Preventing the Grandfather Paradox

Do not, I repeat, DO NOT, travel back in time and kill your own grandfather. You will be erased from existence.

Example:

The Bootstrap Paradox

Be careful when sending messages to your past self. You might cause a bootstrap loop.

Learn more about bootstrap loops

The Novikov Self-Consistency Principle

Traveling back in time can be messy. Make sure to tidy up before you leave.

Cleaning up after Time Travel