Gravity is gone?

[TaxiMan]

OK, so here's an idea for a doomsday device but I need help filling in the details.

1) There's a way to warp space so we can create artificial gravity (rubber science)

2) It's cool, spaceships can fly around really fast

3) But it's not cool - you can flatten out a gravity well also.

There's the doomsday device, and my question. What happens if you remove gravity from the Earth for 10 seconds?

I'm guessing cars fly upwards from compressed springs, the equatorial oceans slosh (not sure how much), pressure is released from the Earth's crust (earthquakes?), that sort of thing.

But how bad would it be?

[TaxiMan]

Extra credit - how bad would it be if you did the same thing to the Sun, say for 1 second?

!!!!!

[Cancer]

Extra credit - how bad would it be if you did the same thing to the Sun, say for 1 second?

!!!!!
Actually, that one's far easier than the first. The answer is not that much.

Yes, stuff would expand once the gravity was cut off. But for only a second, well, it wouldn't do a whole lot. When it was turned back on, stuff would fall back down, and there'd be some transient violence that might be interesting to watch, but in terms of long term effects, nothing.

The reason is that one second is way too short a time. The free-fall time for the Sun is about an hour, which means that major effects caused purely by gravity take about that long to happen.

[Supreme Serpent]

OK, so here's an idea for a doomsday device but I need help filling in the details.

1) There's a way to warp space so we can create artificial gravity (rubber science)

2) It's cool, spaceships can fly around really fast

3) But it's not cool - you can flatten out a gravity well also.

There's the doomsday device, and my question. What happens if you remove gravity from the Earth for 10 seconds?

I'm guessing cars fly upwards from compressed springs, the equatorial oceans slosh (not sure how much), pressure is released from the Earth's crust (earthquakes?), that sort of thing.

But how bad would it be?

Cancelling out just the gravity, without cancelling out the spin? I think everyone would suddenly fly up at a certain angle at ridiculous speeds, quickly dying out in space, if they didn't hit something and go splat on the way up first. For only ten seconds? Don't know how far people would go, perhaps not out into space, but probably high enough to kill most (non super) people. Plus most non-insect animals are probably killed by the fall too, and a lot of plants get uprooted, so the ecosystem's pretty screwed even for the survivors. From what I understand. Not a good situation, for sure.

[keithcurtis]

Thanks Cancer. I had never heard the term "free fall time" before. I googled it and now am edjumicated.

Keith "Favorite doomsday weapon: Ice-9" Curtis

[WhammeWhamme]

I don't think people would go flying off - they would retain _their_ spin as well, wouldn't they?

However, the first person to exert upwards force would leave the atmosphere...

[Zeropoint]

Recall Newton's laws of motion. Specifically, "an object at rest or moving in a straight line at a constant speed will continue in that state unless acted upon by an unbalanced outside force," or F = MA, where F is zero and therefore A is also zero.

Normally, as you stand on the surface of the Earth, the centripital force of the Earth's gravity accelerates you inward, giving you a circular motion instead of a linear motion. When gravity disappears, you will continue to move in a straight line with the direction and speed you had at the time gravity ceased. This will be a tangent line to the circle you were moving on. Early in this process, you will still be close to the ground, which will still be constrained to move in a circle by the tensile strength of the ground material. Thus, the point on which you had been standing will move away from you.

From the point of view of an observer attached to the ground, used to thinking of the surface of the planet as stationary, it will seem that you are "falling upward".

Zeropoint

[TaxiMan]

At the equator, people (and other things) move at about 1,000 mph. They are 4,000 miles from the center of the Earth. So in 10 seconds, they travel 2.78 miles in a straight line. The surface of the Earth also moves, but it's (presumably) curving and dropping out from under the unlucky sap.

Using the Pythagorean theorem, the sap will be 4,000.001 miles from the center of the Earth, while the surface is still (we hope) 4,000. So he'll see the surface drop 0.001 miles out from under him - that's about 5'.

It seems like no one will be flung off into space.

[TaxiMan]

For the Sun, I was thinking (not knowing about the free-fall time by name) that for 1 second, the outward pressure of all those nuclear reactions would be free to shove the outer layers without them shoving back (excepting inertia).

Since the outer layers are normally shoving back so hard that the pressures are great enough to cause fusion, I imagined that there would be one hell of an imbalance once gravity was removed.

F=mA, and normally at a point inside the Sun F=(pressure from explosions) - (gravity pulling in a bunch of gas). Since that point isn't really going anywhere, F=0 so those two forces are equal (I know, I said that already!).

Anyway, I figured there would be a hell of an expansion at the layer where things normally go boom. By "hell" I mean ... I don't know, maybe 100'. That expansion would cool off that layer, and the rate of boom would drop some. Then when gravity came on again, the upper stuff would come crashing down & start the boom again - with a significant transient BOOM.

I'll go read up on free-fall time, but I'm doubting it addresses a mysterious loss of gravity.

[TaxiMan]

OK, read up on free-fall time. That's good for when nuclear fuel is exhausted. So if gravity force = nuclear pressure, then nuclear pressure alone would accelerate the outer layers away from the center at 1 Solar G.

I don't know what that is at the layer fusion occurs, but I'm guessing it's >10g (Earth G). That means the outer layers could move 160' during the first second.

I'm betting there would be one hell of a B A N G !!! when it all collapsed in again. After a time, the shock wave would hit the surface & throw off, at a minimum, the biggest solar storm ever seen. At a maximum, there might be a thin outer shell ejected.

[Rapier]

OK, so here's an idea for a doomsday device but I need help filling in the details.

1) There's a way to warp space so we can create artificial gravity (rubber science)

2) It's cool, spaceships can fly around really fast

3) But it's not cool - you can flatten out a gravity well also.

There's the doomsday device, and my question. What happens if you remove gravity from the Earth for 10 seconds?

I'm guessing cars fly upwards from compressed springs, the equatorial oceans slosh (not sure how much), pressure is released from the Earth's crust (earthquakes?), that sort of thing.

But how bad would it be?

A lot of stuff would hurl up into the air. But it would come crashing back down after 10 seconds. The moon is held into place by the gravitational pull of the Earth. The moon would spin off at a tangent, I'd have to seriously look into some math to see if it would go slingling off permanently.

There would be tidal waves, earthquakes, volcanos etc. LOTS of destruction.

[hyperion]

Heat expands. Without gravity to counter the heat generated by the fusion reaction the sun would expand really really fast.

My guess even a one second lapse would be sufficent to upset the balance and start a very, very, violent expansion. Nova.

[Cancer]

(Cancer puts on his professor hat and hauls out his old ASTR 421 and 422 lecture notes.)

The Sun rotates very slowly (about a month rotation period), so let's forget rotation effects for now.

Suppose you have a bottle of gas. If you open the bottle, the gas will expand since the confinement is gone. The speed at which it expands is the speed of sound for the gas.

The sound speed turns out to be something you can compute fairly easily. The temperature at the solar photosphere is about 5800 Kelvin (there's a range, of course, but that's the standard representative temperature). The photospheric gas differs from air in that it's monatomic, so the ratio of specific heats is 5/3, and the ideal gas law applies. The mean molecular weight for solar gas is about 1.4 (remember, it's ~90% hydrogen by number, ~10% helium, ~<1% other stuff, and the level of ionization in the solar atmosphere is small). The sound speed is just

v = sqrt( gamma * R * T / M )
and that works out to be about 7600 m/second.

So in the one second after you let the solar atmosphere out of its bottle by turning gravity off, it will move outward by about 7.6 kilometers. Sounds big, but the solar radius is 700,000 kilometers. From our viewpoint 1.5e+8 km away, we would not even notice. From Earth that subtends about a tenth of an arcsecond. You'd see it using a space observatory, but you can't make out that level of detail from the ground.

The thermal timescale for the sun, a/k/a the Kelvin-Helmholtz timescale, is the time it takes to respond, thermally, to changes in its structure. "Thermally" means gas expansion or compression due to temperature changes. That timescale is on the order of ten million years. So messing with the Sun's structure by, say, turning gravity off for a second isn't going to make a lot of change. Turning it back on again has about the same effect. In terms of overall structural change, it isn't going to matter.

(If you want to compute the v = g * t impact speeds at the solar surface after your turn gravity back on, the sun's gravity at its photosphere is about 28 times the Earth's gravity at Earth's surface. The impacts are not going to raise the temperatures to the ten million Kelvin temperature regimes -- or cause high enough densities -- to get to the realm where you start fusion on the surface, which is what happens in a nova.)

One second is a piddly-*** short time for something as large and massive as a star.

[Hermit]

Man, if the Earth's gravity suddenly goes away, the Tick could lose all his Stuff!

[hyperion]

(Cancer puts on his professor hat and hauls out his old ASTR 421 and 422 lecture notes.)

The Sun rotates very slowly (about a month rotation period), so let's forget rotation effects for now.

Suppose you have a bottle of gas. If you open the bottle, the gas will expand since the confinement is gone. The speed at which it expands is the speed of sound for the gas.

The sound speed turns out to be something you can compute fairly easily. The temperature at the solar photosphere is about 5800 Kelvin (there's a range, of course, but that's the standard representative temperature). The photospheric gas differs from air in that it's monatomic, so the ratio of specific heats is 5/3, and the ideal gas law applies. The mean molecular weight for solar gas is about 1.4 (remember, it's ~90% hydrogen by number, ~10% helium, ~<1% other stuff, and the level of ionization in the solar atmosphere is small). The sound speed is just

v = sqrt( gamma * R * T / M )
and that works out to be about 7600 m/second.

So in the one second after you let the solar atmosphere out of its bottle by turning gravity off, it will move outward by about 7.6 kilometers. Sounds big, but the solar radius is 700,000 kilometers. From our viewpoint 1.5e+8 km away, we would not even notice. From Earth that subtends about a tenth of an arcsecond. You'd see it using a space observatory, but you can't make out that level of detail from the ground.

The thermal timescale for the sun, a/k/a the Kelvin-Helmholtz timescale, is the time it takes to respond, thermally, to changes in its structure. "Thermally" means gas expansion or compression due to temperature changes. That timescale is on the order of ten million years. So messing with the Sun's structure by, say, turning gravity off for a second isn't going to make a lot of change. Turning it back on again has about the same effect. In terms of overall structural change, it isn't going to matter.

(If you want to compute the v = g * t impact speeds at the solar surface after your turn gravity back on, the sun's gravity at its photosphere is about 28 times the Earth's gravity at Earth's surface. The impacts are not going to raise the temperatures to the ten million Kelvin temperature regimes -- or cause high enough densities -- to get to the realm where you start fusion on the surface, which is what happens in a nova.)

One second is a piddly-*** short time for something as large and massive as a star.

Well I certainly cannot argue with the math since admittedly I am out of my depth. But I have to ask, what about the effects of inertia from the initial expansion? Would gravity, which if I remember correctly as a primary force of nature is extremely weak compared to both thermal and electromagnetic effects.

Also in your computation is the sound speed of gas its expansion in a vacuum?

Your example was using the temperature of the photosphere. What about the Sun's core? Without Gravity to keep the solar mass compressed wouldn't the extremely hot and dense core expand. That would be alot of inertia gravity would have to overcome. I would image a one second expansion of a star's core would generate some incredible energies. Interesting thing to ponder though.

[Cancer]

Well I certainly cannot argue with the math since admittedly I am out of my depth. But I have to ask, what about the effects of inertia from the initial expansion? Would gravity, which if I remember correctly as a primary force of nature is extremely weak compared to both thermal and electromagnetic effects.

Also in your computation is the sound speed of gas its expansion in a vacuum?

Your example was using the temperature of the photosphere. What about the Sun's core? Without Gravity to keep the solar mass compressed wouldn't the extremely hot and dense core expand. That would be alot of inertia gravity would have to overcome. I would image a one second expansion of a star's core would generate some incredible energies. Interesting thing to ponder though.

If you switch gravity off, there is still the pressure of all the stuff around and in the core. Though it got there due to gravity, if you switch gravity off that pressure won't go away. Gravity or no, mass has inertia, and takes time to respond to other forces that try to make it move. So it'd take time for everything to expand ... and estimating that time is what the thermal timescale is. The solar core is about 15 million Kelvin, but the density is about 150 tons/cubic meter and the pressure about 2.3e+11 atmospheres. But that's under a mass of 2e+30 kg, which will take a while to move.

The sound speed depends on the density, though that isn't obvious in that relation I quoted. If you're in a regime where the perfect gas law holds, and you know the composition of the material, and the temperature, then that relation is convenient. Other relations work, if (for example) you know the pressure & density (instead of temperature and composition) ... see here. (http://scienceworld.wolfram.com/physics/SpeedofSound.html)

[hyperion]

Would the inertia of the solar mass be a factor when the expansion would be happening at a molecular level? I mean those are some abusrdly hot molecules pushing against one another. Without gravities pressure I would imagine the entire mass rapidly expanding fueled by superheated molecules explosively pushing against one another. How much pressure would 15MK of heat have against a object that has its primary binding force removed? I am asking hoping you know, because I don't I am just speculating. :)

[TaxiMan]

The thermal timescale for the sun, a/k/a the Kelvin-Helmholtz timescale, is the time it takes to respond, thermally, to changes in its structure. "Thermally" means gas expansion or compression due to temperature changes. That timescale is on the order of ten million years. So messing with the Sun's structure by, say, turning gravity off for a second isn't going to make a lot of change. Turning it back on again has about the same effect. In terms of overall structural change, it isn't going to matter.

Thank you so very much for the intelligent reply! I'm swayed to believe that not much would happen if gravity disappeared for a second, but I have a nitpick -

I'm sure the Kelvin-Helmholtz timescale takes into consideration the force of gravity, since I'm sure it is a scholarly work done right. We're considering a lack of gravity.

Still, there is an enormous amount of matter to move, and the Sun is a really, really large body. I never thought it would nova, but thought there might be the mother of all coronal mass ejections. We ARE talking about ringing the Sun like a bell, so I'm sure SOMETHING measurable would happen...

but we wouldn't see it until it crawled up from the layer of fusion to the surface. That's likely too long for a doomsday device to wait.

[Cancer]

Yeah, the K-H timescale is derived using gravity, so you're right, in this case it isn't quite appropriate.

I'll hunt around for another argument that doesn't include an appeal to gravity. I think there's another K-H derivation that doesn't appeal to gravity, but I need to think carefully before I say so for certain.

My intuition is that you can't make 2e+30 kg of matter do anything collectively in one second ... it just can't "talk to itself" fast enough to respond to something that quickly ... unless you hit it with several orders of magnitude more energy than its gravitational binding energy. (Turning off gravity reduces that binding E to zero, but to really blast the thing apart -- and that's what we're talking here -- takes many times that amount of energy.)

[Gary]

Cancer, would you know enough physics to guess what would happen to a white dwarf, neutron star, or black hole if gravity was turned off for a second or a minute?

[Cancer]

Cancer, would you know enough physics to guess what would happen to a white dwarf, neutron star, or black hole if gravity was turned off for a second or a minute?
For a black hole, the answer is not knowable :D. The physics of that situation is that you can't know what's "inside" a BH, so if you could magically get rid of gravity, you have no idea what's going to come out all of a sudden.

Those other compact objects ... those have very short characteristic times. White dwarf pulsation times are on the order of a second; neutron star pulsation times are on the order of milliseconds. So given a second or more of time, yes, those things would have time to respond to a major structural alteration (such as gravity turning off). And that response would be violent.

My guess is that doing it to a neutron star would look like a gamma-ray burster, though the energy release would not be beamed (I think the models of those now involve energy release which is beamed out the poles of the system). Similarly, my guess is that doing that to a white dwarf would look something like a Type Ia supernova. (Both of these situations are when one of those objects gets torn apart tidally by another object.)

Neither of those is something I want happening within a few hundred parsecs of me, thank you.

[hyperion]

Cancer, would you know enough physics to guess what would happen to a white dwarf, neutron star, or black hole if gravity was turned off for a second or a minute?


My guess would be the same as to a star. Except more. Because you would be dealing with alot more heat due to the absurdly high mass compacted into such a small space.


(edited to add)

Er yes...what Cancer said. :)

[Gary]

Neither of those is something I want happening within a few hundred parsecs of me, thank you.

A few hundred parsecs? Wouldn't bother me. Not unless I have at least 4 pts of Life Support Longevity... :p

[Cancer]

The thermal timescale is can also be derived via an argumetn about the random walk of photons throough the matter. If you make a photon in the middle of some material, it will travel only a short distance before hitting a particle ... that distance is set by the photon-absorption and scattering cross-sections (these are atomic physics) and the density of matter (in the solar core, it's about 1 cm). Each time it's scattered or absorbed/reemitted, it changes directions, randomly. Even though it makes each "step" in its random walk at the speed of light, it suffers so many collisions that it takes rather more time than just the direct light-travel time from solar core to photosphere to get out of the Sun. When you work it out, that random-walk time is on the order of 10 million years. This is the amount of time it takes for temperature change information to work its way out from the core to the photosphere ... and by definition, the photosphere is the part of the Sun we can see.

[TaxiMan]

Dang. That's one sloooowww doomsday device!

[McCoy]

(Cancer puts on his professor hat and hauls out his old ASTR 421 and 422 lecture notes.)

The Sun rotates very slowly (about a month rotation period), so let's forget rotation effects for now.

Suppose you have a bottle of gas. If you open the bottle, the gas will expand since the confinement is gone. The speed at which it expands is the speed of sound for the gas.

The sound speed turns out to be something you can compute fairly easily. The temperature at the solar photosphere is about 5800 Kelvin (there's a range, of course, but that's the standard representative temperature). The photospheric gas differs from air in that it's monatomic, so the ratio of specific heats is 5/3, and the ideal gas law applies. The mean molecular weight for solar gas is about 1.4 (remember, it's ~90% hydrogen by number, ~10% helium, ~<1% other stuff, and the level of ionization in the solar atmosphere is small). The sound speed is just

v = sqrt( gamma * R * T / M )
and that works out to be about 7600 m/second.

So in the one second after you let the solar atmosphere out of its bottle by turning gravity off, it will move outward by about 7.6 kilometers. Sounds big, but the solar radius is 700,000 kilometers. From our viewpoint 1.5e+8 km away, we would not even notice. From Earth that subtends about a tenth of an arcsecond. You'd see it using a space observatory, but you can't make out that level of detail from the ground.

The thermal timescale for the sun, a/k/a the Kelvin-Helmholtz timescale, is the time it takes to respond, thermally, to changes in its structure. "Thermally" means gas expansion or compression due to temperature changes. That timescale is on the order of ten million years. So messing with the Sun's structure by, say, turning gravity off for a second isn't going to make a lot of change. Turning it back on again has about the same effect. In terms of overall structural change, it isn't going to matter.

(If you want to compute the v = g * t impact speeds at the solar surface after your turn gravity back on, the sun's gravity at its photosphere is about 28 times the Earth's gravity at Earth's surface. The impacts are not going to raise the temperatures to the ten million Kelvin temperature regimes -- or cause high enough densities -- to get to the realm where you start fusion on the surface, which is what happens in a nova.)

One second is a piddly-*** short time for something as large and massive as a star.
"You must spread some Reputation around before giving it to Cancer again."

[Trained Chicken]

but we wouldn't see it until it crawled up from the layer of fusion to the surface. That's likely too long for a doomsday device to wait.

Commissioner Gordon: "Quick, Caped Crusader! The Joker's planted a time bomb under Gotham City's main nuclear plant!"
Batman: "How long have we got?"
Gordon: "Twenty years! God help us!"
Batman: "Say again?"
Gordon: "We have our best bomb squad men there right now. They say we've only got 20 years to disable the bomb!"
Batman: "..."
Batman: "I'm going back to bed."

[austenandrews]

A lot of stuff would hurl up into the air. But it would come crashing back down after 10 seconds. The moon is held into place by the gravitational pull of the Earth. The moon would spin off at a tangent, I'd have to seriously look into some math to see if it would go slingling off permanently.

There would be tidal waves, earthquakes, volcanos etc. LOTS of destruction.
I expect a lot of stored-up energy at tectonic boundaries could get released. Nasty quakes and tsunamis.

[Cancer]

Blanking out gravity on Earth for ten seconds is a different matter, because lots of the stuff that we care about is small and can change radically in 10 seconds.

Anyone in a device that depends on dynamic balance of forces is going to be in a world of hurt. The airplanes and helicopters go completely out of control as gravity vanishes while the aerodynamic lift, drag, & thrust don't. Driving in any ground vehicle with a suspension seems likely to be unpleasant also, since everything (that doesn't use a drag chute or retrorockets) brakes via contact with the ground, and as someone said, the compression on the springs will relax, giving everything a gentle push upwards, losing the ground contact that lets you decelerate. If you run into something at 60 mph, you will hurt a lot whether or not you do it in zero g.

About those springs ... 1000 kg car, assume the springs compress 10 cm under its weight, if the compression energy in the springs turns into kinetic energy, then the car will be moving upward at about 1 meter/sec. SO after 10 seconds the car is 10 meters above the ground, and then gravity turns on ... y'know, all those Wile E. Coyote cartoons come to mind here.

10 seconds is enough time for Earth-rotation effects to be potentially nasty, though it's going to sound small (well, to a dingbat astronomer like me it sounds small). Something just rest on the surface will move in a straight line tangent to Earth's surface at the instant gravity vanished. At the equator, it moves at about 0.463 km/sec. Ten seconds later, when gravity turns back on, it will have traveled in its straight line to a point about half a meter above the point on Earth's surface it would be on if it'd stayed on the circular path it would follow if it had stayed glued to the surface. (That half meter is from radius of Earth = 6378 km * 10 seconds / 86400 seconds ... strictly speaking there should be a sine in there, but the angle is so small that the angle and its sine are close to each other.) The effect is smaller as you go away from the equator (I think multiply by cosine(latitude) so in temperate latitudes you have about 70% of that rough half-meter). This would happen to approx anything that was just sitting on the ground stationary at the moment the gravity switched off, and didn't have springs or anything that would make it jump up more.

EDIT: Thinking about this on the bus ride home, I'm off by a factor of pi. Triple that half-meter rough number.

I'd have to look into the compressibility of water to see what the ocean might do. Water's pretty incompressible, but the release of gravity might make it expand vertically a bit, and when gravity turns back on that might give you tsunamis.

Austen's comment about tectonics ... I have no clue offhand how to guess at those effects. I look up, not down ;).

[egyptian]

It starting to sound like you could have more luck tampering with one of the other fundamental forces. Ten seconds without the strong force would probably eliminate all evidence of your terrible crime. :)

[Jaxom]

Ok, so I was gone but this sounds too fun. The tangential velocity sounds so fun but I think it and rigid motion loses. 10 seconds is only .04 degrees rotation or about 0.0007 radians. At that kind of angle, tan(theta) can be approximated by theta. Your verticle height is going to be roughly 0.0007 of your horizontal motion (correctly about 4.3 kms as mentioned before) or about 3 meters at the equator (ouch, but not OUCH). You'd also drift about 2 centimeters to the west as the earth fell away under you (rotational effects are so fun!).

You're going to get a lot more fun from expansive systems.

If you can up your device to 2-3 minutes you get more meaningful scales.

I still say that you can have more fun using real physics in a rotating space station. Coriolis effects are huge on that scale and can be oh so much fun...

"What do you mean I missed by 20 feet? I shot straight at him!" Oh, and all those poor jump-throughs.

[J.J.]

Keith "Favorite doomsday weapon: Ice-9" Curtis

Mayhap a relation!

http://www.newbabynews.net/hospitals/stf33/public/stf33birthannouncement.pl?babyID=h33-440

[BoneDaddy]

I guess that's why they call it the weak force. Turn off the EM force for ten seconds and significantly more catastrophic results occur.

[McCoy]

Blanking out gravity on Earth for ten seconds is a different matter, because lots of the stuff that we care about is small and can change radically in 10 seconds.

Anyone in a device that depends on dynamic balance of forces is going to be in a world of hurt. The airplanes and helicopters go completely out of control as gravity vanishes while the aerodynamic lift, drag, & thrust don't. Driving in any ground vehicle with a suspension seems likely to be unpleasant also, since everything (that doesn't use a drag chute or retrorockets) brakes via contact with the ground, and as someone said, the compression on the springs will relax, giving everything a gentle push upwards, losing the ground contact that lets you decelerate. If you run into something at 60 mph, you will hurt a lot whether or not you do it in zero g.

About those springs ... 1000 kg car, assume the springs compress 10 cm under its weight, if the compression energy in the springs turns into kinetic energy, then the car will be moving upward at about 1 meter/sec. SO after 10 seconds the car is 10 meters above the ground, and then gravity turns on ... y'know, all those Wile E. Coyote cartoons come to mind here.

10 seconds is enough time for Earth-rotation effects to be potentially nasty, though it's going to sound small (well, to a dingbat astronomer like me it sounds small). Something just rest on the surface will move in a straight line tangent to Earth's surface at the instant gravity vanished. At the equator, it moves at about 0.463 km/sec. Ten seconds later, when gravity turns back on, it will have traveled in its straight line to a point about half a meter above the point on Earth's surface it would be on if it'd stayed on the circular path it would follow if it had stayed glued to the surface. (That half meter is from radius of Earth = 6378 km * 10 seconds / 86400 seconds ... strictly speaking there should be a sine in there, but the angle is so small that the angle and its sine are close to each other.) The effect is smaller as you go away from the equator (I think multiply by cosine(latitude) so in temperate latitudes you have about 70% of that rough half-meter). This would happen to approx anything that was just sitting on the ground stationary at the moment the gravity switched off, and didn't have springs or anything that would make it jump up more.

EDIT: Thinking about this on the bus ride home, I'm off by a factor of pi. Triple that half-meter rough number.

I'd have to look into the compressibility of water to see what the ocean might do. Water's pretty incompressible, but the release of gravity might make it expand vertically a bit, and when gravity turns back on that might give you tsunamis.

Austen's comment about tectonics ... I have no clue offhand how to guess at those effects. I look up, not down ;).
"You must spread some Reputation around before giving it to Cancer again."

[Cancer]

It starting to sound like you could have more luck tampering with one of the other fundamental forces. Ten seconds without the strong force would probably eliminate all evidence of your terrible crime. :)

Gah. Ten seconds with no strong force and everything is gone in a dispersing-at-almost-lightspeed cloud (so it's ten light-seconds in radius, about 6 million kilometers in diameter) of photons, leptons, and bare protons and neutrons.

[austenandrews]

"Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light."

[Basil]

At the equator, with a radius of 6,378,000 meters (and ~4,004,7156 circumference), your tangential velocity is 463.8 m/s*. In 10 seconds an object will travel 4638 m tangentially.

This means the object will be 1.69 m above "ground level". The object will be circa .8 mm "behind" where it would've been if it hadn't left the ground.

All in all, pretty unimpressive. Though the effect of objects hitting the ground when that ground is, effectively, travelling faster than the objects could get interesting, at least when you consider the "degravitied" objects would have been slowed by air resistance.



*Important note: the air will be taking off tangentially, so solid objects will not "break the sound barrier".

[TaxiMan]

I think being 1.69m higher than normal could be a very big deal, if you imagine that the ocean is doing that. When gravity returns, there will be an enormous "slosh", bigger than anything we've experienced. Of course, the oceans might not rise that much at the equator, it's very complicated. What will fill the 'void' left by the uprising water? I don't know.

[keithcurtis]

What would happen to very tall skyscrapers? They are under a lot of compression. I think the biggest problems would arise from all those vehicles losing control. Every car becomes a missle. With that many crashes, firefighting companies will be ineffective, particularly since their trucks will be unusable (After they crashback into the ground, ruining suspensions if not breaking axles, and certainly popping tires). We could be seeing firestorms in major cities.

Keith "People below Niagara falls aren't going to be very happy either" Curtis

[HeroPink!]

I say bugger the science, do whatever you think is fun, and will not over-extend your players "suspension of disbelief." If you want everything hurtling up & angled at 100 MPH, go for it!

[austenandrews]

I think being 1.69m higher than normal could be a very big deal, if you imagine that the ocean is doing that. When gravity returns, there will be an enormous "slosh", bigger than anything we've experienced. Of course, the oceans might not rise that much at the equator, it's very complicated. What will fill the 'void' left by the uprising water? I don't know.
Good point about the oceans. The 2004 tsunami was caused by a shift in the entire water column along a limited line of displacement. With all of the oceans displacing simultaneously... that would be extremely ugly.

I don't think there'd be a void at the bottom. Rather the gravity-fed water pressure would, for ten seconds, no longer be maintained. So the deeper waters would push outward. On the underside, it would quickly push into the "void" caused by its own displacement. On the top side, it would push upward on the more shallow waters. I expect the surface of the oceans would be displaced more than just the tangential movement. A pressure wave would fling upward. Come to think of it, the wave would push into the coasts at nearly the same rate. Good bye coastal cities, I'm thinking.