Let's talk about the physics of Gravity :)
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From: Northern California
[QUOTE]Originally posted by StormBringer
[B]I am in a related field I sometimes us the wrong unit in order to simplify things as it makes more since to the casual reader. And yes a gram is a unit of mass and a pound is a unit of weight but typically when you are talking about modifications of gravity you would use grams or kilograms in order to have a variable that you can easily convert.
[B]I am in a related field I sometimes us the wrong unit in order to simplify things as it makes more since to the casual reader. And yes a gram is a unit of mass and a pound is a unit of weight but typically when you are talking about modifications of gravity you would use grams or kilograms in order to have a variable that you can easily convert.
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From: Del Mar/San Diego
I design a lot of the stuff you use older guys use everyday, ever taken a drug for high blood pressure, ever had a heart attack, then you have a good chance of using my products. Ever smoked or seen feeder corn, you have seen my work.
On this board I tend to over simplify stuff in order for the post not to go on for three pages and because there are very few people who could or would brave through the post. As for the 1/2 gravity thing guess I should restate this in a more exact way but to tell you the truth I don't think that I could do it without drawing a bit and we don't have a blackboard on the site nor do I have the inclination a quick search would yield quite a bit more detailed information though.
On this board I tend to over simplify stuff in order for the post not to go on for three pages and because there are very few people who could or would brave through the post. As for the 1/2 gravity thing guess I should restate this in a more exact way but to tell you the truth I don't think that I could do it without drawing a bit and we don't have a blackboard on the site nor do I have the inclination a quick search would yield quite a bit more detailed information though.
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From: Louisville
I tend to disbelieve the thing about the Empire State Building growing that much due to gravity. There may be other reasons.
For example, the Sears tower gets slightly taller during the day due to heating of the superstructure from the sun. In fact, there are heating coils around the structural members (to heat the "cold side") and a complex series of tension cables to counteract this effect and keep the building from leaning excessively.
Likewise, I would assume that the ESB grows, but due to solar heating and not due to gravitational effects.
As to whether or not you'd be pulled by 1/2G or not, my recollection is that Stormbringer would be posting a page or two of the math necessary to calculate it accurately, since it would represent a summation of forces from many points, relative to a specific point, approximating the actual forces of more points than we would care to number (i.e. the atoms of the earth). However, just for fun...
Imagine that there are two spheres, just barely touching, that are each exactly half the mass of the earth. If you're at the point where they touch, you'd see (approximately) 1/2G toward the center of each sphere. The forces are balanced, but are predominatly in one dimension, along the central axis of the two spheres. We could probably shape each mass into a rounded cone (think of it as a stubby ice cream cone), which would only change the force acting on us if the "center of mass" moved closer or further away because of the shape change.
Now, make it four spheres, each with 1/4 the earth's mass. In this scenario, the forces are balanced in two dimensions. However, the sphere's aren't touching at the center anymore. Reshape these into four cones, with the points touching. The forces are still balanced in two dimensions.
Finally, make it 6 cones with 1/6 the earth's mass. At this point, the forces acting on the center are balanced in all three dimensions. Assuming that changing the shape from a sphere to a cone didn't cause the cones to intersect (though it probably would), you'd have roughly 1/6th of the earth's mass in each direction, along three axes.
In reality, the most appropriate shape might be a three-dimensional hexagon (someone with a better memory for geometry could chime in here with the correct shape), where placing six of them together would allow the corners to touch. This shape is not *too* far removed from a sphere.
Given that rough approximating, I suspect you might see something more along the lines of 1/6G in all directions. (However, my math's probably wildly suspect.) Whatever the case, it made for an interesting Sunday-night diversion, even if my logic or math is flawed.
Tim
For example, the Sears tower gets slightly taller during the day due to heating of the superstructure from the sun. In fact, there are heating coils around the structural members (to heat the "cold side") and a complex series of tension cables to counteract this effect and keep the building from leaning excessively.
Likewise, I would assume that the ESB grows, but due to solar heating and not due to gravitational effects.
As to whether or not you'd be pulled by 1/2G or not, my recollection is that Stormbringer would be posting a page or two of the math necessary to calculate it accurately, since it would represent a summation of forces from many points, relative to a specific point, approximating the actual forces of more points than we would care to number (i.e. the atoms of the earth). However, just for fun...
Imagine that there are two spheres, just barely touching, that are each exactly half the mass of the earth. If you're at the point where they touch, you'd see (approximately) 1/2G toward the center of each sphere. The forces are balanced, but are predominatly in one dimension, along the central axis of the two spheres. We could probably shape each mass into a rounded cone (think of it as a stubby ice cream cone), which would only change the force acting on us if the "center of mass" moved closer or further away because of the shape change.
Now, make it four spheres, each with 1/4 the earth's mass. In this scenario, the forces are balanced in two dimensions. However, the sphere's aren't touching at the center anymore. Reshape these into four cones, with the points touching. The forces are still balanced in two dimensions.
Finally, make it 6 cones with 1/6 the earth's mass. At this point, the forces acting on the center are balanced in all three dimensions. Assuming that changing the shape from a sphere to a cone didn't cause the cones to intersect (though it probably would), you'd have roughly 1/6th of the earth's mass in each direction, along three axes.
In reality, the most appropriate shape might be a three-dimensional hexagon (someone with a better memory for geometry could chime in here with the correct shape), where placing six of them together would allow the corners to touch. This shape is not *too* far removed from a sphere.
Given that rough approximating, I suspect you might see something more along the lines of 1/6G in all directions. (However, my math's probably wildly suspect.) Whatever the case, it made for an interesting Sunday-night diversion, even if my logic or math is flawed.
Tim
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From: Sydney
Regarding this centre of the Earth thing, it's not 1/2g or 1/6g or 1/(anything finite) g in all directions. The overall gravitational force experienced by an object is the integral of all infinitessimal attractions over all spatial directions. You're actually pulled in an infinite number of directions by an infinite number of infinitely small forces. The sum of them all happens to be zero, as is easy to determine by symmetry. When you're on the surface of the Earth the same principal applies but this time the integral is non-zero and has a solution that is exactly the same as if we imagine all the mass of the Earth to be concentrated at its centre of mass.
And to the person who says a gram is a unit of mass, it is, but it's also a unit of weight in every country outside the USA. When I stand on a scale in my bathroom my weight is measured in kilograms. By definition a 1 gram mass has a weight of 1 gram on Earth. We sure as hell don't go around quoting our weight in Newtons
And to the person who says a gram is a unit of mass, it is, but it's also a unit of weight in every country outside the USA. When I stand on a scale in my bathroom my weight is measured in kilograms. By definition a 1 gram mass has a weight of 1 gram on Earth. We sure as hell don't go around quoting our weight in Newtons
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I'm w/ naishou. you would be held directly in the center of the room. I believe your extremeties would be compressed inwards towards your CG as well, being pushed towards the equilibrium point unless you held onto a wall of the room in which case the centripital force of the earth's rotation would rip you to shreds.
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From: Glendale/Burbank/LA
Originally posted by MarkS2K
Man Steve, you sure think of some weird things when you're in the shower.
Man Steve, you sure think of some weird things when you're in the shower.
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From: Glendale/Burbank/LA
Another interesting discussion brewing right here:
https://www.s2ki.com/forums/showthread.php?...&threadid=86805
https://www.s2ki.com/forums/showthread.php?...&threadid=86805