Since the mid-twentieth century, two theories of physics have offered powerful yet incompatible models of the physical universe.

General relativity brings space and time together into the (then) portmanteau space-time, the curvature of which is gravity. It works really well on large scales, such as interplanetary or interstellar space.

But zoom into the subatomic, and things get weird. The mere act of observing interactions changes the behavior of what is (presumably) totally independent of observation. In those situations, we need quantum theory to help us make sense of it all.

Though scientists have made some remarkable attempts to bring these estranged theories together, viz., string theory, the math behind the theories remains incompatible.

However, new research from Antoine Tilloy of the Max Planck Institute of Quantum Optics in Garching, Germany, suggests that gravity might be an attribute of random fluctuations on the quantum level, which would supplant gravity as the more fundamental theory and put us on the path to a unified theory of the physical universe.

In quantum theory, a particle's state is described by its wave function. This function allows theorists to predict the probability that a particle will be in this or that place.

However, before the act of verification is made via measurement, no one knows for sure where the particle will be, or if it even exists. In scientific terms, the act of observation "collapses" the wave function.

Here's the thing about quantum mechanics: it doesn't define what a measurement is. Who - or what - is an observer? A conscious human?

Bracketing all explanations to observed phenomena, we're stuck with paradoxes like Schrödinger's cat, which invites us to consider the equal possibilities that a previously boxed cat is, as far as we know, simultaneously dead and alive in the box, and will remain as such until we lift the lid.

One attempt to solve the paradox is the Ghirardi–Rimini–Weber (GRW) model from the late eighties. It incorporates random "flashes" that can cause the wave functions in quantum systems to spontaneously collapse.

This purports to leave the outcome unbesmirched by meddling human observation.

Tilloy meddled with this model to extend quantum theory to encompass gravity. When a flash collapses a wave function, and the particle reaches its final position, a gravitational field pops into existence at that precise moment in space-time.

On a large enough scale, quantum systems have many particles going through innumerable flashes.

If gravity comes from quantum processes, but nevertheless behaves in a classical (or Newtonian) way, what we have is a "semiclassical" theory.

However, Klaus Hornberger of the University of Duisberg-Essen in Germany cautions the scientific world that other problems must be tackled before Tilloy's semiclassical solution can warrant serious consideration as a unifying theory of fundamental forces underlying all modern physical laws.

It fits Newton's theory of gravity, but Tilloy's yet to work out the math to show that the quantum theory also describes gravity under Einstein's theory of general relativity.

With the greatest explanatory power, physics is one of the most exciting scientific disciplines. But the key to unified theories in physics is patience.

As with Schrödinger's cat, the will-to-know alone cannot fill in the gaps of what we simply don't yet know.

This article was originally published by Futurism. Read the original article.

Scientists may just have discovered one of the MISSING pieces of Quantum theory, and it’s very important and unorthodox according to some. After all, you don’t hear every day that the future could affect the past, right? According to a new, revolutionary theory, the future can affect the past and even more mystery to the already enigmatic world of quantum mechanics. It seems that the more we dig, the stranger it gets. 

As if it wasn’t already complicated enough. Scientists still can’t figure it all out and are battling with the quantum world on a theoretical level. In the mysterious world of the quantum theory is one called quantum entanglement. Einstein spoke about it, we still try to understand it. According to many scientists, there are a couple of ways for us to demonstrate what Einstein referred to as “spooky action at a distance” and two physicists have proposed a new view that may help unravel the mysteries behind this quantum effect.

Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others, even when the particles are separated by a large distance—instead, a quantum state must be described for the system as a whole. However, there isn’t really a mechanism that could explain that kind of influence which is why physicists Matthew S. Leifer at Chapman University and Matthew F. Pusey at the Perimeter Institute for Theoretical Physics have offered an alternative which they dubbed “retro-causality”. Ok so let’s bring this down a notch and make it easier to understand. Basically, these two researchers took a closer look at some of the many assumptions in quantum theory and said that unless we found that TIME necessarily ran ONE way, any measurements made to a certain particle could echo back in time as well as forward. Complicated huh?

Umm… here’s a video in case you didn’t quite get what we’re trying to say:

Basically “retrocausality” indicates that a given particle can move backward through time to the point where it is entangled and affects its partner along the way. Dr. Leifer and Dr. Pusey basically worked on Bell’s theorem and swapped space for time saying that unless anyone can prove that time should definitely go forwards then retro-causality is a possibility, meaning that quantum particle could travel back in time affecting their partner.

“The reason I think that retro-causality is worth investigating is that we now have a slew of no-go results about realist interpretations of quantum theory, including Bell’s theorem. These say that any interpretation that fits into the standard framework for realist interpretations must have features that I would regard as undesirable. Therefore, the only options seem to be to abandon realism or to break out of the standard realist framework,” said Dr. Leifer.

This means that when a researcher decides he wants to measure a given particle, that choice can influence the properties of the particle itself—or even an entangled particle in the past., making the ‘action at a distance’ part of Einstein’s definition unnecessary. In other words, the entanglement effect becomes retro-causal influence as Futurism explains it.

Speaking to Phys.org Dr. Leifer said: “There is a small group of physicists and philosophers that think this idea is worth pursuing, including Huw Price and Ken Wharton [a physics professor at San José State University],”

Retro-causality may even offer a better quantum theory but like many other theories, this too includes a number of assumptions, though it is noteworthy to mention that it includes one which drastically reformulates the idea of time symmetry. The only options seem to be to abandon realism or to break out of the standard realist framework,” Leifer explained. “Abandoning realism is quite popular, but I think that this robs science of much of its explanatory power and so it is better to find realist accounts where possible.”

“There is not, to my knowledge, a generally agreed upon interpretation of quantum theory that recovers the whole theory and exploits this idea. It is more of an idea for an interpretation at the moment, so I think that other physicists are rightly skeptical, and the onus is on us to flesh out the idea.”

Their discoveries were published in the journal Proceedingsof The Royal Society A in June. (H/T: Phys.org)

Reference: Futurism

One of the weirder aspects of quantum mechanics could be explained by an equally weird idea – that causation can run backwards in time as well as forwards.

What Einstein called "spooky" action at a distancecould theoretically be evidence of retrocausality, which is the particle equivalent of you getting a stomach ache today thanks to tomorrow's bad lunch.

A pair of physicists from the US and Canada took a closer look at some basic assumptions in quantum theory and decided unless we discovered time necessarily ran one way, measurements made to a particle could echo back in time as well as forward.

We all know quantum mechanics is weird. And part of that weirdness comes down to the fact that at a fundamental level, particles don't act like solid billiard balls rolling down a table, but rather like a blurry cloud of possibilities shifting around the room.

This blurry cloud comes into sharp focus when we try to measure particles, meaning we can only ever see a white ball hitting a black one into the corner pocket, and never countless white balls hitting black balls into every pocket.

There is an argument among physicists over whether that cloud of maybes represents something real, or if it's just a convenient representation.

A physicist by the name of Huw Price claimed back in 2012that if the strange probabilities behind quantum states reflect something real, and if nothing restricts time to one direction, the black ball in that cloud of maybes could theoretically roll out of the pocket and knock the white ball.

"Critics object that there is complete time-symmetry in classical physics, and yet no apparent retrocausality. Why should the quantum world be any different?" Price wrote, paraphrasing the thoughts of most physicists.

Matthew S. Leifer from Chapman University in California and Matthew F. Pusey from the Perimeter Institute for Theoretical Physics in Ontario also wondered if the quantum world might be different when it comes to time.

The pair exchanged some of Price's assumptions and applied their new model to something called Bell's theorem, which is a big deal in this whole spooky action at a distance business.

John Stewart Bell said that the weird things that happen in quantum mechanics can't ever be explained by actions taking place nearby. It's as if nothing is causing the multitude of billiard balls to take such varied paths. At a fundamental level, the Universe is random.

But what about actions taking place somewhere else... or somewhen else? Can something far away influence that cloud without touching it, in a way that Einstein called "spooky"?

If two particles are connected in space at some point, measuring a property of one of them instantly sets the value for the other, no matter where in the Universe it has moved to.

This 'entanglement' has been tested over and over again in light of Bell's theorem, plugging loopholes that might show they are really interacting on a local level in some way, in spite of what seems to be a distance.

As you might guess, the Universe still seems pretty spooky.

But if causality ran backwards, it would mean a particle could carry the action of its measurement back in time to when it was entangled, affecting its partner. No faster-than-light messages needed.

That's the hypothesis Leifer and Pusey were going by.

"There is a small group of physicists and philosophers that think this idea is worth pursuing," Leifer told Lisa Zyga at Phys.org.

By reformulating a few basic assumptions, the researchers developed a model based on Bell's theorem where space was swapped for time. By their reckoning, unless we can show why time must always tick forward, we run into some contradictions.

Needless to say, the idea of retrocausality is a fringe idea.

"There is not, to my knowledge, a generally agreed upon interpretation of quantum theory that recovers the whole theory and exploits this idea. It is more of an idea for an interpretation at the moment, so I think that other physicists are rightly sceptical, and the onus is on us to flesh out the idea."

Now keep in mind, this kind of backwards time travel isn't the sort that would allow you to go back in time and consciously change the present, sorry to say.

Future scientists also won't be able to encode lottery numbers into entangled electrons and mail them back to their younger selves.

In any case, the idea of anything trickling backwards in time might not be an appealing one, but let's face it, when it comes to phenomena like entanglement, nearly any explanation is going to sound downright insane.

This research was published in Proceedings of The RoyalSociety A.