Quantum Physics

‚Spooky Action at a Distance‘

For the Spooky Season I wanted to find a topic that would combine physics and some sort of Halloween vibe :D. And at first I really didn’t know what to write about. Although there are a lot of very creepy mathmatical formulas 😀 But I thought they would not be so fitting for this post. And so, after thinking a lot about what to write about, this quote popped in my head: `Spooky Action at a Distance´. 

This is a quote from Albert Einstein. He once used this phrase in a letter to Max Born in March 1947. In this letter Einstein talks about how he isn‘t convinced that quantum mechanics is the theory that explains how the world works. He does state that he knows about the success of this theory: `I understand of course that the statistical formalism which you pioneered captures a significant truth.´

But further on he explains his problem with quantum mechanics: `I cannot seriously believe (in quantum mechanics) because the theory is incompatible with the requirement that physics should represent reality in space and time without spooky action at a distance…´

Before we talk about what Einstein could have meant with this, we need to talk about how quantum mechanics works.

In quantum mechanics everything is described by a complex valued wave function. This wavefunction has usually the catchy name `Psi´. No, not the singer. The greek letter. With this wave function we calculate probabilities for measurement outcomes. An example would be the probability to locate a particle at a particular place. To do this, we take the absolute square of the wave function.

But what is important is that we can’t observe the wave function itself. We can only observe the outcome of the measurement.

So what did Einstein mean with ‚Spooky Action at a Distance‘? He said this while proposing a thought experiment where, according to the theory, an event at one point in the universe could instantaneously affect another event arbitrarily (as a German trying to say this out loud my tounge gets (en)tangled) far away. And this was weird to him, and that is why he called it ‚spooky action at a distance‘.

Because this would imply faster than light communication between two particles. But that is something that his theory of relativity ruled out. However this thought experiment is a real thing in quantum mechanics. It is called ‚Quantum Entanglement‘. Today there are a lot of experiments, which show that Quantum Entanglement does exist.

But what exactly is quantum entanglement? In this post I will talk about this more briefly because it is a very vast and amazing, but complicated topic. So it deserves its own post :D.

When we talk about quantum entanglement, you can think of two particles which are entangled. That means, we can create a pair of particles that ‚know’ about one another and are separated in space and time. And if we observe that one particle, this measurement instantly changes the state of the other particle back. For example the spin of a particle.

I wanted to portrait this fascinating thing with the little ghosts in the picture. If we observe the one ghost on the left and it is not up side down, instantaneously the other ghost will be up side down.

I would like to go further into detail, because this topic is so interesting. But this would be too long for this halloween blogpost and too much information at once. So I hope this post is a little teaser for the posts to come that are about quantum mechanics. And I would also like to make a post about those letters that Einstein and Born wrote to each other. I think that would be pretty fascinating.

Hopefully you enyojed reading this and maybe you learned something new. And I hope you enjoyed the little anecdote about the letters and I hope you are enjoying the spooky season!

Happy Halloween and a BOOtiful Day! 🎃👻

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  1. Slavica Vukojevic says:

    Love you and so proud😘😘😘

    1. Love you too ❤️💕

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