By Anna Kushnir
I am embarrassed to admit that I have never watched PBS’s (no, not phosphate buffered saline, I mean the other one) award-winning and popular science series, NOVA. This will certainly change after last night.
I had the pleasure of attending a sneak preview of NOVA’s new feature, Parallel Worlds, Parallel Lives, at the Museum of Science. The movie follows Mark Oliver Everett (the talented lead singer of the indie rock band, the EELS)as he journeys to learn more about his father, Hugh Everett III, a brilliant, but emotionally distant quantum physicist who laid the foundation for the Parallel Worlds theory, which states that “every event that could occur in a number of ways… trigger[ing] a split that generates multiple universes, which collectively contain every possible outcome.” (from the NOVA website).
This theory served (and continues to serve) as fodder for multiple episodes of Star Trek and the Golden Compass series by Philip Pullman, among others, in which people attempted to gain access or were thrown into lives closely mimicking their own, but not quite – entire worlds that existed alongside theirs, differing only by one decision. The 50th anniversary of this theory as placed on a 2007 cover of Nature.
As shown in the movie, one of the most famous experiments in quantum mechanics, and the foundation for the Parallel Worlds theory, is the Two Slit Experiment. In this experiment, a focused laser beam – consisting of single photons of the same wavelength – is aimed at a board with two teeny slits, positioned in front of an ultra sensitive camera. The camera records the places behind the board where the photons hit. The Two Slit Experiment demonstrated that a particle can be in two different places at the same time (I am afraid to give any more detail for fear of getting something wrong).
Everett proposed that if two particles can be at the same place at the same time, then so can people, since they are just big collections of particles. Everett’s theory ran directly against the teachings of the physics luminary, Niels Bohr. Bohr refused to acknowledge Everett’s theory and it remained dormant and forgotten until recently, when further work in quantum mechanics gave it serious consideration.
Max Tegmark, an MIT cosmologist and quantum physicist featured in the movie, was on hand at the Museum of Science to answer questions about the science in the movie. He spoke eloquently about physics and answered questions in a fluent and understandable (even to me, a biologist with a B- in college physics) fashion. He also expressed his admiration for Everett and his work, saying that to him, the Parallel Worlds theory is one of the most important scientific advances in recent history.
And that’s when I started to get a little frustrated. The Parallel Worlds theory is not one that can be easily tested, if at all. The experimental scientist in me reared up in protest. I could have really used a Western blot, or some FACS data as a very last resort, to show some support for the theory above and beyond inaccessible mathematical calculations and manipulations. Biologists are, in turns out, a very different breed of scientist than ones profiled in Parallel Lives, Parallel Worlds. Different, but no less interesting.
Read more about the Parallel Worlds theory here and watch Parallel Worlds, Parallel Lives on PBS starting on Tuesday, Oct 21. If I found a movie about physics interesting, so will you.
I think one of the most interesting (and probably difficult, I would imagine) cultural differences from scientists from different fields is the idea of what makes for good, acceptable evidence. I wonder how many arguments/heated discussions there have been between biologists and physicists on this topic? What is the nature of “evidence”?
I think the nature of evidence can be debated even within biology. Physics though… physics I don’t understand. Physics uses mathematical calculations to model the natural world. Mathematics, on some level, obeys man-made rules. In essence then, math describes a man-made world, not necessarily the real world. It’s all modeling and theory and I understand that it’s relevant, but I have a tough time accepting it. An equation, in my narrow biologist’s view, is not direct evidence on the workings of nature.
Oh, would love to hear from some mathies and systems biologists here!
Umm, I think that all biology has some theoretical background, best described using mathematics to describe the natural world. Theories can be expressed in a variety of different ways, but arguably the best way is using maths. Here’s a slightly frivolous example:
Imagine we think there is some relationship between human age and human shoe size.
This can be expressed verbally: “I think that human shoe size will increase with human age.”
Or graphically:
Imagine this is hand drawn
Or, (in my opinion the best way), mathematically:
Relative show size blue = Age(in years) * maximum(Age)
Relative show size green = Age(in years) / 1 + Age(in years)
Unfortunately, people tend to replace useful variable names (like shoe size and age) with greek symbols, which is alien and can be an unhelpful way to communicate for most untrained biologists.
Anyway, now we can go and collect lots of data from real people with real shoe sizes, perhaps use some statistical method of relating our hypothesis to the data, giving us yet another way of modelling the natural world (statistics).
A model is just a more manageable simplification of reality (think of Naomi Campbell – nobody can really be that unpleasant, can they?)
The mathematical representation gives us the best idea about what shape the “true” (actually only likely to be a sample from the population) relationship has – let’s say that green is better at describing the data than blue. Now we have an idea about the mathematical relationship, we can go on to construct a more mechanistic model, that could incorporate info about energy consumption, bone growth and the evolution of shoe manufacturers. This model is more complex, but can give us more insight into why shoe size increases with age, and will still be a simplification of reality, relying on mathematics to express the relationships between constants and variables.
A problem a lot of biologists face (i certainly did) is that they couldn’t relate the concepts important in in high school mathematics to their own experience. My PhD supervisor taught me more about differentiation in 10 minutes, by relating it to population biology, than my high school maths teachers did in 6 years!
The history of maths seems pretty cool, but something I know hardly anything about. I’d love to be able to actually prove that 1+1=2!
By the way, physicists formulae (models) are also based on enormous simplifying assumptions, e.g., the currently accepted view of the age of the world is based on a highly oversimplified formula. More complex formulae exist, but don’t necessarily give us a better insight into the interesting issues.
The “Big Bang” theory is another way of saying “Our formulae (models) give us an infinity value at the start of our universe, which is mathematically too complicated, so we can’t really say anything about it”. The LHC is there to give us an idea about what happened just after the Big Bang, but what happened exactly at the point where our universe came into existence is very uncertain and can’t be answered using LHC.
Hope this convinces you that maths has a vital place in biology!
Sorry, that should have said age of the universe, not world, and the reason I think maths is a better way of describing the world is that the verbal model of the relationship between age and shoe size is too ambiguous – as shown by the two increasing relationships in the graph and equations.
Anna – This theory served (and continues to serve) as fodder for multiple episodes of Star Trek and the Golden Compass series by Philip Pullman, among others – oh please don’t forget Dr. Who!
Anyway, Mike: if I see this correctly, you explain the alteration or feedback between mathematical theory/model → getting more data to prove theory → new, refined theory/model → getting more data.. is this correct? And you say yourself that, at the end, you’re still left with uncertainty. Of course maths has a vital place in biology(!!!), but I think you’re describing the precise reason for Anna’s frustration – we (hands-on type) biologists like to actually see the evidence.
I’ve done a bit of hands on biology myself over the years, but I’ve always had the idea that I’m testing a theory while I’m doing it.
There are different views about the best way to approach science philosophically (Kuhn & Popper spring to mind). I don’t think the kind of circular idea you propose here, Steffi, is really how I see things. Data rarely proves a theory, the best we can hope for is some kind of support for the theory we test. In fact, Popper tells us we’re better served by trying to falsify hypotheses, rather than seeking support for our pet theories.
I would say that it’s vital to start the scientific process with some clear, unambiguous hypothesis. Maths is a pretty good way to do that – assuming we make our underlying assumptions in the mathematical model clear and easy to understand!
Of course, one reason we start asking scientific questions is because we’ve noticed something interesting in the natural world. In my case, that might be regular multi-year cycles in the annual abundance of some species. Another person might be interested in the fact that some people in sub-Saharan Africa suffer more from malaria than others.
The way to find out why these interesting things happen is to formulate sensible questions that can eventually be tested in the real world. This can be a long process (e.g., there are still conflicting theories about the mechanisms driving Canada lynx cycles, even after collecting data for nearly 200 years), with many wrong questions asked along the way, but if we start with small, manageable questions, with many simplifying assumptions, we can proceed with baby steps in the right direction, understanding the explanatory limitations of our answers.
This simplification occurs across a wide range of scales in practice, from mathematical models, to carefully controlled lab experiments, to field trials, with many intermediate steps. But I’m a
legbottom-up kind of guy, so I think the best way for me to really understand anything is by understanding how the smallest component parts work, then seeing if any syntheses arise from interactions between the components as we piece them together. Robert Pirsig chats about this in Zen and the art of motorcycle maintenance amongst other angst ridden, drug fuelled madness.I’m gonna stop hogging Anna’s thread now – sorry! I hope I’ve made my thoughts a bit clearer here though.
Hey Mike, I think we basically agree on what we’re saying. What I was trying to describe was nothing ‘circular’, but rather the (iterative) baby steps you mention, with a little bit of progress each time. Maybe it’s a neverending spiral… should keep both mathematicians and biologists happy into eternity, I reckon.
Mike, the idea that Physicists use massively simplifying assumptions may be true at the big end of the scale. At the small end it is not so true. Many theories based on quantum mechanics start from no assumptions ab initio and can produce predictions that are tested experimentally. The same is certainly rrue with Newtonian Mechanics as is seen in the many complex engineering structures that have been built.
@Anna – The use of maths in physics is often to show how a set of simple assumptions lead to more complex predictions that are more easily tested than the initial assumptions. For example in quantum mechanics we produce a statistical distribution of likely outcomes that can then be tested.
If we return to the original subject – Many Worlds v. Copenhagaen Interpretation – it is difficult to see how these can be tested in a world that is one of many (whether existing in parallel or selected randomly).
David Deutsch has suggested that there is a way to experimentally test the many worlds approach, but you do have to be able to construct a self-aware quantum computer.
This sounds to me a bit like those phyicists who say, ‘sure, you can build a time machine. All you have to do is assemble a near-infinitely long cylinder of neutron star material and rotate it very quickly.’ It ain’t going to happen soon.
At the movie screening, Max Tegmark was asked how one could test the Many Worlds theory. His answer was precisely yours, Brian (Clegg). He said that the generation of a quantum computer would prove Everett’s interpretation. The most advanced quantum computer currently in existence has the computing power of just 7 bits – just enough to factor the number 15. It is not impossible that a fully functional machine is constructed in the next 5-10 years, but that’s a big if.
Brian (Derby) – I totally agree! Physics and quantum mechanics certainly have an empirical side to them, at the lower end. it’s when you get into the hypothetical theoretical stuff that I feel the discipline loses touch with reality.
Mike – I would like to comment on your wonderful and thorough responses, but I think I have to read them 15 more times. Give me a moment.
Anna, take your time. I’m off to dig into some food & wine. That should distract me for a while from these otherwise interesting discussions. Who’da thought the humble haggis could be so attractive?
My plucky dinner, earlier this haggis hunting season
damn – I’ve just checked my 1st post above, and noticed a couple of very obvious typos. I kept writing “show” instead of “shoe” when I 1st wrote this, but noticed most of the mistakes at the time. Unfortunately, the y-axis label and 2 “equations” both say “show” instead of “shoe”. What’s the greek symbol for shoe anyway?
That film was shown on the BBC earlier this year. It was quite simply the best science documentary I’ve ever seen (but then Eels are among my favourite bands). I remember buying the first Eels album—way back in 1997—on the very same day I learned about many-worlds theory during a quantum mechanics class, only finding out later on that the two geniuses behind the theory and my new album were father and son.