to clarify, your sentence really doesn't make sense unless it [your sentence] is corrected by either the following:This machine, searching for extraterrestrial life, will not find it.
In this example, i made the present participle + prepositional phrase modifier (searching for ET life) a nonessential (nonrestrictive) modifer. To do this, i need to specific the machine with the word This
. [Note also that searching
is NOT a gerund in this example; searching
is serving as an adjective (present participle to be exact) that modifies machine
Or, you can correct the sentence by removing the comma:A machine searching for extraterrestrial life will not find it. It
can be referred to machine or to life... ask the question: does it make sense to say, a machine will not find this machine?
sounds quite funny, but still, it
can be ambiguous even if it's quite obvious that the it
should refer to life
hope that helps
kudos if you like me (or my post)