Physicists still divided about quantum world, 100 years on.

 

The theory of quantum mechanics has transformed daily life since being proposed a century ago, yet how it works remains a mystery—and physicists are deeply divided about what is actually going on, a  in the journal Nature said Wednesday.
 
 
 
 

For the last century, equations based on  quantum mechanics  have consistently and accurately described the behavior of extremely small objects.

However, no one knows what is happening in the physical relatity behind the mathematics.

The problem started at the turn of the 20th century, when scientists realized that the classical principles of physics did not apply to things on the level of atoms.

Bafflingly, photons and electrons appear to behave like both particles and waves. They can also be in different positions simultaneously—and have different speeds or levels of energy.

In 1925, Austrian physicist Erwin Schroedinger and Germany's Werner Heisenberg developed a set of complex mathematical tools that describe quantum mechanics using probabilities.

This "wave function" made it possible to predict the results of measurements of a particle.

These equations led to the development of a huge amount of modern technology, including lasers, LED lights, MRI scanners and the transistors used in computers and phones.

But the question remained: what exactly is happening in the world beyond the math?

 

 

A confusing cat.

To mark the 100th year of quantum mechanics, many of the world's leading physicists gathered last month on the German island of Heligoland, where Heisenberg wrote his famous equation.

More than 1,100 of them responded to a survey conducted by the leading scientific journal Nature.

The results showed there is a "striking lack of consensus among physicists about what quantum ,theory says about reality," Nature said in a statement.

More than a third—36%—of the respondents favored the mostly widely accepted theory, known as the Copenhagen interpretation.

In the classical world, everything has defined properties—such as position or speed—whether we observe them or not.

But this is not the case in the quantum realm, according to the Copenhagen interpretation developed by Heisenberg and Danish physicist Niels Bohr in the 1920s.

It is only when an observer measures a quantum object that it settles on a specific state from the possible options, goes the theory. This is described as its wave function "collapsing" into a single possibility.

The most famous depiction of this idea is Schroedinger's cat, which remains simultaneously alive and dead in a box—until someone peeks inside.

The Copenhagen interpretation "is the simplest we have," Brazilian physics philosopher Decio Krause told Nature after responding to the survey.

Despite the theory's problems—such as not explaining why measurement has this effect—the alternatives "present other problems which, to me, are worse," he said.