system
Given the following post, respond as if you're commenting on Reddit:
human
How much does quantum uncertainty effect the macro world?
gpt
Very little. Schrödinger's cat was meant to be a thought experiment showing how non-sensical it was to assume that quantum mechanics scaled to the macroscopic world. In modern physics, the concept of decoherence explains why the cat is not in a superposition of dead and alive states that collapse when you open the box (note that even the idea of wave function collapse isn't very popular anymore either). Here is a brief explanation of what that means.

A single electron can be placed in a superposition of up and down spins. This is also known as a pure state, containing all the information that we can possibly know about the electron. Even knowing all the possible information, we can't predict if the spin will be up or down. A pure state can also exhibit interference with other pure states, producing things like the double slit interference pattern.

An electron can also be entirely spin up. This is a different pure state, but now we know what value we will get if we measure the spin of the electron.

Of course, we can also just have an electron that is in a decoherent mixture of up and down spins. This is not a pure state. We still might not be sure if the electron will be spin up or spin down, but that is because we don't have all the information. In some sense, the electron is really entirely in a spin up state or entirely in a spin down state, but we don't know which one. This is also what much of the macroscopic uncertainty in the world resembles - if we had better measurements, we could reduce the uncertainty.

So, if electrons can be placed in a pure state, why can't we place macroscopic objects in a pure state as well? Why can't we we create a double slit experiment using baseballs instead of electrons, for instance? Because interactions with the rest of the world tend to push pure states into a decoherent mixture of states, and macroscopic objects are interacting with the rest of the world all the time.

There are a few places where you can actually experience quantum mechanical uncertainty. The shot noise on a given pixel of your camera can be true quantum uncertainty, or the timing between the counts on a geiger counter near a weak radioactive sample. These types of processes are useful for making perfect hardware based random number generators, since nobody could reduce the uncertainty in the results with more information. But usually our uncertainty is caused by lack of information, not quantum mechanics.