You can see a clock running backwards in time

摘要

The epitome of a causal or anti-chronological behavior would be to see a clock running backwards in time. In this essay, we point out that this is indeed possible, but there is no problem with causality. What you see is not what is really happening. Locally, causality is always respected. However, our observation should be cause for pause to astronomers and cosmologists, who strictly observe events occurring at very large distances or very long ago and certainly not locally. It can be that what you see is not what you necessarily get.