Is the PN junction inside a diode what makes the electrical current only flow in one direction and not in the opposite direction? If this is so, why does it happen?
Also
Why is the P-type material said to have empty holes and the N-type material to have free electrons?
I very often see in movies and works of fiction that scientists explain that with a black hole you can travel in time and how the characters use black holes to travel in time, more precisely to the past
Do scientists really believe that time travel through black holes is likely? If so, why?