the déjà vu movie introduces an idea that we can see the actual past , by making a wormhole in the space , in other way build a bridge in time to find the past
let me explain what I have understood
We actually view the past , the light take some time _ although it's very little _ to reflect from all thing we see , similarly the sun light takes about 8 minutes and 20 seconds to reach the earth as the light travel into the space with a speed of 300 km/sec and the distance from here to the sun is about 150 million km .
Another important example that will explain , the stars we see in the sky are not actually the stars , because they are far away from the earth , but in reality we see the stars from some time ago , probably hundreds of years , the time taken for the light of the star to reach our telescopes .
the idea is : what if we bring that point of space here in our earth , by bending the space , or making a wormhole by black holes , so we can see the past
What Black Holes do as I think is minimizing the speed of light so it can travels slower and reaches us after a specific time , 4 days 6 hours as in our movie .
If we can reach past , are we able to change in past , the mind says no , because the past has consequences done already in his future which is our present time , and that is the second important idea discussed in the film .
The common idea between all the science fiction films , is that if u can travel in past u will be a cause for a something done in the future , and it's impossible to change the past that God has made .
The big director of the film " Tony Scott " let us imagine that we really can change the past to change our future , in many cases we hope that it's possible to save lives , or to make success .