I have a somewhat proprietorial interest in planetariums. For the uninitiated, a planetarium is a big room with a dome ceiling and a projector which projects a distorted, kind of fisheye image into that ceiling. The curvature of the ceiling and the distortion of the image cancel each other out, meaning the image you actually see is a reasonable facsimile of what you’d see if you went out in a dark field at night, away from any built up areas or light pollution, and looked up at the sky – except because the image is computer generated and controlled, we can do some pretty spectacular things in a planetarium that we can’t in real life due to being stuck on dreary old Earth. There’s an excellent piece of free software called Stellarium that should give you a fairly decent idea of what planetariums are capable of: high detail renderings of planets, moons, constellations and nebulae; the ability to advance time and see how moons orbit around planets; bringing up a search box that can locate pretty much any stellar object on demand, that sort of thing.
Anyway, planetariums can be pretty amazing things, and the reason I’m so interested in them is because I used to go round schools giving planetarium talks. Our planetarium was basically just a big tent and our projector wasn’t up to much, but it did the job reasonably well and while the videos we showed to the kids had voiceovers that were cringe-worthy in their sheer badness, they also had a basic grasp of the sort of images we should be showing people in planetariums – animations of colliding galaxies, explanations of stellar redshift, breakdowns of the electromagnetic spectrum with a step by step guide detailing the sort of celestial object that would emit each type of radiation —basically stuff that might be a bit dry and boring when described in words or diagrams, but which the planetarium can really ram home in an interesting and special way.
Which is why I was more than a little bit aghast to discover that the Peter Harrison planetarium at Greenwich Royal Observatory – a proper, heavy duty planetarium with expensive equipment, air conditioning and incredibly comfortable chairs – is doing planetarium shows that wouldn’t even make the cut as a bad space documentary on the Science Channel. The particular show we were booked in to see was all about the Voyager probes (“Across The Universe”). When I read about this I thought it was a fairly neat way of teaching people some basic solar system science since the Voyager probes visited all four of the outer gas giants and made some pretty amazing discoveries in the process. What it actually turned out to be (and if you’re a regular reader of this blog you’ll know I should have intimate knowledge of this sort of thing) was a word-for-word summary of the Wikipedia article on Voyager. It was obvious almost from the start that the people who had written this thing didn’t have the first clue about science and were parroting all their information from another source, especially given the amount of stuff the show got flat-out wrong.
It started off with an incredibly bad render of the Titan II rocket that launched the Voyager probes along with some blurb about what the rockets were capable of, which was to me the equivalent of a giant flashing red light and an alarm klaxon screaming “WARNING. WARNING. ACTUAL SCIENTIFIC CONTENT OF SHOW PRACTICALLY NIL.” Nobody cares about rockets. I’m a space scientist and I don’t care about rockets except in so far as I can diss them for being crap ways of getting into space. People came here to learn about journey the Voyager probes and what they found out, not the damn rocket that kicked it along the first 0.000001% of its trip. The only reason you would start out a show about Voyager by talking about the rocket is if you have literally no sense of scientific proportion, which these people clearly didn’t.
Of course it then got worse. After the crappy render of the rocket we were then treated to a crappy render of one of the Voyager probes and a breakdown of what it could do. I was expecting this, but what I wasn’t expecting was for it to go on for ten minutes. Instrument after instrument on the probe was pointed out and described in excruciatingly vague detail; “The magnetometer is placed away from the main body of the probe to avoid interference from the electronics and was designed to take measurements of Jupiter’s immense magnetic field.” That’s great, guys, but why is this important? What did the probes find out about Jupiter’s magnetic field? There was no attempt to connect the instruments on the probe to any kind of concrete scientific outcome, just “This is thing X, and it does thing Y, and this is thing Z…” Even I was getting tired of this halfway through, and the friend who accompanied me said she thought it was by far the worst part of the show. I’m inclined to agree. It was the equivalent of somebody reading out a list of information they didn’t understand, which is what makes me think they were cribbing half of this stuff from Wikipedia.
This was followed by a little segment on the gravitational slingshot maneuvers the Voyager probes used to boost their speed and an animated render of the trajectory they took out of the solar system. This was the only legitimately good part of the show; it was proper science which effectively used the planetarium to show something counterintuitive that even scientists find tricky to visualise in their heads. The entire show should have been like this, not just two minutes out of twenty-five. Unfortunately it was soon over and was replaced by the guided tour of the gas giants that I thought I’d come to see – except because this thing has been picked out by astronomers and not astrophysicists (there’s a big difference) it was far more concerned with the pretty pictures the Voyager probes took rather than what they found out about these hitherto unvisited solar system bodies. I think the bit on Uranus was literally “Voyager didn’t find anything interesting about Uranus, but it took this great picture! Look! Look!” Assholes.
Then came the bit which made me mutter “Oh God!” out loud and which led to actual fist-shaking when I went on a rant about it a little later on in the day. First they made some assertions about Miranda that made zero fucking physical sense; basically they said that the weird-ass geological makeup of Miranda could be a result of the moon being shattered by an impact and then reforming under its own gravity (very plausible) or being pulled apart by Uranus’s gravity and then somehow reforming afterwards. If you remember my post about the Roche limit you should be able to figure out why this second assertion is bollocks: moons are pulled apart when the gravitational force of the planet they orbit exceeds the gravitational force of the moon that keeps it in one piece. Once they stray inside the Roche limit and get pulled apart it is physically impossible for them to reform under their own gravity unless they somehow manage to make it back outside it again, and I really cannot imagine how that would happen. Assholes.
After the previous twenty minutes of awfulness I should have known the perpetrators of this crime against science teaching would be saving the worst for last. After some blurb about the golden records attached to each probe (which I classify as harmless fluff) the show went completely off the rails, babbling about how the probes might eventually reach Andromeda, and then somehow fall into the atmosphere of an alien world and burn up, and from the surface of that alien world you can look up, and see the Milky Way, and orbiting a small pinprick of light in one of the spiral arms is the planet where the civilization that launched it might still exist!
Uh, no. Here are some numbers, assholes: the Andromeda galaxy is two million light years away. Voyager 2 (the faster of the two probes and the one squarely aimed at Andromeda) is travelling at 15.447 km/s relative to the Sun. 15.447 km/s is 0.00005% of the speed of light, meaning Voyager 2 takes about 20,000 times longer to travel the same distance as light does. This shakes out to it taking about 40 billion years to get to Andromeda, and a couple of things are going to happen before then.
1) The Sun is going to swell up to a red giant in about 4 billion years, burning the Earth to a hot cinder.
2) Andromeda is going to collide with the Milky Way in about 5 billion years, which I suppose means that Voyager 2 won’t quite take 40 billion years to get out there even if it’s Andromeda doing most of the hard work. Curiously given the fact you’re smashing a galaxy with 200 million stars in it into another galaxy with 1 trillion stars in it, there are going to be very few star-star collisions – or even near misses – thanks to galaxies being overwhelmingly made up empty space. If you can’t score a direct hit on a star with a fucking galaxy, what are the odds that your punk-ass little probe will magically manage to find its way into the gravity well of an alien world?
Jesus. There was so much bad information and woolly thinking in this planetarium show that it doesn’t even deserve to be called science, and it breaks my heart that the first-class facilities they have up there are being wasted on this crap. If you’re inLondonI’d avoid the planetarium this year, and if you do end up going there then for the love of god avoid “Across The Universe”. It’s bloody terrible.