Like a time capsule. I write something, put it in a capsule, bury it underground, in hope that someone in the future sees it and send it to the past, is that possible?

At our current time frame, receiving a message from the past is easy, receiving a message from the future is hard

Edited March 16, 20187 yr by fredreload

Based on our current understanding, sending a message from the future to the past is not hard - it is impossible. The one apparent loophole is that something called a closed time-like loop, or curve, is not excluded by general relativity theory. It is specualtive as to whether such loops actually exist, whether they could be accessed by technology, or whether they may be subsequently shown to be impossible based upon refinements to relativity theory. You can read a little more here in a rather weak wikipedia article.