How To: Understand time travel

Has time travel always sparked your interest? Are you weirded out by wormholes? Flummoxed by your flux capacitor? Strap yourself in for this time-travel primer.

You Will Need:
•A basic knowledge of the theory of relativity
•An open mind
•A PhD in Physics (optional)

Step 1: Understand "special relativity"
Brush up on your Einstein: His special theory of relativity revolutionized physics by suggesting that traveling into the future is possible. The idea is that time slows down when you're traveling at high speeds relative to stationary objects. So if you're in a spaceship going very close to the speed of light for five years, you could return home to find that it's 50 years later on Earth.

Step 2: Rule out traveling faster than light speed

Step 3: Make the quantum leap

Step 4: Say hello to wormholes

Step 5: Get to know your granddad
Get to know your granddad. The so-called Grandfather Paradox – going back in time and killing your grandfather, thus preventing your own birth and making it impossible for you to travel back in the first place – has been used to help illustrate why backward time travel is impossible.

Step 6: Understand that you can't change the past
Understand what's done is done. Most ideas about backward time travel include the "chronology protection conjecture," meaning that nature would prevent you from changing the past. For example, you could try to go back in time to shoot your grandfather, but the gun wouldn't fire.

Step 7: Be open to the many-worlds interpretation
Open your mind to the "many-worlds" interpretation. Some theorists have gotten around the rigid "whatever happened, happened" idea by claiming that every different action you take in the past splits off into a parallel universe. So there might be hope yet for preventing those embarrassing moments, at least in one universe.