Jun 12 2012

The Science of Prometheus

I’m a huge fan of science fiction, especially hard science fiction, and also of scientific deconstructions of popular works of science fiction. I also enjoy other forms of speculative fiction – I don’t require scientific accuracy, or even plausibility, to enjoy a good book or movie. I’m perfectly willing to suspend disbelief or allow for “gimmies” – OK, there’s subspace and you can travel faster than light. I’m good with that. I appreciate, however, when sci fi writers try to work within the scientific framework as much as possible, to minimize “gimmies”, and to extrapolate thoughtfully from established science. What I am not tolerant of, however, is gratuitous errors in science. There’s just no excuse for that in science fiction.

I saw Ridley Scott’s Alien prequel, Prometheus, over the weekend. What follows is a sequence of spoilers, so be warned. I will try not to discuss plot points unnecessarily, but if you don’t want any spoilers wait until after you see the movie to read further. This is also not going to be a movie review, just a discussion of some of the science in the movie.

Let me start with something that I really enjoyed. The planet that the ship Prometheus and its crew visit in the movie is actually a moon of a gas giant. I find this idea fascinating, and have speculated about this before myself. We are in the midst of an explosion of exoplanet discoveries. We are just now starting to get some data about what the typical configuration of other stellar systems is likely to be. We still don’t have enough data to answer this question, and our methods of finding exoplanets are biased toward large planets close to their suns. But we are starting to find smaller Earth-sized worlds far enough out to be in the goldilocks zone where liquid water can exist on the surface.

Obviously there is a great deal of curiosity about how many planets out there might be capable of harboring life. We may need to expand our concept of what such a planet might be like, and one possibility is that it could be a large moon of a gas giant planet. This would certainly make for a beautiful sky, and it would be very interesting to work out what the experience of someone living on such a world would be like. A moon of a gas giant would likely be tidally locked, so that the planet would always be in the same place in the sky. It would also likely be frequently eclipsed by its giant companion, so the day-night cycle would be partly a factor of the rotation of the planet, which would likely be slow, and also a function of passing into the shadow of the gas giant.

I appreciated that the film involved a habitable planet that is a moon of a gas giant, but they did not explore this more complex astronomy at all, so that was an opportunity lost. In fact there is a suggestion in the timeline of a typical 24 hour day, or something close to that, which would likely not be the case.

Now on to what is perhaps the worst science gaff in the movie. At the beginning of the film archaeologists find evidence that many primitive human cultures had the same legend of contacting gods from the sky, and left behind paintings or carving depicting a specific pattern of five dots. The implication is that this pattern of dots is a map. They explain in the movie that there is only one system with that configuration, and there is a star in that system. This left me wondering what the hell they were talking about.

First, what do the dots represent? It would seem that they must be stars and that the pattern of dots is a star map of sorts. This is problematic for multiple reasons. There are so many stars, even just in our neighborhood, that there would likely be many possible matches to a random clustering of five stars. Further, is the clustering their real location with respect to each other, or their apparent position as seen from earth? Either way, there is an additional problem that the star map was tens of thousands of years old, and stars move, so the precise real or apparent relationship would be slowly shifting over this time. Any star map, in other words, would be outdated – even if a cave painting could depict the star relationship with sufficient precision to be useful as a map.

All of this, however, is difficult to reconcile with the statement that “there is a star in the system” – so what were the five dots if not stars? Are they planets? That would make absolutely no sense, many systems would have five planets and in any case the five dots did not give relative positions of planets. Finally – what kinds of systems don’t have stars in them? I guess they could be referring to stellar systems in which the star is no longer on the main sequence and is now a white dwarf or something. In any case, the star map bit made no sense.

Another main scientific pillar of the movie is the notion that (just another warning – this is a big spoiler) the race that made the aliens were essentially human (although bigger, balder, and paler). The crew discover that their DNA is a perfect match to human DNA, which then makes it difficult to explain the morphological differences that do exist. Far worse, however, is the explanation for the genetic similarity.

At the beginning of the movie we see a humanoid seeding his DNA into the oceans of what appears to be the early Earth. We then see that DNA reproducing and leading to cells dividing – the implication being that life has now been kickstarted on Earth. There is no scientific problem with the notion that aliens seeded the early Earth with RNA or DNA and that these replicating molecules eventually evolved into life on earth. This is, in fact, a serious scientific hypothesis known as panspermia – the idea that life may have evolved elsewhere and the components of that life came to earth via comets or meteors, and those bits of life seeded life on Earth. Panspermia does not involve deliberate seeding by aliens, but that is the same idea. In fact it’s more plausible in that living organisms would be unlikely to survive millions of years in space, and even DNA would tend to break down from exposure to cosmic rays. Panspermia is not impossible, but it would be helpful for aliens to dump fresh DNA onto a virgin planet to get the whole evolution thing going. (None of this is to imply that seeding is necessary for life to get started.)

Other than this basic concept of seeding, there are major problems with this aspect of the plot. How long ago did the alien seed the Earth? It would have to have been 3.5 or so billion years ago. That’s a long time, and it’s hard to imagine that the same humanoid aliens (to be clear, not the weaponized aliens that give the franchise its name, but the humanoid aliens that created them) would be around a few billion years later without any physical change. That’s remarkable evolutionary stability.

The solution that the seeding occurred more recently in the past, say tens or hundreds of thousands of years ago, or even a few million years ago, creates more problems than it solves. I will just say that there is copious evidence for life on Earth going back billions of years, not thousands or millions.

Another possible solution is that the humanoid alien seeded its DNA on an Earth let’s say hundreds of thousands of years ago while there was already native life no the planet that evolved without alien help, but the alien’s DNA is what led to humans. This, however, creates the problem of why the alien DNA was so similar to not only human DNA but Earth DNA. Why would this alien have DNA that is identical in terms of its genetic code to life on Earth. That would be an amazing coincidence (so much so that it can be treated as impossible).

The biggest problem with this whole idea is that seeding the Earth with alien DNA would lead, somehow, to the evolution of humans. This is simply not the case. The implication is that the program for humans, or at least humanoids, was somehow in the DNA, but there is simply no mechanism for this.

It is impossible to make scientific sense of the information presented in the movie. The only way to rescue the science is to assume that there are massive gaps in the information presented. We would need to fill in an elaborate back story in order to jerry rig the science to have it make sense (perhaps there is a Star Trek fan with some extra time who can help out). This would mean, however, that the scientists in the movie were unaware of the massive scientific gaps in the information they had. They seem to take in stride that the humanoid aliens had human DNA, and never question the incredible implications of this fact. They simply conclude that they must have created humans, but never address the massive scientific problems with this.

In the end I am left not knowing what happened, or what the movie is even trying to say. I’m OK with mystery. I love the film 2001 and the fact that not everything is explained and wrapped up in a bow at the end. There is good mystery in fiction, however, and then there is just head-scratching confusion created by sloppy science writing. Unfortunately Prometheus is the latter.

It’s too bad. Overall the movie was good (not great), and fell short of being epic primarily, in my opinion, because of superficial writing. I recommend that such big budget blockbuster science fiction movies in the future add a tiny budget to pay for some science consultants to get the science not only correct, but also interesting and thought provoking. Great 3-D special effects are no longer enough. We want good writing too.

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