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If a tree falls in the forest and someone is there to hear it, does it make a sound? Perhaps not.

Once again, quantum physics is calling our concept of reality into question.

If you are familiar with quantum physics, you know that on very tiny scales, the Universe is very weird. Particles act like particles and waves at the same time. An electron may be in one location, and then suddenly in another location, without ever passing through a point between those two spots. Or even a single particle can interact with itself.

But on the macroscopic scale, things are more normal. At least, we think. But perhaps quantum physics also affects us, as macroscopic observers. And recent research published in Nature Physics says for even macroscopic observers, quantum physics may call our reality into question.

As macroscopic observers, we can say three things about reality.

If we observe something, we believe it really did happen.

Lets compare these with reality on a quantum level.

These two realities are very different. If our normal, macroscopic world started acting in a quantum way, the world would be a very different place.

But perhaps, our world is not as clear cut as we thought it is.

Lets try to mess with our macroscopic reality a bit.

To do this, we can do a thought experiment, where the observer of the particle is also observed.

The experiment, known as Wigners friend, goes like this. You have a scientist, lets call him Charlie, who is sealed inside a lab. He makes an observation of a particle as either red or blue. His friend, Alice, waits outside. From Alices perspective, she doesnt know whether Charlie measured the particle as red or blue. According to her, until she opens up that lab door and asks Charlie what he saw, the particle is both red and blue at the same time. This is similar to the outcome we see in the Schrdinger'scat experiment, where a cat in a box is both alive and dead until observed.

Like Schrdinger's cat, from Alice's perspective, Charlie would have measured his particle as both ... [+] red and blue.

Eugene Wigner, the physicist who came up with this thought experiment, thought this was absurd. Charlie has a consciousness - he cant be in two states at once (one where he observed the particle as red and one where he observed the particle as blue). Thus, Wigner claimed, human consciousness causes all of this uncertainty to collapse.

This makes sense to us in a macroscopic world. But whats so special about human consciousness? And why (or are) observers so special?

This is where Wigner left off. But another version, first proposed by aslav Brukner, was recently extended by a group of scientists at the Centre for Quantum Dynamics at Griffith University and the Department of Physics and Center for Quantum Frontiers of Research & Technology at the National Cheng Kung University.

In their version, there are two observers locked in their labs on opposite sides of the planet, Charlie and Debbie. They both observe entangled particles, say, as red or blue. Remember, if Charlie observes his particle as blue, Debbies entangled particle must also be blue. This causes Charlie and Debbie to now be entangled with one another. Charlie and Debbie, in turn, have two observers, Alice and Bob.

Alice and Bob then each flip a coin. If its heads, they open the door to the lab of Charlie and Debbie and ask for the result of their experiment. If tails, they do another measurement, that will come out positive if Charlie and Debbie are entangled with their particles.

No information inside the lab should leak out at all, except if Alice and Bob open the door and ask their friends about the result of their experiment. Even Charlie and Debbie, after the experiment, cant remember the result.

At this point, lets go back to our tenets of reality and see how they relate to this experiment. Charlie and Debbie really see the particle as red or blue, and this reflects some sort of objective reality. In addition, this reality should not be dependent on the choice that Alice and Bob make when they flip their coin.

After thousands of realizations, the researchers found that the number of correlations that Alice and Bob see with whether Charlie or Debbie measure their particle as blue or red exceeds the amount expected if our three tenets of reality hold up.

What this means is that something strange is happening when consciousness interacts with quantum physics. Either our idea of quantum physics needs to be revised, or we dont have a full grasp on reality.

If this experiment holds for human observers, our reality may not be objectively true.

For one, the correlations we discovered cannot be explained just by saying that physical properties don't exist until they are measured, says Dr. Eric Cavalcanti, one of the authors on the paper. Now the absolute reality of measurement outcomes themselves is called into question.

Now, there are some limitations to this experiment. For one, Alice, Bob, Charlie, and Debbie werent real people. However, if the same results arent obtained with real people in some future example of this experiment, that means conscious observers really are special. If we do get the same results, then one of our tenets of reality must not be true. Reality for one person may not be the reality seen by another person.

In any case, this work sets the stage for how quantum physics and consciousness can come together to help us understand the true nature of reality.

Read this article:

Quantum Physics May Upend Our Macroscopic Reality In The Universe - Forbes