So once you leave the solar system, the next star with planets is dozens of light years away. Meaning that if you could travel at the speed of light it would take you most of your life to get there. At speeds we actually -can- travel it would take centuries to get to the closest other solar system. Meaning if there was life there we have no way of knowing.
In fact it's only been a few decades, since we began stationing telescopes in space, that we have even been able to detect planets in other star systems. Since then we've found hundreds of planets of other stars. Some COULD be earth-like, they COULD support 'life as we know it'. But they're so far away we would have no way of visiting them or even communicating with them (radio signals would take literally years to get there and back).
But the universe is just so HUGE that we know there must be literally billions of stars with planets that could support life. Considering how many there are, it seems almost inevitable that life exists somewhere beside here. But most of the universe is at least thousands or even millions of light years away.
Some people believe that we are being visited by beings from other planets. I don't believe it, but if it's true, these are people who have figured out how to travel much faster than light, meaning they are perhaps thousands of years advanced from us. Their intelligence and technological development is to ours as ours is to squid and octopi. If they're coming, they must have great 'cloaking' technology, a way of hiding from us.
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