If we entangle particles and seperate them by a large distance, can the action of measuring one cause decoherence at the other's location? If yes then does this violate relativisitic causality? Could we not use this proccess to transmit information instantaneously? If no then why not? Is there a fundamental difference between the process of direct measurement of the local particle and the indirect measurement of the distant particle? Is decoherence any observer relative phenomena?