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 survey in the journal Nature said Wednesday.<\/p>\n
“Shut up and calculate!” is a famous quote in quantum physics that illustrates the frustration of scientists struggling to unravel one of the world’s great paradoxes.<\/p>\n
For the last century, equations based on quantum mechanics have consistently and accurately described the behaviour of extremely small objects.<\/p>\n
However, no one knows what is happening in the physical reality behind the mathematics.<\/p>\n
The problem started at the turn of the 20th century, when scientists realised that the classical principles of physics did not apply to things on the level on atoms.<\/p>\n
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.<\/p>\n
In 1925, Austrian physicist Erwin Schroedinger and Germany’s Werner Heisenberg developed a set of complex mathematical tools that describe quantum mechanics using probabilities.<\/p>\n
This “wave function” made it possible to predict the results of measurements of a particle.<\/p>\n
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.<\/p>\n
But the question remained: what exactly is happening in the world beyond the maths?<\/p>\n
– A confusing cat –<\/p>\n
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.<\/p>\n
More than 1,100 of them responded to a survey conducted by the leading scientific journal Nature.<\/p>\n
The results showed there is a “striking lack of consensus among physicists about what quantum theory says about reality”, Nature said in a statement.<\/p>\n
More than a third — 36 percent — of the respondents favoured the mostly widely accepted theory, known as the Copenhagen interpretation.<\/p>\n
In the classical world, everything has defined properties — such as position or speed — whether we observe them or not.<\/p>\n
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.<\/p>\n
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.<\/p>\n
The most famous depiction of this idea is Schroedinger’s cat, which remains simultaneously alive and dead in a box — until someone peeks inside.<\/p>\n
The Copenhagen interpretation “is the simplest we have”, Brazilian physics philosopher Decio Krause told Nature after responding to the survey.<\/p>\n
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.<\/p>\n
– Enter the multiverse –<\/p>\n
But the majority of the physicists supported other ideas.<\/p>\n
Fifteen percent of the respondents opted for the “many worlds” interpretation, one of several theories in physics that propose we live in a multiverse.<\/p>\n
It asserts that the wave function does not collapse, but instead branches off into as many universes as there are possible outcomes.<\/p>\n
So when an observer measures a particle, they get the position for their world — but it is in all other possible positions across many parallel universes.<\/p>\n
“It requires a dramatic readjustment of our intuitions about the world, but to me that’s just what we should expect from a fundamental theory of reality,” US theoretical physicist Sean Carroll said in the survey.<\/p>\n
The quantum experts were split on other big questions facing the field.<\/p>\n
Is there some kind of boundary between the quantum and classical worlds, where the laws of physics suddenly change?<\/p>\n
Forty-five percent of the physicists responded yes to this question — and the exact same percentage responded no.<\/p>\n
Just 24 percent said they were confident the quantum interpretation they chose was correct.<\/p>\n
And three quarters believed that it will be replaced by a more comprehensive theory one day.<\/p>\n
ber\/dl\/jj<\/p>\n
\u00a9 Agence France-Presse<\/p>\n","protected":false},"excerpt":{"rendered":"
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