The Sword and Laser discussion
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Leviathan Wakes
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LW: Spinning asteroids/dwarf planets to create gravity
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I think having the centrifigal forces pushing me towards the walls all the time would take a lot more getting used to!Plus I'd proably get a crick in my neck
It wouldn't push you toward the wall. It would push you away from the center of Ceres and what would be the roof here on earth would be your floor on Ceres. The closer to the center of Ceres you get the less the gravity there would be.
I think Cattfish means the Coriolis effect rather than centrifugal force.Centrifugal force will simulate gravity, but on smaller bodies such as asteroids or spacecraft/space stations a high spin rate would be required for this simulation. At higher spin rates you would notice the Coriolis effect which might feel like a force pushing you around (although probably towards the floor in a different part of the room rather than directly at a wall).
Well they always talk of the belt as being around a third to half the gravitational force of earth. So.... Wouldnt it be centrifugal? Idk what kind of spin rates we're talking but its nothing like the death star.
It is the centrifugal force. It's just that objects experiencing centrifugal force at high spin rates* will also experience a noticeable Coriolis effect.So you would feel like you're experiencing gravity, but you'd also feel a sideways force away from the direction of spin, hence Cattfish's comment.
You would think that Ceres is large enough that this effect would be negligible, but Eros is another thing entirely.
This is even referenced in the book in Chapter 2:
"Havelock led the way to their cart, bouncing too high with every step. He didn’t come up to the low gravity levels very often, and it made him awkward. Miller had lived on Ceres his whole life, and truth to tell, the Coriolis effect up this high could make him a little unsteady sometimes too."
and also in Chapter 28:
"As the new guy on the contract, he’d gotten the shit jobs: patrolling levels so high the Coriolis made him seasick"
and in Chapter 38 Miller notices the difference between the two asteroids:
"The air recyclers were eerily quiet, and even though the spin gravity was nearly the same as Ceres’, the Coriolis felt subtly wrong."
* The smaller the object, the higher the spin rate required to generate noticeable centrifugal force.
Lindsay wrote: "It is the centrifugal force. It's just that objects experiencing centrifugal force at high spin rates* will also experience a noticeable Coriolis effect.So you would feel like you're experiencing..."
Having a bit of trouble wrapping my mind around the Coriolis effect. I understand the feeling of gravity because of the spinning. Would the Coriolis be the feeling of the floor moving one way and your head staying in the same place?
Yes, that's exactly it. It's basically an issue of inertia acting against rotation.
This book has convinced me that in my fantasy world where I'm living in space in the future, I should probably go with a terraformed planet and not a hollowed-out asteroid. I mean, I get motion sickness going up and down elevators too fast.(Will Blue Remembered Earth change my mind again? Only time will tell...)
I don't understand anything you guys just said. I couldn't wrap my mind around it in the book either, so I just accepted it and kept going.
The Coriolis effect is what makes water rotate when you pull the plug in the bathtub. Because the rotation is around the circumference of the earth the effect is quite minor. In a tighter faster circle, such as spinning for artificial gravity, the effect would be more noticeable. In particular, it would effect the fluids of the inner ear causing some strange dizziness and motion sickness.
Thank you, guys!I was really having a hard time figuring this out. It makes so much sense now!
AndrewP wrote: "The Coriolis effect is what makes water rotate when you pull the plug in the bathtub. Because the rotation is around the circumference of the earth the effect is quite minor. In a tighter faster ci..."This is actually a myth, the Coriolis effect doesn't make the tub water rotate. I mean if it did effect your bath tub it would probably affect your inner ear as well. The effect is just that as a wind gust or a cannonball goes north or south then the speed of the earths rotation varies, but it still has some of the acceleration from where it started. You can see why it'd be a problem on a small spinning rock going up and down the elevator, since your the speed of rotation would vary as you traveled.
(Though I wonder if someone who grew up on Ceres wouldn't notice the effect, since it seems like the brain might adapt to ignore the issue since it would be so common)
However the earth's rotation on the north and south side of the bath tub drain doesn't vary much. :D
I agree with Nick though; these spun asteroids would be deeply weird places. - When walking under this sort of "gravity" you're actually upside down compared to walking on a planet.
- When the characters are talking about going "up" levels they're actually talking about going closer to the centre of the asteroids.
- If you went out on the surface untethered you would be flung off into space, but you'd still slowly fall back to Ceres for a hell of a gravel rash (3 m/s fling force doesn't come close to the escape velocity of 510 m/s). I guess that would continue to happen for a while.
- Speaking of gravel rash ... Imagine what would be happening with any loose rock or regolith on the surface.
- Landing a ship would be difficult process to say the least.
Ships would have to "land" at the poles, where rotation would be slowest. I think.
People land on Earth and it rotates way faster I think then the Ceres in LW. Even if we aren't pulling Gs, we still rotate once a day and Earth is so much bigger. Pretty much everything is moving relative to everything in space, that's the fun.Just looked it up for Earth, it's 1670 kilometers/hour. That's why it's better to locate your launchpad closer to the equator, you get that extra boost.
I'm trying to imagine the Coriolis effect. I'm picturing the water inside a bucket that you swing around quickly - it stays in due to centrifugal, and slants due to Coriolis, right? So if you slant the floors, would that combat the effect to an extent?
The Coriolis effect is a sideways force on your whole body, so I'm not sure if adjusting the floors would help.
Yeah, so picture a floor that's tilted 45 (or however many) degrees, so that sideways force plus the outward force point at the floor?
The Coriolis effect is noticeable because the force differential from your head to your feet is different. On earth this isn’t noticeable because the planet is big and you are small. If you want to experience this effect to a much greater extent go on one of those spinning fair rides next time you go to an amusement park or fair and lift your head off the rest while the ride is in full spin. It will affect people differently, just as those rides do. Also, don’t forget that while the earth spins pretty fast, so does everything on it, so it has no noticeable acceleration. Gravity on the other hand is always there at 9.8m/s^2. That’s why you notice gravity and not the rotational velocity of the earth.
I know this is nothing too out there and while watching 2001 you notice this when you watch Frank Poole runs around the "Discovery One". While it makes sense it feels counter intuitive when speaking of rocks which subconsciously you'd think of having a normal gravity of some kind given enough mass and not needing a centrifugal force to create gravity.
The reasoning behind this makes sense but mentally it would take getting used to if you were actually there.
The Physics of Science Fiction: Artificial Gravity and Centrifugal
http://youtu.be/WdECeGRXIxQ