Speed of Information

The encyclopedia "Brockhaus" defines the expression Information (I) in science as instruction not only from men but also from organisms or technical devices about facts, events or expirations. To transmit I, physical signals are used, for example electromagnetical or acoustical ones. The velocity of a signal extending from point A to point B can be defined as speed of information v_I. I is regarded as being incorporated in waves or groups of waves. However, experiments (at Duke University, Durham 2003) proved that I is not extending with the velocity of the group v_G. This mathematical term may have values smaller than zero and greater than c (velocity of light). There are references defining v_I = c_vacuum. Due to the Special Theory of Relativity the velocity of matter, resp. energy, cannot be transferred faster than light in vacuum. Otherwise the Principle of Causality would be hurt. This means that an action always follows the cause. Signals with speeds greater than the velocity of light could therefore influence the past. However, this is not possible!