How future affects past in the Quantum World

To better understand this we have to take a look at the Delayed Choice Quantum Eraser.

But before that, it’s necessary to take a look at the Double Split Experiment. This experiment is quite simple — all you need is a beam gun(or a laser), a wall and two slits.

Now the interesting part comes in. We expect the light to be a particle, hence we would expect a pattern on the screen corresponding to the size and shape of the slits creating two parallel lines. However, instead of that, we will see the following pattern:

This is called the Interference Pattern. This happens when waves collide and their troughs and crests add up to make a single wave with a bigger amplitude — meaning that light is a wave, not a particle. But other experiments showed that light is a particle, so who should we believe?

This phenomenon is known as the particle-wave duality.

What scientist did next is alter the experiment a little. They still had two slits and a wall, but this time they shot the particles one at a time. Now that there was only one particle, it had nothing to interfere with right? Wrong. The same pattern was seen again. What happens is, the particle duplicates itself and passes through both slits and then interferes with itself on the other side.

This is not the mind-blowing part yet. What scientists did next is put a detector next to the slits to determine through which slit the light particle goes through. And what did they see on the wall?

No interference pattern. So how can a photon know that a conscious being is observing it? The problem here is, whenever you measure an aspect of the experiment, you affect it. So the detector affects the particle preventing it from behaving as a wave.

Now, for a while, let’s blow our minds with another scientific fact and then combine these two for the ultimate big bang of our minds. I present to you The Quantum Entanglement.

Quantum entanglement is when two particles share the same properties. Measurements on one particle are correlated with the measurements on the other. Einstein himself called this phenomenon

Spooky Action At A Distance

So scientists, not yet satisfied with the number of mysteries, wanted to connect these two. They made it so that one particle goes to the wall, while the other(entangled one) travels to the detector. So again, because the entangled particle was measured, the particles that went to the wall didn’t create an interference pattern. I do not have the words or the knowledge of Physics to explain how perplexing this is, so I’ll just move on.

Here comes the main part. The big bang of your brain.

This is the setup for the last experiment we are going tot alk about. There is a beam shooting particles and a crystal which split the photon into two entangled particles. As you see a particle would get to the wall before it’s entangled one would get to the detector. Hence there should be an interference pattern, after all, particle can’t know that it’s entangled companion will be detected in the future, right? Wrong.

When scientists looked at the screen, they saw an interference pattern. Somehow in the quantum world, time works in a mysterious way.

This experiment completely flabbergasts me and it just makes you think how little we know of the reality surrounding us.