Review: Star Wars: The Phantom Menace

Before we start, you should know that this is a heavily revised page. My initial page about Star Wars had a couple of bad errors in it, errors which I should have known better than to make. I admit my mistakes (at least, the ones that make a difference) and so if you want to see the dumb stuff I said you can find them here.

A brief introduction: I'll state here I like the Star Wars movies (except Return of the Jedi, yikes!) and I liked the Phantom Menace (hereafter: tPM). There wasn't a whole lot of astronomy in it, actually, so there isn't much to review. There are a few things in it worth noting, though, keeping in mind that the whole purpose of reviewing the Bad Astronomy isn't to be picky, but to make you think about what you're seeing, and to show you how things really are. Don't take any of this as a real critique of the movie. Also, I am not going to talk about such things as sounds in space, spaceships banking to make turns and the like. The main reason is I already wrote a review like that for Astronomy Magazine in 1998, and I want to make a separate generic movie Bad Science page with typical physics errors made by movies. So I'll stick with what I consider to be within the realm of straight astronomy here. Keeping that in mind, let's get going!

Bad:
In a scene from high above Naboo, we see a fleet of Trade Federation ships silhouetted against the planet, and beyond that the sky is full of stars.

Good:
This is a common scene in science fiction movies, but ask yourself a question: have you ever seen anything like it in real life? The answer is no. When NASA broadcasts live scenes from outside the Space Shuttle, you usually see the Earth in vivid blues, browns, greens and dazzling white, but you never see stars at the same time. And if you can see stars, the Earth is tremendously overexposed. The reason for this is contrast. Stars are fairly faint, while the Earth (or the Shuttle, or astronauts floating in space) are very bright. They're sitting in full sunlight!

So the Earth, when lit by the Sun, is many hundreds or thousands of times brighter than the stars behind it. When the astronauts set the camera to take pictures, they need to adjust it for that brightness. To expose the Earth correctly, they need to shut out most of the light hitting the camera, and the faint stars cannot be seen. If they adjust the camera to let in enough light to see stars (or more accurately, use a camera which amplifies the light of the stars), the Earth floods the camera with light, vastly overexposing itself. So even though the sky looks black, there will be no stars in the picture.

I have received a few emails about this part, asking if the human eye would see things differently than a camera. In other words, the human eye is capable of seeing higher contrast than a camera, so is my objection still valid? Yes, it is. Ron Parise is a Shuttle astronaut who happens to work down the hall from me (how cool is my job?), so I asked him if he could see lots of stars out the Shuttle window when the sunlit Earth was below him. He said no; the only stars you can see are the very brightest ones, and only a few of those. As with a camera, the human eye only has a limited range of brightness it can perceive, and the Earth (or Naboo!) is so bright it swamps all the stars.

As a side note, I'll add that some people, remarkably, think that NASA never actually sent men to the Moon; that all the Apollo films were faked. As a piece of key evidence, they cite that all the pictures taken from the Moon have no stars in them! So instead of asking someone who might understand photography, they jump to the conclusion that NASA managed to undertake the largest conspiracy in history. This is Bad reasoning in its absolute highest form.

Bad [added July 12, 2002; my thanks to Bad Readers Vicker and Lev Astov for pointing this one out to me]:
In a related Bad scene, we see Queen Amidala's ship in space. It is highly reflective, but we see it clearly.

Good:
If it's highly reflective, what's lighting it up? It's out in space! When it is over a planet, we see it as a shiny, silvery object reflecting buildings and the like. In the inky blackness of space. All we should see of it is a distorted reflection of stars. Yet there it is. This is a common Star Trek phenomenon too.

Bad:
Tatooine orbits a binary star system. Yet in all the scenes we only see single shadows.

Good:
First, let's look at Tatooine's orbital situation. How does an orbit work around a binary star? There are three instances where we are shown that Tatooine orbits two stars. One is in the first movie, ``A New Hope''. When Luke ponders his life after his Aunt and Uncle tell him he cannot join the pilot academy, we see him watching the two suns setting in the desert. In ``The Phantom Menace'', when a starship is leaving Tatooine we get a short glimpse of two suns in the sky. Also in the movie, Anakin's mother says to him, ``You cannot stop change, any more than you can stop the suns from setting.'' Note the plural.

Just to be clear: a binary star is a system of two stars (more than that is called a multiple system) that are gravitationally bound; that is, they orbit each other. I initially thought that it was hard to get a planet orbiting a binary star. Actually, it may very well be hard, but not impossible. Astronomers know of at least two planets orbiting binary stars: the planets around the binaries 16 Cygni B and Rho Corona Borealis. In these cases, the planets orbit one of the two stars in the system.

There are actually three ways a planet can orbit in a binary star system. It can orbit one star close in, both stars farther out, or both stars in a figure 8 orbit. Let's look at the three cases briefly:

1. Figure 8: This is an orbit where the planet literally orbits both stars making a figure 8 shape. It goes around one star, between the two, then around the other, then between them again. This type of orbit is extremely unstable, and unlikely to last very long. The planet can get ejected from the system! It's highly unlikely the planet can stay in such an orbit for long enough to make it useful as a colony planet. Also, there would be very large extremes of temperature making habitation basically impossible.

2. Orbiting one star: This is the case for the two known planets orbiting binary stars. However, it's unlikely to be the case for Star Wars. We actually see both stars at once in the two scenes they appear, and they look to be roughly the same size. If the planet orbited one star, the other would be much smaller because it's so much farther away. The only way they could be about the same apparent size would be if the other star were a giant. This is possible, I suppose, but in my opinion unlikely. Giant stars don't last long on the time scales of stellar lifetimes, and so it is a coincidence that we happen to have a habitable planet orbiting a companion to one. Of course, we only have one planet to judge by, so anything's possible!

3. Orbiting both stars: This, in my opinion, is the likely case for Star Wars. If the planet orbits far enough out, the orbit is stable enough to last for the lifetime of any civilization likely to either arise locally or settle Tatooine. If I recall correctly, one star was yellow and the other orange, implying one is like our own Sun and the other slightly cooler. If stars get too close together, their mutual gravity can distort them into egg-shapes rather than spheres. This was not the case for Tatooine's stars, so they were relatively far apart. Tatooine is a Sahara-type desert, hot and dry (see the next example below); it is possible to orbit both stars far enough out that the orbit is stable while still being close enough in to be hot. If the two stars are, say, 50 million kilometers apart the mutual gravity is too small to see any effects with the eye (using a very rough back-of-the-envelope gravity calculation). The planet could be about as far from the stars as the Earth is from the Sun. It would be hot, yet still far enough away to be stable.

   Note added May 29, 2001: Bad Reader Ibrahim Semiz points out that there is a special case of this kind of orbit, where the two stars and the planet form the points of an equilateral triangle. This type of system is very stable. It would mean the two stars would always be 60 degrees apart in the sky of the planet. In this system, the planet is said to be at the L4 or L5 point, where the "L" stands for Lagrangian point, after the French mathematician who first figured this out. Check out the Microwave Anisotropy Probe webpage for more about the lagrangian points. Anyway, this type of system is not the case of Tatooine, where the stars were seen to set together in "A New Hope"; an impossibility since the stars would always be far apart in the sky.

   A problem with two stars is with shadows. A sharp, single shadow like in this picture is unlikely. If the stars are very far apart in the sky you'd get two distinct shadows; but we know they were close together from other scenes. Surprisingly, if the stars are close together you might not see two shadows, but rather a fuzzy, somewhat indistinct shadow. This is because the stars are not point sources; that is, they have an actual size. Your shadow on a clear day may look sharp, but actually if you study it closely there is a sharp part and a fuzzy part, called the umbra and penumbra. Imagine the Sun is chopped in half: your shadow from one side of the Sun goes in one direction, while your shadow from the other side of the Sun is at a slightly different angle. Where these two shadows overlap is the dark umbral region of the shadow; where they don't on either side of the umbra you see a less deep shadow. The diagram shows this for the Earth, but hopefully you can see this works for you on the ground as well. (By the way, the diagram is from Dr. Nick Strobel's excellent Astronomy Notes website, one of my Top Ten links.)

   Anyway, in the surface shots of Tatooine in Star Wars, we always see one sharp shadow like in the image above. George Lucas paid a lot of attention to some details in tPM, and it surprises me he left that one out!

   ---

   Bad:
   After Anakin is brought aboard Queen Amidala's ship. He is cold. Padme, the Queen's handmaiden, says to him, ``You are from a hot planet, and space is cold''.

   Good:
   No doubt, Padme is being poetic here, but for the sake of a quick and fun astronomy lesson, let's take her at her word. This all depends on how you define ``space''. Space itself has no temperature! You need to have something there to be hot, and space is technically a vacuum. However, if you had a thermometer out in space, you would actually register a temperature. It's not really space itself you would measure, but the temperature of the thermometer as photons hit it; these photons are simply light from a source somewhere. For example, near a star, it's pretty hot! Far from a star, the temperature can get very cold, as low as about 3 degrees above absolute zero. It's hard to get colder than that because the Universe itself radiates at that temperature, so no matter where you are you'd feel at least that tiny amount of heat (there are rare special places that do get colder than that, but that's getting nitpicky). I should point out that heat and temperature are really two different things, and I urge you take a moment and read one of my Bitesize Snacks I wrote on that topic.

   ---

   Good: After the pod race, Qui-Gon tends to Anakin's cut. Anakin, who has dreamed of leaving Tatooine, looks up at the stars and says, ``There are so many of them! Do they all have planet systems?'' Qui-Gon looks up as well, and slyly smiles. ``Most of them,'' he replies.

   Ah, I like this one. Qui-Gon is most likely right. As recently as ten years ago, we knew of no other planets outside our solar system, and all we could do was speculate on how many there were. Now we know of over a dozen. (Note (March 25, 2002): at the time this page was written, that number was true. As of March 2002, 80 or so extrasolar planets have been found, and more keep coming. You can assume that the longer it's been since this page has been updated, the more planets have been found.) Most of these are solitary giant planets orbiting close in to their parent stars, but in early 1999 a three planet system was found as well. The remarkable thing about that system is that it's only 44 light years away, which is right next door on the scale of the Milky Way. It's usually dangerous to extrapolate, but it's easy to imagine that if one planetary system is so close, the Galaxy must be littered with them. You can even find a list of the ones found so far at Extrasolar Planets Encyclopedia website or at Extrasolar Visions.

   So perhaps in one sense George Lucas got it exactly right: the Galaxy (even one far, far away) may have millions or even billions of planets, waiting for us to explore them. In my mind, that's one of the greatest and most exciting dreams of all.

   ---

   Looking for Star Wars links? Doing a web search on ``Star Wars'' will net you about a thousand sites. Here are some good ones:

   • The most obvious is www.starwars.com. It has lots of info, and good links too.

   • Another I liked was theforce.net. It has lots of current news about the series. Also on that site is Star Wars Technical Commentaries, a frighteningly in-depth look at the scientific and technical aspects of the movie series.

   My thanks to Geoffrey Landis, another science-in-science-fiction type guy for pointing out a couple of egregious errors I had in this page, Wayne Bell for reminding me that deserts are dry, not necessarily hot, as well as many folks that have emailed me with suggestions!

   This page last modified