The Speed of Travel

The fastest spacecraft developed by humans has managed to reach approximately 150 km/s relative to the sun (NewScientist). In contrast, light travels at about 3,000,000 km/s. Proxima Centauri, the nearest star to our solar system, is still about 4 light-years away. Even with a speed of 10% of light, a journey to this star would take around 40 years, and it’s unlikely that any habitable planets lie in such proximity.

Thus, it could take centuries, if not millennia, for beings to reach Earth from another habitable world. Humanity has existed for about 300,000 years, and for the majority of that time, our influence on the planet was negligible.

The Impact of Civilizations

The agricultural revolution marked the beginning of significant geological changes, but progress was still gradual. It wasn’t until the industrial revolution that our modifications to the environment became more pronounced, potentially creating detectable signals for distant observers. While radio signals are clearer indicators of intelligent life, we've only been emitting these for a little over a century (IEEE).

Would We Detect Them?

Determining whether we’d notice a colony ship is relatively straightforward. If the vessel were stationed far from Earth, such as near Pluto, it’s possible we wouldn’t detect it. Our own missions can reach Pluto in about ten years, depending on orbital positions (Universe Today). A colony ship could dispatch scouts capable of making the journey in a much shorter time.

Imagine the challenge of locating a massive colony ship 50 AU away (50 times the distance from Earth to the sun). If we visualize the sun as a flat disc, its area would require roughly 500 million suns to fill. Consequently, even a celestial body as significant as the sun would occupy a mere fraction of the search area. Planets, which are often aligned within the same plane and reflect light, are much simpler to detect than camouflaged ships.

The Actions of the Colony Ship

The actions taken by the colony ship would likely be influenced by how long they have been here. If they arrived centuries ago, their approach would differ greatly from those who came just decades prior. If we consider that many UFO sightings throughout history might be linked to this colony ship, it’s plausible they arrived during the agricultural revolution.

Closer examinations of humanity and Earth would likely ensue, as the colony ship deliberated on its next steps. Should these aliens share traits with humans, they might endeavor to manipulate the situation to their advantage, carefully steering Earth’s evolution.

While such a long-term conspiracy seems implausible, the idea of a 10,000-year plan is daunting for most organisms. The complexity of orchestrating such a scheme, particularly involving a species as unpredictable as humanity, is significant. If governments were indeed aware of this and chose to keep it hidden, it raises questions about how rival regimes could maintain cooperation on such a sensitive issue.