12 was the age I started designing a time machine. Even sent a detailed letter to Stephen Hawking, and got a reply. (His assistant called it physically impossible, but who knows?) My idea was based on a theory I had that something, or someone, could be reduced in size beyond zero. At that point, he/she/it would enter a negative universe, where time flows backward at the same rate as it does forward here. I even thought forward time would slow for the object being shrunk, so that if your regular size is "50", than the size you need to be to travel backward in time at 1.0x speed would be "-50". Then, wait in Negative Space for a day, then transfer yourself back to positive space with the machine, entering positive space a day previous to when you left. Same idea as turning a cassette tape over, playing it for a few seconds, and turning it back over -- at an earlier position.