More on Thought Experiments


In this blog post, we briefly touched on computer models and thought experiments.

There we said this:

“They are nothing more than automated thought experiments and prove no more than would a thought experiment. If you conduct a thought experiment in your mind, it proves nothing about external reality. If you want to learn how reality works, you have to study nature by performing experiments and collecting data.”

And this:

“Even if your computer model is based on valid assumptions and happens to correspond with reality, it still proves nothing. It is effectively a thought experiment delegated to your computer.”

But, do thought experiments have any value at all? Yes.

A thought experiment can be very useful. Not as a replacement for conducting experiments, but as part of a process of trying to reason through or illustrate the implications of something. Let me explain …

What is a Thought Experiment?

For the purposes of our discussion, a thought experiment is a mental process of thinking through the implications of a hypothesis. Usually by running through a simplified experiment in one’s mind.

This is basically a process of reasoning where one tries to analyze what might happen if one was to perform an experiment. It is not a substitute for performing the experiment, but it can be a useful precursor to running an experiment.

What is the point of doing this? It can be useful in reasoning through the possible implications of a hypothesis before one performs an experiment. This can help one plan an experiment or decide whether one should run an experiment in the first place.

For instance, suppose you have a hypothesis about the existence of a new kind of particle. You decide to think about how you might try to test for its existence. So, you think about the steps to experimentally verify that the particle exists.

Lets hope you put more rational thought into your particles than people did into those of quarks …

You realize you will need a particle accelerator. So, you start thinking about how you are going to configure that particle accelerator in order to test for this exotic particle.

You deduce that you will probably need expensive equipment that you do not have. Perhaps you need a particle accelerator beyond the one you have access to. Or, you need to add extra detection equipment to the particle accelerator you have access to.

All this seems to suggest that you might not be able to test your hypothesis the way you were thinking about. Or, perhaps you can. But now you have some idea of how you might be able to do so. And what potential problems you might have to face if you want to detect this theoretical particle.

Sometimes a thought experiment helps you tease out the implications of a hypothesis. You might realize potential complications or ways in which you might be able to test your hypothesis. Or details that you might want to keep in mind when conducting experiments.

More Examples…

This time let us take an example from the exciting field of bio-medicine. Suppose that you have the hypothesis that AIDS is caused by a specific kind of virus, HIV (which we know that it is). And you perform a thought experiment in your head to try to figure out what this implies.

You imagine the process of trying to test this hypothesis and you start to wonder how to differentiate AIDS from HIV, which seems to be related in some way. You then start to wonder if HIV causes AIDS. Well, that is an interesting avenue of investigation, now isn’t it?

Obviously, you thought experiment does not prove that HIV causes AIDS. You have merely uncovered a possible implication of your hypothesis and now have an interesting idea to perform research on.

In both cases, you still need to perform an experiment. You still must perform an experiment to try to detect the particle you think might exist. You still must discover whether HIV and AIDS are connected.

Besides, experiments can be some of the most interesting parts of science! You get to see intersting stuff like these viruses.

However, now you have a better grasp of how to detect your particle and what kinds of problems you might face when conducting your experiments.

Similarly, you now have an exciting hypothesis about the connection between HIV and AIDS. Only a hypothesis, to be sure, but that is still more than you had before.

Here you have identified other possible implications of your hypothesis. In such cases, this can be useful in identifying what it might mean if your hypothesis was true and other possible avenues of investigation.

The Thought Experiment on Schrodinger’s Cat

Now let us take a classic example, that of Schrodinger’s Cat. In this thought experiment, you imagine the following:

You set up a cat in a box. In the box, you set up a Geiger counter or some other method of detecting radioactive emissions. Now, here is where it starts to get diabolical …

You attach some radioactive substance with a 50% chance of releasing radiation to the Geigercounter. Then you set up some poison in a glass vial and set up a hammer so that if the Geiger counter detects any radiation, it smashes the vial, unleashes the poison and kills the poor cat.

Now, we seal up the box and do not look inside until a little later. We eventually open the box to see what happens. If the Geiger counter has gone off, the cat is poisoned and it is dead. If the Geiger counter does not go off, the cat is not poisoned and is alive. It will certainly be annoyed about being shut up in a box.

Remember, we said that the radioactive substance has a 50% chance of releasing radiation. If it does this, it will kill the cat. So, this means that there is a 50% chance that the cat dies and a 50% chance that the cat lives, right? The cat lives or dies and we will find out which is the case when we look inside the box.

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