Events that occur in the future
can affect the events of the past
According to the double slit experiment (Figure 2) done by the physicist John Wheeler in 1978, and carried out by researchers in 2007, the double slit experiment shows that light can behave as both a wave and a particle, and the way we observe it makes it one or the other.
http://www.sfgate.com/science/article/Science-hopes-to-change-events-that-have-already-2655518.php
If you observe which of the two slits the light passes through, it behaves like a particle. However, if you observe the screen where the light falls, it behaves like a wave.
Then, if you wait for the light to pass through the slit, and again observe which way it came through, it will retroactively force it to have passed through one or the other. This indicates that a particle can change what happened to another one in the past.
This experiment only affects a very tiny fraction of a second because the distance of the experiment setup is every short. However, Wheeler commented that light from distant stars can be observed in the same way; which means that observing things happening now could change what happened thousands years ago.