# Thread: How the observed probability is obtained in the Many Worlds Interpretation.

1. I have a question about how the observed probability of an event is obtained in the Many Worlds Interpretation. For example, if the known probability of a particle decaying in one minute is 1% and when the measurement is made, the world 'branches' into both possibilities with the observer in each, how is the 1% probability obtained (actually observed)?

Since there is not a 99% chance the observer is in the non-decay 'world' and a 1% chance he is in the decay world--but is (if taken literally) in both world 100% of the time--it would seems that when repeated numerous times, most of the observers over their 'histories' would not experience a 1% decay rate (But rather something between 1% and 50% rate of decay.)

The only solution I can think of is the the 'non-decay' world decoheres into 99 'worlds'. But since I have not seem either this problem raised or this solution offered, I must be missing something.  2.

3. Originally Posted by WVHills I have a question about how the observed probability of an event is obtained in the Many Worlds Interpretation. For example, if the known probability of a particle decaying in one minute is 1% and when the measurement is made, the world 'branches' into both possibilities with the observer in each, how is the 1% probability obtained (actually observed)?

Since there is not a 99% chance the observer is in the non-decay 'world' and a 1% chance he is in the decay world--but is (if taken literally) in both world 100% of the time--it would seems that when repeated numerous times, most of the observers over their 'histories' would not experience a 1% decay rate (But rather something between 1% and 50% rate of decay.)

The only solution I can think of is the the 'non-decay' world decoheres into 99 'worlds'. But since I have not seem either this problem raised or this solution offered, I must be missing something.
What you're missing is that there is no change in how one calculates anything for our universe, Everett's MWI or no. The key point of Everett's MWI is the "I" part -- it's an interpretation, not a separate theory. It fully reproduces exactly the same experimental outcomes as, e.g., the Copenhagen interpretation of QM. So derive the wave function and compute the squared norm. That's your probability density, just as Born said.  Tags for this Thread
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