I know I've been asking a lot of questions lately about tenses. But please bear with me here.

NASA scientists have decided to delay the space shuttle's launch in order to determine whether recently repaired parts will cause damage if they break off in orbit.

So for the above example, I know will is correctly used. But I don't understand why there needs to be Present Perfect. Since this happened in the past shouldn't there be Simple Past?

Is this because NASA's decision is continuing into the present?

  • You confuse simple perfect tense and cintinuous perfect tense. Simple Perfect has nothing to do with ongoing action from the past to the time now. – rogermue Jun 10 '15 at 20:33

The simple past is used to relate or narrate past eventualities. It makes no reference to the present.

The present perfect, however, is not used to relate past events or states: it is a present tense and expresses a present state which in some respect arises out of the past eventuality. That present state is not explicitly named, but is left to the hearer/reader to infer from the discourse context.

One standard use or inference type is the resultative or stative perfect, in which the prior event is inferred to be the cause of a current state. That's what's in play here: the past eventuality, the decision, is understood to explain why the shuttle's departure time is not what was previously expected.

You may read more about this here, or here if you want a much deeper technical analysis.

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They are using Present Perfect to convey that the decision to delay the shuttle launch happened at an unspecified time before the current time (the time the article was published and being read, i.e. the present time).

We use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important.

- EnglishPage.com

The simple past tense would be used if they had mentioned a specific time or had one in mind:

Use the Simple Past to express the idea that an action started and finished at a specific time in the past. Sometimes, the speaker may not actually mention the specific time, but they do have one specific time in mind.

- EnglishPage.com

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  • Can someone explain the downvote? I checked again and everything seems correct to me. – Alex W Jun 10 '15 at 22:41

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