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I wonder what the difference between the two phrases given in the title is. For example:

As time goes by, people have learned that the earth is not the center of the universe.

As time has gone by, people no longer think the earth is the center of the universe.

As time goes by, people have no longer thought that the earth is the center of the universe.

As time has gone by, people think the earth is not the center of the universe.

Here is my confusion:

  • Are both phrases correct? (present simple vs. present perfect)

  • What's the correct combination for "As time goes by"/"As time has gone by", the existence of "no longer" (for things that has changed), and whether the following sentence uses a simple tense or a perfect tense?

1 Answer 1

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When you start a sentence with a clause based on as time goes by, the second clause describes what happens as the time is passing, and so it has to be of the same tense as the as time goes by clause. You can't, for example, use present simple in the first clause and present perfect in the second clause.

We use the simple present to talk about general truths: things that were true in the past, are true now and always will be true.

As time goes by, we realise that nothing in life is certain, apart from death.

We use present perfect to talk about things that have taken place over a period of time and are still happening, or things that happened in the past and have some lasting effect (for example making a reservation).

As time has gone by, people have become more dependent on their phones.

Realising that the earth is not the centre of the universe is something that happened a long time ago: it is no longer an issue. It therefore makes more sense to use past simple. For past simple, we want a verb that expresses an event rather than a state, so learn works better than think:

As time went by, people learned that the Earth is not the center of the universe.

Two other comments about your sentences. First, people is plural, so it's people think, not people thinks. Second, if we want to talk about the planet we live on, we ususally (but not always) use the definite article the earth. The capital letter on Earth is optional.

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  • My understanding went wrong.
    – iBug
    Jan 23, 2018 at 12:04
  • Is it all clear now?
    – JavaLatte
    Jan 23, 2018 at 12:05
  • Yup. Waiting for some more time before accepting this one.
    – iBug
    Jan 23, 2018 at 12:06
  • Always good to wait and see whether somebody can produce a better answer :-).
    – JavaLatte
    Jan 23, 2018 at 12:17

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