Answer:
stating that the task being described is impossible
Step-by-step explanation:
When any writer says "hunting for a needle in a cosmic haystack" they are basically stating that the task being described is impossible. This phrase is a play on words from the original phrase which is "finding a needle in a haystack". A haystack is has a specific volume while a "cosmic haystack" is represented as being extremely vast and neverending like the cosmos. The writer uses this to represent a truly impossible scenario.