Realism

I finally finished reading Walter Isaacson's biography of Albert Einstein, and it was extremely good. I highly recommend it.

Isaacson does a good job of explaining Einstein's resistance to the Copenhagen Interpretation of quantum mechanics, the idea that some or all elements of the universe are in an indeterminate state that is resolved by the act of observation.


Einstein rejected this interpretation throughout his life and to his death. He held to the tenet of realism, the idea that the world is in a definite state, even in the absence of observation. Most people have heard of Schrödinger's cat, but don't realize that the ideas for such a paradox came mostly from Einstein, whose own example was a keg of gunpowder hidden from observation which paradoxically exists in an exploded and unexploded state.

But apparently the vast majority of physicists currently hold to the Copenhagen Interpretation, with a smaller number holding to a Many Worlds explanation, with a very small minority still in Einstein's camp (I can't seem to find the stats on this right now, though).

Now Einstein never said that quantum mechanics was wrong. He just said it was incomplete.

Typically we use statistics to describe the degree of certainty we have about the state of the world. If a dealer shuffles a legal deck of cards and deals them into two piles of equal size, what is the probability that the ace of spades is in pile #1? It's 0.5, right? This is a description of the extent of our knowledge about the system before observing the relevant variables. If we pick up the piles and flip through them, then we have certainty about the location of the ace, and a statistical description is no longer needed.

What's weird about quantum mechanics is that it asserts that the statistic description is the complete one. In other words, the ace is half in one pile and half in the other. It exists in an indeterminate state, simultaneously in both places, until an observation takes place.

So what Einstein was arguing was that a statistical description was still a description of the limits of our knowledge about the system, while his opponents argued that the statistical description was complete description of reality.

I'm afraid I find it very hard to swallow the Copenhagen Interpretation. I should probably defer to the majority of experts in the field, but I'm afraid I can't...at least until I get a satisfactory explanation why the statistical description should be interpreted as complete, and not as an approximation.

There are a number of experiments which are meant to verify the Copenhagen Interpretation, including the Double Slit Experiment and the Beam Splitter Experiment. Every account I've seen describes the results as "weird", but fail to give a satisfactory account of what is actually going on (at least to me...maybe I'm just being stubborn).

One of the main problems I have with an observer-defined reality is the same problem Einstein had. What constitutes an observer, or an observation? Is a piece of recording equipment an observer? Einstein asked about a mouse. If you show a mouse the readout on a piece of machinery measuring the location of a particle, but don't look yourself, does this resolve the indeterminacy of the system?

And what about the state of the world before life arose? There was a time when there were no observers. Was the world in some kind of constant state of flux? If matter really is in a completely different state before observation, then how did such a fluctuating state give rise to life in the first place?

Another thing I haven't heard explained to my satisfaction is exactly what the act of observation is supposed to do to a system. Here's another example: active and passive sonar. When something like a submarine uses active sonar, that means they generate their own sound waves, and read the information that bounces back from objects the waves bump into. With passive sonar, the submarine doesn't generate its own waves, but relies on sounds that are already bouncing around in the water.

Now I could see how active observation would alter the state of the system being observed. You're injecting a new dynamic into the system when you're bombarding it with sound waves or photons or any other active process. But how exactly does passive observation affect a system?

Maybe there are answers to these questions, and I'm just not smart enough, or haven't read enough, to wrap my head around them. Maybe nobody knows.

For now, though, I'll remain in an indeterminate state.

Why Two Things Never Really Happen at the Same Time

I'm still reading and enjoying Walter Isaacson's biography of Einstein. He hasn't yet gotten to the Copenhagen interpretation of quantum mechanics and Einstein's famous quotation "God does not play dice", but you can see some foreshadowing of why he might find it so distasteful.

In describing Einstein's theory of Special Relativity, Isaacson uses the following example (let's see if I get this right...if you're interested in the subject you should definitely browse around and make sure I didn't screw up this explanation). Let's say Joe is standing at point X when two lightning bolts strike at A and B:










The light from both strikes reaches Joe at precisely the same time, so he perceives the events as occurring simultaneously. So we can safely say that lightning struck the two places simultaneously, right?

Wrong.

Bob is traveling at a very high, constant velocity toward point X. He is directly on X when the lightning strikes occur. However, the light from the lightning strike at A will reach him sooner than the light from lightning strike B because of his motion toward A and away from B. So from his frame of reference, the lightning will strike A slightly before it will strike B.

Thus, there is no such thing as absolute simultaneity. You can only describe two things happening at once in relative terms. What determines whether two things happen at the same time depends on how fast an observer (or measurement device) is traveling relative to them.

I think I got that right.

And I think this is part of the reason why Einstein had such a problem with "spooky action at a distance", the idea that two particles that are entangled could affect one another simultaneously regardless of how far apart they were. As far as I understand, this phenomenon has been tested in the lab, at very short distances, but there are criticisms. However, if two particles were entangled, and one stayed on earth while the other was transported to the moon, and then the spin of one was modified and it affected the spin of the other...that would certainly be strong evidence.

I'm looking forward to Isaacson's account of Einstein and quantum mechanics.