Inherent Uncertainty

We regularly use the concept of uncertainty whenever we don’t have definite knowledge of something that might happen. If the weather lady says there is a 60 percent chance of rain at a certain location tomorrow, she can’t predict that it will definitely rain. She can only ascertain that rain is more likely than not to happen.

Over time, weather forecasts have improved, and these days there is less uncertainty in the forecast than there was a few generations ago. This is because the tools used to gather data and then crunch the numbers have improved with time. In principle, there is nothing stopping us from developing better and better tools and therefore making better and better forecasts. It won’t be easy, and it will certainly cost a lot of money, but there is nothing really stopping us from shrinking the uncertainty in the forecast to ever smaller values.

In quantum physics, however, there is a limit to how certain you can understand a quantum system but for now suffice it to say that in the microscopic world you will always be saddled with some degree of uncertainty. As we’ll see, this has very real consequences—not least in our ability to deploy the laws of physics to make future predictions. Inherent uncertainty, and the associated loss of predictability, is the third major difference between quantum and non-quantum physics.