10 Famous Thought Experiments That Just Boggle Your Mind Part 9

Read part 8: The Chinese Room

2. Schrodinger's Cat

Schrödinger’s Cat is a paradox relating to quantum mechanics that was first proposed by the physicist Erwin Schrödinger. He hypothesized a scenario where a cat is sealed inside a box for one hour along with a radioactive element and a vial of deadly poison. There is a 50/50 chance that the radioactive element will decay over the course of the hour. If it does, then a hammer connected to a Geiger counter will trigger, break the vial, release the poison, and kill the cat. Since there is an equal chance that this will or will not happen, Schrödinger argued that before the box is opened the cat is simultaneously both alive and dead.

Schrödinger meant to use this thought experiment to demonstrate the absurdity of Bohr's Copenhagen interpretation of quantum mechanics, where a quantum system remains in superposition until it interacts with, or is observed by the external world. Turned out that:

Successful experiments involving superpositions of relatively large (by the standards of quantum physics) objects have been performed.

I still remember the day when my Statistics Professor Dr. Reese threw a coin to the floor and then immediately put his foot on top of it. "The event has already occurred. But what is the outcome?" he asked. That was a great example of the Bayesian world, where the reality has already happened, but we still don't know -- the uncertainty.

Uncertainty is actually everywhere in AI/Machine Learning/Robotics challenges. For example, an object detection model detected a person, but only with 50% confidence. That means the object detected could be a person or not a person at all. And the bounding box detected could be spot on, perfectly bound the person inside, or it could be 50% off with a 50% IOU (Intersection Over Union). So how do you use this information if you have to decide if there is a visitor by your door? In this case, the event has already happened (there's an object there, whether person or not). There are also cases where you don't know what future holds. If you are in a self-driving car, the self-driving car has no idea what the car next to it will do in the next minute, it could just stay in its lane, or it could change into your lane and collide with your car. A well-designed self-driving car has to be able to deal with uncertainty, maybe when it notices the car next lane starts to weave, maybe it's a good idea to break a bit and keep a good distance from it. But just like Schrödinger’s Cat, before you open the box, anything is possible.

One solution is to try to obtain more observations that might give you more information and reduce the uncertainty. Maybe if you shake the box and hear the cat meow, then you know the cat is likely still alive. Maybe you wait 20 years, and then likely the cat is dead. Actually you don't even have to wait that long, a cat probably will die if it eats no food for a week? What is the cat is pregnant when you put it in the box. You would now have multiple cats that are both dead and alive and you don't even know how many cats you have.

Let's end this with a picture of cute kittens. Didn't Jeff Dean build a deep neural network that learned the concept of a cat all by itself simply by watching lots and lots of youtube videos?


Read part 10: Brain in a Vat

BTW: The easiest way to remember my blog address is http://lanny.lannyland.com