OT: Ceres more interesting than previously thought

[inigma]

I believe spinning up the astroid would do more harm than good.

At the very least it would do nothing, and at most, it would cause centripetal force to the point that weakens its integrity.

I happen to believe that the 9 hour spin is natural, since gravity is created by the mass of an object, its speed relative to space-time, and the initial alignment of the first atom. I say this because even for Ceres to exist in the first place, it would have had to "settle" into its natural space-time spin, and such a settlement is the lowest-energy result. It would take more energy for it to spin slower, and more mass for it to spin faster.

The best example of this would be to hop on a merry-go-round and have someone toss you a sandbag and for you to bring it to the center of the merry-go-round. As you do, the increased mass equalizes and you spin around much much faster. This is what would happen if you put a large rocket on Ceres to spin it up. But once you remove the rocket, its like throwing the sandbag off the merry-go-round - the mass decreases, and so does the spin. Eventually, as your body returns to the center of the merry-go-round, equilibrium is reached and all that energy you poured into spinning faster was lost to the sandbag you threw off.

If the rocket was ever turned on, though, assuming you could invent the impossible and ensure that the mass you are using to power the rocket wasn't depleted into space as a result (and thus cancel out the effect of the rocket, in a sense, wasting your time), the stability of the merry-go-round would be called into question, and Ceres would fly apart - the natural concequence of adding energy to any object that is already at equilibrium.

So in short: spinning up Ceres would be a physical impossibility because mass is the key ingredient to the gravitational equation.

The best that could be hoped for is some campaign of accreting astroids into it and so increase its mass, but in a controlled manner so as not to obliterate the mass of Ceres that already is stable.

Hollowing out Ceres would more than likely cause Ceres to spin down much slower, to the point that it might even break up entirely. Spinning it up faster to a 1G centriptal force inside a hollowed out band in the core, would probably tear Ceres apart.

The answer would most likely be to find a way to add more mass to Ceres so that 1G centripital could be attained. But then again, if 1G centripital could be obtained, by that point you have enough mass to hold a decent atmosphere and live on the surface.

Except the surface gravity of such a mass would be enough to probably crush you several times over.

[inigma]

Oh and the coin idea would be great, if it weren't such an engineering challenge to create a transparent material strong enough to hold back an ocean of water from flinging into space.

And I don't know if such a boat would float like earth ships, because unlike earth, the deeper in the coin ocean you go, the stronger the centripetal force. I wonder if such a force would practically suck ships down.

Imagine the fish in such an ocean... stuck to the bottom because it takes effort to "climb" up. Swimmers would sink faster than they can float... and boats would have their fishing lines be the straw the breaks the camel's back and starts a chain reation that sucks the whole ship down to the bottom with increasing velocity. Not to mention the force of such a slam on the transparent plating holding in the water.

Sounds like fun!

[Wolfman77]

Give the size, the gravity change (or force acting like gravity) would not be that sudden. also the water would not need to be that deep, there should only be a few percent difference from the surface to the floor. Even if there was a large change, remember that the water is pulled down just as hard as anything in it. The force that keeps us floating (or swimming)is the pressure of the water below is larger than that above. This would still apply, and a more sudden change in force would magnify this, making it harder to get to the outside wall.

[inigma]

I would think that it works in theory. But practically, it'd be quite the challenge.

I think it would far easier to build self-replicating robots which would automatically plant rockets on nearby asteroids and slowly drive them towards Ceres for a concerted accretion.

[NullAshton]

I think we could just wait till we have artificial gravity.

[Hunpecked]

If an object's average density is less than water, then it will float in water under one gravity, two, or fifty. However, boat and submarine hulls would be under increased pressure under higher G.

[narf poit chez BOOM]

It would take more energy for it to spin slower, and more mass for it to spin faster.

...Did I miss some basic physics here? Last time I checked, heavier things need more energy to move, and more energy makes things go faster.

[inigma]

narf poit chez BOOM said:

...Did I miss some basic physics here? Last time I checked, heavier things need more energy to move, and more energy makes things go faster.

Mass and energy convert between one or the other. The thing with gravity is, you need mass not energy.

Since I believe the spin of a body in space is naturally dependent on mass, by adding mass the spin would increase. By adding energy (which cancels out mass) spin would decrease.

[Suicide Junkie]

inigma said:

Mass and energy convert between one or the other. The thing with gravity is, you need mass not energy.

Since I believe the spin of a body in space is naturally dependent on mass, by adding mass the spin would increase. By adding energy (which cancels out mass) spin would decrease.

Heck no.
E = MC^2, remember? Increasing energy -> increasing mass (by a very small amount since c^2 is huge)

The angular momentum of a body depends on its shape, mass and spin rate.
If you make the object smaller it spins faster since the angular momentum must be conserved.
If you add mass without changing the angular momentum, the body will be spinning slower because there is only so much momentum to go around.

The spin of an asteroid is essentially random as the tiny rocks whang it from random directions at random speeds. However there is an upper limit to how fast they could be spinning, since they are generally not solid bodies.
If they spin too fast then rocks on the surface will be swung off by the centrifugal force, and the asteroid breaks up.

[inigma]

If they spin too fast then rocks on the surface will be swung off by the centrifugal force, and the asteroid breaks up.

That's my point. To generage 1G of centripetal, the astroid would fly apart, or be so big that you wouldn't need to hollow out the core.

E=MC^2 does not take into account gravitational physics. Einstien couldn't figure out exactly how it played into it.

It is my belief that mass contributes to the natural spin of a body in space-time, up to a certain equilibrium point.

Even though you are correct that initially adding mass to Ceres would cause it to slow down, equilibrium would be reached over time and it would naturally speed up by gravitational physics up to a certain point of equilibrium.

Adding too much mass would obviously cause Ceres to spin down too quickly and the weakened gravity well would essentially force Ceres apart.

What I'm essentially saying is that the faster mass moves, the greater the gravity effect - up to a certain point of course where centripetal force starts to overcome object's structural integrity. This is all due to the increase in mass as energy is converted to mass to move something faster.

By forcing Ceres to spin faster, that balance is offset, and eventually cetripetal force will fly it apart. Mathematically, for purposes of this coin idea, I can guestimate that the centripetal force of a spinning body can never be greater than its optimal gravitational force (and structural integrity).

In short, by the time you could spin Ceres to 1G centripetal force, its would fly apart as 1G of centripetal force would be greater than the escape velocity of the surface which is dependent on the equilibrium of 0.03Gs (guessing its 0.03Gs) generated by Ceres.

That 0.03G is what is holding Ceres together. Force Ceres to spin at a 1G centripetal rate, and you can imagine the concequence.