"go back in time" actually a concept of Relativity Physics--wide which it is believed (not proved) that if anything moves faster than light, it shall move back in time. For example, if you start your journey today from Earth and go to some star with a speed greater than the speed of light (300000 Kilometers per second), you can return to Earth yesterday or a month earlier than today's date. Sounds crazy, but Einstein and Company believed in it--and all our relativity physicists believe it as Muslims believe in Koran.

However, in the current context, the term has an ordinary meaning, that is just evaluating or remembering some past occasion, event, day, period, history, etc.

हम समय में पीछे जाएंगे और उसकी गलतियों को देखेंगे

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Note added at 19 mins (2010-09-30 09:11:49 GMT)
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माहेश्वर जी, आपने जो वाक्य लिखा है उसके पहले और बाद का वाक्य और दें तो अनुवाद और साफ़ हो सकता है.

हम बीते समय की छानबीन करेंगे और उसकी गलतियां देखेंगे।

अतीत में झांकना by Lalit is a good alternative, except that it indicates the distant past. It would be appropriate if we had to say,

अतीत में झांककर हम पृथ्वीराज चौहान की गलतियां देखेंगे।

But if we are referring to the present time, i.e., a few days ago, or even a few hours ago, then अतीत seems a heavy word. If the near past is your context, then बीते समय is much lighter and better than अतीत.

As Rameshji said, it indeed is a concept of Relativity Physics. But it is being used here as remembering something.