I found native people prefer to use passive voice in a sentence.
For example:
Tonight's moon can be seen from anywhere worldwide.
We have reason to believe that progress can be made.
Be honest, it's difficult for an English learner to understand.
Why not phrase it this way:
We can see the moon from anywhere worldwide.
In which cases do people prefer to use passive voice rather than active voice?
The passive voice exists for a reason; as far as I can tell all languages have some way of creating a construction equivalent in semantics (and pragmatics) to the English passive.
At the semantic level, the passive voice operates on transitive verbs (=2 or more arguments; note that the subject is included as an argument) and "promotes" the transitive object to a subject. The meaning is equivalent semantically (barring idiomatic usages), as the subject of a passive construction is still the object of that transitive verb. Consider these two sentences below, where the event (=what happens to the object) is the same, in either active or passive voice.
1) John ate [the cake]
2) [The cake] was eaten (by John).
In either 1) or 2), this information is the same: there was a salient cake and it was eaten. However, note that the passive allows one to drop out the agent.
So, why would one use the passive voice over the active? Perhaps the writer/speaker wants to give attention to the object. In English the subject position is often where topics go, and so is considered the "important" element. Promoting the object to a subject via passive allows one to emphasize this. Another possible case: we simply don't know who the agent was or perhaps the agent doesn't really matter. The passive is also helpful for generalizing / avoiding assigning blame / being polite.
Consider these cases:
3) The trash can was blown over (by the wind).
4) John was really screwed.
5) That project got really messed up. (<= note how it doesn't blame anyone in particular)
In 3), it probably obvious what blew the trash can over (in general people don't go around blowing down trash cans, etc.). For 4), this begins to get idiomatic--we could try to attribute reason(s) why John is not in a good situation, but usually this is secondary to stressing that John is really screwed.
We can apply this reasoning to the example sentence you gave:
6) [Tonight's moon] can be seen from anywhere worldwide.
In this sentence, the fact that the moon is visible from anywhere in the world is being stressed, hence why the writer probably chose to use the passive. We really don't care who is seeing the moon.
You should use the passive when its the idiomatic way to talk about an event (e.g. the agent usually is implied or not important) or when you want to focus on the object of such an event, and therefore promote it to subject position via the passive construction.
The passive voice can be used in English for a number of reasons, some of which have been mentioned already.
1) To emphasize the "patient" (the object becomes the subject). In my opening sentence for example, I used the passive because we don't know who the agent of the verb is. Other Eurpean languages often don't use the passive for this purpose because they have things called "reflexive verbs" (I washed myself vs. I washed the car, I returned vs. I returned the library book). Furthermore, languages that use word endings to mark subjects, objects, receivers, or objects of prepositions tend to have a much looser word order than English.
In the example you gave, many languages might use - "It is possible to see the moon from anywhere in the world" - I guess English doesn't use that because the phrase "it is possible" is very long and awkward sounding.
In conversational English it is possible to use constructions that sound unusual to some foreigners like - "You can use the passive voice for a number of reasons in English" - But this doesn't look good written down, because the "you" is pronounced differently (jə) to communicate that I'm not talking to YOU! Also it cannot be used in formal contexts. Which brings me to...
2) Tone. There are those of the opinion that only the passive voice should be used in academic communication. I am ambivalent about that, because using it in unnatural contexts can make it very difficult for readers to understand the sentence. Regardless, the passive can raise the tone of communication from informal to formal, or from conversational to elevated or poetic.
3) Manipulation. Language can be used to manipulate people. If I ask our secretary where the new books are and she says "they haven't been ordered yet", she is consciously shifting the blame away from herself (cf. "I haven't ordered them."). This tactic DOES ACTUALLY WORK if the listener is not primed, or even not concentrating (I've been caught out a few times, even though I'm familiar with it). Just don't try it on English teachers or writers, because they'll figure you out. I had one colleague who used to do it, and honestly, I was never able to trust anything she said afterwards because I knew she was happy speak dishonestly. In fact, if I can give you some advice, don't use it at all, it's deceitful. It's good to be aware that other people use it though so you can catch them out.
4) Meaning. There are examples where the meaning of a sentence can only be expressed clearly by the passive voice. Consider - "Four languages are spoken in Switzerland" vs. "People speak four languages in Switzerland." - The first example communicates the correct meaning, whereas the second implies that EVERYONE in Switzerland speaks those four languages, which is not the case (as far as I'm aware).
Hope that was helpful. It was good for me to have the opportunity to think it through again.
Bye!
People will often begin a sentence with the thing that is the most salient for them; in your example: tonight's moon. When that happens, they will have to decide, perhaps not at a fully conscious level, between two ways of expressing the idea they have about the moon:
will be visible to...
or
can be seen by...
What makes them sometimes decide on the latter? Well, if they're thinking about people looking up at the moon, they might choose the latter, since it more directly conveys the idea of looking. To say the moon "will be visible" is a weaker or less direct expression of that idea of looking up at it.
Also, "seen by" is comprised of words they learned at a very young age, whereas "visible to" is a more complex expression. The simpler more familiar words may come more readily to their lips.
It may very well be the case that
be < past participle > by
will often consist of "simpler" words and phrases than the
will be < adjective > < preposition > < noun >
counterpart.
