galactic travel from a society they have only read about in historical accounts, they would possess a technological capacity for self-destruction that would most likely far exceed their wisdom. Without guidance from their older and hopefully wiser home society it is highly likely that they would destroy themselves within a few millennium.

The chances for us to detect them then exceedingly small given their brief existence. This would also serve to lower the chances that they became colonizers, ending that branch of colonization and increasing untouched voids in intergalactic space.

Is this then a plausible answer to the fermi paradox? If intelligent life is ubiquitous in the galaxy where is everybody? Does our region of space (say a few tens of light‑years around the Sun), exist within a void?

The fact that we have not detected or met alien intelligence strongly argues against warp drives, sub-luminal warp bubbles, Krasnikov tubes, worm holes, and cosmic-string travel, for if they existed more than enough time has passed where a rich and massive galactic presence should have already occurred and their signals and even spacecraft should be ubiquitous.

But there may be another possible answer to the paradox given relativistic effects. Even if advanced civilizations dedicate themselves to exploring as much of the galaxy as possible using ships that cruise at 99.5-99.99% c, the crews might experience years or decades patrolling space while thousands of years pass in the galaxy’s “rest frame.” From their perspective, they can sample many stars over a career; from our perspective, each specific system might only be visited extremely rarely, with long gaps between passes.

So, for “our region of space”, near‑light-speed transport by aliens would result in fewer opportunities to be in the right place at the right time for a direct encounter, because visits are widely separated in local time.

If such galactic explorers exist, isolated in their own timeline, our chances of meeting them in our timeline is quite small. Nevertheless their ships should be detectable. Such ships would interact strongly with background photons and particles, generating detectable radiation; calculations show a ship at relativistic speeds should have a visible infrared or high‑energy “wake.” So near‑c travel might make indirect detection (seeing their ships as transient signatures or fast interstellar objects) more likely even while direct contact events would remain rare.

Here’s the thing. We are not looking for these signatures. There are no large, dedicated searches ongoing raising yet another potential answer to Fermi’s paradox - are we just not looking for them with the right tools?