What's New?

Bad Astronomy

BA Blog
Q & BA
Bulletin Board

Bitesize Astronomy
Bad Astro Store
Mad Science
Fun Stuff
Site Info

Search the site
Powered by Google

- Universe Today
- The Nine Planets
- Mystery Investigators
- Slacker Astronomy
- Skepticality

Buy My Stuff
Bad Astronomy at
Keep Bad Astronomy close to your heart, and help make me filthy rich. Hey, it's either this or one of those really irritating PayPal donation buttons here.

Review: Contact

image of Contact theater poster First things first: I loved ``Contact''. It was sweeping, it was interesting, it was thought provoking. When it came out, I got email from people that complained that nothing happened. I couldn't disagree more! Just because it wasn't a shoot-em-up scifi flick doesn't mean that there was not drama and excitement. I enjoy the odd over-the-top movie, but you can't live on cotton candy. Sometimes you need something more meaty. ``Contact'' was a main course.

The movie was based on the novel of the same name by the famous astronomer Carl Sagan. Sagan was a brilliant researcher, and found that he was even better at describing the wonders of the Universe. He explained science to people in a way that not only could they understand, but so that it also moved them and made them appreciate the awe and majesty of the sky around them. I could write reams about the man and his influence both on the public and astronomers, but that's already been done. Let's talk about the movie instead.

``Contact'' stands out from almost every other science fiction movie ever made in that it went to great pains to be accurate. Almost all of the plotline is based on either solid physics, or extrapolated from current theories. Some of the astronomers were slightly exaggerate in character, but it's safe to say that every stereotype depicted in the movie has seen its moment in real live astronomers. I'm glad that the Ellie Arroways outnumber the David Drumlins though! Mind you, some of the characters are based at least in part on real people: there is a blind SETI astronomer named Kent Cullers (in the movie the character was named Kent Clark). Despite her denials, I think Jill Tartar was in large part the inspiration for Ellie. If Sagan had an inspiration for Drumlin, he never said who it was.

Those of you familiar with my reviews know that I take a dim view of science errors in movies. However, I loved ``Contact'' and so I am willing to give it more leeway. Does that sound unfair? Too bad! It's my website! ;-) Actually, I am willing to give it more leeway because to went to such lengths to be accurate. While there are some errors in it, most are small, and some of the parts it got right are so amazing that I am astonished at the level of detail. In light of that, this review will be a bit different than the others: along with the errors, I will point out little details that were correct. The next time you watch the movie, check them out!

So: on to the review!

image of Contact logo

In the opening sequence, we pull back from the Earth, listening to radio broadcasts. As we pass the planets one by one, we realize that the get farther from the Earth, the further back in time the radio broadcasts are.

OK, let's get this straight: this is, in my opinion, the best opening sequence of a movie ever shot. It is beautifully animated, gives a concise allegory of the science of the movie and is just really dramatic.

That said, there are some problems with it astronomically. One of the points it is making is that the farther from a source, the farther back in time it appears to be. Light waves (of which radio is a part) travel at 300,000 kilometers per second. The Sun, being about 150 million kilometers away, is about 8 minutes away at the speed of light. So, in a sense, we see it as it was 8 minutes ago. As we pull back from the Earth in that opening sequence, the radio broadcast we hear represents that by playing older and older songs and other radio bits as we get farther away from home. The problem is, the radio goes back in time too fast. We are hearing radio shows from years gone by before we ever leave the solar system. However, it only takes light about 6 hours to go from the Sun to Pluto, so really at that distance we'd hear radio from 6 hours before.

Having said that, I'll add that this doesn't bug me. I'll chalk it up to artistic license. They are trying to make a point ,and had to compromise on the timing. As far as I'm concerned, that's okay. If you want to get really picky, we shouldn't hear radio at all: we're apparently moving faster than light in the sequence, and would leave radio waves behind us. If we heard them at all, they'd sound backwards!

As we pull back, we pass the Moon, Mars, the asteroid belt, Jupiter and Saturn. We see Jupiter's Great Red Spot spinning,

As far as I could tell, up to this point we are moving in a straight line away from Earth. That would mean an extraordinary alignment of the planets!. The planets are very rarely that close together in the sky. Again, however, they are simply trying to make a point by showing us the solar system. I don't have a problem with this.

They do show too many asteroids though! On average, there is about 2 million kilometers between asteroids out in the belt. They are also small and relatively faint, so you could be in the middle of the thickest part of the belt and not even see a single asteroid with the naked eye! So the flurry of asteroids shown in that sequence is overestimating how many there really are.

image of Jupiter with Great Red Spot Also, Jupiter's Great Red Spot doesn't rotate quickly enough to see in that short a time. The Red Spot is a giant hurricane, over twice the size of the Earth and so as you can imagine it takes a long time to spin around. They show it being a bit too close to the equator of Jupiter too, but that's being way too nitpicky, even for me!

One more note: they show the Red Spot rotating counterclockwise. I was suspicious; it's in the southern hemisphere, and hurricanes on the Earth's southern hemisphere rotate clockwise. However, the Red Spot is a high pressure system, while terrestrial hurricanes are low pressure systems. A high pressure system rotates in an opposite sense from a low pressure system. They got that right! Pretty neat.

HST image of Eagle Nebula Still pulling backwards, we pass through the Eagle Nebula.

Good: The Eagle Nebula image is probably the most famous Hubble picture ever taken. The composition and color are beautiful, eerie and dramatic. The problem is, in the opening sequence, after we pass through it we see as if we were still seeing it from Earth. The point is, we should be seeing it from the other side, and so it should at least look flipped left-to-right. In reality, the structure has three dimensions, so it probably looks very different from the backside. Still, this was a very cool effect.

Later in the movie, we see Ellie Arroway, Upstart Young Astronomer, listening to the radio signals while the telescopes behind her scan the sky for life.

Radio telescopes work in much the same way as ``regular'' telescopes: they collect light (in this case, light in the radio frequency) and combine it into a signal. In most cases, the signal is so weak it takes a computer and sophisticated software to actually pull the signal out from all the noise of background objects (and foreground objects too; cars, appliances, everything that runs or uses on electricity can interfere with radio telescopes). So radio astronomers don't have a habit of using headphones to listen to the signals. Also, astronomers look at millions of ``channels'' simultaneously to try to figure out just which frequency an alien race might use to communicate with us. Headphones can only check one at a time. Not very efficient!

image of Ellie listening with headphones However, as I recall, in the book, Ellie simply like listening to the ``white noise'' of the background static. As it turns out, it pays off, because The Message is so strong that it overwhelms the background. Matter of fact, in the movie they mention the power is about 100 Janskys. A Jansky is a unit of radio energy, and most sources in the sky can be measured in millijanskys (a thousandth of a Jansky). So 100 Janskys is a pretty big signal!

One more note on this one: when we see Ellie listening on her headphones, in the background is the Very Large Array (VLA), a collection of 27 large radio telescopes near Socorro, New Mexico. You can see a few of them in the image above. This is a real site, and they simply filmed the scene there. However, when the scene first appeared, the guy in the seat in front of me at the theater leaned over to a friend and said ``What a great effect!''. He thought it was a computer image! How cool is it that we astronomers have instruments so impressive that people think they aren't real? ;-)

Another One More Note (August 24, 2000): I get email from people asking if her walkie-talkie would interfere with the signal being received (when she first hears the Signal, she grabs her radio and starts yelling coordinates to her assistants). Bad Reader Ted Brattstrom asked Dave Finley, an astronomer at VLA, about this. Dave replied that since there are multiple dishes, interference at one is no big deal. They also have electronic techs who make sure the walkie-talkies are ```clean'', and do not interfere with the observations. Dave also told me that they allow cars as well; at some observatories, the spark plugs from cars messes up the signal as well. Only diesel cars are allowed; they have no spark plugs. Again, at VLA that's not such a big problem.

Ellie says ``You know, there are 400 billion stars out there, just in our Galaxy alone. If only one out of a million of those has planets, and one out of a million of those have life, and just one out of a million of those has intelligent life, there would be literally millions of civilizations out there."

Oops! A million times a million times a million is a quintillion, which is a lot bigger than 400 billion! She meant to say that there are 400 billion stars in our galaxy, and a hundred billion galaxies like our own. Even then, that's only 40,000 civilizations in the entire Universe! That's not very many. Even a pessimistic estimate would be a lot bigger than that!
Note (added May 22, 2003): Speaking of oops, I made either an error or a typo in this paragraph when I originally wrote it; I said 10,000 civilizations instead of 40,000. The latter is the correct number, and I thank the astronomy class at Emma Willard School in Troy, NY for catching me in that mistake!

In a pivotal scene, Ellie flashes back to the night her father dies. There's a meteor shower, and they have a couple of small telescopes set up.

You don't watch meteor showers through a telescope! Meteors flash across the sky in a few seconds, while telescopes magnify a small part of the sky. Watching a shower through a 'scope is like trying to find a coin you dropped on the ground with a microscope. It won't work! The best way to watch meteors is lying in a lounge chair, so you can watch a large fraction of the sky comfortably.

Also, it is established later in the movie that her father died on November 10. There are no good showers on that date! The Leonids peak a week or so later, but are usually a fairly weak shower (except every 33 years). She wouldn't have been that excited about them; as a matter of fact, she sees a couple of meteors within a few seconds, which implies a pretty dense shower. As always, I am willing to forgive this because really, I am not that picky, and it's not that big a deal.

While receiving the message, the astronomers worry that Vega will set and they'll miss a part of the signal. They set up a worldwide network of radio telescopes to watch Vega.

They need not have panicked. Vega is circumpolar from Sweden. A star that is circumpolar never sets; for example, Polaris, the North Star, never sets for anyone north of the Earth's equator. It appears glued to the sky. That's because it sits almost directly above the Earth's north pole, and as the Earth spins, the axis always points very close to Polaris (try spinning in a chair while looking straight up and you'll see that the point directly above doesn't seem to move). If you are far enough north, Vega will never set, but instead circle Polaris in the sky. So all they really needed was a single 'scope in Sweden to watch Vega, and they would never miss a moment of The Message. Of course, better safe than sorry; if something happened to that 'scope they would still need more. So, again, this part of the movie is forgivable.

When the Machine is activated, some sort of strong gravity field is activated. The ships in the harbor all lean toward the Machine.

Good: This one is subtle, but neat. Actually, the ships should heel the other way, so that the decks lean away from the Machine. Why? Because buoyancy works such that the deck of the ship will float horizontally with respect to gravity. A ship in still water will have the deck perfectly horizontal. If the gravity were to tilt, then the deck would tilt the other way, so that it stays horizontal (what physicists call "normal") to the direction of gravity. Like I said, subtle. So subtle I completely missed it, and it took Bad Reader Kyle McIntire to point it out to me!
[Previous comment added on July 27, 2001]

When Ellie travels to Vega in The Machine, she sees a beautiful blue star surrounded by a thick cloud of particles.

Vega is indeed surrounded by a cloud of dust. It was discovered in the 1980s. Astronomers noticed that Vega put out too much infrared (IR) light compared to other stars of its type. That means something nearby must be emitting IR, and the most common source of that is dust. Vega is also a young star, and young stars commonly have disks or clouds of material around them. these clouds are left over from the formation of the star, and after billions of years they get blown away by light pressure and the solar wind. Vega is too young to have completely swept away its cocoon.

The problem is the movie had too much dust around Vega. Measurements show that the total amount of dust is about one-half the mass of the Moon. That ain't much! Imagine it spread out over trillions of cubic kilometers of space... you could be in the middle of it and never notice. To be fair, that mass would be in the form of dust, and there might be bigger particles that we haven't detected. But that wouldn't add up to much.

I remember an undergrad class I had shortly after the dust cloud was discovered. We were told how much extra IR light was coming from Vega, and we had to calculate the mass of the dust! My poor primitive computer could barely work out the number, but I was shocked to find out it was less than the mass of the Moon. My vision of planets circling a nearby star were dashed. I had to wait 15 years before the first real extrasolar planet was discovered.

Another note: it wasn't as clear as it could be in the movie, but the aliens were not from Vega. They had an automatic radio telescope of sorts orbiting the star, listening to nearby stars. That's how they detected us. We don't know from where the aliens themselves came, but I'll note that just before Ellie is whisked away from Vega by the wormhole, some sort of array can be seen in the corner of the screen. I thought that was a very nice touch. She actually glimpsed the telescope that detected Earth in the first place!

[NOTE (May 11, 2000): This next Bad/Good section deals with Ellie's trip taking no time to the outside world. I originally argued that this was not possible. I was wrong; at least, I was wrong in the context of the movie. Sagan established both in the book and in the movie that the aliens have faster-than-light travel, and even may have the limited ability to travel in time. Basically, they took Ellie out of her coordinates in space and time, chatted with her for a while, then put her back to her original coordinates in space and time. Therefore, no time elapsed for people back on Earth. I have received copious emails about this pointing out my error! I have left it in so you can read it anyway.]

When Ellie returns to Earth, 18 hours have passed for her, but no time at all has passed on Earth.

This point isn't really astronomy, but physics. What is implied is that the travel through the wormhole took no time at all, as if she were moving at some super-relativistic speed. Einstein showed that an object moving near the speed of light relative to some outside observer has time slow down relative to that observer (for more detail about relativity, take a look at the Relativity FAQ). It's possible, if you fudge it a bit, to assume that no time elapses at all if you are moving faster than light, which Ellie did. However, she had a conversation with her ``father''. That conversation took up time. No matter what, some small amount of time must have elapsed during her trip.

The only way around that is to assume that the aliens could somehow manipulate time, and I have to draw the line there. Her ``father'' admitted they did not build the transit system, so I have severe doubts they could shape time the way they want. It's a neat plot twist, but the zero-time trip won't work.
My thanks to Bad Reader Marshall Philips for bringing this one to my attention.

A lot of what I have said here may sound like real nitpicks. I fully admit that's true. The reason is that this movie is almost unrelentingly accurate, and beside a few bigger mistakes, the only ones to find are pretty small!

If you liked the movie, or even if you didn't, you really should read the book. It's a lot better than the movie, and has many concepts only hinted at in the movie. I have read it several times, and the hair on the back of my neck stands up every time I read the second to last chapter... If you want to buy it, you can order it from through my website, or go to a used bookstore and pick up a copy. I think you won't regret it.

There are a lot of links for the movie, and for SETI on the web.

  • For the movie, the best site out there is Larry Klaes's. He has a plethora of links, a review that makes this one look short by comparison, and analyses of the movie that should keep you busy for hours.

  • Another good site belongs to Michael Rapp, who also has quite few links listed.

  • The SETI Institute is devoted to (what else) the Search for Extraterrestrial Intelligence. This is the real thing, folks: dedicated astronomers and engineers who look for aliens. The site has images and descriptions of what real scientists are doing to look for life in the Universe.

  • Do you want to help the search for ETI? Take a look at Seti@home, a way for you to use your own home computer to look Out There.
This page last modified

Buy the book!

Check out my book "Bad Astronomy"