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The Home Parallel Universe Test
Sam Sachdev writes "David Deutsch, a physcicist at Oxford, has designed a home test for parallel universes. Using a pin, a red laser pointer, a piece of paper, and a relatively dark room, he claims that the results from this experiment confirm the existence of parallel universes." Okay, so it may not really be proof of parallel universes, but it's a fun trick to try with a laser pointer nonetheless.
In other words, they're using the term "parallel universe" to get people to read this. They found a neat effect with photons, yes. Might as well just call it a Terroristic Particle Exploitation, and then maybe the real media will examine it at that point. Nothing to see here, move along.
Second of all, he credits David Deutsch with an idea that most certainly is not his. Both the notion of wave functions (what this article is talking about) and the idea that this somehow relates to parallel universes are older than I am.
This is not a revolutionary idea, and it is not really a controversial one either, as the author of the article seems to indicate. This is just one explanation of a curious quantum mechanical effect. There are other explanations, and they all describe what happens quite accurately. They may each have their own proponents, but really none of them is wrong--they are just different interpretations.
I generally do not like griping, but this write up is positively abysmal. It is no offense to David Deutsch--I am sure he is a quite competent individual. But I do not think the author of this paper actually read his book. It sounds too much like the BS I would string together from reading the first few chapters and the epilogue when I had a book assignment in schoool.
Go here for a decent, intuitive, layman's introduction to various quantum mechanical oddities.
When things get complex, multiply by the complex conjugate.
David Deutsch is a really bright guy, but he has a problem understanding how other people think, including lots of other really smart physicists.
He believes the many-worlds interpretation of quantum mechanics adamantly, and thinks that any other interpretation is, if not outright wrong, not a useful frame of mind to understand QM.
I am also a many-worlds person, as are many other physicsts I know, but I also know many very smart quantum physicicst who are not, and I am not willing to say they are wrong (yet).
I think a historical analogy might be appropriate: Back in the day. there was substantial scientific contention over whether the sun revolved around the earth or vice versa (I am not considering the religious contention -- for a while the scientific evidence was not sufficiently clear). You see, you could reproduce all the observable motion of the planets in the geo-centric model using finer and finer epicycles. So, planets would revolve the earth, and had wobbles in their orbits that faithfully represented their entire movement patterns. Or, you could adopt a helio-centric model, in which all the retrograde motion and other strange behavior cleanly fell out of the equations. You could do the math either way, but in retrospect, the helio-centric model is a much better "interpretation" of the data than the geo-centric model, because it is useful for figuring out all sorts of other things, like gravity and conservation of momentum.
Deutcsh feels similarly about the many-worlds interpretation. But as I said, among quantum physicsts you will find the whole range of people with different levels of commitment to different theories. or interpretations.