If a minor unimportant thing comes to our time from a very far future, is it able to cause a time paradox?

Like a single grain of sand. Not carrying a deadly pathogen that will wipe out the entire humanity, just a regular grain of sand.

Will it cause a time paradox? Is anything that comes to our time from the future guaranteed to cause a time paradox? If so, why?

Its pure existence now would already be a time paradox because it would appear out of nothing.

Needs random tag

Only if it forms a predestination paradox, or causal loop. In order to create a fermi/etc paradox, the event has to become the source of itself, ex:

- Fry is his own grandfather (futurama, specifc reference to the grandfather paradox analogy)

Outside of "loops" you encounter simply timeline deviation (ex: killing baby hitler). There are a number of possible theoretical outcomes of this:

1. Self-healing: a series of events will take the place of the original event to create the same outcome, so the future is immutable (wwII still happens, genocide, etc etc)
2. Multiverse: altering a timeline creates another timeline, and you now exist on that alternate dimensional timeline (WWII doesn't happen, world takes alternate path, WWII still happened in original timeline)
3. Timeline erasure: the timeline that is interfered with ceases to exist and the new timeline becomes the absolute reality (WWII never happens, any universe it happened in ceases to exist)

And of course 4:

Time travel is impossible because it would take the creation of a paradox for it to occur mechanically, and therefore it cannot occur.

Grain of sand... that is part of a mountain of sand, that is part of earth's ecosystem

I doubt it'll change much in humanity existence, but who knows what might have happened if it appeared during earth's creation

"Chaos theory"

Yepp. That means you cannot crush/dissolve/destroy that grain. If you destroyed it after it arrived -- then how could it arrive if it's already destroyed in the future?

@netikras you're assuming we're not talking about mere standardized time travel bullshit anyways. If the grain of sand is sent back in time it cannot exist without beginning, which is in the future. However, because it does *begin* to exist in the future, it'd have to be a concurrent existence, so it'll still pop up again in the future even if it's "killed" in its traveled-back state in the past. Hence why if someone dies while going to the past, they're still born: if nothing is fucked with creation-wise and as long as it still travels back in time, it can be destroyed in the past just fine. This also means its past self could coexist with its future self just fine, with none of that "touch and everything ceases to exist" bullshit.

Additionally to the answers above, it would break the first law of thermodynamics and thus will affect our system.

@PonySlaystation why haven’t I think of that? You’re genius!