In science, it’s not good enough to have observed something just once.
Possible links between cause and effect needs to be investigated many, many times, and under conditions which allow you to make reasonable conclusions about how things work.
It’s called scientific testing, and relies on the capacity of humans to observe and then make conclusions – also referred to as empiricism.
To grab a 2.31 minute animated summary of empiricism, check out This Thing Called Science Part 2: Testing, testing 1, 2, 3 (produced by Bridge8).
*not to be confused with getting teste