Many-Worlds Interpretation (MWI)
The Many-Worlds Interpretation (MWI) is an idea in science that suggests whenever there is a choice or event with multiple outcomes, all those outcomes actually happen — but in separate, parallel worlds.
These worlds do not affect each other and exist simultaneously, each with its own version of reality based on different choices or events.
Parallel Universes in MWI
MWI suggests that for every decision you make, or for every event that has multiple possible results, a new parallel universe is created.
For example, if you flip a coin, it can land on heads or tails. In one parallel universe, it lands on heads; in another universe, it lands on tails.
These parallel universes exist alongside each other, each with a different outcome. They do not affect each other, but each universe represents a different version of reality.
Time Travel and Interference in MWI
What happens if you could travel back in time? In MWI, if you were to go back and change an event, it would not affect your original universe. Instead, you would create a new parallel universe where the change happens.
For example, if you went back in time to stop a car accident and saved someone's life, in your original universe, the accident would still happen, but in a new universe, the person survives because of your interference.
The Grandfather Paradox in MWI
The grandfather paradox is a famous problem in time travel stories. It suggests that if you went back in time and accidentally prevented your grandfather from meeting your grandmother, you would never be born. So, how could you have traveled back in time to prevent the meeting in the first place?
In the Many-Worlds Interpretation, the grandfather paradox would be solved by creating a new parallel universe. In this new universe, your grandfather never meets your grandmother, and you were never born. But this doesn’t affect your original universe, where you were born and were able to travel back in time.
In simple terms, MWI says that if you do something like stop your grandparents from meeting, you don’t erase your existence. Instead, you just create a new universe where you were never born, while your original universe remains unchanged.
Examples of Parallel Universes and Time Travel Interference
Example 1: Flipping a Coin
Imagine you flip a coin. It can land on heads or tails.
- In one universe, it lands on heads.
- In another universe, it lands on tails.
Example 2: Saving Someone's Life
You go back in time and save someone from dying.
- In your original universe, the person still dies.
- In the new universe you created, the person survives.
Example 3: The Grandfather Paradox
You travel back in time and stop your grandfather from meeting your grandmother.
- In the new universe you created, you were never born.
- In your original universe, you are still born and able to travel back in time.
Do You Create a New Universe or Shift to One?
According to the Many-Worlds Interpretation (MWI), if you interfere with a timeline (like going back in time and changing something), you **don’t create a new universe**. Instead, you **move into an already-existing parallel universe** where that change has already happened.
Why You Don't Create a New Universe
In MWI, all possible outcomes of events already exist in separate universes. When you take an action or make a decision, you don’t create a new universe — you simply shift to an existing universe where that outcome has already occurred.
Example:
- If you go back in time and stop an accident from happening, the original timeline (where the accident occurs) still exists.
- You don’t create a new universe. Instead, you shift into a **parallel universe** where the accident didn’t happen.
When you interfere with a timeline, you are not creating a new universe. You are simply **experiencing** one of the many universes that already exist, where a different outcome has occurred. All possibilities are already present in parallel universes!
Conclusion
In MWI, time travel doesn’t erase your original universe. Instead, it creates new parallel universes where different versions of events occur. This solves paradoxes like the grandfather paradox, because each action you take creates a new world, rather than changing the past or erasing your existence.
So, in simple terms: **parallel universes** are different worlds where different outcomes happen, and **interfering with the past** creates new versions of reality without changing the original world.