Weiye Loh's Library tagged Physics →  View Popular, Search in Google

"Indeterminacy means that there is not sufficient cause fully explaining an individual event." But events having no cause does not imply that we act freely. Whether you killed someone because you were pre-destined to do so, or as a result of some random blip in your brain, you're still not free and you are just as exonerated from responsibility. This is assuming that random quantum blips can actually impact on your brain, which is highly debatable.

But the absence of a physical cause does not preclude a hidden un-physical cause. Could a human mind that's entirely separate from physical reality, as described by René Descartes and later   Karl Popper, be behind the seemingly random outcome?  "One could argue that indeterminacy and the fact that we can only make predictions [on average] means that for a small fraction of individual events there could be a cause that we don't know about," says Zeilinger.  "This is pure speculation, but it is logically possible."

However, the freedom afforded the disembodied mind in this way would be highly limited: it may be able to nudge the outcome of an individual event this way or that, but it cannot change the overall probabilities without violating the laws of physics

There is however another interpretation of quantum mechanics which does not require the catastrophic collapse into one reality. According to the many worlds view, first proposed by Hugh Everett in the 1950s, the world splits into several branches whenever a measurement is made. Each of these parallel worlds corresponds to one possible outcome.

This can be extended to human choices. When you make a decision about whether to turn right or left, the Universe immediately splits into two. In one version you've turned right and in another you've turned left. Looking at this as the you just before the decision, this means that there's no choice at all involved. You'll end up doing both things. But looking at it as one of the yous just after the decision, your choice was made and for all you care it was made freely. As Paul Davies writes in his book God and the new physics, "saying that you have [turned left] in preference to [turning right] amounts to no more than a definition of 'you'."

second technical definition of random – true physical randomness. I can thrown dice to generate a statistically random sequence of numbers, assuming the dice are fair and I am sufficiently “randomizing” each throw. But from a physical point of view, the result of each throw is not random, but determined by the laws of physics. The number that results on the die must occur given all the physical parameters of the throw. Once the die is cast, the number that will result is determined and not random. In this sense “random” also means “unpredictable.”

The only truly random physical system known to science results from quantum effects. Certain quantum properties are undetermined and unpredictable – they are truly random. In fact, researchers last year developed a random number generator based upon quantum properties – the first truly random number generator.

In the crystallising block Universe time does not roll out quite as uniformly as film spooling out from a reel. Wavefunctions created at the same moment need not collapse in unison, Ellis points out. Two photons, created in the same instant and headed toward a physics experiment where they will be observed, may hit the apparatus at different moments. One photon would then move into the past just a little sooner than its twin.

There is another pretty dramatic wrinkle in the neat line between past and present, too: sometimes, the present can influence the past.

"What you think is the present is not yet quite crystallised," explains Ellis. In other words, the film may roll through the camera, but the image sets in fits and starts, like a Polaroid in which one smiling face appears in advance of another.

The crystallising block Universe may help to describe peculiar photon paradoxes, but it leaves itself open to a major criticism: what if wavefunction collapse is not the correct description for the emergence of objective reality? There are dozens of other ways to think about quantum physics. For instance, Hugh Everett III famously suggested that every potentiality represented by a wavefunction actually comes to be — in a separate universe. In this many worlds view, fresh universes split off at every quantum fork in the road.

Theoretical physicist Julian Barbour, based in Oxfordshire, UK, imagines how this might work if Ellis himself were performing an experiment: "According to quantum mechanics, taken at the face value of its equations, George himself is split into many different copies of himself whenever he makes a quantum measurement."

Ellis, however, is far from convinced: "I just find that a fantastic thing. I simply can’t believe it!"

Most processes we feel are irreversible in time are those that (for whatever reason) start out in some very special, highly ordered state — Davies uses a pack of cards as an example. When you first open up a new pack the cards will be ordered according to suit and numerical value. When you shuffle them for a while they will become disordered, so it seems that, as time passes, things will always move from order to disorder. "We might think that this is very strange because there is nothing in the act of shuffling that chooses a direction in time, yet we see a distinct arrow," says Davies.

However, there is nothing in the laws of physics that prevents the act of shuffling from producing a perfectly ordered set of cards. It's just that the ordered state is only one of a total of around 8 × 10⁶⁷ possible states, so the chance that we come across it while shuffling the cards is vanishingly small. So small that it would never happen even within several lifetimes of shuffling.

One thing we have neglected to say so far is that Einstein's theory, which describes the macroscopic world so admirably well, doesn't work for the microscopic world. To describe the world at atomic and subatomic scales, we need to turn to quantum mechanics, a theory that's fundamentally different from Einstein's. Reconciling the two, creating a theory of quantum gravity, is the holy grail of modern physics.

When Schrodinger and Heisenberg formulated quantum mechanics in the 1920s, they ignored Einstein's work and treated time in Newton's spirit, as an absolute that is ticking away in the background. This already gives us a clue as to why the two theories might be so hard to reconcile. The status of time in quantum mechanics has also created profound problems within the theory itself

"If you try to write down a quantum mechanical description of the whole Universe, you find that the time parameter actually drops out [of the equations], it's not there at all," says Davies. Time is replaced by correlations. "For example, you might have a correlation between the size of the Universe and the value of some [physical] field. We would describe this by saying 'as the Universe evolves over time and gets bigger, so this field changes in value'. We use that language, but actually all you're talking about is a correlation [between physical quantities] and time can be removed completely."

Some people have interpreted this to say that time doesn't exist at all, but Davies disagrees. "I think time exists just as telephones do. It's a real thing and we can measure it. But it does suggest that the way it enters into our description of the world is different from other quantities we're used to."

So, if Collins can talk gravitational waves as well as an insider, who cares if he doesn't know how to crunch the numbers?

Alan Sokal does. The New York University physicist is famous for an experiment a decade ago that seemed to demonstrate the futility of laymen discussing science. In 1996, he tricked the top humanities journal Social Text into publishing as genuine scholarship a totally nonsensical paper that celebrated fashionable literary theory and then applied it to all manner of scientific questions. ("As Lacan suspected, there is an intimate connection between the external structure of the physical world and its inner psychological representation qua knot theory.") Sokal showed that, with a little flattery, laymen could be induced to swallow the most ridiculous of scientific canards—so why should we value their opinions on science as highly as scientists'?

key concept of the paper is to define a continuum of uncertainty from the less radical to the more radical. You get into trouble when you think there is a higher level of certainty than there really is.

1. Complete Certainty

2.  Risk without Uncertainty (randomness when you know the exact probability distribution)

3. Fully Reducible Uncertainty (known set of outcomes, known model, and lots of data, fits assumptions for classical statistical techniques, so you can get arbitrarily close to Type 2).

4. Partially Reducible Uncertainty (“model uncertainty”: “we are in a casino that may or may not be honest, and the rules tend to change from time to time without notice.”)

5: Irreducible Uncertainty:  Complete Ignorance (consult a priest or astrologer)

Physics Envy in Development leads you to think you are in Type 2 or Type 3, when you are really in Type 4. This feeds the futile search for the Grand Unifying Theory of Development.