> 1. Make the distances really really big 2. Put a speed limit in the environment Or 3. Don't give humans capabilities to see them. Hell, I'd go even further,

> 1. Make the distances really really big 2. Put a speed limit in the environment Or 3. Don't give humans capabilities to see them. Hell, I'd go even further, what if the "others" are already living on our planet, but we can't see them?