Not planets - Dimensions.
Every possible variation of every possible variation exists.
A universe where you have one extra grey hair on your head and all else is as it is here, and every variation thereof, exists.
The past and future variations also exist.
But NOT in the same PLACE!
'ISOTOPES' are NOT alternate atoms - They are PAST & PRESENT states (FRAMES) of the same process.
Trapped in an infinite realm of atonement.