Does consciousness create reality?

From New Scientist...

The human universe: Does consciousness create reality?

01 May 2015 by Douglas Heaven

While not a complete figment of our imagination, the universe may only become real because we're looking at it

Samuel Johnson thought the idea was so preposterous that kicking a rock was enough to silence discussion. "I refute it thus," he cried as his foot rebounded from reality. Had he known about quantum mechanics, he might have spared himself the stubbed toe.

Johnson was responding to Bishop Berkeley, a philosopher who argued that the world was a figment of our minds. Could he have been right?

With its multiverses and cats both alive and dead, quantum mechanics is certainly weird. But some physicists have proposed that reality is even stranger : the universe only becomes real when we look at it.

This version of the anthropic principle (see "Was the universe made for us?") – known as the participatory universe – was first put forward by John Archibald Wheeler, a heavyweight of 20th-century physics. He likened what we call reality to an elaborate papier mâché construction supported by a few iron posts. When we make a quantum measurement, we hammer one of those posts into the ground. Everything else is imagination and theory.

For Wheeler, however, making a quantum measurement not only gives us an objective fix on things but changes the course of the universe by forcing a single outcome from many possible ones. In the famous double-slit experiment, for example, light is observed to behave either as a particle or as a wave, depending on the set-up. The most baffling thing is that photons seem to "know" how and when to switch. But this assumes that a photon has a physical form before we observe it. Wheeler asked: what if it doesn't? What if it takes one only at the moment we look?

Even the past may not yet be fixed. Wheeler proposed a cosmic version of the double-slit experiment, in which light from a quasar a billion light years away reaches us by passing around a galaxy that distorts its path, producing two images, one on either side of the galaxy. By pointing a telescope at each, observers would see photons travelling one of two routes as particles. But by arranging mirrors so that photons from both routes hit a detector at the same time, they would see light arrive as a wave. This time, the act of observation reaches across time to change the nature of the light leaving the quasar a billion years ago.

For Wheeler, this meant the universe couldn't really exist in any physical sense – even in the past – until we measure it. And what we do in the present affects what happened in the past – in principle, all the way back to the origins of the universe. If he is right, then to all intents and purposes the universe didn't exist until we and other conscious entities started observing it.

Sound crazy? Then try this one on for size. Another interpretation of quantum mechanics is Hugh Everett's many worlds hypothesis, which posits that everything that could happen has and does, in an infinite number of universes. Every time you make a decision, the universe splits in two, with you in one branch and an alternative you in the other, living the other possibility. The universe you occupy is, in some sense, an individual universe of your own making.

This idea is enough to give anyone a reality check. "My natural inclination is to be a realist," says Chris Timpson, a philosopher of physics at the University of Oxford. "But if you're going to be a realist about the quantum world then you're left with a world that's very peculiar." So peculiar, in fact, that the idea that it only exists because of us seems almost sensible.