...Exploring Stephen Hawking's Flexiverse
20 April 2006
by Amanda Gefter
The history of the cosmos has yet to be decided. At last, a chance to play God
HERE'S how to build a universe. Step one: start at the beginning of time. Step two: apply the laws of physics. Step three: sit back and watch the universe evolve. Step four: cross your fingers and hope that it comes out looking something like the one we live in. That's the basic prescription for cosmology, the one physicists use to decipher the history of the universe. But according to Stephen Hawking of the University of Cambridge and Thomas Hertog of the European Organization for Nuclear Research (CERN), the steps are all backward. According to these physicists, there is no history of the universe. There is no immutable past, no 13.7 billion years of evolution for cosmologists to retrace. Instead, there are many possible histories, and the universe has lived them all. And if that's not strange enough, you and I get to play a role in determining the universe's history. ...
It is a very sad statemet about the state of theoretical physics that assumptions about infinites and quantum weirdness have enabled this kind of causality-lacking approach to become the norm for resolving the fine-tuning problem.
...the sum over histories is formed by calculating the various probabilities for a universe like ours to arise out of literally nothing: that means we can never know anything for certain about how our universe got to be as it is.
We shouldn't be surprised, Hertog says: quantum theory has long shown us that it is impossible for us to know everything about the world around us. In "classical" physics, we can predict both the exact momentum and position of a particle at any time, but quantum mechanics doesn't allow it. No one suggests that quantum mechanics is wrong because of this, Hertog points out - and experiments have shown that it is not.
Whoa, wait a minute there, Tom. No one suggeststs that QM is wrong, but a number of respected theorists, like Roger Penrose, think that quantum theory will have to be modified more than relativity will, so don't pretend that your assumptions aren't up for dramatic revision just because you think that you understand something from an interpretation that can be thrown right back in your face given only very little new information.
For many, it remains a difficult argument to swallow. Science since Copernicus has aimed to model a universe in which we are mere by-products, but top-down cosmology turns that on its head, rendering the history of the universe a by-product of our observations. All in all, it is very like the "anthropic landscape" argument that is causing controversy among string theorists.
Which is a really nice way of saying that Hawking too is grasping at infinities and uncertainty, and that is a cop-out on the long-held understanding that there must be a good physical reason, (a stability mechanism), why the universe is the way that it is. Thank "god" that I'm not alone:
Princeton University physicist Paul Steinhardt says:
"It's kind of giving up on the problem. We've all been hoping to calculate things from first principles. Stephen doesn't think that's possible, but I'm not convinced of that. They might be right, but it's much too early to take this approach; it looks to me like throwing in the towel."
Stanford University's Andrei Linde is similarly unconvinced:
There are a number of technical assumptions that make him sceptical. "I don't buy it," he says.
I don't either, but I'm not arrogant enough to believe that first principles can possibly be disassociated from the human evolutionry process in an anthropically constrained universe... *duh*
Sit back and watch it "evolve".