Would be possible if tachyonic existed to send info to the past or see the future? since the tachyons according to special relativity could travel to the past?
i have searched in wikipedia and the most accurate info was this link
http://en.wikipedia.org/wiki/Tachyonic_antitelephone
if so could we use the spin of tachyons to send bits of information to the past? :D
Unfortunately (or fortunately, depending on your viewpoint) we cannot use tachyons for signalling to the past. I suggest the following as reading:
The Physics SE Question "Do Tachyons Move Faster than Light" and its answers
My answer to the Physics SE question "Would a tachyon be able to escape a black hole?"
Basically, for the consideration of faster-than-light signalling questions, tachyons are very like light in optical mediums in anomalous dispersion frequency bands where the phase velocity of the light can be greater than $c$. A monochromatic wavetrain with a greater-than-$c$ phas velocity has infinite length (like any monochromatic wavetrain), so it is meaningless to talk about signalling with such a thing. When you try to build localized signalling pulses from superpositions of faster-than-$c$ phase velocity sinusoidal waves the pulse travel / spreading speed is always $c$ or less.
