We described the process of measurement and discussed how important this was to developing and refining the laws of physics. In the macroscopic world the process of measurement can usually be done independently of, and without having any influence on, the system you are trying to observe. If you want to know the length of a table, you pull out your tape measure and have a look. If you want to know how warm it is, you glance at a thermometer.
In quantum physics, as you have probably guessed, physicists no longer have the luxury of independent measurement. In the microscopic world, the moment you measure some property of a physical system, you perturb it in some uncontrollable way. This happens not because quantum physicists are clumsy. It also has nothing (or at least very little) to do with the fact that quantum systems are small and therefore very sensitive.
This is a fundamental and inseparable link between the process of measurement and the physical state of a system. This connection is unique to quantum physics and, as you might imagine, forces quantum physicists to rethink the standard process of observation, theory, and experiment.
ATOM TRAP
We will cite many examples where successful pre-quantum theories were overturned by the discovery of quantum physics. We will therefore mention that many great pre-quantum physicists turned out to have gotten a few things wrong. We do so with the utmost respect, recognizing that their accomplishments were still noteworthy given the tools and knowledge available to them at the time.
Although we have spoken of four new features that arise in quantum physics, you can see that there is potential for overlap between each of these. Truth be told, there are additional surprises lurking that we haven’t mentioned here. Rather than wave our hands any further, though, the time has come to sit back and begin the story of quantum physics.
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