Entropy and the Arrow of Time

                                       

Arrow of causal time.

Causes normally precede effects. The future can be controlled, not the past. But the problem of using causality as an arrow of time is that, as the philosopher David Hume pointed out, the causal relationship can not be perceived by itself, since the observer is only capable of perceiving "chain", the sequence Of events, of cause and effect, but not a link, so to speak, material or otherwise recordable.

On the other hand, it is extremely difficult to provide a clear explanation of the real meaning of the terms cause and effect. It is clear that dropping the crystal glass is the cause and its breaking the effect, however, it could be that the asymmetry that the observer perceives in such a case is not that of the arrow of causal time really, but of thermodynamics. If the thermodynamic arrow were inverted, then one might think that the pieces of glass were the cause and the vessel was resting on the table the effect.

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Source: In a place of the cosmos

Credits: The Royal Institutio