Imagine life's journey to humans as a series of difficult steps. The chance of completing these steps grows with time. Experts studied when smart life like us could appear in the universe. They found that most of it might come after today, unless these steps are few and planets last a long time. This suggests we might be early.

Why is that? Maybe because there are 'loud' aliens. They follow strict rules to appear and expand quickly. They change how parts of space look, stopping smart life from popping up there. 'Quiet' aliens, on the other hand, are almost invisible.

Researchers used a three-step model to understand these loud aliens. They guessed how often they appear based on Earth's history. They assumed the number of alien civilizations we know compared to the total. They also guessed their expansion speed, as we can't see their space territories.

They found that loud alien civilizations control a large part of the universe. Each will control many galaxies in the future. We could meet them in a few hundred million to a couple billion years.

But if these loud aliens come from quiet ones, the chance of another quiet alien civilization in our galaxy is quite low. This isn't great news for scientists searching for extraterrestrial intelligence (SETI).

However, it's possible that alien civilizations' appearances are subtler, and they expand slower. In this case, we might find many curved lines in the sky.

Why Quiet Aliens Are Tough to Find, but Loud Ones Might Be Everywhere

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