... because it can change the past that had already happened

[Anna232]

I am confused by the tense choice. Should it be present or past perfect? Does "cause" sound idiomatic?

I think a time machine is not a great idea because it can change the past that had/has already happened and the future that will happen. It can cause bad consequences.

 

[5jj]

1. present perfect
2, cause
result in

 

[Rover_KE]

Where did you read that text, Anna232? We need the source and author of any text you quote.

If you wrote it yourself, why, and in what context?

 

[SoothingDave]

1. present perfect
2, cause
result in

Or "lead to."

 

[Anna232]

Where did you read that text, Anna232? We need the source and author of any text you quote.

If you wrote it yourself, why, and in what context?

I wrote it myself. I just shared my opinion about it. I do believe it is not impossible

 

[Anna232]

1. present perfect
2, cause
result in

But it is not clear to me why past perfect or just past simple arent't correct if I am talking about the past. Do you mean if it is recent then present perfect is the correct option. But if it is not recent then past simple and perfect are correct, aren't they?

 

[Tarheel]

I suppose you want to emphasize that you cannot change something that has as already happened (the past).

 

[Anna232]

I suppose you want to emphasize that you cannot change something that has as already happened (the past).

Yes. And in that case either past simple or past perfect is correct. Right? But if I want to emphasize recent past then present perfect is correct. I hope I understand correctly.

 

[5jj]

I think a time machine is not a great idea because it can change the past that has already happened ...

In BrE, 'the past' in this context is a time period that extends up to, and is relevant to, the present.

 

[Anna232]

In BrE, 'the past' in this context is a time period that extends up to, and is relevant to, the present.

But if I want to emphasize past events that had already happened something that can't be changed, can I either past simple or past perfect?

 

[5jj]

Only if there is a reference to a later past time.

 

[emsr2d2]

I'm not sure why you think you need the whole section after "the past".

I think a time machine isn't a good idea because people [using it] could change the past. This has the potential for disastrous consequences.

 

[5jj]

I'm not sure why you think you need the whole section after "the past".

That's a far more efficient response than mine.