Actually, it’s very likely that it’s not aliens.

The aliens are silent because they are extinct

Early life is fragile, so we believe it rarely evolves quickly enough to survive.”

“Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable.”

About four billion years ago, Earth, Venus, and Mars may have all been habitable. However, a billion years or so after formation, Venus turned into a hothouse and Mars froze into an icebox.

Early microbial life on Venus and Mars, if there was any, failed to stabilize the rapidly changing environment, said Charley Lineweaver from ANU.

“Life on Earth probably played a leading role in stabilizing the planet’s climate,” he said.

I take this to mean that life on a planet has to reach a critical mass to be able stabilize the environment. It’s hard, if not impossible, to say what the critical mass is. Dinosaurs roamed the planet for roughly 110 million years. They then became extinct almost instantly in geographic time for reasons that are still less than completely clear. Humans have lived on the planet for a blink of the eye so far, yet we seem to have achieved some control over our environment. “Seem to” being the operative term here.

The odds are against a planet producing a stable life form, or at least one above the single cell level, because such simple creatures are at the mercy of a mercurial environment.

Despite numerous documentaries on TV purporting to prove that aliens have visited earth, there is no evidence that aliens even exist let alone have developed advanced civilizations.

Carl Sagan once said,

In the vastness of the Cosmos there must be other civilizations far older and more advanced than ours.

Experience suggests otherwise as even he once acknowledged.

Because it is clear from the fossil record that almost every species that has ever existed is extinct; extinction is the rule, survival is the exception.

I think the answer to the question is that we’ll know when we know.

If humans survive that long.