As for life on other planets, there probably is or was life on other planets, but, like cat bells said, we will never detect it. Even if we send a machine out to look for it, that's a one way trip. Once the machine is about a light year away, we will not be able to receive its signals anymore. That machine would have to send another machine with mass back to us, back into our radio range, for us to get communication about what it saw. So even communication between worlds that are 50 light years away or less will take hundreds of years each way.
So it doesn't matter either way
Unless
There is another intelligent species that lives long enough or has a social memory long enough for those kinds of centuries long incommunicado trips to be sensible. But such a species would see no threat from us and leave us alone, most likely.

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