In my book it says that the Lorentz group O(3,1) includes 'discrete reversals of the time direction'.(adsbygoogle = window.adsbygoogle || []).push({});

What on earth does this mean?

So I get that time reversal is making time go backward instead of forward, but what is the word 'discrete' doing there?

Thanks in advance!

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# What is a 'discrete reversal of the time direction'?

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