Looking into the past

Being able to look into the future would be an incredible power. But what about being able to look into the past? We have that power, but in limited quantities based on our own experience. But what about the extreme past?

Sure scientists and historians try to do this all the time, but is there some sort of tremendous advantage we would have if one could look exactly into the past? i.e. looking into the future, you can predict stock markets.

Seems like the only direct influence is if you could go INTO the past and change future events.