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    Re: Spaceship navigation
    From: Frank Reed
    Date: 2017 Jan 15, 12:34 -0800

    Gary LaPook, you wrote:
    "Without giving away too much and ruining the movie, we find out that the 120 year travel time is as measured on earth and the ship is traveling at 0.9 C. So the time, as measured by clocks on the ship, runs at about 44% of earth time. "

    Um.... no... no, we don't find that out. The 120-year travel time is clearly intended to be the shipboard travel time throughout the film, right until the very end. There's no "reveal" about speed being 0.9 c, nor anything suggesting that the actual time was reduced. One character mentions 50% of light speed late in the film while some of the quoted numbers are roughly consistent with 75% of c. And the whole plot depends on the voyage duration of 120 years as the approximate shipboard time, or at least something considerably beyond the expected lifespans of our lead characters.

    There are loads of science problems with this film and plot holes a mile wide, and it depends on boy-geek wish fulfillment of the worst sort. I'll stick to the science for now...

    When you have a rotating spacecraft that is producing gravity-like centripetal accelerations, if the power goes out, the spinning parts won't just stop spinning, like a light going out. That's just plain dumb. There's huge rotational inertia. If that spinning motion did come grinding to a halt, either slowly or rapidly, the effect would be to slam or roll all loose objects (and pools of water) up against the nearest bulkhead in the direction of rotation during the deceleration. You certainly wouldn't sleep through it! Heck, even if gravity were simply "turned off" suddenly, completely ignoring the laws of physics, you wouldn't just float gently out of your bed, snoring as you go, like a cartoon character. Falling out of bed wakes you up. The falling sensation --that loss of downward acceleration-- is quite disturbing. A sleeping passenger would go from normal gravity to freefall. Yeah, that would wake you up!

    As for water, it won't just form a big blob of water in zero-g from which there is no escape. The little spheres of water we see in NASA videos do not scale up. You swim out, you wipe the water off your face, and you're done. Water in zero-g is potentially very dangerous, and an astronaut aboard the ISS was at risk of drowning on a spacewalk a few years ago, but that was only because he was inside a spacesuit and couldn't just brush the water away with his hands. As noted above, in anything like a real scenario, the water would slam hard against the bulkhead. A spaceship swimming pool (as seen in the trailers so not a spoiler) would slosh out onto the nearest bulkhead and down the corridors "up wheel" from the pool, just like a swimming pool on a capsizing ship at sea. If you were swimming in it, it would be like getting rolled in a crashing wave.

    The view out into space from a spacecraft in deep space would not look like much. It's not "so beautiful... no words... no words... they should have sent a poet!" (quoting a corny line from the movie "Contact" that is so laughable it was even riffed in the bawdy comedy "Ted 2"). Space is dark, really dark. If you want to know what space looks like, go outside on a clear night, except imagine the bowl of stars extending all the way around you. What you see of the night sky from here on Earth is what you would see in space. But in order to see those stars, you have to turn out all the lights nearby, and you have to let your eyes dark adapt, and you need to be looking through optical quality glass. Have you seen the night sky looking out the windows from an ordinary airliner at night? Not much to look at --because the interior lights are never turned out (at best they are dimmed), local lights, like from watching movies in-flight, prevent dark adaptation, and of course you don't have windows of optical quality glass. Similarly in this movie, none of those conditions were met. The view should have been dull blackness, but instead we were fed brightly glowing Milky Way star clouds that looked like something right out of 1960s-era "Lost in Space". Space looks really cool in science-fiction.

    More trouble with the stars: at a good fraction of the speed of light, there would be a bunching together of the constellations and a brightening in the bow direction due to aberration and Doppler effect, respectively. Similarly, constellations astern would appear spread out and dimmer. Apart from those effects, there would be little to notice, except when approaching close to a star, and then it's more or less the same as looking at the Sun. It's amusing that Arcturus just looms up out of nowhere for their imaginary "slingshot" maneuver, which as I already mentioned does not work at relativistic speeds. Since this encounter occurs about two years after the story begins, the ship was about two lightyears from that star at the beginning and progressively closer with each passing day. For days leading up to the encounter, Arcturus would have been blindingly bright. It's not as if they would have needed a voice on the intercom annoucing, "Hey everybody, look out the window at the pretty star going by!" (near enough to what happened in the film).

    Minor spoiler alert:

    They get hit by a "meteor". I don't count this as much of a spoiler because, of course, they get hit by a meteor! That's what happens in cheesy science-fiction. At 50% of more of the speed of light, being struck by a tiny meteor would be like being hit with a beam of white-hot plasma at a temperature of millions of degrees. The kinetic energy of a one-gram projectile would be equal to a 3.5 kiloton nuke at 50% of c or a 10 kiloton nuke at 72% of the speed of light. The spacecraft is said to be 1000 meters long so it might not be completely destroyed by dumping 3.5 ktons equivalent of energy into it, but then again it surely wouldn't be suffering a few minor systems failures.

    Another minor spoiler alert:

    There's a plot point that's semi-science, semi-culture. Our heroine says she planned to spend a year on the colony world, then fly back to Earth so that she can publish a book about her experiences (on Earth, more than 250 years in the future). But books can be transmitted! Information does not need to travel by slow boat anymore --not since the invention of the telegraph, for Pete's sake! Now the bitrate has got to be damn slow at such distances, but even if it's intolerably expensive, just stick the book in some corner of the tiniest flash drive going back to Earth. Books are bytes, not paper, and definitely not biology. The fact that she wants to publish her story does not imply that she has to go back to Earth herself --unless she's incredibly vain ...or ignorant.

    OK, one plot hole (significant spoiler alert):

    Near the end, they realize that the medical pod --the only one on the ship (bad emergency planning)-- can serve as a temporary "stasis pod" but, oh no, she can't bear to leave him now that she loves her sleazy kidnapper again. So that's that. Wait... wait... wait... They couldn't figure this out? Stick her in the pod, and then thaw her out for Christmas week every year! I think our hero can manage 51 weeks living in luxury with his robot friends with the promise of a week of sex with the hot girl every year. Plus she gets to decide, and she gets her life back! After 50 years of these holiday cycles (before the old goat dies), she'll only be 50 weeks older upon arrival. Problem solved. But no... it's "Hollywood Happy Every After" in a cottage in the woods in the middle of the shopping mall... Beauty and the Beast in spaaaaaace...

    Needless to say, it's just a movie. ;)

    Frank Reed

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