Schrödinger’s cat experiment illustrates the uncertainty principle of quantum mechanics, which led to the exploration of how observations affect physical reality. The experiment reveals a fundamental difference between classical physics and quantum mechanics, sparking debate among physicists and having important implications for modern physics.
‘Steven Hawking’ said. “When I hear someone talking about Schrödinger’s cat, I get my gun,” because he was so tired of hearing about Schrödinger’s cat. If you’re a physics major, you’ve probably had enough of Schrödinger’s cat to never want to hear about it again. The thought experiment has been repeated and discussed countless times, from textbooks to academic papers to public lectures, so it can feel like an old joke to physicists. However, Schrödinger’s cat is a fascinating thought experiment that doesn’t require a physics background to appreciate the weirdness of the quantum world. You might be wondering what the story of Schrödinger’s cat is, and if Steven Hawking would have ever told it.
Schrödinger’s cat is a thought experiment proposed to criticize the Copenhagen School’s interpretation of the introduction of indeterminacy into physics. Suppose there is a cat in a box, and the box is filled with a poisonous gas that is connected to a valve, and next to the box is a machine that detects radiation, so that the moment it detects radiation, the valve opens and the cat dies, and if no radiation is detected, the cat lives. Now, if we say that here is a radioactive substance that has a 50% chance of decaying in one hour, is the cat dead or alive after one hour, or is it in a strange state where it is neither dead nor alive?
The Copenhagen School’s interpretation, which Erwin Schrödinger hated so much, is as follows. Before we open the box, the living and dead states are in superposition, but as soon as we observe them, they become one. If the physics of superposition seems a bit daunting, here’s a simple example to help explain it. You have a ball in a box, and it must be either red or blue. However, in the quantum world, it can be both red and blue at the same time, and only when you take it out of the box and observe it can you see that it is one color. In other words, a state in which an object (a ball) can probabilistically have two states (red and blue) at the same time is called a superposition state. Thus, the Copenhagen School broke the conventional physics view that an object must have one state and proposed a new quantum mechanical view that two states can probabilistically coexist.
This interpretation caused a major backlash among physicists at the time, including Erwin Schrödinger, who argued that scientific facts were not deterministic, independent of observation, but rather stochastic, dependent on observation. In the world of classical physics, founded by Isaac Newton, all objects were always accurately predictable by the laws of physics, and therefore could not have two states at the same time. However, according to the quantum interpretation of physics created by the Copenhagen School, it was necessary to recognize superposition, where two states coexist. This was tantamount to a complete collapse of the existing physical worldview. Quantum mechanics revealed a reality that was completely different from the physical world we experience every day, a reality that was “uncanny,” and the debate about it went far beyond the scientific community into philosophy, the humanities, and other fields.
Ironically, however, the thought experiment designed by Erwin Schrödinger to disprove the Copenhagen School’s theories ended up helping to further develop them. It led the Copenhagen School to redefine observation as a very important interaction that they had been missing. When we think of observation, we often think of what we see with our eyes, but a more accurate description of observation in science is interaction with an experimental system. When we see what’s inside a box, it’s the interaction between the photons reflected by the objects in the box and the photons entering our eyes. In other words, in quantum mechanics, we realize that the act of observation can no longer be independent of the system we observe, but is an act of interaction.
Schrödinger’s cat was designed to criticize quantum mechanics. But in the end, it is a thought experiment that helps us to understand the paradoxical aspects of quantum mechanics and at the same time to appreciate the new physical worldview that it brings. It also helps us understand how the act of observation takes on a new meaning when compared to classical physics. In classical physics, everything is deterministic, and observation is merely the act of confirming results. In quantum mechanics, observation is the act of creating results, which completely changes our fundamental understanding of the physical world. We hope that this article has given you a chance to visualize Schrödinger’s cat experiment in your own mind and feel the mystery and strangeness of the quantum world.
