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Physicists Demonstrate How Time Can Seem To Run Backward, and the Future Can Affect the Past

[DIGEST: Digital Journal, Science Daily, Nature Physics]

We all agree, past events can affect the present. And present events can affect the future. But few would credibly argue that future events can affect the past.

That might all change soon. Welcome to the world of quantum physics.

To the average person, the observable, classical world of Newtonian physics feels like common sense. Time moves forward; things exist in only one place at a time; if a tree falls in the woods but no one sees it, we assume it still fell. But a team of physicists at Australia National University are saying, “Not so fast.” Enter quantum physics. And it’s really weird.

Quantum hunters... Associate Professor Andrew Truscott, left, with PhD student Roman Khakimov. Source: ANU
Quantum hunters… Associate Professor Andrew Truscott, left, with PhD student Roman Khakimov. Source: ANU

A new study published in Nature Physics appears to show that time in fact may move backward, things may exist in multiple states, and whether a tree fell in the woods not only may depend on whether anyone ultimately saw it, but also on whether something somehow knew it would be seen. “It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it,” said Associate Professor Andrew Truscott from the ANU Research School of Physics and Engineering.

This absurd-sounding conclusion derives from two experiments, one of which has been around for some time, and one of which was just successfully performed only a few weeks ago.

(Credit: pmrb.net)

First, the older experiment. Scientists have long observed the strange behavior of light particles, photons, in something called the Double Slit Experiment. Here’s how that worked: When light was shone at a screen with two narrow slots in it, the photon particles acted rather schizophrenically. On the one hand, the photons acted like particles, casting a direct glow on the wall behind the slits. But they also acted like waves, generating an “interference pattern” like waves of water might, creating a mysterious second pattern beyond two simple strips of light.

This principle lies at the heart of quantum physics. A particle like a photon acts as if it has indefinite, suspended states. It lacks any physical properties, and is defined instead as a set of “probabilities” that it exists in any one particular state. (These “probabilities” aren’t just some laboratory or academic theory. They underlie all of our

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