a time xx years ago


Senior Member
Hi everyone! :)
I have a question.
It is from one of my test.

Runoff channels on Mars speak of a time 4 billion years ago (the age of the Martian highlands), when the atmosphere was thicker, the surface warmer, and liquid water widespread.

I'm having trouble understanding the structure of the part "a time 4 billion years ago". I have a guess. I would like to hear what you think about my guess.

[my guess]
To me, the structure of "a time 4 billion years ago" resembles a structure of "a long time ago".
= [a time 4 billion years ago = a long time ago (in terms of structure)]

So my guess is that instead of 'long', the writer put '4 billion years'.
= [a 4 billion years time ago ]

And for some reason, it is not right to put '4 billion years' before 'time'. So it is moved behind 'time'
= [a time 4 billion years ago]

What do you think about my guess?

Thank you for reading my question.
  • natkretep

    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    Yes, I think you're on the right track. Although in English, modifiers often come before the head noun (time in your example), a phrase as a modifier can come after the head noun.

    So we can say a long time ago as well as a time long ago. We talk about a beautiful girl but might still say She was a girl beautiful in an ethereal way.


    Senior Member
    English - England
    I think you are over-complicating things. The sentence is simply saying ' . . . speak of a (period of) time (that passed) 4 billion years ago (the age of . . . '


    Senior Member
    Thank you natkretep for the explanation and examples! :thumbsup:
    I didn't know that I can say "a time long ago". I thought it was wrong! :)

    Please tell me know if I'm wrong.
    What you mean is that both "a time 4 billion years ago" and "a4 billion years time ago" are OK.

    Do I understand you correctly?
    < Previous | Next >