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Q. Trying to understand concept in gravity
Hi.
If it where possible to create or to send 2 incredibly huge boulders into outer space from Earth and just let them float out there , would they eventually revolve around each other ? Is that how masses in outer space work? They just find their gravitation point, and start to "do si do" ? What if launched from the moon ? Or, would our solar system reject them? If so, what would it do with these 2 new intruders, which did not come from way out there, but from our modest little planet ? Would they hook up with the asteroid belt outside of mars ? Would they stay together at all, if when on earth they had absolutely no magnetic properties ? Does the pull of gravity get stronger on larger planets and weaker on smaller planets ? Why do the planets and moons pull (gravity) anyway? Is it because they're so large? Is it the activity at the core? Thanks in advance, Jim |
#2
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Q. Trying to understand concept in gravity
"Jim Jones" wrote in message ... Hi. If it where possible to create or to send 2 incredibly huge boulders into outer space from Earth and just let them float out there , would they eventually revolve around each other ? Is that how masses in outer space work? They just find their gravitation point, and start to "do si do" ? More or less, yes. What if launched from the moon ? Would make no difference. Or, would our solar system reject them? If so, what would it do with these 2 new intruders, which did not come from way out there, but from our modest little planet ? The solar system could care less. Would they hook up with the asteroid belt outside of mars ? Not necessarily. They would orbit wherever you launched them to. Would they stay together at all, if when on earth they had absolutely no magnetic properties ? Gravity is the operator here, not magnetism. Does the pull of gravity get stronger on larger planets and weaker on smaller planets ? Yes. Why do the planets and moons pull (gravity) anyway? Is it because they're so large? Is it the activity at the core? It is because of their mass. RM |
#3
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Q. Trying to understand concept in gravity
On Tue, 29 Jul 2003 06:01:14 -0400, "Ron Miller"
wrote: "Jim Jones" wrote in message .. . Hi. If it where possible to create or to send 2 incredibly huge boulders into outer space from Earth and just let them float out there , would they eventually revolve around each other ? Is that how masses in outer space work? They just find their gravitation point, and start to "do si do" ? More or less, yes. What if launched from the moon ? Would make no difference. Or, would our solar system reject them? If so, what would it do with these 2 new intruders, which did not come from way out there, but from our modest little planet ? The solar system could care less. Would they hook up with the asteroid belt outside of mars ? Not necessarily. They would orbit wherever you launched them to. Would they stay together at all, if when on earth they had absolutely no magnetic properties ? Gravity is the operator here, not magnetism. Does the pull of gravity get stronger on larger planets and weaker on smaller planets ? Yes. Why do the planets and moons pull (gravity) anyway? Is it because they're so large? Is it the activity at the core? It is because of their mass. RM Ron, Thanks for your prompt response and your help in clearing up those things, but I may be unclear on what you mean, in the last statement, about "It's their mass". Let me rephrase my question. And please don't think you're being too simple in answering: Q. Why does earth hang onto it's loose objects ? What about "mass" might I not be understanding. ALSO: Does gravity gradually drop off, as we get higher and higher into the atmosphere, OR, is there a fine line where gravity goes from gravity to no gravity? Thanks again, Jim |
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Q. Trying to understand concept in gravity
Let me correct the equation before somebody else does. :-)
F = (G * m1 * m2) / r^2 Where G is the gravitational constant. "Bill Nunnelee" wrote in message thlink.net... The outcome of the boulders would depend on their velocities relative to each other. If zero (and they were sufficiently close to each other), their mutual gravitational attraction would pull them together---instead of orbiting, they would collide. (Gravity works over any distance, but if they were too far apart, the influence of other solar system bodies would probably overwhelm any mutual attraction.) It wouldn't matter if they were launched from the earth or the moon. Whether they would stay or go depends on whether they were given enough of an initial push to reach escape velocity or not. The initial speed and direction would also determine their orbit around the sun if they stayed. They could also be ejected by passing close to another body and picking up some of the body's energy. Gravitational assists were used with many space probes, and close passages of Jupiter have been responsible for ejecting many comets over time. Magnetism is an entirely different force. The strength of gravity depends on the mass of the two objects involved and the distance between them. Newton expressed it as F = m1*m2 / r^2, where m1 and m2 are the two masses and r is the distance between them. "Jim Jones" wrote in message ... Hi. If it where possible to create or to send 2 incredibly huge boulders into outer space from Earth and just let them float out there , would they eventually revolve around each other ? Is that how masses in outer space work? They just find their gravitation point, and start to "do si do" ? What if launched from the moon ? Or, would our solar system reject them? If so, what would it do with these 2 new intruders, which did not come from way out there, but from our modest little planet ? Would they hook up with the asteroid belt outside of mars ? Would they stay together at all, if when on earth they had absolutely no magnetic properties ? Does the pull of gravity get stronger on larger planets and weaker on smaller planets ? Why do the planets and moons pull (gravity) anyway? Is it because they're so large? Is it the activity at the core? Thanks in advance, Jim |
#5
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Q. Trying to understand concept in gravity
Jim wrote:
Thanks for your prompt response and your help in clearing up those things, but I may be unclear on what you mean, in the last statement, about "It's their mass". As an amateur myself I can put it the layman's terms I learned for you. I hope you and Ron don't mind my jumping in. Mass is what determines an object's gravity, not its size. Mass is simply the amount of "stuff" in something. For example: a tennis ball and a tennis ball-sized rock. The rock has more mass (stuff in it) than the tennis ball. In your hands the rock weighs more than the ball, since there is more stuff in it for gravity to draw upon (i.e. it weighs more). Naturally, on the moon the rock would weigh less than it does on Earth, and on Jupiter it would weigh more. So mass is the term used to describe "stuff" astronomically, rather than size or weight, in regards to gravity. Size only comes into it because there's so much more room for "stuff" to be in. But that doesn't necessarily mean there *will* be more "stuff" in the bigger object. So you can see that if Jupiter (mostly gassy) were the same size as Earth (mostly rock), Earth would have more mass and therefore more gravity. Same goes for if Earth were the same size as Jupiter. Let me rephrase my question. And please don't think you're being too simple in answering: Q. Why does earth hang onto it's loose objects ? Gravity, coupled with the fact the loose objects aren't going fast enough to break away, nor slow enough to plummet to the ground. ALSO: Does gravity gradually drop off, as we get higher and higher into the atmosphere, OR, is there a fine line where gravity goes from gravity to no gravity? The first. The "Dropping Off Equation", IIRC, is 1/R(squared). Where R = radius of the Earth = 4000 miles = surface Gravity, or 1 G. So if you fly out to 4000 miles *above* the surface = 1/2(squared) = 1/4th the strength of surface Gravity = .25 G's. At the moon (ignoring its own gravity) = .00028 G's. At Jupiter (ignoring its own gravity) = .000000000000000002 G's As you can see, we'll never reach 0. Gravity will just drop off into really, REALLY small numbers the farther out we go. Hope this helps a bit. Cheers, Kent |
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Q. Trying to understand concept in gravity
Jim wrote:
Let me rephrase my question. And please don't think you're being too simple in answering: Q. Why does earth hang onto it's loose objects ? What about "mass" might I not be understanding. Every body with mass attracts every other, in proportion to the masses of both and in inverse proportion to the square of the distance between their centres. Bill posted this same statement in the form of an equation. On earth our principal experience of mass is in the form of weight; a "heavy" object has a large mass, while the mass of a "light" object is small. The weight of an object measures the strength of its attraction to the earth, whose mass is so enormous that it dominates everything near it. We don't notice the attraction of one 'ordinary-sized' object for another because gravity is very weak -- except when things as big as planets and moons are involved. But using extremely sensitive torsion balances, the gravitational attraction between very large weights suspended very close to each other can actually be measured in a laboratory. An object resting on the earth's surface stays where it is because the ground 'pushes back' with an equal force; if unsupported it will fall with an acceleration called "g", making its speed constantly increase by a little under ten metres (about 32 feet) per second every second. In order to raise an object off the surface one has to supply a lifting force *greater* than the pull of gravity, i.e. the object's weight. ALSO: Does gravity gradually drop off, as we get higher and higher into the atmosphere, OR, is there a fine line where gravity goes from gravity to no gravity? It drops off gradually at first, then faster and faster, but never disappears altogether. In principle the earth's gravity field goes out to infinity, and in turn we experience gravitational attraction from every star in our galaxy and beyond -- but at great distances the forces become too small to have any noticeable effect. The key here is the "square" part of the inverse square ratio I mentioned above: the 'weakening' effect of great distance overcomes the 'strengthening' effect of great mass. -- Odysseus |
#7
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Q. Trying to understand concept in gravity
"Kent" wrote in message
... snip At Jupiter (ignoring its own gravity) = .000000000000000002 G's As you can see, we'll never reach 0. Gravity will just drop off into really, REALLY small numbers the farther out we go. Hope this helps a bit. snip Is this true? Gravity never quites get to 0? I am having one of those moments. This is shocking. Can someone expound on this? The concept sounds very important. How far can we actually measure before we can't "sense" the field anymore? BV. |
#8
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Q. Trying to understand concept in gravity
Surely gravity is nullified when an object
equi-distant from two bodies having equal gravitational pull? It's called the barycenter (or barycentre to the Brits), the gravitational null point, or effective center of mass, between two co-orbiting bodies. In some situations, the barycenter can actually be below the surface of the larger body. oc |
#9
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Q. Trying to understand concept in gravity
Jonathan Silverlight wrote:
The forces are still at work. It's like a tug of war, equally balanced and just as unstable. After all, the moon pulls on the Earth even though it's well outside the sphere where the Earth dominates (and vice versa). Of course for other planets the force becomes so small it's undetectable. I doubt we can detect the pull of Venus, for instance. It's not too hard to 'ballpark' the numbers: given that Venus has a mass of about 80% of the earth's, and at inferior conjunction it's about fifty million kilometres away, nearly eight thousand times the distance from the earth's centre to the surface. Dividing 0.8 by 8000^2 yields an acceleration value of somewhat over ten billionths (i.e. 10^-8) of one g -- as you say, pushing the limits of our ability to detect. By way of comparison the pull of the moon is over 250 times as strong, and that of the sun nearly 50,000 times; another way to get an idea of our experience of the gravity of Venus might be to compare it to a ten-tonne weight two metres away. -- Odysseus |
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Q. Trying to understand concept in gravity
"Jonathan Silverlight" wrote in message
... In message , Andrew McKay writes On Wed, 30 Jul 2003 09:04:21 -0400, "BenignVanilla" wrote: Is this true? Gravity never quites get to 0? I am having one of those moments. This is shocking. Can someone expound on this? The concept sounds very important. How far can we actually measure before we can't "sense" the field anymore? Surely gravity is nullified when an object equi-distant from two bodies having equal gravitational pull? In other words it's effect is additive, suggesting that there is indeed a zero-gravity situation available. The forces are still at work. It's like a tug of war, equally balanced and just as unstable. After all, the moon pulls on the Earth even though it's well outside the sphere where the Earth dominates (and vice versa). Of course for other planets the force becomes so small it's undetectable. I doubt we can detect the pull of Venus, for instance. So if it's undetectable...is it there? I am seriously asking, not being a smart ass. I am curious how far out these fields go. I am wondering if some day distant planets could be found based on some kind of signature. BV. |
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