The universal war-now?

I) We are on a composite planet and all life is composite. Composites can break down. There is nothing to obviate that.

II) War games! We are expendable, even by ourselves. Our fantasies take us on stories of the balances of the universe at times being at fragile compositions.  Anything out there could bring an unannounced end, e.g. real gamma ray blast, etc. So we like to speculate on what may bring about the end, e.g. Star Wars and the many likes both from alleged professionals and writers.

III) Earth-final war game. As fantastic the above may sound, it could happen here. All speculation brought to a permanent stop!

There does not have to be an outside cause.

All the speculative fantasies brought about deadlier weaponry in some societies. Now, perhaps, the unbalance of power can derive from the Kremlin followed by nuclear winters, ala "On the Beach". The Star Wars saga may close down participation from this tiny corner of the universe. Silence for sure, thereafter

And, if 'we' are gone, where else would there be sentience?

Note: the material herein is not necessarily a reflection of entropy of current societies.