# How can I send a message to myself in the past? [duplicate]

This question already has an answer here:

It is easy to send a message to myself in the future: I can put a letter in the post and will receive it tomorrow.

Can you think about a way to send a message to myself in the past; it does not need to be a complex message, only a bit of information would be enough.

Moreover, consider that money, physical resources, and manpower are infinite.

## marked as duplicate by Peter Diehr, user10851, CuriousOne, John Rennie, Qmechanic♦Jun 26 '16 at 10:25

Indeed, it is this postulate that leads us to the conclusion that there is no physical inertial frame that travels at greater than $c$ relative to any other; as long as this is true, then relative motion cannot make event order observer dependent. On the other hand, if there were such a frame, one can always find a physical process whose events are reversed in time by the supraluminal boost.