Quantum Gravity Could Reverse Cause and Effect

Article by

The famous Schrödinger's cat thought experiment asks a viewer to imagine a box holding a cat and a radioactive particle, which, once decayed, will kill the unfortunate feline. By the principle of quantum superposition, the cat's survival or death is equally likely until measured — so until the box is opened, the cat is simultaneously alive and dead. In quantum mechanics, superposition means that a particle can exist in multiple states at the same time, just like Schrödinger's cat. 

The new thought experiment, published Aug. 21 in the journal Nature Communications, combines the principle of quantum superposition with Einstein's theory of general relativity. General relativity says that the mass of a giant object can slow down time. This is well established as true and measurable, Pikovski said; an astronaut orbiting Earth will experience time just a smidge faster than his or her twin back on the planet. (This is also why falling into a black hole would be a very gradual experience.) 

Thus, if a futuristic spacecraft were near a massive planet, its crew would experience time as a little bit slower than would people in a fellow spacecraft stationed farther away. Now, throw in a little quantum mechanics, and you can imagine a situation in which that planet is superpositioned simultaneously near to and far away from the two spacecraft. 

Time gets weird

In this superpositioned scenario of two ships experiencing time on different timelines, cause and effect could get wonky. For example, say the ships are asked to conduct a training mission in which they fire at each other and dodge each other's fire, knowing full well the time the missiles will launch and intercept their positions. If there's no massive planet nearby messing with time's flow, this is a simple exercise. On the other hand, if that massive planet were present and the ship's captain didn't take the slowing of time into account, the crew might dodge too late and be destroyed. 

With the planet in superposition, simultaneously near and far, it would be impossible to know whether the ships would dodge too late and destroy each other or whether they would move aside and survive. What's more, cause and effect could be reversed, Pikovski said. Imagine two events, A and B, that are causally related. 

“A and B can influence each other, but in one case A is before B, while in the other case B is before A” in a superposition state, Pikovski said. That means that both A and B are simultaneously the cause and effect of each other. Fortunately for the likely-confused crews of these imaginary spacecraft, Pikovski said, they would have a mathematical way to analyze each other's transmissions to confirm that they were in a superpositioned state.

Obviously, in real life, planets don't move around the galaxy willy-nilly. But the thought experiment could have practical implications for quantum computing, even without working out an entire theory of quantum gravity, Pikovski said. By using superpositions in computations, a quantum-computing system could simultaneously evaluate a process as a cause and as an effect. 

“Quantum computers may be able to use this for more efficient computation,” he said. 


This article was first published on livescience.com

Total
0
Shares

#64 AI and the Global Brain

Podcast with

Trying to wrap our minds, hearts, and bodies around the rapidly evolving field of AI

Decolonizing Science

Article by

We are witnessing a resurgence of indigenous knowledge and growing acknowledgement of its scientific value worldwide

Wholeness & Fragmentation

Video with

The problem with our "civilized" and compartmentalized ways of thinking, which is fragmented.

Assembly Theory

Article by

Bold New 'Theory of Everything' Could Unite Physics And Evolution

The Star Compass: kāpehu whetū

Article by

Indigenous Polynesian technology for navigating using the stars

#55 Cerebrospinal Fluid

Podcast with

A fascinating lecture on the potential mystical properties of fluid in our bodies

The Convergence of Science and Spirituality

Video with ,

A video version of our popular Sounds of SAND Podcast episode

A 9-minute journey inside a black hole

Video with

Ever wonder what would happen if we got sucked into a black hole? Turns out we could live in it — if it was big enough.

Support SAND with a Donation

Science and Nonduality is a nonprofit organization. Your donation goes directly towards the development of our vision and the growth of our community.
Thank you for your support!