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BigPapaSmurf
SFN Die Hard
3192 Posts |
 Posted - 09/16/2009 : 08:08:52
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So Im sure you are familiar with the whole objects of different weights falling at the same speed thing so my question is,
Wouldnt the heavier mass object strike the ground first by a tiny fraction due to the earth being pulled towards that more massive object faster? Assuming they were dropped at different times or different sides of the world or something...
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Hal
Skeptic Friend
USA
302 Posts |
Posted - 09/16/2009 : 08:22:31 [Permalink]
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| I think that counts as one of those factors, such as density, that are not considered in this simplified expression. The statement, obviously, has to do with the rate of acceleration, rather than the time of impact. |
Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity.
Martin Luther King Jr.
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 09/16/2009 : 08:45:23 [Permalink]
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| So it's the rate of acceleration if the main body is hypothetically fixed. Thats what I thought, thanks Hal. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
| Edited by - BigPapaSmurf on 09/16/2009 08:45:53 |
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Simon
SFN Regular
USA
1992 Posts |
Posted - 09/16/2009 : 13:07:46 [Permalink]
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Yes, the rate of acceleration depends on the mass of the Earth and is, therefore, constant.
I guess, if you want to be extra-nit picky, the object that is falling is also attracting the earth, so the larger the mass, the larger the attraction, and, hence, the heavier object will touch a tiny bit of a fraction earlier, as the earth would have fallen toward it a tiny bit of a fraction more. Obviously, it's is safely negligible.
It is, of course, free fall, into a vacuum. Therefore, not taking into account the resistance from the air which will depend on the density and shape of the object falling. Take a rocket, put it head down and drop it and it will be on the ground faster than the same weight represented by a sheet of paper.
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Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
Carl Sagan - 1996 |
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bngbuck
SFN Addict
USA
2437 Posts |
Posted - 09/16/2009 : 13:23:00 [Permalink]
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BPS.....
You pose a fascinating and complex question. I suspect that the literal answer is impossible to give because of the multiplicity of factors involved. Physicists and astronomers differentiate between the terms "gravity" and "gravitation", and as Hal has pointed out, "acceleration" is a different thing altogether.
Speaking in respect to "gravitation", theoretically your premise would be incorrect if no other factors were involved other than the mass of the Earth and the relative masses of the two objects "dropping".
In other words, if all we were considering here was the acceleration of objects of different masses toward one another, they would all arrive at exactly the same time! The Earth is simultaneously "dropping" (accelerating) toward the objects in a very minute way. In absolute terms, the acceleration of the Earth toward the object of smaller mass is the same as it's acceleration toward the object of greater mass --- as is the reverse, objects accelerating toward Earth --- and the objects should contact the Earth at exactly the same instant. More from wiki
Obviously, (besides the evident non-gravitational effect of air resistance) an enormous number of other gravitational, inertial, centrifugal, centripital, and other forces are acting on both the Earth and the the objects of less mass at exactly the same moment that they are accelerating toward each other. The inertia of the greater mass (Earth) being larger than the inertia of the smaller objects masses is a factor. Multitudes of other gravitational interactions are determining the exact moment that the Earth and the "falling" objects make contact. This premise is not an ideal candidate for experimental investigation!
And if you are looking for real Emirilean kick-it-up-a-notch complexity, consider Einstein's definition of gravitation as the distortion of the time-space continuum by the presence of objects of mass (matter). Or, for that matter (ouch), from wiki , some of this shit:In the modified Newtonian dynamics (MOND) (1981), Mordehai Milgrom proposes a modification of Newton's Second Law of motion for small accelerations
The self-creation cosmology theory of gravity (1982) by G.A. Barber in which the Brans-Dicke theory is modified to allow mass creation
Nonsymmetric gravitational theory (NGT) (1994) by John Moffat
Tensor-vector-scalar gravity (TeVeS) (2004), a relativistic modification of MOND by Jacob Bekenstein |
Great oaks from little acorns grow!
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 09/16/2009 : 22:51:22 [Permalink]
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Here's something I ran into in my random peregrinations. Anyone care to try to parse and comment upon this section of the Wiki article on "Hollow Earth" (especially the last part)? I'm flatly perplexed, and don't understand it at all. (Unless, as I half-suspect, it's just an unsubstantiated and deliberately confusing defense of a hollow earth.)
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 09/16/2009 22:53:21 |
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bngbuck
SFN Addict
USA
2437 Posts |
Posted - 09/17/2009 : 00:08:27 [Permalink]
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What's to be perplexed about? It's an old science-fiction theme from the '20's and '30's that I remember reading as a child more than seventy years ago. Hugo Gernsback's Amazing Stories were exactly that -- amazing stories with little or no science in the 100% fiction.
As to Martin Gardner, he is simply pulling your leg with his petition to seriously consider the mathematics and geo/astrophysics of a "hollow Earth", or more properly a hollow universe. He is no more serious than the good Reverend Dodgson was with his tales of Alice in the alternative world.
If you can get a copy of "The Annotated Alice", copiously annotated by Gardner, you will gain an understanding of Gardner's sly, enigmatic sense of humor. He strives to make the patently ridiculous appear feasible and revels in taking in a sophisticated reader.
Martin is a superb puzzle master, an impractical joker, a mathemagician, an equal to James Randi as a debunker of fraud and pseudoscience, a skeptic's skeptic---and his style is to bamboozle the reader into believing that something that is impossible, is really possibly possible. All the time, he is laughing at his audience. You may answer only yes or no, did you stop beating your wife? I condemn you, sir, for your brutality and intolerence!
I can only hope when I reach his redolently ripe age of 95, that I retain half the edge that Martin still has! |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 09/17/2009 : 03:24:29 [Permalink]
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Originally posted by bngbuck
What's to be perplexed about? It's an old science-fiction theme from the '20's and '30's that I remember reading as a child more than seventy years ago. Hugo Gernsback's Amazing Stories were exactly that -- amazing stories with little or no science in the 100% fiction.
As to Martin Gardner, he is simply pulling your leg with his petition to seriously consider the mathematics and geo/astrophysics of a "hollow Earth", or more properly a hollow universe. He is no more serious than the good Reverend Dodgson was with his tales of Alice in the alternative world.
If you can get a copy of "The Annotated Alice", copiously annotated by Gardner, you will gain an understanding of Gardner's sly, enigmatic sense of humor. He strives to make the patently ridiculous appear feasible and revels in taking in a sophisticated reader.
Martin is a superb puzzle master, an impractical joker, a mathemagician, an equal to James Randi as a debunker of fraud and pseudoscience, a skeptic's skeptic---and his style is to bamboozle the reader into believing that something that is impossible, is really possibly possible. All the time, he is laughing at his audience. You may answer only yes or no, did you stop beating your wife? I condemn you, sir, for your brutality and intolerence!
I can only hope when I reach his redolently ripe age of 95, that I retain half the edge that Martin still has!
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No, I was writing about the last paragraph of the "gravity" section of the "Hollow Earth" Wikipedia article. Nothing to do with Gardner that I'm aware of. But I loved The Annotated Alice! I read it as a teen.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 09/17/2009 : 03:53:23 [Permalink]
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Originally posted by HalfMooner
Here's something I ran into in my random peregrinations. Anyone care to try to parse and comment upon this section of the Wiki article on "Hollow Earth" (especially the last part)? I'm flatly perplexed, and don't understand it at all. (Unless, as I half-suspect, it's just an unsubstantiated and deliberately confusing defense of a hollow earth.) |
It's not a defense at all, it's a criticism (it's under the section titled "Contrary evidence"). |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 09/17/2009 : 04:16:23 [Permalink]
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Originally posted by Dave W.
Originally posted by HalfMooner
Here's something I ran into in my random peregrinations. Anyone care to try to parse and comment upon this section of the Wiki article on "Hollow Earth" (especially the last part)? I'm flatly perplexed, and don't understand it at all. (Unless, as I half-suspect, it's just an unsubstantiated and deliberately confusing defense of a hollow earth.) |
It's not a defense at all, it's a criticism (it's under the section titled "Contrary evidence").
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Okay, I see the problem. That article, including that section, is under intense back-and-forth editing. When I'd read it, it was definitely pro-flat-earth:However, the center of gravity is NOT at the center, geometrically speaking. This would be impossible, as one half of the Earth's volume (MASS if solid) exists between the depths of 3958.8 miles(6371km) being the surface and 3140.0 miles (5056.67km) constituting a depth of only 818.8 miles. Newton and Einstein alike did NOT propose that the "center" of a ''body'' of mass attracts mass (gravity) or distorts "space-time". They both proposed that MASS causes these effects. Therefore, if the earth were solid, then center of gravity must be 818.8 miles deep from any place.
But it's not. It is commonly known in the scientific community that the center of gravity is about 380 miles deep. This is the center of the previously mentioned shell. This leaves the reasonable conclusion that the earth must be hollow. |
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 09/17/2009 : 06:19:27 [Permalink]
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Originally posted by HalfMooner
Okay, I see the problem. That article, including that section, is under intense back-and-forth editing. When I'd read it, it was definitely pro-flat-earth:However, the center of gravity is NOT at the center, geometrically speaking. This would be impossible, as one half of the Earth's volume (MASS if solid) exists between the depths of 3958.8 miles(6371km) being the surface and 3140.0 miles (5056.67km) constituting a depth of only 818.8 miles. Newton and Einstein alike did NOT propose that the "center" of a ''body'' of mass attracts mass (gravity) or distorts "space-time". They both proposed that MASS causes these effects. Therefore, if the earth were solid, then center of gravity must be 818.8 miles deep from any place.
But it's not. It is commonly known in the scientific community that the center of gravity is about 380 miles deep. This is the center of the previously mentioned shell. This leaves the reasonable conclusion that the earth must be hollow. |
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Yeah, that's definitely pro-flat-Earth, and very looney-tunes. Or at least in denial of physics. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 09/17/2009 : 11:45:38 [Permalink]
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Originally posted by BigPapaSmurf
So Im sure you are familiar with the whole objects of different weights falling at the same speed thing so my question is,
Wouldnt the heavier mass object strike the ground first by a tiny fraction due to the earth being pulled towards that more massive object faster? Assuming they were dropped at different times or different sides of the world or something...
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Near the earth's surface any expiriment we can do is not going to involve any mass that can exert enough gravitational force on the earth that we can measure it. The earth clocks in at 5.9742 ?10^24 kilograms. So even if you could pick up TX and drop it there is likely to be no detectable difference between that and dropping a marble. (well, the energy of impact would be measurably different, just not the acceleration due to earth's gravity)
It is important to note that this only holds near the earth's surface, because the force of gravity is proportional to the mass of an object. It is also inversely proportional to the square of the distance between objects.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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Gravity question...
