# Is black hole formation reversible if physics law holds even in time reverse?

As we know many situations still fulfill physics law if time is reversed, such as particle collision. But how about black hole formation?

Suppose a star is turning to a black hole and starts to have event horizons. If now I can reverse all travel directions of all matter in the universe, can the 'black hole' turn back to a star again? If not, which part makes this situation asymmetry?

• The time reversed metric of a black hole is a white hole, not another black hole. – Slereah Dec 2 '15 at 7:58

• @innisfree All possible scenarios leading to a black hole with mass $M$ are equally (un)likely to occur in reverse. In the improbable event that a black hole un-forms, it'd be improbable that you would get your own information back out. – rob Dec 3 '15 at 0:29