Passengers

“Gravitational accelerations can’t be felt.” The more I think about this, the more it makes sense. After all, astronauts in orbit don’t feel the gravitational acceleration. Instead, they experience free-fall.

I confess I’ve never thought about how this applies to other gravitational accelerations, such as gravity assists. (At least not recently–it’s been 15 years since I last taught physics.) Thanks, Chronos.

To expand on this, then, would it indeed be possible for a ship to do a dramatic course change at 0.5c without affecting the crew? (I understand that it also depends on the mass and density of the object being flown by and how close the flyby takes place.) For example, could a ship do a 90-degree course change at 0.5c using a gravity assist around a neutron star without subjecting the crew to a large acceleration? (Let’s leave tidal forces aside for now.)

Finding the exact angle would require knowing the mass and distance of the object they’re flying by… but I can tell you right now that for anything short of a black hole or maybe a neutron star, the angle is going to be too tiny to be worth worrying about for anything going at 0.5 c. The limiting factor isn’t what acceleration the crew or ship can survive; the limiting factor is just that if you get too close, you crash into the surface.

EDIT: That said, it’s tough for me to get too worked up about Hollywood screwing up the physics. I mean, it’s Hollywood. They always screw up science.

Ah.

I took the fact that it was maintaining 0.5c from the send and return times for the message Pratt sent to Earth. I don’t remember the numbers but the quick math I did in my head when they gave them he me thinking it was 0.5c the whole time.

But I could have been wrong.

Of course, Arcturus is apparently 37 light years from us so since they were only 30-32 years into the trip when they did a slingshot around it, either someone involved did the math wrong, it was a different Arcturus, or they didn’t leave from Earth.

So more math: If they maintained steady thrust to the midway point (60 years) and had reached 0.5c at 30 years, how fast would they be going when they started decelerating? (Am I correct that due to relativistic effects increasing mass, steady thrust would produce increasingly diminished acceleration?)

And considering the relativistic effects of those speeds, if Lawrence had succeeded in making the round trip with one year on the destination world, how wrong was her statement that she’d return to Earth 250 years in the future (essentially correct from her frame of reference but some amount longer from Earth’s)?

Found this interview with the movie’s science advisor. Among other things he acknowledges that sometimes you lose some of the arguments. Also that there probably wouldn’t be much value in a slingshot but it looked cool, and that the ship does have a constant-thrust ion drive:

http://www.geekwire.com/2016/jon-spaihts-physics-interstellar-travel-passengers-movie/

And finally, on the way home today I was reminded of one of the biggest mysteries of the movie:

Why in the world did they cast Andy Garcia for a role that has no lines and is on screen for maybe 4 seconds. I’m wondering if there was originally much more to that part of the movie.

Contrary to popular belief, relativity does not increase mass, and a constant thrust will result in a constant proper acceleration. Which is convenient, because proper acceleration is both the acceleration that the passengers will experience, and the acceleration that you use to determine how long the trip will take for the passengers.

Now, proper acceleration is not the same thing as acceleration, which is what you’d use to find the ship’s velocity at any given time. That will in fact go to zero as the ship’s speed increases, but that’s because the relationship between acceleration and proper acceleration isn’t linear.

It was 55 years to get a response from Earth; a long time, but Jim and/or Aurora could’ve still been alive to receive it. You’re right about the content though; there’s nothing helpful the message could possible include (well other than “Your ticked price will be refunded to your next of kin”.) Aurora could’ve serialized her novel and transmitted it both to Earth & Homestead II instead of just leaving it for the crew to find, but assuming any communications go Homestead Company servers why would they ever release it? It seems like it would be *horrible *PR for them; at least assuming they still exist in the same form (instead of say being bought out by Walmart).

Lawrence’s suit had her [character’s] name on it. I assume Pratt’s did, too, although I didn’t notice it. This implies that every passenger has a suit fitted to them, and they’re held in storage somewhere until you ask for your suit to be brought out into the EVA room.

As he mentions, the onboard gravity would have been created by the constant thrust (though, not particularly necessary if everyone’s asleep). So the whole “artificial gravity went out” / swimming pool scene seems to directly conflict with what all else we can see in the movie.

Eh, maybe. A spinning ship will keep on spinning without power, but it’s plausible that a power failure could shut down the propulsion system. Though if that happens, you’ve probably got bigger problems than a floating swimming pool.

I don’t think he meant that the propulsion provided the gravity. He also talks about how fast the ship spins to generate 1g. I think he was saying you’d have two directions of force (mostly the spin plus some from the thrust) ans so the angles of the interiors have to be adjusted to keep the “floor” flat.

Of course that would mean that everything would feel sloped (I think, I’m getting everything else wrong apparently) if the ship is doing anything other than a specific forward acceleration in conjunction with a specific rate of spin.

If that isn’t a textbook example of “damning with faint praise,” I don’t know what is. :slight_smile:

If Jim had remained dead, would Aurora have opened another pod?

I thought it would have been a much better movie if he’d died and she wound up waking up someone else.

As discussed, the ship appears to be constantly under thrust and accelerating. We are also told that they are 30 years into the journey, and that the ship’s current speed is 0.5c.

A simple back-of-the-envelope calculation using the classical kinematics equations indicates that the required thrust necessary to accelerate the ship from rest to 0.5c over 30 years is just 0.317 m/s[sup]2[/sup], or 0.03g. This steady, slow thrust is in keeping with what you would expect to see with an ion drive.

It therefore seems that the contribution of the ship’s thrust to the perceived “gravity” felt by the ship’s occupants would be negligible. Virtually all of the perceived gravity would be due to the rotation of the ship. (Which as noted, would not stop rotating due to a loss of power.)

I wholeheartedly agree with this.

I haven’t seen it, but I would much rather have seen the Robert Silverberg short story.

Accept ultimately he was a weird sicko (if not a borderline psychopath) who was willing to ruin the life of a stranger for his own comfort.

I think it is overly harsh to label Pratt’s character (as portrayed in the movie) as a “weird sicko,” much less a borderline psychopath.

I think that a lot of people would succumb to the temptation to end their solitary confinement, especially after an extended period of years of isolation with no hope whatsoever of a reprieve. People are capable of a great deal of rationalization for their actions. Such an extended period of isolation might also cause a person to start losing it–see the thread about how people fare in Supermax prisons.

There are much worse things someone in his position could do that fall into the “weird sicko” or psychopath category–killing the other passengers or sabotaging the ship, for example.

Waking up a single other passenger was a selfish, terrible act, to be sure, but understandable given the situation, in my opinion.

He was a psychopath. What he did was no different than the lonely men who have kidnapped women off the streets and held them prisoner in their homes. It was a syfy version of the movie Room without the possibility of rescue for Jennifer Lawrence. He doomed her to the miserable existence he was faced with. At one point, she even correctly describes it as murder. I honestly wish the movie had ended with her trapping him in the airlock to die then going back into the medical center and re-entering hibernation. That would have been a good and just ending, not her turning victim to Stockholm Syndrome and staying with him for “love”. It’s absolutely disgusting to have her fall in love with this jerk who destroyed her life for his own selfish needs.

Being quite harsh ZPG. “Destroyed her life”? I don’t think so. Where the nave was headed was an huge unknown. The designers could not have predicted what the planet would be like, in the time it took for the nave to arrive there.

Changed her life? Definitely, and without without her consent.

But, all the passengers had given their consent to an this unknown life.

And Jim’s awakening Aurora was just one of the possibilities.

It was just a standard Sleeping Beauty romance with some space stuff thrown in.

He didn’t come off as “psychopath” to me at all. He struggled for months with the idea and he was losing his mind from loneliness while all these sleeping people surrounded him. It seems like a fairly human response to such a strain. He’d tried for a year to get to the only people who might have helped make the repairs and get them back to sleep. It wasn’t possible. If he was sensible he’d have looked at all the profiles to see if there was anyone on board outside staff who might be able to help but he was hardly in his right mind. “Psychopath” is hardly the condition I’d label him with though, considering how long and hard he struggled with the idea of waking someone else.